Table of Content

25 August 2020, Volume 41 Issue 16
Food Chemistry
Stability of Antioxidant Peptides Extracted from Fermented Sausages
LUAN Xiaoxu, FENG Meiqin, SUN Jian
2020, 41(16):  1-7.  doi:10.7506/spkx1002-6630-20200229-340
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To study the stability of antioxidant peptides extracted from fermented sausage under conditions simulating those occurring during industrial processing and gastrointestinal digestion, we investigated the effects of temperature, pH, food additives, metal ions, and simulated gastrointestinal digestion on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, Fe2+-chelation ability and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical scavenging activity. The results showed that the radical scavenging rate decreased significantly (P < 0.05) at high temperature and in acid and alkaline environment, while the Fe2+-chelation rate increased, but only slightly. NaCl, glucose and sucrose were beneficial to improve the radical scavenging activity, while they inhibited the Fe2+-chelation activity. NaNO2 had little effect on the antioxidant activity of the peptides when added at levels within the range permitted by the national standard. The antioxidant peptides were more sensitive to Cu2+ than to K+. The DPPH radical scavenging activity was completely lost after the simulated gastrointestinal (GI) digestion, but the Fe2+-chelation activity increased by 1.4 times compared with that before the digestion. The ABTS cation radical scavenging rate was stable at about 40%, and the total free amino acid content gradually increased.
Effect of L-Lysine on Phosphorylation of Myofibrillar Proteins from Chicken Thigh Meat
FANG Rui, ZHU Zongshuai, GUO Xiuyun, PENG Zengqi, ZHANG Yawei
2020, 41(16):  1-6.  doi:10.7506/spkx1002-6630-20190825-267
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In order to investigate the effect of adding L-Lys on the phosphorylation of myofibrillar proteins from chicken thigh meat under high (3% NaCl) and low salt (1% NaCl) conditions, myofibrillar proteins were extracted from the salted chicken meat samples and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the phosphorylated myofibrillar proteins were identified by fluorescence staining and liquid chromatography-tandem mass spectrometry (LC-MS). The differences in the phosphorylation level of chicken myofibrillar proteins among different treatment groups were explored. The results showed that the phosphorylation level of myofibrillar proteins in the 1% NaCl + 0.06% L-Lys group was significantly lower than that of the 0% and 1% NaCl groups (P < 0.05), but did not significantly differ when compared with that of the 3% NaCl and 3% NaCl + 0.06% L-Lys groups (P > 0.05), showing that the addition of L-Lys reduced the phosphorylation level of myofibrillar proteins under low salt condition. The phosphorylation levels of α-actinin-2, β-enolase, tropomyosin α-1 chain, myosin light chain 2, and myosin light chain 3 in the 1% NaCl + 0.06% L-Lys group were significantly lower than those in the 1% NaCl group (P < 0.05). The phosphorylation levels of myosin heavy chain, M protein, β-enolase, myosin light chain 2, and myosin light chain 3 in the 1% NaCl + 0.06% L-Lys group were significantly lower than those in the 3% NaCl group (P < 0.05). The results of this study indicated that the addition of 0.06% L-Lys had an overall positive effect on the phosphorylation of myofibrillar proteins.
Digestion Characteristics of Naringin-Loaded Nanoemulsion Delivery Systems
2020, 41(16):  7-13.  doi:10.7506/spkx1002-6630-20190519-208
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In this paper, the in vitro digestion patterns of naringin-loaded monolayer and bilayer nanoemulsions constructed by using whey protein isolate (WPI) alone and in combination with ι-carrageenan (ι-Car) or gum arabic (GA) as emulsifiers, named as NA/WPI-e, NA/WPI/ι-Car-e and NA/WPI/GA-e, respectively were studied. The analysis of droplet size, zeta potential and microstructure during simulated gastrointestinal digestion indicated both the single and bilayer nanoemulsions underwent different degrees of hydrolysis. During simulated gastric digestion, the emulsion droplets aggregated, resulting in a significant increase in their average particle size (P < 0.05), and the zeta potential absolute value also increased. During simulated intestinal digestion, deflocculation of the naringin-loaded nanoemulsions was observed. After simulated gastrointestinal digestion, the release rate of free fatty acids (FFAs) and naringin bioavailability of NA/WPI-e were 97.3% and 10.06% respectively. The FFA release rate and naringin bioavailability of NA/WPI/ι-Car-e were lower than those of NA/WPI-e, while NA/WPI/GA-e at 1 mg/mL GA concentration showed the highest naringin bioavailability (12.13%). The FFA release rates of the single and bilayer nanoemulsions were significantly higher than that of the control group (34%), indicating that the nanoemulsion delivery system can effectively improve the bioavailability of naringin.
Functional Properties of Normal and Waxy Barley Starch Blends with Various Mass Ratios in Excess Water
ZHAO Shenchi, LI Xin, LIU Qian, KONG Baohua, HU Gongshe
2020, 41(16):  8-14.  doi:10.7506/spkx1002-6630-20190704-054
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This study investigated the functional properties of blends of normal barley starch (NBS) and waxy barley starch (WBS) with different mass ratios (75:25, 50:50 and 25:75) in excess water (water content 95%, m/m) such as solubility, swelling power, water absorption capacity, pasting properties, gel strength, and freeze-thaw stability. The results showed that with increasing amount of WBS, the solubility and puncture force of the blends significantly fell (P < 0.05), whilst the swelling power and water absorption capacity reached the maximum at WBS50. The pasting curves measured by a rapid viscosity analyzer showed that with increasing amount of WBS, the peak viscosity significantly increased (P < 0.05). Meanwhile, NBS75:WBS25 possessed the highest pasting temperature (P < 0.05). Furthermore, with increasing amount of WBS, the freeze-thaw stability of starch blends significantly improved after different freeze-thaw cycles (P < 0.05), which was verified by the results of electron microscopy scanning. Our present study indicated that changing the mass ratio of NBS to WBS had a significant effect on the functional properties of starch blends. This study provides a theoretical basis for the application of WBS and NBS blends in the food industry.
Effect of Fat Content on Texture, Rheology and Microstructure of Yak Milk Hard Cheese
SHI Yongqi, LIANG Qi, SONG Xuemei, ZHANG Yan
2020, 41(16):  14-19.  doi:10.7506/spkx1002-6630-20190617-181
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The effects of fat content on the texture, rheology and microstructure of yak milk hard cheese were clarified by measuring the functional properties of yak milk cheeses containing different proportions of fat. Full-fat, semi-skimmed and low-fat hard cheeses were made from defatted and whole yak milk mixtures at ratios of 0:1, 1:1 and 2:1, respectively, and their physicochemical indicators were tested and texture characteristics were analyzed using texture profile analysis (TPA). Moreover, the correlation between fat content and each of the measured texture parameter was analyzed. The microstructure of cheese was observed by confocal laser scanning microscopy, and rheological properties were measured in the temperature range of 25–80 ℃. Furthermore, a regression equation between elastic modulus and viscoelasticity and temperature was set up. The cheese yield increased with increasing fat content. There were significantly negative correlations between fat content and water content, hardness, elasticity or chewiness with correlation coefficients of ?0.909, ?0.851, ?0.795 and ?0.768, respectively, while it was significantly positively correlated with cohesiveness with a correlation coefficient of 0.898. The areas of fat granules in full-fat, semi-skimmed and low-fat cheese were 1 800.20, 1 317.59 and 792.02 μm2, respectively, accounting for 10.0%, 7.3% and 4.4% of the total area, respectively. The lower the fat content, the greater the elastic modulus; conversely, the higher the fat content, the greater the viscoelasticity. The fat content was closely related to the physicochemical properties, texture, microstructure and rheological properties of cheese. This experiment provides a basis for the study of the mechanism of the effect of fat content on yak milk cheese.
Effect of Soymilk Components on Inactivation Degree of Bowman-Birk Inhibitor
ZHEN Shaobo, WANG Jianshe, HE Hui, LIU Yiren, CHEN Yeming
2020, 41(16):  15-20.  doi:10.7506/spkx1002-6630-20190423-299
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Considering that soymilk is a complex system, this study designed three model systems (glucose + Bowman-Birk inhibitor (BBI), fructose + BBI, and soybean protein (SP) + BBI) to examine the contribution of reducing sugar, SP and heat treatment to BBI inactivation. Without heating, glucose could enhance the activity of BBI, but fructose could not. With heating, reducing sugar could obviously affect trypsin inhibitor activity (TIA) of BBI, but only slightly affect its chymotrypsin inhibitor activity (CIA); glucose affected BBI more obviously than did fructose. SP could affect CIA of BBI more obviously than its TIA; BBI could link to basic peptide chains of glycinin by disulfide bonding to form a dimer, and also could interact with SP to form a polymer by disulfide bonding; in addition, BBI could interact with itself to form a BBI dimer. Under the conditions of incubation in boiling water bath for 3 h, and BBI, glucose, fructose, and SP concentrations of 2 mg/mL, glucose made the greatest contribution to TIA inactivation, followed by heat-induced conformation change, fructose and SP, while SP made the greatest contribution to CIA inactivation, followed by heat-induced conformation change, and glucose/fructose.
Radio Frequency Improves the Stability and Quality of Rice Bran
YU Dianyu, HAO Kaiyue, CHENG Jie, CHEN Kuiren, JIANG Lianzhou, WANG Liqi, ZHANG Zhi
2020, 41(16):  20-26.  doi:10.7506/spkx1002-6630-20200413-162
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A radio frequency (RF) heating system was employed to treat fresh rice bran for the purpose of improving its stability. Optimization of operating parameters for reduced relative activity of lipase was carried out using a combination of one-factor-at-a-time method and response surface methodology. The results showed that the optimal operating conditions were as follows: spacing distance between RF plates 10.5 cm, temperature 92 ℃, and treatment time 5.3 min. Under these conditions, the relative activity of rice bran lipase was as low as 18.25%. was After being stored at 35 ℃ for 6 weeks, the relative activity of lipase increased from 18.35% to only 22.63%, the acid value was only 22.32% as compared to that of untreated rice bran at the same storage period, and the peroxide value remained below the threshold of 5 mmol/kg. The protein content of rice bran decreased slightly but not significantly during storage. The water-holding capacity of rice bran protein reached its maximum after one week of storage, which increased by 37% in the treated rice bran compared with the untreated rice bran. Therefore, RF treatment could not only extend the storage life of rice bran, but also enhance the functional properties of rice bran protein. This study provides a good theoretical basis for expanded application of rice bran.
Inhibitory Effect of Polyphenols on Key Off-odors in Thermally Processed Muskmelon Juice
SUN Yuqing, KONG Fanyu, WU Jihong, PANG Xueli
2020, 41(16):  21-28.  doi:10.7506/spkx1002-6630-20190715-199
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This study investigated and compared the inhibitory effect of various polyphenols on the formation of off-odors in thermally processed muskmelon juice using sensory evaluation combined with the Friedman test and multiple comparison analysis. Qualitative and quantitative analysis of the off-odor compounds in muskmelon juice with and without added catechin, genistein, daidzein, phlorotannins or pyrogallol was conducted using headspace solid phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS), and orthogonal partial least squares discriminant analysis (OPLS-DA) was used to characterize the inhibitory action of each polyphenol on the off-odor compounds. The results revealed that the sensory evaluation was consistent with the instrumental analysis of the types of inhibited off-odor compounds and the percentage inhibition. The five polyphenols at the same concentration of 0.1 mg/mL had different inhibitory effects on the formation of thermally-induced off-odors. Catechin exhibited the strongest inhibitory effect, followed by phlorotannins, daidzein, genistein and pyrogallol, and the effects of catechin, phlorotannins and daidzein were significant (P < 0.05). The combined use of catechin and daidzein could serve as the best way to prevent and minimize the generation of heat-induced off-odors in muskmelon juice. This study provides theoretical guidance to overcome the problem of heat-induced off-odors in muskmelon juice as a representative of thermosensitive fruits and vegetables and to develop deeply processed products.
Effects of pH on Wheat Gliadin-Quercetin Interaction and Properties of Pickering Emulsions Stabilized by Their Complex
WANG Qiming, TANG Yuwan, YANG Yaxuan, LIU Shijian, ZHAO Jichun, ZHANG Yuhao, MING Jian
2020, 41(16):  27-34.  doi:10.7506/spkx1002-6630-20200107-089
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The interaction between quercetin (Q) and wheat gliadin (G) under different pH conditions were studied by fluorescence spectroscopy. The properties of Pickering emulsions stabilized by G or G-Q complexes were investigated. The results showed that under all pH conditions tested, the fluorescence of G was quenched by Q in both dynamic and static modes, mainly through hydrophobic interaction for pH 3.0, and hydrogen bonds and van der Waals forces for pH 5.0 and 7.0. Scanning electron microscopy showed that the protein could more easily form a compact and dense reticular structure with increasing pH. Differential scanning calorimetry demonstrated that protein molecule denaturated in a more collaborative manner at pH 5.0. The emulsion stabilized by G-Q complex at pH 5.0 possessed the highest viscosity and strongest gel performance. The emulsion was stable without oil deposition during storage for 90 days. At pH 3.0, the continuous network structure of protein particles in the continuous phase greatly contributed to the stability of the emulsion, while at pH 5.0, the interaction between particles adsorbed at the interface between oil droplets and water and the interaction between oil droplets stabilized the emulsion.
Effects of Three Amino Acids on Quality and N-Nitrosamine Formation of Western-style Smoked Sausage
ZHOU Yajun, WANG Qiuying, MA Yongqiang, CHEN Yan, WANG Shujie
2020, 41(16):  29-36.  doi:10.7506/spkx1002-6630-20200303-047
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This study investigated the effects of amino acids on the quality of western-style smoked sausage and the formation of N-nitrosodimethylamine (NDMA), N-nitrosodi-npropylamine, NDPA) and N-nitrosopyrrolidine (NPYR). Different concentrations of sodium nitrite (0, 150 and 480 mg/kg) and three amino acids (arginine, alanine and proline) at 1 000 mg/kg were added to study their effects on the texture, color, pH, thiobarbituric acid reactive substances (TBARS), moisture, cooking loss, residual nitrite and the formation of N-nitrosamines in western-style smoked sausage. The results showed that arginine and alanine reduced residual nitrite, while proline had the reverse effect. The three amino acids significantly increased NDPA content. Proline resulted in a significantly higher NPYR content compared with the other amino acids. The three amino acids significantly increased hardness, cohesiveness, chewiness, a* value and pH value, and reduced L* value, b* value, TBARS value and cooking loss. Arginine increased springiness while alanine and proline reduced springiness. Adhesiveness was increased by arginine and proline, but was reduced by alanine. All three amino acids could improve the product quality and inhibit the oxidation of the product. Thus, they could be used as quality improvers. However, they could also promote the formation of N-nitrosamines. The contents of these three amino acids in the product should be reduced to inhibit the formation of N-nitrosamines. This study can lay a theoretical foundation and provide reference for further research to improve the product quality, inhibit the formation of N-nitrosamine and understand its formation mechanism.
Effect of High-Gluten Flour Addition on the Quality of Youtazi, a Traditional Halal Wheaten Food in Xinjiang
CHEN Shuchang, SHEN Aqian, FENG Zuoshan, BAI Yujia, CHEN Qi, ZHANG Yue, TU Saili, HUANG Wenshu
2020, 41(16):  35-40.  doi:10.7506/spkx1002-6630-20190618-207
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Youtazi were made from ordinary wheat flour incorporated with different proportions of high-gluten flour, and their microstructure, physicochemical properties and sensory quality were analyzed. Principal component analysis (PCA) was carried out on their physicochemical properties. The results showed the appearance, mouthfeeling, skin color and overall sensory score of Youtazi increased significantly (P < 0.05) with increasing the amount of high-gluten flour up to 40%. PCA showed that the first four principal components explained 91.998% of the total cumulative variance. The PCA scores for the quality of Youtazi with different proportions of high-gluten flour added decreased in the following order: 40% > 50% > 60% > 30% > 20% > 10% > 0%. The sensory evaluation demonstrated that the highest sensory score was attained at an addition level of 40%, which was basically consistent with the results of PCA. It was concluded that the quality of Youtazi was the best with the addition of 40% high-gluten flour.
Preparation and Purification of Antioxidant Peptide from Porphyra haitanensis Protein and Its Antioxidant Activities in Vitro
HU Xiao, YU Jiao, CHEN Shengjun, YANG Xianqing, LI Laihao, WU Yanyan
2020, 41(16):  37-44.  doi:10.7506/spkx1002-6630-20190822-231
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In this study, single factor experiment and response surface methodology (RSM) based on Box-Behnken design (BBD) were used together to optimize the hydrolysis process of Porphyra haitanensis protein by acid protease. The antioxidant activity and molecular mass distribution of the hydrolysates at different hydrolysis times were measured. The results showed that under the optimized hydrolysis conditions (substrate concentration of 2 g/100 mL, enzyme/substrate of 4 240 U/g, pH value of 3.7, temperature of 54 ℃, and hydrolysis time of 4 h), the highest degree of hydrolysis (DH) of 11.40% was obtained. The relationship between DH and antioxidant activity of the hydrolysates was investigated. It was found that the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of the 4 h hydrolysate (DH = 11.40%) was the strongest with a half maximum inhibition concentration (IC50) of 0.68 mg/mL, and that small molecular mass peptides (< 1 kDa) accounted for 73.46% of the total peptides in the hydrolysate. This hydrolysate was fractionated by gel filtration chromatography, yielding an antioxidant peptide (named PHAP). PHAP at 1 mg/mL concentration scavenged DPPH and hydroxyl radicals by 73.32% and 30.15%, respectively. It was confirmed that PHAP could repair H2O2-induced oxidative damage in HepG2 cells by enhancing the activity of superoxide dismutase and decreasing the content of malondialdehyde.
Removal of 3-Monochloro-1,2-propanediol Esters and Glycidyl Esters from Corn Oil by Molecular Distillation
HUANG Huina, LIU Yulan, YANG Zhengguang, WANG Jiandong, WANG Yuehua
2020, 41(16):  41-45.  doi:10.7506/spkx1002-6630-20190822-234
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3-Monochloro-1,2-propanediol (3-MCPD) esters and glycidyl esters (GEs) were removed from corn oil by molecular distillation. The results showed that under the conditions of molecular distillation temperature of 220 ℃, scraping speed of 230 r/min and feeding speed of 50 drop/min, the removal rate of GEs was 85.0%, and its content was reduced from 5.909 to 0.885 mg/kg, which was lower than the EU maximum limit of 1 mg/kg of GE for edible oils. The removal rate of 3-MCPD ester was 79.3%, and its content was reduced from 2.686 to 0.556 mg/kg. After molecular distillation, the content of sterols and VE decreased by 38.2% (from 912.2 to 563.7 mg/100 g) and 28.6% (from 407.8 to 291.3 mg/100 g). These results show that molecular distillation can be used as an effective and reliable method for removing 3-MCPD esters and GEs from edible oils.
Effects of Adding Different Proteins on Retrogradation Properties of Proso Millet Starch
XIAO Yu, YANG Xinbiao, LIN Nan, ZHENG Mingzhu, LIU Jingsheng
2020, 41(16):  45-51.  doi:10.7506/spkx1002-6630-20190709-121
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Effects of adding zein, soy protein isolate (SPI) or whey protein isolate (WPI) on the retrogradation of proso millet starch were investigated by textural profile analysis (TPA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The results showed that adding the three proteins decreased the hardness of proso millet starch gel, making the mixed gels softer. Particularly, upon the addition of WPI, the hardness decreased from 407.32 g to 196.12 g at day 7. FTIR showed that no new functional group appeared, indicating that the starch-protein system is closely linked together by hydrogen bonding interactions, forming a tightly wound three-dimensional gel network structure. XRD analysis showed that in the retrogradated sample a strong diffraction peak appeared at around 17° as a typical B-type structure. Adding the proteins significantly reduced the retrogradation enthalpy, thus suppressing the recrystallization of proso millet starch and consequently retarding its retrogradation. By fitting the aging kinetics with the Avrami equation, it was found that the rate of recrystallization was reduced upon the addition of the proteins, and the nucleation type of recrystallisation was close to rod-like growth of sporadic nuclei (1 < n ≤ 2). Overall, addition of zein, SPI and WPI affected proso millet starch in varying degrees, with the greatest effect being observed with WPI. This study shows that the proteins act not only as nutrients but also as a starchy food anti-aging agent, which provides a theoretical basis for delaying starch aging and is of guiding significance for actual production.
Effect of Adding Different Amounts of Pre-gelatinized Highland Barley Flour Supplemented with Hericium erinaceus Powder on the Quality Characteristics of Crisp Cakes
MA Ning, CHEN Yuting, FANG Donglu, PEI Fei, SU Anxiang, ZHAO Liyan, ZHENG Huihua, HU Qiuhui
2020, 41(16):  46-53.  doi:10.7506/spkx1002-6630-20200507-068
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In order to address the problems with traditional crisp cake such as monotonous nutrition and deterioration in the palatability when directly added with mushroom powder, in this study we used a twin-screw extruder to prepare pre-gelatinized highland barley flour incorporated with Hericium erinaceus powder with a gelatinization degree of 86.13%. The nutritional composition, microstructure and gelatinization characteristics of the mixture were measured before and after extrusion. Crisp cakes were made with the addition of different amounts of the extruded mixture to wheat flour, and their nutrition, physical characteristics, sensory properties and digestive characteristics were explored. The results showed that the nutritional composition of the extruded mixture was improved, the gelatinization temperature was decreased, and the stability was enhanced compared with before extrusion. The amount of the extruded mixture added was in direct proportion to the contents of minerals such as K and Mg, protein and dietary fiber in crisp cake, but in inverse proportion to carbohydrate content, calories and predicted glycemic index. The composition of amino acids in crisp cake made from 100% highland barley mixed with H. erinaceus was most similar to the Food and Agriculture Organization (FAO)/World Health Organization (WHO) recommended pattern. Nevertheless, addition proportions exceeding 50% caused negative impacts on the physical characteristics and taste of crisp cake. This study provides a theoretical basis for the development of cereal products incorporated with edible fungi.
Effect of Hot Blanching on the Quality of Nang (Baked Crusty Pancake) Added with High Proportion of Raw Dehydrated Potato Flour
ZOU Shuping, ZHANG Qian, MENG Yina, MA Yan, XÜ Mingqiang, TAI Xiaoliang, TONG Litao
2020, 41(16):  52-56.  doi:10.7506/spkx1002-6630-20190828-311
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This study analyzed the farinographic properties and starch viscosity properties (rapid viscosity analyzer (RVA) parameters) of wheat flour doughs with 0%, 40%, 45% and 50% replacement of wheat flour by raw dehydrated potato flour, and compared the stretching characteristics and gas production capacity of wheat doughs incorporated with unblanched and blanched raw dehydrated potato flour at the different proportions and the wall hanging rate and sensory quality of the resultant Nang, in order to determine the effect of hot blanching on the quality of raw dehydrated potato flour incorporated Nang. The results showed that addition of raw dehydrated potato flour changed water absorption rate, dough formation time, stability time, weakening degree and farinograph quality number (FQN) to different extents, and increased starch RVA parameters overall and setback value. Incorporation of blanched raw dehydrated potato flour at proportions above 40% could significantly increase the tensile resistance and stretching ratio of dough, enhanced the fermentation capacity and gas production capacity, and resulted in a wall-hanging rate of Nang up to 100%. However, the sensory attributes such as flavor and color of Nang incorporated with blanched raw dehydrated potato flour were significantly lower than those of Nang made from pure wheat flour.
Yeast Glucan Pretreatment and Its Deodorization Effect for Silver Carp Mince
HUANG Jingjing, ZHANG Huimin, ZHAO Liyuan, XIONG Shanbai, HUANG Qilin
2020, 41(16):  54-60.  doi:10.7506/spkx1002-6630-20190918-223
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In this work, hot water washing and alkali extraction were used separately to pretreat yeast glucan, and then the overall flavor and volatile compounds of minced silver carp meat added with the pretreated yeast glucan were evaluated by sensory evaluation, electronic nose (E-nose) and headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Furthermore, the deodorization mechanism of yeast glucan was investigated. The results showed that hot water washing could greatly remove the volatile compounds of yeast glucan, and addition of the treated yeast glucan affected the flavor of minced fish meat, as manifested by a decrease in the fishy, grassy and earthy-musty odor, and a reduction in the contents of hexanal, nonanal and 1-octene-3-ol contributing to the off-odor of fish. The contents of hexanal, nonanal and 1-octen-3-ol calculated by the internal standard method decreased by 22.9% (486.94 versus 375.49 μg/kg), 24.5% (318.59 versus 240.53 μg/kg) and 30.0% (183.81 versus 128.86 μg/kg), respectively, after addition of the yeast glucan, revealing that it could adsorb off-odor compounds from fish meat. Besides, hot water-wash yeast glucan reduced the thiobarbituric acid reaction substrate (TBARS) value of fish meat, thus inhibiting lipid oxidation and consequently reducing the production of off-odor in silver carp meat.
Effect of Mung Bean Protein on Gelatinization and Rheological Properties of Buckwheat Starch
XIU Lin, ZHANG Miao, XU Xiuying, ZHENG Mingzhu, LIU Jingsheng
2020, 41(16):  57-61.  doi:10.7506/spkx1002-6630-20190630-417
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In an attempt to explore the effect of protein on starch properties, we measured the pasting, rheological and textural properties and microstructure of buckwheat starch added with different proportions of mung bean protein utilizing a rapid visco analyzer, a rheometer and a texture analyzer. The results showed that the pasting time and temperature of buckwheat starch were increased while peak viscosity, final viscosity, breakdown value and setback value were reduced by adding mung bean protein. As the addition of mung bean protein increased, shear stress and consistency coefficient K declined while the starch paste was still a pseudoplastic fluid. An 8:2 ratio of mung bean protein to buckwheat starch showed more significant shear thinning. Both storage modulus (G’) and loss modulus (G”) were reduced, loss angle tangent (tanδ) was increased and gel strength was weakened by the addition of mung bean protein. Moreover, the hardness, gumminess and chewiness of the starch gel were significantly decreased and the elasticity became slightly lower. As observed by scanning electron microscopy (SEM), the starch gel showed a honeycomb-like microstructure with the pores becoming larger and the cell wall becoming thinner with increasing addition of mung bean protein.
Isolation, Purification and Physicochemical Properties of Polysaccharides from Chlorella
SHI Ruiqin, LIANG Jingjing, LI Dawei, WANG Jie, GUO Shuxian, MA Yanli
2020, 41(16):  61-67.  doi:10.7506/spkx1002-6630-20190515-173
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In this study, the crude polysaccharides extracted from Chlorella were deproteinized by Sevag method and then fractionated by DEAE-Sepharose Fast flow column chromatography into three fractions (F1, F2, and F3). The microstructure, monosaccharide composition, congo red reactivity, and rheological properties of the purified polysaccharides were investigated. The results showed that these three polysaccharides exhibited different morphological characteristics, mainly existing in the form of flakes or filaments. The monosaccharide composition of F1 and F2 consisted mainly of galactose (Gal), while arabinose (Ara) was the most abundant monosaccharide in F3. All three polysaccharides were present in aqueous solutions in a random coil conformation. Static and dynamic rheological properties showed that these polysaccharides were pseudoplastic fluids and non-gelling polysaccharides. This study will provide reference for the development and application of algae products.
Effects of Sweet Potato Residue Cellulose with Different Particle Sizes on Rheological Properties of Wheat Dough
ZHENG Wanqin, XIE Yong, QIN Xiaoli, LIAO Chao, HU Xiao, LIU Lin, LIU Yue, LIU Xiong
2020, 41(16):  62-67.  doi:10.7506/spkx1002-6630-20191031-355
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Three sweet potato residue cellulose (SPRC) powders with different particle sizes (129, 64, and 25 μm) were obtained by ordinary pulverization, ultra fine pulverization and nano-ball milling, respectively. Each of them was separately added at 7% to wheat flour in order to determine their effects on the rheological properties of wheat dough. The results showed that SPRC increased the water absorption rate of dough, prolonged the dough formation time, and reduced the dough stability time, maximum viscosity index, thermal gel stability, retrogradation value and gelatinization value. In addition, SPRC increased the viscoelasticity of dough. Temperature had a great influence on the elastic modulus (G’) of the mixed dough, but had no significant influence on the viscous modulus (G’’). Scanning electron microscopy showed that the gluten network structure in dough incorporated with large-particle-size SPRC exhibited rupture and holes, but reducing the particle size of SPRC improved its density uniformity. Compared with ordinary pulverization and ultra fine pulverization, nano-ball milling SPRC enhanced the farinographic properties and thermomechanical properties of dough. Accordingly, the particle size of SPRC had a significant impact on the rheological properties of wheat dough. Reasonable control of the particle size of added dietary fiber in wheat flour can be useful to improve dough quality.
Effects of Pitaya Stem Phytosterol on Stability and Release Properties of Curcumin Nanoliposomes
LI Yuhao, LI Zhaoying, ZHOU Wei, FU Tiaokun, ZOU Liqiang, PENG Shengfeng, CHENG Ce, LIU Wei
2020, 41(16):  68-76.  doi:10.7506/spkx1002-6630-20190402-024
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This study investigated the effect of pitaya stem phytosterol (PSP) on stability, membrane properties and in vitro release property of curcumin nanoliposomes (NLs-Cur). The stability of PSP-incorporated Cur-NLs was evaluated by particle size, polydispersity index (PDI), zeta potential and instability index in different environments. The results showed that the average particle size and PDI of curcumin-phytosterol nanoliposomes (PNLs-Cur) increased significantly with increasing content of PSP. Stability experiments showed that PNLs-Cur was more stable than NLs-Cur was under the same pH and ion conditions, and PNLs-Cur had higher retention rate of curcumin than NLs-Cur did at 80 ℃ for an hour (61.25% versus 57.48%). In addition, the cumulative release rates of PNLs-Cur and NLs-Cur were 50.08% and 63.64% within 72 h, respectively. In vitro release experiments indicated that the incorporation of PSP led to slower release of curcumin encapsulated in the nanoliposomes
Effect of Water Soluble Dietary Fiber from Star Anise on Digestibility of Oil Emulsion
WU Kegang, WEI Hao, CHAI Xianghua, DUAN Xuejuan, LIANG Wanxia, LIAO Jingfei, SHEN Xuerong
2020, 41(16):  68-75.  doi:10.7506/spkx1002-6630-20190509-079
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In this study, water soluble dietary fiber from star anise (SASDF) was prepared by a microwave-assisted double enzymatic method and the effects of SASDF on the effective particle size, particle size distribution, zeta potential, apparent shear viscosity and microstructure of protein-coated nano-emulsion before and after digestion were studied. Its effect on the digestive properties was also studied by in vitro digestion model. The results showed that SASDF had a significant effect on the physicochemical and digestive properties of the emulsion before and after digestion in a concentration-dependent manner. The digestion curves of the nano-emulsion showed a second-order pseudo first-order reaction irrespective of the presence of SASDF. The reaction rate constant k1 in the rapid reaction stage decreased with the increase of SASDF concentration, while in the slow reaction stage, the reaction rate constant k2 showed no correlation with SASDF concentration. However, the final digestibility of fat in the nano-emulsion decreased with the increase of SASDF concentration in the system.
Effect of Limited Enzymatic Hydrolysis on the Structural and Antioxidant Properties of Oat Protein Isolate
ZHENG Zhaojun, WANG Man, LI Jiaxin, LI Jinwei, LIU Yuanfa
2020, 41(16):  76-82.  doi:10.7506/spkx1002-6630-20190916-181
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Oat protein isolate hydrolysates with different degrees of hydrolysis (DH, 2%–7%) were prepared by limited enzymatic hydrolysis with papain, and their structural and antioxidant properties were investigated. Our results showed that papain hydrolysis could favor the formation of low-molecular-mass peptides, demonstrating changes in protein structure. This was further confirmed by the results of ultraviolet absorption and fluorescence spectroscopy. Also, the enzymatic hydrolysis could change the secondary structure of oat protein, as demonstrated by a decline in α-helical structure and an increase in random coil and β-turn structures. This implied that the enzymatic hydrolysis might be beneficial to the antioxidant potential of oat protein hydrolysates. Interestingly, papain hydrolysis (particularly at DH of 4%) led to an increase in 1,1-dipheny1-2-picrylhydrazyl (DPPH) radical scavenging activity and metal ion chelating activity of oat protein hydrolysates, demonstrating half-maximum inhibitory concentration (IC50) of 36.83 μg/mL and 33.42 μg/mL, respectively. More intriguingly, the hydrolysate at 4% DH could not only prolong the induction period of sunflower oil, but also improve the oxidative stability of sunflower oil-in-water emulsion. Therefore, limited hydrolysis with papain could result in the improved antioxidant activities of oat protein, which was closely associated with the changes in protein structure.
Food Chemistry
Effects of Different Salt Concentrations on Lipid Oxidation, Protein Oxidation and Eating Quality of Cured Chicken Meat
QU Cheng, HE Zhifei, WANG Zhaoming, LIU Chao, LI Junhong, LI Hongjun
2020, 41(16):  77-85.  doi:10.7506/spkx1002-6630-20190504-012
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This study aimed to compare the differences in lipid oxidation, protein oxidation and eating quality among cured chicken meat with different NaCl concentrations (0%, 3%, 6%, 9%, 12% and 15%). The results showed that with the increase in NaCl concentration, the carbonyl content and surface hydrophobicity increased significantly while the sulfhydryl content decreased significantly, and the thiobarbituric acid reactive substances (TBARS) value and protein solubility increased first and then decreased. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the increase in NaCl concentration promoted the formation of disulfide bonds, resulting in increased protein cross-linking and aggregation. With regard to the eating quality, as NaCl concentration increased, both the pH and moisture content first increased and then decreased, whereas the opposite trend was noted for the cooking loss. L* value was significantly reduced with increasing NaCl concentration, and a* value significantly increased upon the addition of NaCl, but did not significantly change with increasing NaCl concentration. b* reaches the maximum when NaCl concentration is 3%. Overall, the increase in NaCl concentration promoted lipid oxidation and protein oxidation, and consequently affected the eating quality of chicken.
Effect of Adding Different Prebiotics on Free Amino Acids and Flavor of Yogurt
LI Rui, WANG Yiran, LIU Yiming, SHI Haisu, CHEN Xu, ZHAO Yingbo, WU Junrui
2020, 41(16):  83-89.  doi:10.7506/spkx1002-6630-20190903-038
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To study the effect of different prebiotics on the free amino acids and flavor of yogurt, the contents of basic nutrients such as protein, fat and non-fat milk solids were measured in yogurts with added xylooligosaccharide, oligomeric isomaltose, galacto-oligosaccharide, or sucrose (as a control) using a milk composition analyzer, and free amino acids were determined by electronic tongue and high performance liquid chromatography-mass spectrometry. Furthermore, a comprehensive evaluation was carried out based on taste activity value and amino acid score using principal component analysis and correlation analysis. The results showed that the contents of protein, fat, total solids and non-fat milk solids in all yogurts with added prebiotics were in line with the national standards. There was little difference in all flavor attributes except for sour taste, and the sour taste intensity of various yogurts was ranked in the following order: xylooligosaccharide < galacto-oligosaccharide < oligo-isomaltose < control. In total, 17 free amino acids were detected in the three prebiotic yogurts, and the content of total free amino acids in the yoghurt with added xylooligosaccharide was about 119.31 mg/g, which was significantly higher than in those added with the other probiotics and the control group. The content of total free amino acids in the control group was 112.49 mg/g, which was significantly higher than that (79.48 mg/g) in the yogurt with added galacto-oligosaccharide, but was not significantly different from that (108.93 mg/g) in the yogurt with added oligo-isomaltose. The contents of sweet, umami and bitter amino acids in the yogurt with added xylooligosaccharide was significantly higher than those in the control group and the other prebiotic addition groups. The contents of sweet and bitter amino acids in the control group were higher than those in the yogurt with added oligomeric isomaltose or galacto-oligosaccharide. The content of each class of taste-active amino acids was the lowest in the yogurt with added galacto-oligosaccharide. For the four yogurts, amino acid scores were mostly higher than the amino acid standard pattern values. On the whole, not all prebiotics had a positive effect on yoghurt fermentation. The yoghurt with added xylooligosaccharide had the highest free amino acid content and good flavor. This study will provide reference for regulating the basic nutrient composition and flavor of industrial produced prebiotic yogurt.
Food Chemistry
Formation Mechanism and Functional Properties of β-Lactoglobulin-Folic Acid-Retinol Ternary Complexes
BAO Xiaomei, ZHONG Junzhen, ZHOU Ruonan, ZHOU Lei, LIU Chengmei
2020, 41(16):  86-93.  doi:10.7506/spkx1002-6630-20190710-144
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In our study, the formation mechanism of the ternary complex of β-lactoglobulin (β-LG) with folic acid (FA) as a hydrophilic molecule and retinol (VA) as a hydrophobic molecule was explored by fluorescence spectroscopy. The changes in the antioxidant activity and allergenicity of β-LG after complexation were examined by 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging, 1,1-diphenyl-2-picrylhdrazyl (DPPH) radical scavenging and ferric ion reducing antioxidant power (FRAP) assays as well as indirect enzyme-linked immunosorbent assay (ELISA), respectively. Fluorescence spectroscopy indicated that FA and VA had a strong ability to quench the fluorescence of β-LG mainly in a static mode.FA and VA could form stable ternary complexes with β-LG through hydrophobic interaction, which was reflected by the binding constant (Ka) > 104 L/mol, the number of binding sites of β-LG for FA and VA (about 1) and the thermodynamic parameters. The presence of VA affected the affinity of FA for β-LG, while the presence of FA did not affect the affinity of VA for β-LG. The results of ABTS, DPPH and FRAP assays showed that the antioxidant activity of β-LG-FA and β-LG-VA was not significantly different compared with that of β-LG, but lower than that of β-LG-FA-VA. Different binding sequences had no significant effect on the antioxidant activity of the ternary complex. Indirect competitive ELISA showed that β-LG-FA-VA gave a lower inhibition of 42.23% against β-LG antigenicity, while β-LG-VA-FA exhibited a higher inhibition of 70.32%. These results indicate that different binding sequences had different effects on the antigenicity of β-LG.
High-throughput Sequencing Analysis of Bacterial Diversity of Different Types of Traditional Chinese Bacon
ZHAO Rui, SHAO Changchun, GAO Shigong, LIU Guangrui, YANG Fumin
2020, 41(16):  90-96.  doi:10.7506/spkx1002-6630-20200416-210
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To understand the bacterial diversity in different types of traditional Chinese bacon, we evaluated the microbial community structures of traditional Chinese bacons produced using different processes in different regions by high-throughput sequencing of the V3-V4 region of the 16S rDNA sequence as well as using traditional isolation and culture methods. A total of 99 bacterial isolates cultured were identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). The dominant bacterial genera were Staphylococcus saprophyticus (27.3%), Escherichia coli (24.2%) and S. equorum (14.1%), while the rest included Lactobacillus paracasei, L. sake, Enterococcus faecium. High-throughput sequencing revealed that a total of 751 737 effective sequences and 12 122 operational taxonomic units (OTUs) were obtained from 13 samples. The analysis of bacterial community composition showed that the bacterial diversity and abundance of smoked bacon from Sichuan and Chongqing were significantly lower than those of the other samples (P < 0.05). At the level of phylum, Firmicutes, Actinomycetes and Proteobacteria were dominant in all samples. At the genus level, the abundance of Staphylococcus was high in smoked bacon from Sichuan and Chongqing, accounting for 87.33%–97.35% of the total bacterial community, while in smoked bacon from Hunan, the relative abundance of Staphylococcus was 7.76%–37.37%. The predominant genera of non-smoked bacon from Longxi, Gansu were Psychrophilus, Staphylococcus, and Acinetobacter. The bacterial community of Zhejiang style-bacon contained mainly Acinetobacter (13.48%–32.51%). This study provides insights into the microbial diversity of different types of traditional Chinese bacon products.
Food Chemistry
Effect of Different Oils on Benzo(a)pyrene Content in Fried Foods
ZHENG Yi, JIN Chenjing, HE Jiguo
2020, 41(16):  94-100.  doi:10.7506/spkx1002-6630-20190705-075
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This study investigated the effects of five frying oils (peanut oil, soybean oil, rapeseed oil, 24° palm oil and 42° palm oil) on the content of benzo(a)pyrene in French fries, Youtiao (fried dough stick), and chicken nuggets in order to control the content of benzo(a)pyrene in fried foods. The content of benzo(a)pyrene in French fries, Youtiao and chicken nuggets sequentially fried with each of the oils at 176 ℃ for 165, 150 and 210 s (two batches daily for 5 successive days) was investigated using liquid chromatography. The results showed that with increasing number of frying cycles, the content of benzo(a)pyrene in all three fried foods also increased gradually. All the foods fried in peanut oil contained the highest level of benzo(a)pyrene, which was 1.64 μg/kg in French fries, 1.73 μg/kg in Youtiao and 1.15 μg/kg in chicken nuggets. In contrast, all the foods fried in 42° palm oil contained the lowest level of benzo(a)pyrene, which was 0.04 μg/kg in French fries, 0.10 μg/kg in Youtiao and 0.05 μg/kg in chicken nuggets. In conclusion, this study showed that 42° palm oil had better frying stability and the fried foods with it contained lower content of benzo(a)pyrene compared to the other oils.
Effect of Starter Cultures on Protein Degradation and Antioxidant Capacity of Peptides from Fermented Sausages
FENG Meiqin, YU Di, SUN Jian
2020, 41(16):  97-104.  doi:10.7506/spkx1002-6630-20200521-251
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Fermented sausages were manufactured with a mixed starter culture of Lactobacillus plantarum CD101 and Staphylococcus simulans NJ201, and naturally fermented samples were used as a control. We investigated protein degradation in fermented sausages by the mixed starter culture by determining physicochemical properties, performing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and measuring peptide content, and free amino acid content. In vitro 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical cation scavenging and ferric ion reducing antioxidant power (FRAP) assays were used to evaluate the antioxidant capacity of crude peptides and peptide fractions with molecular mass lower than 3 kDa extracted from fermented sausages. The results showed that the content of non-protein nitrogen in the inoculated group was significantly higher than that in the control group (P < 0.05). According to the results of SDS-PAGE, both sarcoplasmic and myofibrillar proteins were degraded in the two groups, and the degree of protein degradation in the inoculated group was higher than that in the control group, notably the accumulation of bands with a molecular mass of less than 20 kDa. The DPPH radical scavenging activity, ABTS radical cation scavenging activity and FRAP value of crude peptides and small molecular peptides extracted from the inoculated group were significantly higher than those in the control group (P < 0.05). The small molecular peptides may be the main contributor to the antioxidant capacity of the peptides extracted from fermented sausages. The release of free amino acids from fermented sausages was promoted by the mixed starter culture. This mixed starter culture could promote protein degradation in fermented sausages to produce more peptides with antioxidant activity, helping inhibit fat oxidation in fermented sausages and thereby reducing the production cost and prolonging the shelf life.
Whole Genome Sequencing and Sequence Analysis of Lactobacillus helveticus TR13 from Air-dried Mutton
TIAN Jianjun, ZHANG Kaiping, ZHAO Yanhong, LI Quanwei, MA Muran, MA Junjie, CAO Kaihui, JIN Ye
2020, 41(16):  101-109.  doi:10.7506/spkx1002-6630-20190707-086
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For a better understanding of its metabolic mechanism and function during mutton fermentation, the whole genome of Lactobacillus helveticus TR13, a strain with high lipase activity isolated from naturally air-dried mutton was sequenced using the PacBio Illumina HiSeq sequencing platform. The results showed that the genome of TR13 was a set of circular plasmid-free molecules, and the total length of the genome sequence was 2 172 224 bp with a GC content of 36.82%. It was predicted to contain 2 536 protein-coding genes with a total length of 1 883 532 bp, an average length of 799.46 bp, and an average density of 1.08 per kb, and the average sequence length of the coded proteins was 265 amino acids (aa), accounting for 86.71% of the genome. The genome of TR13 contained 15 rRNA operons and 63 tRNA, 75 virulence genes and 150 drug resistance genes being predicted from the genome. Moreover, functional annotation of the genome and metabolic pathway information annotation were accomplished by aligning the coding genes to the GO, COG and KEGG databases, which would provide a theoretical basis to explore the application of strain TR13.
Analysis of Bacterial Diversity of Salted Peppers (Capsicum annuum)
ZHAO Lingyan, HUANG Jiaxin, YANG Jian, QING Yuwei, PAN Jinwei, ZHOU Yi, DENG Fangming
2020, 41(16):  105-111.  doi:10.7506/spkx1002-6630-20190829-318
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The composition and relative abundance of the microbial community in salted peppers were explored by 454 pyrosequencing technology, aiming to provide a theoretical basis for the isolation and screening of superior strains from salted peppers for the production of pickled peppers. The results showed that the bacteria in salted Capsicium annuum L. var. dactylus M could be assigned to 101 species in 94 genera in 31 families in 26 orders in 15 classes in 8 phyla. The bacteria in salted C. annuum L. var. conoides Irish could be assigned to 42 species in 58 genera in 44 families in 29 orders in 15 classes in 6 phyla. The dominant phyla in salted C. annuum L. var. dactylus M were Cyanobacteria (77.01%), Proteobacteria (14.78%) and Firmicutes (6.36%). The dominant phyla in salted C. annuum L. var. conoides Irish were Proteobacteria (51.5%) and Firmicutes (46.92%). A total of 19 genera with relative abundance greater than 1% were found in both varieties. The dominant genera in salted C. annuum L. var. dactylus M were Lactococcus (24.51%) and Rhizobium (13.17%). The dominant genera in salted C. annuum L. var. conoides Irish were Halanaerobium (38.99%), Marinospirillum (24.86%), Halomonas (9.67%) and Chromohalobacter (12.36%).
Effects of Solid-state Fermentation with Aspergillus niger on Phenolics Release and Antioxidant Activity of Sugarcane Leaves
YAN Yuxiao, SU Guijiao, HE Yongqiang
2020, 41(16):  110-116.  doi:10.7506/spkx1002-6630-20190703-033
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Solid-state fermentation of sugarcane leaves was performed with Aspergillus niger for the purpose of extracting secondary metabolites. The effects of inoculum size, the water content of fermentation substrate and fermentation time on the release of phenolics from sugarcane leaves were investigated. The activities of cellulase and β-glucosidase were determined during the fermentation process. The antioxidant activity of the flavonoids extracted from native and fermented sugarcane leaves was investigated. The results showed that the contents of polyphenols and flavonoids in sugarcane leaves significantly increased after fermentation, reaching 10.40 and 13.82 mg/g on a dry basis under the following conditions: inoculum size 28 mL/100 g, water content of culture medium 50%, and fermentation time 5 days, which increased by 135% and 92% as compared with those in the unfermented samples, respectively. The activity of cellulase reached its maximum at 632.17 U/g on the fourth day of fermentation and the activity of β-glucosidase peaked at 75.02 U/g on the fifth day. Positive correlations were found between the contents of phenolic compounds and the activities of cellulase and β-glucosidase. By calculating the IC50, the flavonoids extracted from fermented sugarcane leaves exhibited stronger scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals than did those from the unfermented samples.
Purification and Characterization of Bacteriocin Produced by Lactobacillus pentosus LS1
LI Zhiru, HAN Jianchun, LIU Rongxu, LIU Danyi, LIANG Junfeng
2020, 41(16):  112-118.  doi:10.7506/spkx1002-6630-20190826-278
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Bacteriocin-producing strain LS1 was isolated from Chinese sauerkraut juice and it was identified as Lactobacillus pentosus by 16S rRNA gene sequencing. The bacteriocin was separated from the fermentation supernatant of this strain by ammonium sulfate precipitation, desalted and purified by sequential column chromatography on Sephadex G-10, SP Sepharose Fast Flow, and Superdex 30 Increase. The specific activity of the purified bacteriocin was 1 238.1 AU/mg, which was 110.5 times higher than before the purification. The molecular mass of the bacteriocin was 1 123.8 Da and its N-terminal amino acid sequence was ACDFCFCGMK as determined by liquid chromatography-ion trap tandem mass spectrometry (LC-MS/MS). Pentocin LS1 showed a bacteriostatic activity against some Gram-negative and positive food spoilage bacteria. In addition, pentocin LS1 still retained 80.2% of its original antibacterial activity after being heated at 100 ℃ for 15 min, had strong activity in the range of pH 2.0-8.0, and was sensitive to proteolytic enzymes but insensitive to amylase, lipase catalase, and some chemical reagents. The results showed that pentocin LS1 can be potentially applied in food preservation.
Effect of X-Prolyl-dipeptide acyl-aminopeptidase Produced by Lactobacillus on Antioxidant Activity and Quality of Cheddar Cheese
ZHAO Mingqi, ZHANG Xiuxiu, LI Xiaodong, LIU Lu, ZHANG Hongda, ZHANG Hongwei, BAI Jie
2020, 41(16):  117-125.  doi:10.7506/spkx1002-6630-20190703-037
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In order to study the effect of X-prolyl-dipeptide acyl-aminopeptidase (Pep X) activity of Lactobacillus on the antioxidant activity of Cheddar cheese, we obtained mutants with Pep X activity (named as UV-C3, UV-H3, UV-R3, and UV- P3, respectively) from Lactobacillus casei 1.0319, L. helveticus 1.0612, L. rhamnosus 1.0911, and L. plantarum 1.0202 by three rounds of UV mutagenesis and separately added them to Cheddar cheese. We analyzed the changes in Pep X activity and antioxidant activity during cheese ripening and established the correlation between them. Furthermore, we studied the effect of adding Pap X-producing Lactobacillus on cheese quality. The results showed that the activity of Pep X produced by Lactobacillus had a significant effect on the antioxidant activity and quality of Cheddar cheese. There was a significantly positive correlation between Pep X activity and the antioxidant activity of Cheddar cheese (P < 0.05). As maturation proceeded, the Pep X activity and antioxidant activity of cheese increased gradually up to the maximum on the 90th day. The activity of Pep X produced by UV-R3 was significantly higher than those produced by other strains (P < 0.05), and the maximum value was 10.16 U/g. The antioxidant capacity of the cheese inoculated with UV-R3 was significantly higher than those of the cheeses inoculated with other strains (P < 0.01), as evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rate, hydroxyl radical scavenging rate, and reducing ability, and their maximum values were 68.43%, 67.56%, and 0.684 3 in the former sample, respectively. After the 120th day, as casein was hydrolyzed, bitter peptides were produced in a large amount, and the texture was remarkably lowered. The highest sensory flavor score of greater than 9.0 points was observed for all cheese samples, leading to the conclusion that they were edible at 120 days of ripening.
Breeding and Application of Salt-Tolerant Ethanol-Producing Yeast for Soy Sauce Brewing
LÜ Bianmei, JIANG Xuewei, PENG Dong, XU Xiaogang, DING Yuan, LUO Xiaoming, ZHOU Shangting
2020, 41(16):  119-126.  doi:10.7506/spkx1002-6630-20190824-251
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High-salt-tolerant ethanol-producing mutant L6-1 was obtained by ultraviolet mutagenesis of Zygosaccharomyces rouxii L6, isolated from soy sauce mash in our previous work, followed by screening using 2,3,5-triphenyltetrazolium chloride (TTC) plates. it could accumulate 2.71% (V/V) ethanol in bean sprout juice medium with 10% (m/m) NaCl, which increased by 54.86% as compared with that of the original strain L6. On day 45 of the 90-day fermentation period, L6-1 accumulated the highest amount of ethanol (up to 1.00%) in high-salt fermented mash, which increased by 78.57% as compared with that of the control group. A total of 47 volatile flavor compounds (VFCs) were detected in the mash fermented by L6-1 using solid-phase microextraction followed by gas chromatography-mass spectrometry (SPME-GC-MS) method, as opposed to 27 VFCs in that fermented by L6. The L6-1 fermented mash contained two more esters, ten more alcohols (excluding ethanol), four more aldehydes, one more phenol, and three ketones compared with the L6 fermented mash. The total ethyl ester content of the L6-1 fermented mash was 605.64 ng/g, which increased by 6.79% and 20.61%, respectively compared with the L6 fermented mash and the control not inoculated with yeast. Furthermore, principal component analysis (PCA) showed that the L6-1 fermented mash scored the highest. In addition to increasing the types and contents of alcohols (mainly ethanol), L6-1 could promote the formation of esters as the major aroma components of soy sauce especially ethyl esters, indicating that L6-1 could improve the alcoholic aroma and effectively enhance the richness of soy sauce flavor.
Isolation and Identification of Antimicrobial Peptides Produced by Bacillus amyloliquefaciens and Characterization of Their Antibacterial Spectra
YAO Jiaming, TIAN Yaping
2020, 41(16):  126-131.  doi:10.7506/spkx1002-6630-20190505-020
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Antibacterial substances against Staphylococcus aureus from the fermentation supernatant of Bacillus amyloliquefaciens with improved antibacterial activity were separated and purified by sequential acid precipitation, organic solvent extraction, DEAE anion exchange chromatography and reversed phase-high performance liquid chromatography (RP-HPLC). Two antibacterial peptides were found in the purified product by liquid chromatography and mass spectrometry (LC-MS). One was a reported Surfactin homologue containing 13–15 carbon atoms; the other was a bacteriostatic peptide having the amino acid sequence of L-V-N-P-P-T with a molecular mass of 639.75 Da. The hexapeptide had an isoelectric point of 5.52, a GRAVY of 0.100, and a fat solubility index of 113.33 as analyzed by ProtParam software. The highest homology between this peptide with the bacteriopeptides reported in the APD database was only 37.5%, and it was inferred that it was a novel antimicrobial peptide. Surfactin and the hexapeptide showed antibacterial activity against both Gram-positive and Gram-negative bacteria.
Analysis of the Structure and Diversity of Yeast Community in Main Chinese Maotai-Flavor Liquor-Producing Areas of Maotai Town Using High-throughput Sequencing
LUO Fangwen, HUANG Yongguang, TU Huabin, HU Feng, YOU Xiaolong
2020, 41(16):  127-133.  doi:10.7506/spkx1002-6630-20190810-110
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In this paper, the structure and diversity of the yeast communities in the environment of 7 main Maotai-flavor liquor-producing areas in Maotai town, Guizhou province and in Daqu from these areas were analyzed using high-throughput sequencing. A total of 53 yeast genera were detected, of which, 33 were found in Daqu, and 52 in the environment. The dominant yeast genera in Daqu were Saccharomycopsis and Wickerhamomyces, while those in the environment were Wickerhamomyces, Saccharomycopsis, Debaryomyces and Cryptococcus. The structure of the yeast community in the environment was significantly different from that in Daqu, with the former being more abundant than the latter. The environment was the main source of yeast genera in Daqu during Maotai-flavor liquor brewing, 96.97% of the yeast genera in Daqu being originated from the environment. Gibellulopsis, Filobasidium, Kuraishia, Agaricostilbum, Arachnomyces, Bullera, Cystofilobasidium, Dioszegia, Erythrobasidium, Fellomyces, Yamadazyma, Eremothecium, Ballistisporomyces, Aessosporon and Kurtzmanomyces were detected and reported for the first time during Maotai-flavor liquor brewing.
Component Analysis
Evaluation of the Taste-active Values of Chinese Mitten Crabs (Eriocheir sinensis) from Different Geographic Origins Using a Taste Sensing System
LIU Hongbo, JIANG Tao, LUO Renjun, XUE Junren, CHEN Xiubao, YANG Jian
2020, 41(16):  132-137.  doi:10.7506/spkx1002-6630-20190408-090
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A taste sensing system (SA402B) was applied to evaluate the taste characteristics of the meat samples of Eriocheir sinensis from five geographic origins, purse seined in lakes, wildly grown in natural waters or cultured inrice-crab coculture systems. The electronic tongue data showed that umami was the most predominant taste in steamed meat with a taste-active value (TAV) of 15.78–17.78, followed by bitterness (TAV = 7.33–13.53) and saltiness (TAV = 3.83–12.39). TAV for astringency (0.11–7.68) varied widely among geographic origins. There were no difference in sourness and only slight differences in richness (0–1.89), aftertaste-B (0–1.03) and aftertaste-A (0–0.38) among the samples, as reflected by the TAVs below ?30 and around zero, respectively. Linear discriminant analysis revealed that the accuracy of initial verification was as high as 100%. The scatter plot showed that all the five geographical origins could be clearly separated from each other. The results of the present study suggest that the taste sensing system can accurately profile the taste characteristics of E. sinensis from different geographic origins and that the electronic tongue data have the potential to discriminate the taste characteristics.
Isolation and Identification of the Succinic Acid-Producing Bacterium Escherichia fergusonii LW-2 and Optimization of Fermentation Conditions
LI Ruiling, LUO Yiping, LIU Xiaofeng, SUN Yong, LI Dong
2020, 41(16):  134-140.  doi:10.7506/spkx1002-6630-20191008-027
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In this study, a strain named as LW-2 producing high levels of succinic acid was isolated from bovine rumen contents with a culture medium containing disodium fumarate as the carbon source. Morphological analysis, physiological and biochemical characterization, and phylogenetic analysis based on the 16S rDNA sequence indicated that the strain was Escherichia fergusonii. Using glucose as the carbon source, the optimum fermentation conditions for the production of succinic acid by the strain were as follows: temperature 40 ℃, time 24 h, inoculum amount 2.5%, and MgCO3 as pH regulator at a concentration of 30 g/L. The concentration of succinic acid produced under the optimized conditions was 6.36 g/L, which was 41.96% higher than that before optimization, and the yield of succinic acid was calculated as 21.2%. Using xylose as the carbon source, the optimum fermentation conditions were as follows: temperature 37 ℃, time 66 h, inoculum amount 7.5%, and MgCO3 as pH regulator at a concentration of 30 g/L. The concentration of succinic acid produced under the optimized conditions was 7.51 g/L, which was 42.50% higher than that before optimization, and the yield of succinic acid was calculated as 25.03%. It was found that this strain could produce succinic acid by utilizing glucose or xylose as the carbon source, and xylose gave a higher yield of succinic acid than did glucose. This strain has a huge potential for the production of succinic acid.
Component Analysis
Rapid Quantitative Characterization of Water Distribution Uniformity of Noodle Dough Sheet
SHI Jiyong, LIU Chuanpeng, WU Shengbin, HUANG Xiaowei, LI Zhihua, ZOU Xiaobo
2020, 41(16):  138-144.  doi:10.7506/spkx1002-6630-20190701-016
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This study aimed to rapidly and quantitatively characterize subtle changes in the water distribution uniformity of noodle dough sheet by hyperspectral imaging technology combined with distributional homogeneity index (DHI) method. Firstly, noodle dough sheets with different water content gradients were set up, and different spectral pretreatment methods and pattern recognition methods were used to establish water prediction models. Then, visualization of the water content distribution in dough sheet was achieved using hyperspectral imaging technology. Finally, DHI was used to quantitatively characterize the water distribution uniformity in dough sheet at different mixing times. The results showed that the model constructed by least-squares support-vector machine (LS-SVM) based on spectra pre-processed by standard normal variate (SNV) had the best prediction performance. The water distribution was the most uniform when the dough mixing time was 15 min. This study verified the feasibility of using hyperspectral imaging technology combined with DHI for measuring the water distribution homogeneity of dough sheet, which would provide a theoretical guidance for the automatic monitoring of the noodle dough mixing process.
Discrimination of Three Famous Teas in Jiangxi Using Gas Chromatography-Mass Spectrometry Combined with Chemometrics
XU Chunhui, WANG Yuanxing
2020, 41(16):  141-150.  doi:10.7506/spkx1002-6630-20190925-309
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The volatile components of Gougunao tea, Lu Mountain Cloud-Mist tea, and Wuyuan green tea were extracted and identified by headspace solid phase microextraction followed by gas chromatography-mass spectrometry (HS-SPME-GC-MS). Further, their qualities were discriminated by chemometrics. The results showed that principal component analysis (PCA) could effectively distinguish among Gougunao tea, Lu Mountain Cloud-Mist tea, and Wuyuan Green tea. The results of cluster analysis were consistent with those of PCA, and could objectively reflect the difference in the contents of volatile components among the tea samples. Least squares discriminant analysis revealed 20 characteristic volatile components in the three kinds of tea, namely heptane, 2-pentyl furan, 3-carene, isopulegol, α-terpineol, verbenone, linalool, nonanal, β-cyclocitral, dihydroactinidioide, geraniol, allyl hexanoate, hexenyl butyrate, himachalene, caryophyllene, β-ionone, δ-cadinene, olivetol, nerolido, and cedrol.
Determination and Multivariate Statistical Analysis of Functional Components of Moringa oleifera Seed Oil
WANG Tiedan, YANG Min, YANG Fang, DU Ping
2020, 41(16):  145-150.  doi:10.7506/spkx1002-6630-20190828-314
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The contents of fatty acids, tocopherol and sterol in Moringa oleifera seed oils from eight areas in Yunnan province were analyzed. The differences in the fat-soluble functional components of the eight M. oleifera seed oils were analyzed by principal component analysis (PCA) and cluster analysis (CA). The results showed that a total of 20 fatty acids were found in these M. oleifera seed oils, mainly oleic acid (50.16%–56.51%), docosanoic acid (7.01%–12.03%), palmitic acid (4.91%–9.51%), stearic acid (6.76%–9.61%) and arachian acid (5.12%–7.24%), with unsaturated fatty acids accounting for 65.39% of the total fatty acids. The samples of M. oleifera seed oil all contained α-tocopherol (45–80 mg/100 g), δ-tocopherol (0.21–0.53 mg/100 g), and stigmasterol (243–495 mg/100 g). The results of PCA and CA showed that the compositions of functional components of the eight M. oleifera seed oil samples were similar, which fell into two distinct clusters according to different contents of functional components. The M. oleifera seed oil from Jinghong city, Xishuangbanna prefecture gained the highest comprehensive score, indicating a wide application prospect. This study provides data support and a scientific basis for further development of M. oleifera resources in Yunnan province.
Enzyme-like Activity of Gold-Magnetic Nanocomposite Particles for Enhanced Electrochemcial Detection of Ascorbic Acid
GONG Dezhuang, GUAN Huanan, WU Qiaoyan, SONG Yan, LIU Bo, YANG Fan, ZHANG Na
2020, 41(16):  151-157.  doi:10.7506/spkx1002-6630-20190409-114
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In this research, gold magnetic nanoparticles (Fe3O4@Au) were formed by self-assembling method. Its physical and chemical properties were characterized. A highly sensitive and selective enzyme-free enhanced electrochemical sensor based on the peroxidase-like activity of composite nanoparticles was prepared for the detection of ascorbic acid (AA). Electrochemical cyclic voltammetry (CV) was used to measure AA and the electrochemical detection system was optimized. The results showed that the established enzyme-free electrochemical sensor showed an extremely high sensitivity towards AA under the optimized conditions, with a good linear relationship between the current response (y) and the concentration of AA (x) in the range of 1–100 mmol/L, which was fitted with the equation: y = 867.81x + 3.860 8 (R2 = 0.991 9), and the detection limit was 0.011 7 mg/L. In addition, the electrochemical sensor was successfully applied in the detection of AA in real samples. In view of this, the proposed new enzyme-free electrochemical assay has great potential in the fields of food quality control and safety detection.
Effects of Fermentation Strains on the Aroma Quality of Black Tea Infusion
LIN Qi, LI Lijun,, WU Ling,, HUANG Gaoling,, WENG Shuyi, NI Hui,, LI Qingbiao,, ZHANG Shuwen, HUANG Youlin
2020, 41(16):  151-158.  doi:10.7506/spkx1002-6630-20190809-106
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The purpose of this work was to explore the effect of fermentation with lactic acid bacteria, yeast or acetic acid bacteria on the flavor of black tea infusion. The volatile components of fermented tea infusion were analyzed by sensory evaluation and headspace solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). It was shown that fermentation remarkably increased the fruity aroma and decreased the flowery, sweet and grassy aroma of black tea infusion. Besides, the roasted aroma was reduced after fermentation with yeast or lactic acid bacteria, but was increased after acetic acid bacterial fermentation. A total of 46 volatile components were identified in the tea infusion fermented by yeast, in which the contents of alcohols, esters and acids increase to 1 605.93, 7 715.82 and 596.15 μg/L, respectively, whereas the content of aldehydes decreased (69.48 μg/L) compared with those before fermentation. A total of volatile components were identified in the tea infusion fermented by acetic acid bacteria, in which the contents of alcohols and ketones increased respectively to 178.33 and 14.15 μg/L, while the content of olefins decreased to 19.37 μg/L relative to those before fermentation. A total of 32 volatile components were identified in the tea infusion fermented by lactic acid bacteria, in which the contents of alcohols, esters and ketones increased respectively to 90.70, 53.91 and 19.82 μg/L, while the content of olefins decreased to 10.89 μg/L relative to those before fermentation. This study showed that lactic acid bacterial fermentation could improve the aroma acceptability of black tea infusion, mainly because the intensity of fruity aroma was enhanced with increasing amounts of alcohols, esters and ketones. The results of this study provide a theoretical rationale for applying fermentation to improve the flavor of black tea products.
Physicochemical Properties and Structural Analysis of Lycium barbarum L. Polysaccharides at Different Growth Stages
ZHANG Xikang, ZHAO Yuhui, LIU Jun, LI Peipei, MA Lu, WANG Cong, WANG Liping, LIU Dunhua
2020, 41(16):  158-164.  doi:10.7506/spkx1002-6630-20190427-353
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Chinese wolfberries (Lycium barbarum L.) harvested at different developmental stages were analyzed for their physical and chemical properties. L. barbarum polysaccharides were purified and their structures were analyzed. The molecular mass, monosaccharide composition, sugar chain structure, thermal properties and surface morphology were determined by high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared (FTIR) spectroscopy comprehensive thermal analyzer and scanning electron microscopy (SEM). The HPLC results showed that L. barbarum polysaccharides were small molecules at different growth stages. The analysis of monosaccharide composition by GC-MS showed that L. barbarum polysaccharides were mainly composed of arabinose, rhamnose, glucose, xylose, mannose and galactose. The results of infrared spectroscopy indicated that the structure of the purified L. barbarum polysaccharides, found to be acidic polysaccharids, contained a β-pyran ring. Thermal analysis showed that the thermal characteristics of L. barbarum polysaccharides were both similar and different at different growth stages. The entire changes could be seen as mass losses sequentially caused by moisture release and polysaccharide breakdown. The observation by SEM showed that the structure of L. barbarum polysaccharides was different at different growth stages, and gradually changed from dense and lamellar to loose and peak-shaped and finally completely collapsed.
Comparison of Volatile Components of Six Potato Cultivars Cooked by Three Different Methods
LI Kaifeng, ZHOU Yuanping, WANG Qiong, GUO Huachun
2020, 41(16):  159-166.  doi:10.7506/spkx1002-6630-20190919-247
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Using solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS), we detected the flavor components in potato tubers of the cultivars Hezuo 88, Dianshu 23, Dianshu 1412-T100, Dianshu 108, Dianshu 1217 and Qingshu 9 cooked by three different procedures, namely steam, air frying and traditional charcoal roasting. The effects of cooking methods and cultivars on the flavor compounds of potato tubers were investigated overall. The results showed that a total of 58 compounds were detected in all cooked samples. The content of aldehydes derived from lipid degradation was the highest in boiled potatoes while the content of pyrazines produced by the Maillard reaction was the highest in roasted potatoes, and the content of either class of compounds in air fried potatoes was between steamed and roasted potatoes. A total of 13 compounds with significant differences among cultivars were found. In Dianshu 23, the contents of 1-octanol and 2-methylfuran were significantly higher than those in the other varieties. In Qingshu 9, the content of methylthiopropanal was significantly higher than that in Hezuo 88. Qingshu 9 was more suitable for steam, Hezuo 88 for air frying, and the remaining cultivars including Dianshu 1412-T100 for traditional charcoal roasting due to the high pyrazine content.
Changes of Free Sugars and Amino Acids in Table Corn during Development
NIU Liying, LI Dajing, LIU Chunquan, SONG Jiangfeng, CHEN Jiluan, CHEN Yanping, YUAN Jianhua
2020, 41(16):  165-172.  doi:10.7506/spkx1002-6630-20190628-395
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Changes in the contents of 3 free sugars and 18 free amino acids in two table corn cultivars (Jingtian 5 sweet corn and Jingnuo 8 waxy corn) during development from pollination after silking to milky maturation were determined using high performance liquid chromatography (HPLC). The contents of sucrose and alanine, as well as total sugars and total amino acids in both cultivars showed low-high-low trends with development time. Principle component analysis (PCA) and cluster analysis (CA) were applied to analyze the changes of these 21 compounds in the two cultivars at different developmental stages. Three PCs were extracted which explained 39.9%, 24.4%, and 13.3% of the total variance, respectively. Sweet amino acids and sugars presented high loadings on PC1 and PC2, illustrating that PC1 and PC2 are responsible to the sweet related informations. In addition, PC3 most correlated with the umami taste amino acids, aspartic acid and glutamic acid, and the samples from the different cultivars were separated on PC3. Moreover, CA showed that the samples were clustered into groups according to similar developmental stages. In conclusion, the PCA and CA performed on free amino acids and sugars clearly allowed to discriminate the developmental stages, and the cultivars to a lesser extent. These results would provide a practical reference for quality control of processed table corn products especially for corn juice flavor enhancement.
Comparative Analysis of Functional Composition of Different Parts of Alisma orientale (Sam.) Juzep. for Medicinal and Food Purposes
LAN Mengliu, YANG Lili, YAN Guijie, ZHU Huaichang, LI Xiaoyan, XU Wen, WU Shuisheng
2020, 41(16):  167-174.  doi:10.7506/spkx1002-6630-20190919-250
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Objective: This study aimed to determine and compare the functional components (total protein, total fat, amino acids, total polysaccharides, total flavonoids and total phenolics as well as five unique anthraquinones, alismoxide, alismol, alisol B, alisol B 23-acetate and 11-deoxy-alisol B) for medicinal and food purposes of different parts (edible flower buds, leaves and stems; medicinal tubers) of Alisma orientale (Sam.) Juzep. in order to provide a basis for the application of these plant parts in health and functional foods. Methods: The contents of total amino acids, protein, fat and total polyphenols were determined by the methods specified in the national standards. The contents of total polysaccharides and total flavonoids were determined by the sulfuric acid-phenol method and the NaNO2-NaOH-Al(NO3)3 ultraviolet spectrophotometric method, respectively. Ultra-high performance liquid chromatography (UPLC) was applied to determine alismoxide, alismol, alisol B, alisol B 23-acetate and 11-deoxy-alisol B. Results: Each of the plant parts contained protein, fat, amino acids and other bioactive ingredients tested. The contents of total protein, amino acid, fat and polyphenol in flower buds were (328.0 ± 19.1), (219.7 ± 10.5), (48.0 ± 11.5), and (17.63 ± 0.60) mg/g) respectively, higher than those in the other parts. The contents of polysaccharides, flavonoids and bioactive terpenoids were higher in tubers, (9.26 ± 0.86), (2.07 ± 0.12), and (5.315 ± 0.545) mg/g), respectively. The content of each component in stems and leaves was relatively low. Conclusion: All tested parts of A.orientale contain bioactive ingredients for medicinal and food purposes. Its flower buds are rich in various nutrients and thus have great development potential.
Identification of the Key Odorants in Fresh Amomum tsaoko Fruit
HU Zhihui, BAI Jiawei, YANG Wenxi, LIU Yuping, SUN Baoguo
2020, 41(16):  173-178.  doi:10.7506/spkx1002-6630-20190827-290
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The volatile components in the pericarps and seed kernels of fresh Amomum tsaoko (ATK) from Nujiang, Yunnan were extracted by direct solvent extraction combined with solvent-assisted flavor evaporation (SAFE), and were analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Thirty odor-active components (OACs), including 13 alkenes, 10 alcohols, 6 aldehydes and 1 ether, were identified by comparing the odor characteristics, mass spectrometry (MS) data, and retention indices with those of authentic compounds. Twenty-seven OACs were quantitated by using 2-octanol and 2-isopropylphenol as the internal standards. According to the quantitative results and the thresholds of OACs, the odor activity values (OAVs) of 22 OACs were calculated. Based on the OAVs obtained, a total of 17 key odorants (KOs) in the pericarps and 16 KOs in the seed kernels were determined. Some KOs, including 1,8-cineole, (+)-α-pinene, (E)-2-octenal, (E)-2-decenal, β-ocimene, linalool, α-terpineol, elemol, (E)-nerolidol, β-pinene, sabinene and 4-terpineol, were common to the pericarps and seed kernels, contributing to their similarities in odor notes. However, some odorants, including geranial, α-phellandrene, neral, terpinolene, (E)-2-dodecenal, β-myrcene, hexanal, d-limonene and β-caryophyllene, only occurred in either the pericarps or kernels, which made a distinction between their odors.
Cheddar Cheese with Different Ripening Times: Analysis of Volatile Aroma Components and Electronic Nose Discrimination
WANG Jiao, XU Lingyun, ZHANG Jinhua, WANG Xiaoyu, AI Nasi, WANG Bei, CAO Yanping
2020, 41(16):  175-183.  doi:10.7506/spkx1002-6630-20190726-349
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The volatile flavor components of three commercial Cheddar cheeses with different ripening times were analyzed by solvent-assisted flavor evaporation (SAFE) or solid phase micro-extraction (SPEM) combined with gas chromatography-mass spectrometry (GC-MS) and electronic nose. The results showed that a total of 78 volatile aroma compounds were identified, mainly including 13 fatty acids, 9 esters, 8 lactones, 9 aldehydes, 5 ketones, 12 alcohols, 19 aromatic or heterocyclic compounds, and 3 sulfur-containing compounds. Principal component analysis (PCA) performed on the volatile compounds identified in Cheddar samples showed that the main volatile aroma components of mild Cheddar cheese were fatty acids, methyl ketones and heterocyclics, the main volatile substances of medium Cheddar cheese were fatty acids, methyl ketones and lactones, and the main volatile aroma components of mature Cheddar cheese were fatty acids, esters,methyl ketones and lactones. Moreover, the Cheddar samples with different ripening times could be perfectly distinguished by electronic nose.
Isolation and Preparation of Poricoic Acid A and Poricoic Acid B from Poriae Cutis by High-speed Counter Current Chromatography
YIN Mengzhou, LIU Ying, ZHANG Lijia, WANG Yi, HUANG Wen
2020, 41(16):  179-184.  doi:10.7506/spkx1002-6630-20190807-081
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The epidermis of Poria cocos (Schw.) Wolf was used as the raw material to separate and prepare poricoic acid A and poricoic acid B by high-speed countercurrent chromatography (HSCCC). Total triterpenoids were extracted with n-butanol/water two-phase solvent system and fractionated into four peaks by HSCCC using a two-phase solvent system composed of hexane, ethyl acetate, methanol and H2O (3:6:4:2, V/V) under the conditions of clockwise rotation at a speed of 800 r/min, and a flow rate of 3 mL/min. The four peaks were collected and their purity was determined by high performance liquid chromatography (HPLC), and peaks III and IV with high purity were further identified by mass spectrometry (MS) and nuclear magnetic resonance (NMR). The results showed that peak III was identified as poricoic acid B and peak IV as poricoic acid A, which were 90% and 92% pure, respectively. The results of this study provide a simple and efficient method for the separation and preparation of poricoic acid A and poricoic acid B from Poriae Cutis, which is of great significance for the application of Poriae Cutis in the food and medical fields.
Effect of Sterilization Temperature on Flavor Compounds in Spiced Lamb Spine
WU Qianrong, PAN Xiaoqian, ZHU Ning, ZHOU Huimin, LI Su, ZHANG Shunliang, LIU Meng, ZHAO Bing, WANG Shouwei, QU Chao
2020, 41(16):  184-190.  doi:10.7506/spkx1002-6630-20191203-036
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The contents of free amino acids (FAAs) and volatile flavor compounds in raw lamb spine and spiced lamb spine sterized or not at different temperatures (90, 105, and 121 ℃) were analyzed by amino acid analyzer, dynamic headspace sampling combined with gas chromatography-mass spectrometry (DHS-GC-MS) and electronic nose (E-nose). The results showed that a total of 17, 16, 16, 16, and 16 free amino acids were detected in the five samples, respectively. The sample sterilized at 105 ℃ had the highest contents of total FAA (TFAA) and essential amino acids (EAAs) of all sterilized samples, and its aspartic acid and glutamic acid contents were significantly higher (P < 0.05) than those of the other sterilized samples, both of which made important contributions to the overall taste of spiced lamb spine. A total of 30, 40, 46, 45, and 47 volatile flavor compounds were detected these five samples, respectively, among which the highest content of volatile flavor compounds was found in unsterilized spiced lamb spine. The total amount of volatile flavor contents in the 105 ℃ sterilized sample was significantly higher (P < 0.05) than that in the 90 ℃ and 121 ℃ sterilized samples, the former containing relatively higher contents of each class of volatile compounds and more types of compounds with an odor activity value (OAV) greater than 1. The sterilized samples could be clearly distinguished by E-nose. On the bais of there results combined with sensory evaluation, the flavor of the 105 ℃ sterilized sample was the best and closest to that of unsterilized spiced lamb spine. This study provides support for the industrial production of spiced lamb spine.
Analysis of Sour Substances in the Muscle of Ryukyu Squid (Symplectoteuthis oualaniensis)
FU Mingwen, CAI Yanping, LIU Jianhua, LÜ Fei, LI Zhigang, DING Yuting, LIU Shulai,
2020, 41(16):  185-192.  doi:10.7506/spkx1002-6630-20190828-300
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The sour substances in the muscle of Ryukyu squid (Symplectoteuthis oualaniensis) were determined and its sourness characteristics were evaluated by sensory omission experiments. The results showed that free amino acids, nucleotide-related compounds, opines, organic acids, inorganic ions and quaternary ammonium salts were the main sour substances of S. oualaniensis. The contents of alanine, taurine, glutamic acid, arginine, ATP, ADP, β-alanopine, meso-alanopine, tauropine, betaine, acetic acid, K+, Na+, and NH4+ were high. meso-Alanopine, β-alanopine, and tauropine were the characteristic sour substances in the muscle of Ryukyu squid, and they directly influenced the strength of sourness. Glu, Asp, Arg, Tar, Ace, K+, Na+, NH4+ and Cl- were the minor factors that constitute sourness.
Analysis of Volatile Composition and Key Aroma Compounds of Liupao Tea
MA Shicheng, WANG Mengqi, LIU Chunmei, MA Wanjun, ZHU Yin, LIN Zhi, LÜ Haipeng
2020, 41(16):  191-197.  doi:10.7506/spkx1002-6630-20190920-252
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The volatile components in a representative batch of Liupao tea were extracted and analyzed using head space-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME/GC-MS) and the key aroma compounds were identified by relative odor activity value (ROAV) combined with gas chromatography-olfactometry-mass spectrometry (GC-O-MS). A total of 81 volatile compounds including 16 alcohols, 9 aldehydes, 12 ketones, 6 esters, 21 hydrocarbons, 10 heteroaxygens, 2 acids and 5 phenols were identified, the most abundant being undecane, cedrol, and D-camphor. Moreover, 1-methyl naphthalene, decanal, β-ionone, and nonanal were confirmed as the key aroma compounds, indicating that they may contribute significantly to the aroma quality of Liupao tea.
Flavor Components of Liquid Smoke Analyzed by GC-MS Combined with Electronic Sensory Systems
SONG Li, CHEN Xingxing, GU Fenglin, HU Ke, WU Guiping, ZHU Qiujin, TAO Rui
2020, 41(16):  193-201.  doi:10.7506/spkx1002-6630-20190823-238
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In this study, four domestic hawthorn kernel liquid smokes: I, II, II-2002 and II-2003 and five liquid smokes produced by Red Arrow (USA): Smokez poly C-10-03, C-10-05, C-10-10, C-10-11, and C-10-22 were evaluated and compared for their flavor components using electronic nose and electronic tongue technology combined with gas chromatography-mass spectrometry (GC-MS). The results of electronic nose showed discrimination of the domestic liquid smokes from the imported ones, which had similarity in flavor. Principal component analysis performed on the electronic tongue data revealed that there were differences in overall taste profile among all liquid smokes except for oil-soluble C-10-11 and C-10-22, and C-10-03 and C-10-10 were mainly affected by salty taste while the five others were affected by salty taste, bitterness and astringency and richness. Besides, liquid smoke I was also affected by sourness. A total of 156 flavor compounds, including ketones, phenols, acids, aldehydes, alcohols, esters, nitrogen and other compounds, were identified by GC-MS. Ketones were dominant, followed by phenols and acids. Finally, a comprehensive evaluation model for the flavor of liquid smokes was obtained by principal component analysis. The comprehensive flavor scores of the nine liquid smokes were in the following decreasing order: C-10-05, C-10-10, C-10-03, C-10-11, C-10-22, II, II-2002, I, and II-2003, revealing the difference in flavor between hawthorn kernel liquid smokes and Red Arrow-produced liquid smokes.
Detection of Sulforaphene Content in Radish Seed Oil and Influence of Processing Conditions on Sulforaphene Content
LI Nannan, HAN Lijuan, ZHANG Weinong, QI Yutang, HE Junbo, WANG Qingsong, LIU Chen
2020, 41(16):  198-204.  doi:10.7506/spkx1002-6630-20191015-142
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Through optimization of sample pretreatment conditions as well as spiked recovery experiments, a two-step extraction method was proposed to detect the sulforaphene (SFE) content in radish seed oil. The effect of radish seed pretreatment on SFE production was investigated. Acetone, dichloromethane, diethyl ether, and n-hexane were separately used to extract crude oil from pretreated radish seeds, in order to compare the effects of conventional refining and anhydrous room temperature refining on the retention rate of SFE in the oil. The results indicated that when detected using two-step extraction with water followed by dichloromethane radish seed oil showed good peak shape, high response value and good recovery and repeatability. The optimal water adjustment and pretreatment conditions that provided maximum SFE content were as follows: directly spraying crushed radish seeds with water to a moisture content of 8%, and then enzymatically hydrolyzing it at 25 ℃ for 10 min. Acetone was found to be the best extraction solvent, giving an SFE content of up to 832.36 mg/kg in the crude oil. SFE in the oil was completely lost after the first step of hydration degumming in the conventional refining process. However, the SFE content of the oil refined by anhydrous room temperature refining was 760.35 mg/kg, with a retention rate of SFE of up to 91.3%. Besides, the basic indexes of the refined oil could reach the national standard for the third grade of edible oil. This study provides useful guidance for the processing, development and utilization of radish seed oil.
Flavored Peanut Oil Bodies: Optimization of Pretreatment Parameters Based on Fuzzy Mathematic Evaluation and Analysis of Aroma Components
WEI Songli, sun xiaojing, zhang lixia, lu xin, meng zhaojian, sun qiang, huang jinian, zhang manyu
2020, 41(16):  202-209.  doi:10.7506/spkx1002-6630-20200121-258
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Flavored peanut oil bodies prepared with nine combinations of pretreatment parameters (roasting temperature and time) were evaluated by fuzzy mathematic evaluation combined with gas chromatography-mass spectrometry (GC-MS) in order to select the best one. Subsequently, the volatile aroma components of flavored peanut oil bodies and the effects of characteristic compounds on the overall flavor were explored through principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). The results showed that the sample with roasting pretreatment at 140 ℃ for 30 min gained the highest comprehensive score, with a light odor of raw peanut and strong characteristic flavor and without off-flavor, indicating good agreement between GC-MS analysis and fuzzy mathematics evaluation. Thus the optimal pretreatment parameters were determined to be 140 ℃ and 30 min. The results of PCA and OPLS-DA showed that heterocyclics, aldehydes and ketones, alcohols and phenols, and other components were the important components affecting the aroma of flavored peanut oil bodies. The key characteristic compounds in the four classes were 2-ethyl-6-methylpyrazine, N-methylpyrrole, 2,5-dimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, 2,3-dihydrobenzo furan, 3,5-diethyl-2-methylpyrazine; benzaldehyde, phenylacetaldehyde; 2-methoxy-4-vinylphenol; and 1-methylpyrrole-2-carboxylic acid methyl ester, respectively.
Effects of Salt Treatment on Volatile Components of Kushui Rose (Rosa setate × R. rugosa) Hydrosol Analyzed by SPME-GC-MS
WU Yi, HU Jianzhong, HAN Xue, YIN Liqiang, YUAN Weiqiong, SHI Hao, LÜ Zhaolin
2020, 41(16):  205-210.  doi:10.7506/spkx1002-6630-20190516-177
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The difference in the volatile composition of Kushui rose hydrosol under different salt treatment conditions was studied in an attempt to reveal the influence of salt treatment on the quality of rose hydrosol. In this experiment, Kushui rose hydrosol was prepared from the flowers of Rosa setate × R. rugosa using a device developed by ourselves, and its volatile components were analyzed by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). The study results showed that a total of 86 volatile compounds were identified from the hydrosols of fresh and NaCl treated flowers, 57 volatile compounds of which were present in the fresh hydrosol mainly citronellol and linalool, and 61 volatile compounds in the salted hydrosol mainly citronellol, linalool and terpineol. Compared with the fresh one, the contents of linalool and terpineol in the salted hydrosol were significantly increased (P < 0.05), while the content of citronellol was significantly decreased (P < 0.05). The contents of phenolic compounds in the two hydrosols were similar (P > 0.05), which were 3.84% and 3.81%, respectively; there were also 10 aldoketones (0.42%) and 3 terpenes (0.21%) in the fresh hydrosol. Additionally, there were 11 aldoketones (0.69%) and 1 terpene (0.17%) in the salted hydrosol. Although the two types of hydrosols were mainly composed of alcohols, the types, quantities and relative percentages of alcohols were quite different between them. At the same time, the aroma of the fresh hydrosols was more abundant and sweeter than the salted one, and the color was clearer. This study provides theoretical support for the preparation and quality identification of rose hydrosols.
Analysis of Taste Components of Yeast Extract and Effect of Composite Seasoning Containing It on the Flavor of Silver Carp
REN Jiayi, ZHAI Yingying, HUANG Jingjing, ZHANG Huimin, XIONG Shanbai, HUANG Qilin, ZHU Jianzhong, LI Pei, LI Ku, SHEN Shuo
2020, 41(16):  210-217.  doi:10.7506/spkx1002-6630-20190628-392
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The taste components in yeast extract were analyzed by an automatic amino acid analyzer and high performance liquid chromatography (HPLC). Then the contribution of each taste component to the taste of yeast extract was evaluated by calculating the taste activity value (TAV), and the synergistic interactions between umami components were demonstrated through the calculated equivalent umami concentrations (EUC). Furthermore, the main taste components were determined by omission and addition test. Finally, yeast extract, salt and sucrose were used as raw materials to develop an umami-enhancing and deodorizing seasoning, and the optimal combination of the three ingredients was determined by single factor experiments and orthogonal array design. The changes in the taste of steamed silver carp fillets before and after the seasoning treatment were analyzed by electronic tongue. Results showed that sodium glutamate, alanine, 5’-GMP, 5’-IMP, sodium aspartate, arginine, tyrosine and 5’-AMP contributed the most to the taste of yeast extract. The EUC was calculated to be 184.48 g/g, indicating a strong synergistic interaction between umami amino acids (sodium glutamate and aspartate) and umami nucleotides (5’-GMP, 5’-IMP and 5’-AMP). The optimum formulation of seasoning for enhancing umami and reducing fishy odor consisted of 1% yeast extract, 1.5% salt, and 0.5% sucrose. After being pickled with the seasoning, the umami taste of silver carp fillets was obviously improved and the fishy odor was mitigated.
Sensory Characteristics of Beijing Douzhi (Fermented Mung Bean Juice)
LIU Wenying, SUN Jiaqi, CHENG Xiaoyu, LI Xiang, JIA Xiaoyun, WANG Le
2020, 41(16):  211-221.  doi:10.7506/spkx1002-6630-20200225-271
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In order to quantitatively analyze the flavor and flavor characteristics of Douzhi (fermented mung bean juice), we collected 10 Douzhi samples sold in Beijing, and analyzed their main flavor and taste characteristics, free amino acid compositions, amino acid compositions and volatile organic components. Results showed that each sample had its own unique flavor and taste characteristics, but some samples shared a high similarity to each other. Total amino acid contents decreased, while the contents of free amino acids and free pleasant taste amino acids increased when raw Douzhi was heated. Moreover, the total content of pleasant taste amino acids in raw Douzhi was higher than in cooked Douzhi. A total of 223 volatile organic compounds were detected in the 10 Douzhi samples, the most abundant being alcohols and ketones.
Characteristic Flavor Compounds Fingerprinting of Mutton from Different Producing Regions of Xinjiang, China by Gas Chromatography-Ion Mobility Spectrometry
MENG Xintao, QIAO Xue, PAN Yan, ZOU Shuping, ZHANG Ting, ZHANG Qian
2020, 41(16):  218-226.  doi:10.7506/spkx1002-6630-20190429-383
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The characteristic flavors of 71 mutton samples from Altay, Bashibai, Bayinbuluk, Duolang, Hetian and Kazakh sheep from six different regions of Xinjiang respectively were analyzed by gas chromatography-ion mobility spectrometry (GC-IMS). Out of these, 52 samples with similarities more than 85% were selected to establish flavor fingerprints according to the results of clustering analysis by Matching matrix in LAV (Laboratory Analytical Viewer) software. The differences between the characteristic flavors of mutton samples from different regions were compared, and the characteristic components, characteristic peaks, and characteristic marker substances and their contents were determined. The results indicated that 2-ethyl-1-hexanol was identified as characteristic ?avor compounds of Altay sheep meat; ethyl acetate, 3-methyl butyraldehyde and n-butanal as characteristic ?avor compounds of Bashibai sheep meat; benzaldehyde, 3-methylpentanoic acid and 5-methyl-2-furanmethanol as characteristic ?avor compounds of Bayinbuluk sheep meat; ethyl acetate and octanone as characteristic ?avor compounds of Duolang sheep meat; 2-octanol as characteristic ?avor compounds of Hetian sheep meat; and hydroxyacetone, (E)-2-heptenal and 3-hexen-1-ol as characteristic ?avor compounds of Kazakh sheep meat. Based on the fingerprints, principal component analysis (PCA) was performed, showing that there were differences among the characteristics flavors of Altay, Bashibai, Bayinbuluk, Duolang, Hetian and Kazakh sheep meat, especially among Altay, Bashibai, Duolang and Kazakh sheep meat, indicating that the flavor fingerprints can be used for evaluating the quality, tracing the origin and identifying the authenticity of mutton from different regions of Xinjiang.
Comparative Analysis of Major Characteristic Components of Tea Seed Oils (Camellia oleifera Abel.) from Different Geographic Regions
YE Minqian, WU Fenghua, RUI Hongfei, CHEN Tong, LIU Xingquan
2020, 41(16):  222-226.  doi:10.7506/spkx1002-6630-20190701-007
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In order to compare the differences among tea seed oils from different geographic regions, we applied systematic cluster analysis (SCA) and principal component analysis (PCA) to analyze the oil content, fatty acid composition, and characteristic components including sterol, squalene and tocopherol of tea seeds from eight different producing regions. The results showed that oil contents of the tea seeds ranged from 41.38% to 54.71%. A total of 12 fatty acids, squalene, 8 sterols and tocopherols were detected in the eight tea seed oils. The oil from Jiujiang, Jiangxi province contained the highest content of saturated fatty acids (133.79 mg/g), the oil from Suizhou, Hubei province contained the highest content of unsaturated fatty acid (659.40 mg/g), the oil from Quzhou, Zhejiang province contained the highest content of total sterol (316.14 mg/100 g), and the oil from Shaoyang, Hunan province was the richest in total tocopherol (338.74 mg/kg) and squalene (29.27 mg/100 g). The results of SCA and PCA indicated that the eight producing regions were clustered into four groups: Group 1 including Quzhou of Zhejiang province, Southeast Guizhou Miao and Dong Autonomous Prefecture of Guizhou province, Jinzhai of Anhui province, Suizhou of Hubei province and Heyang of Guangxi Zhuang autonomous region; Group 2 including Shaoyang of Zhejiang province; Group 3 including Jiujiang of Jiangxi province; and Group 4 including Kunming. Moreover, PCA analysis showed high scores for tea seed oils from Shaoyang of Hunan province, Suizhou of Hubei province and Jiujiang of Jiangxi province. In summary, there were significant differences (P < 0.05) in the characteristic components of the tea seed oils from different producing regions and the oil from Shaoyang contained high contents of the characteristic components and ranked the highest overall.
Differential Volatile Metabolites between Sichuan Baoning Vinegar and Shanxi Aged Vinegar Determined by GC-MS Fingerprint and Multivariate Statistics
KUANG Geling, LI Shu, NING Tiantian, ZHAO Guozhong
2020, 41(16):  227-232.  doi:10.7506/spkx1002-6630-20190827-289
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This study aimed to analyze the differential volatile metabolites between Sichuan Baoning vinegar and Shanxi aged vinegar, both among the four famous vinegars in China. The volatile compounds of six samples of Sichuan Baoning vinegar and nine samples of Shanxi aged vinegar were qualitatively and quantitatively determined by gas chromatography-mass spectrometry (GC-MS). Using SIMCA-P+14.1 software, principal component analysis (PCA) was performed to examine the overall distribution between the two groups and the stability of the whole analysis process, and then orthogonal partial least-squares discriminant analysis (OPLS-DA) was used to discriminate the overall difference in metabolite profile between the groups. Finally, the points located at both ends of the S-plot with variable influence on projection (VIP) > 1 were selected as the potential markers that contribute the most to the differentiation between the two vinegars, and the differential metabolites between them were found. Multivariate data analysis showed that six flavor substances, furfural, ethyl acetate, 2,4-bis(1,1-dimethylethyl)-phenol, acetic acid, phenyl ethyl acetate and phenyl ethanol, were the potential markers that contributed the most to the discrimination between the two vinegars.
Taste Evaluation of Various Sweeteners by Electronic Tongue
HUANG Jiali, HUANG Baohua, ZUO Shanshan, GUO Chenglong, ZHOU Jinlin, LU Yujing
2020, 41(16):  227-233.  doi:10.7506/spkx1002-6630-20190916-195
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In order to objectively evaluate the sweetness and characteristics of sweeteners, we investigated the feasibility of electronic tongue (ET) to evaluate the taste of 10 sweeteners, including sucrose, stevia, glycyrrhizin, mangosteen extract, neohesperidin dihydrochalcone (NHDC), naringin dihydrochalcone (NDHC), cyclamate, sucralose, sodium saccharin and acesulfame by comparison with sensory evaluation. The results showed that the sweetness sensor GL1 could effectively detect the sweetness of sucrose, NHDC, NDHC, sodium saccharin, acesulfame and cyclamate, and the response to cyclamate was negative. Based on the ET data, the 6 sweeteners were clearly classified by principal component analysis (PCA) and cluster analysis. Relative to sucrose, the sweetness of the other 4 sweeteners was expressed. A quantitative prediction model between the results of ET detection and sensory evaluation was established for each of the five sweeteners with positive sweetness response by least square method. The results showed a good correlation for the five sweeteners and good linear relationships for sucrose, NHDC and acesulfame. The correlation coefficient of prediction set (Rp) for each of the sweeteners was greater than 0.96, and the root mean square error was less than 0.9, indicating that the prediction model has high accuracy and good prediction performance.
Processing Technology
Effects of Processing Techniques on the Quality Properties and Lipid Concomitants of Flaxseed Oil
YU Kun, YU Xiao, CHENG Chen, CHEN Peng, ZHENG Chang, HUANG Qingde, DENG Qianchun
2020, 41(16):  233-243.  doi:10.7506/spkx1002-6630-20191020-208
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This study aimed to investigate the effects of processing techniques, including cold pressing, microwave-assisted cold pressing, accelerated solvent extraction, supercritical CO2 extraction, and subcritical fluid extraction on the yield, physicochemical properties, typical lipid concomitants contents, oxidation stability and in vitro antioxidant capacity of flaxseed oil. The results showed that microwave-assisted cold pressing significantly increased the yield of flaxseed oil by 4.3%–10.66% when compared with other techniques (P < 0.05). The physicochemical properties of flaxseed oils produced by the above five methods were different from one another but met the requirements of the Chinese national standard. Supercritical CO2 extraction possessed a better potential in the accumulation of α-linolenic acid in flaxseed oil (54.06%), which was 3.70%–5.31% higher than those of other techniques (P < 0.05). Moreover, the different processing techniques had specific effects on the typical lipid concomitants in flaxseed oil. The highest contents of tocopherols, carotenoids, chlorophyll, flavonoids and phospholipids were found in the flaxseed oils obtained by accelerated solvent extraction and microwave-assisted cold pressing. Subcritical fluid extraction significantly increased the contents of phytosterols in flaxseed oil (429.78 mg/100 g) by 5.07%, 9.34%, 15.57%, and 30.26% in comparison with other techniques (P < 0.05). The flaxseed oil obtained by supercritical CO2 extraction possessed the maximum total phenol content (13.60 mg/100 g), showing a 7.77%–68.53% increase when compared with those prepared by other techniques. Notably, the processing techniques had significant effects on the in vitro antioxidant capacity and oxidation stability of flaxseed oil (P < 0.05). The flaxseed oils prepared by accelerated solvent extraction and microwave-assisted cold pressing showed stronger oxidation stability and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity than those obtained by other methods, but the flaxseed oil obtained by supercritical CO2 extraction had a strong iron ion reducing power. These results will provide a theoretical basis for processing various kinds of flaxseed oil.
Component Analysis
γ-Oryzanol Content and Ferulic Acid Ester Composition in Brown Rice from Heilongjiang Province
ZHANG Chao, LI Dan, ZHANG Chang, LI Hongliang, YIN Kun, ZHANG Xue, ZHANG Dongjie
2020, 41(16):  234-241.  doi:10.7506/spkx1002-6630-20190929-354
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By high performance liquid chromatography (HPLC), we analyzed the difference in total γ-oryzanol content in brown rice from five different rice-producing regions (Fangzheng, Xiangshui, Chahayang, Wuchang, and Jiansanjiang) in Heilongjiang province, and we determined the correlation between ferulic acid ester monomers in rice. The results showed that the total content of γ-oryzanol changed from 10.88 to 33.53 mg/100 g, with cycloartenol ferulate, 24-methylenecycloartanyl ferulate being the most abundant, followed by campesterol ferulate and β-sitosterol ferulate. In addition, the γ-oryzanol content varied at different maturity stages. The total content of γ-oryzanol significantly varied under natural conditions. The average content of γ-oryzanol in brown rice from Wuchang was the highest, (21.48 ± 5.04) mg/100 g, and the lowest value (16.56 ± 6.29) mg/100 g was found in brown rice from Xiangshui. There was a linear relationship between the ferulic acid ester monomers.
Effect of Bacillus on Amino Acids and Volatile Aroma Components of Fermented Soybean
ZHANG Yan, WU Junrui, CAO Chengxu, QIU Boshu, MA Ying, SHI Haisu, YANG Hui, WU Rina
2020, 41(16):  242-248.  doi:10.7506/spkx1002-6630-20190829-324
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The free amino acid composition and volatile aroma components of fermented soybean made with nine Bacillus strains were analyzed by amino acid analyzer and gas chromatography-mass spectrometry (GC-MS) and the obtained data were analyzed by factor analysis with SPSS software. The results showed that all the Bacillus strains played an essential role in the formation of free amino acids and flavor substances during soybean fermentation. The amino acid contents and aroma-producing abilities of the different fermented samples were different. Through factor analysis, it was concluded that esters, alcohols and aldehydes were the main aroma components in Bacillus fermented soybeans. This study can provide a reference for flavor enhancement of fermented bean products.
Processing Technology
Stability of Enzymatic Hydrolysate of Soy Protein Isolate-Phospholipid Composite Emulsion
ZHENG Jianzhang, GUAN Junjun, LU Xinkai, LIU Xue, ZHU Hao, JI Xuyang
2020, 41(16):  244-251.  doi:10.7506/spkx1002-6630-20190606-063
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In this paper, soy protein isolate (SPI) was hydrolyzed by pepsin and then used to establish a stable SPI enzymatic hydrolysate-phospholipid complex emulsion system, aiming to find out a natural carrier that remains stable when passing through the stomach. Based on microscopic observation, particle size, potential, emulsion emulsification activity index (EAI), emulsion stability index (ESI) and creaming index (CI), we applied single factor experiment and orthogonal array design to determine the optimum composition of composite emulsions at pH 2.0 and 7.0. The results showed that the hydrolysis process was completed in 120 min. With increasing concentration of the protein hydrolysate, the stability of complex emulsions increased first and then remained unchanged. Maximum stability was observed for the complex emulsion with phospholipid concentration of 0.001 0 g/mL. With the increase of oil phase volume fraction, the stability of composite emulsions increased first and then remained unchanged. The emulsion with SPI hydrolysate concentration of 0.020 0 g/mL, phospholipid concentration of 0.000 5 g/mL and oil phase volume fraction of 10% was the most stable at pH 2.0, as determined by orthogonal array design
Component Analysis
Comparative Analysis of Flavor Quality of Chrysanthemum Tea (Chrysanthemum morifolium cv. ‘Fubaiju’) Processed by Different Drying Methods
LU Qi, XUE Shujing, YANG De, WANG Shaohua, LI Lu
2020, 41(16):  249-255.  doi:10.7506/spkx1002-6630-20190823-249
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In order to explore the effect of different drying methods on the flavor quality of ‘Fubaiju’ chrysanthemum tea, this study compared the color, bioactive ingredient contents, antioxidant capacity and sensory characteristics of chrysanthemum teas processed by hot air drying (HD), vacuum drying (VD) and nature drying (ND), and their flavor components were analyzed by gas chromatography-mass spectrometry (GC-MS) and electronic nose (E-nose). A total of 67 volatiles were detected in the three chrysanthemum tea samples, of which VD sample contained the highest content of volatile components, while ND sample contained the largest number of volatile components. The odor and volatile components of the three chrysanthemum tea samples were significantly different as revealed by analyzing the E-nose and GC-MS data using principal component analyses (PCA). ND chrysanthemum tea showed the highest total phenolic and flavonoid contents and strongest antioxidant capacity, as well as abundant and well-balanced volatile components, and it had a mild aroma and pleasant mouthfeeling, but its drying efficiency was low. VD retained the original color and aroma of chrysanthemum flowers, and the tea infusion had the highest amino acid content. Although the tea infusion had a strong aroma, its mouthfeeling was undesirable. HD drying displayed the highest drying efficiency but it seriously affected the color, shape and aroma of chrysanthemum flowers, and was also destructive to volatile components and antioxidant ingredients in chrysanthemum tea.
Processing Technology
Effects of Raw Material Composition and Processing Conditions on Quality of Yuba
LAN Weijie, LIN Ying, KANG Qing, HUANG Ting, MA Erlan
2020, 41(16):  252-258.  doi:10.7506/spkx1002-6630-20191111-145
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The physical properties of yuba were determined with a texture analyzer, a chromometer and a scanning electron microscope. We studied the correlation between the raw material components and the yield and eating quality of yuba, and we optimized the processing conditions. The results showed that when the soybean milk concentration was 6%, pH 8.0, temperature 90 ℃, the ratio of protein to fat 3:1, and the ratio of protein to carbohydrate 4:1, the highest yield of yuba of 43.13% was obtained with a tensile strength of 12.46 g/mm2 and an elongation at break of 9.85%. The eating quality of yuba prepared from soybean milk with a ratio of 11S to 7S protein of 4:1 was the best. Compared with the traditional production process, the yield and tensile strength at break of yuba produced using the optimized process were increased by 10.11% and 74.02%, respectively. In comprehensive evaluation of yield, mechanical properties and color, the optimized yuba scored 17.7% higher than that produced using the traditional process.
Component Analysis
Comparative Analysis of Anthocyanins in the Fruits of Three Varieties of Blue Honeysuckle (Lonicera caerulea L.) by Ultra-high Performance Liquid Chromatography-Time of Flight-Tandem Mass Spectrometry
ZHANG Shangshang, ZHENG Shuning, WANG Xuetao, NI Yang, WANG Ying
2020, 41(16):  256-262.  doi:10.7506/spkx1002-6630-20190822-223
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In this study, we performed a comparative analysis of anthocyanins in the fruits of three varieties of blue honeysuckle (Lonicera caerulea L.), namely Iliad, Berel and Gerda, using ultra-high performance liquid chromatography-time of flight-tandem mass spectrometry (UPLC-TOF-MS/MS). The results showed that a total of 24 anthocyanins were identified in all the samples, including 14 cyanidin anthocyanins, six peonidin anthocyanins, two delphinidin anthocyanins and two pelargonidin anthocyanins. Among them, nine anthocyanins were found in the fruits of blue honeysuckle for the first time. The main anthocyanins in the fruits of all three blue honeysuckle varieties were cyanidin-3-glucoside, peonidin-3-glucoside, cyanidin-3-rutinoside and cyanidin-3,5-diglucoside. Comparative studies showed that the composition of anthocyanins was different in the three varieties of blue honeysuckle. A total of 24, 23 and 12 anthocyanins were detected in the fruits of Iliad, Belegli and Gerda, respectively. In addition, the relative contents of anthocyanins in the fruits of Iliad and Berel were significantly higher than in Gerda. This study will provide the foundation for further study on the molecular genetic mechanism of anthocyanin synthesis and accumulation in blue honeysuckle and for the selection and breeding of new varieties of blue honeysuckle rich in anthocyanins.
Safety Detection
Establishment of Droplet Digital PCR System for Absolute Quantitative Detection of Escherichia coli O157:H7 in Foods
WEI Yongxin, MA Dan, LI Dan, XU Leirui, WEI Haiyan, ZHANG Ximeng, LIU Li, ZENG Jing
2020, 41(16):  259-265.  doi:10.7506/spkx1002-6630-20190320-266
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A droplet digital polymerase chain reaction (ddPCR) method was developed for the rapid and quantitative detection of Escherichia coli O157:H7 in foods. A pair of primers and a probe were designed specific for the single copy gene of hlyA in E. coli O157:H7. The specificity, sensitivity and repeatability of this method were evaluated. At the same time, the plate counting method, real-time PCR and the ddPCR method were compared through the detection of artificially contaminated salmon samples using them. The results indicated that the ddPCR method had excellent specificity, sensitivity and repeatability in E. coli O157:H7 detection. The limit of detection (LOD) and limit of quantification (LOQ) for pure bacterial culture were 105 and 25 CFU/mL, respectively. The sensitivity of this developed method was 110 CFU/g in artificially contaminated salmon samples. At different levels of artificial contamination in salmon samples, there was no significant difference (P > 0.05) between the results of ddPCR and plate counting, which were more stable and accurate than the results of real-time PCR. Therefore, the established ddPCR method can detect E. coli O157:H7 in food samples more rapidly, accurately, sensitively and specifically.
Component Analysis
Effects of Roasting, Steaming and Extrusion on the Flavor and Bitterness of Quinoa
ZHOU Yang, LI Lu, LÜ Ying
2020, 41(16):  263-269.  doi:10.7506/spkx1002-6630-20190613-141
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In this study, quinoa was processed in three different ways: roasting, extrusion and steaming. Sensory evaluation and headspace solid phase micro-extraction followed by gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with relative odor activity were used to investigate the main volatile flavor compounds of the processed quinoa. The results showed that the different heat treatments had different effects on the flavor of quinoa. Benzene acetaldehyde, (E)-2-octenal, nonanal, (E)-2-nonenal, and decanal were found to be the key flavor substances in all thermally processed quinoa samples. (E,E)-2,4-nonadienal was the unique key flavor compound of steamed quinoa, while benzeneacetaldehyde contributed greatly to the cooked peanut-like flavor of roasted quinoa. The volatile compounds of quinoa with different heat treatments were further analyzed by principal component analysis (PCA). It turned out that extrusion and steaming had great influence on the volatile flavor substances of quinoa. In addition, each of the three treatments could reduce the bitterness of quinoa, which was associated with reduced saponin content as determined by high performance liquid chromatography (HPLC). This study provides a theoretical basis for the processing of quinoa.
Safety Detection
Determination of Deuterium Content in Packaged Drinking Water Labeled Low Deuterium by Thermal Conversion/Elemental Analysis-Isotope Ratio Mass Spectrometry
HAN Li, LIU Di, YU Tingting
2020, 41(16):  266-271.  doi:10.7506/spkx1002-6630-20190716-219
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A method for the determination of deuterium content in drinking water labeled low deuterium by thermal conversion/elemental analysis-isotope ratio mass spectrometry (TC/EA-IRMS) was established. The water sample was filtered through a 0.22 μm filter membrane, and 2 mL of the sample was transferred to a vial. The sample volume was 0.1 μL. The reactor temperature was 1 380 ℃, the column temperature was 85 ℃, and the carrier gas flow rate was 100 mL/min. Each sample was analyzed 4 to 6 times. The accuracy of the calculated deuterium content was improved by eliminating the first data point and the top space of the sample vial to avoid the influence of the void space and memory effect on the measurement of δ2H. This method was suitable for the determination of deuterium content in drinking water within the range of 12.624–155.760 μg/g, and the relative standard deviation (RSD) between the measured and theoretical values was less than 0.6%. The relative deviation (SD) of deuterium content in one deuterium-depleted water sample was 0.08 μg/g for 8 consecutive measurements, and 0.086 μg/g for 3 measurements within 30 days, indicating good repeatability and reproducibility. The RSD for the determination of water samples with low deuterium content by different instrumental methods was lower than 1 μg/g. The deuterium contents of 8 deuterium-depleted packaged drinking waters were tested. Generally, the measured and labeled values were not consistent with each other. Determination of deuterium content in deuterium-depleted water by TC/EA-IRMS can provide technical support and a theoretical basis for supervision and testing of deuterium content in packaged drinking water labeled low deuterium.
Processing Technology
Separation of Capsanthin and Capsaicin by Three-phase Salting-out Extraction and Cluster Analysis of Different Varieties of Chili (Capsicum annuum L.)
FAN Sanhong, WANG Jiaojiao, BAI Baoqing, ZHANG Jinhua
2020, 41(16):  270-277.  doi:10.7506/spkx1002-6630-20190919-236
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A high performance liquid chromatography (HPLC) method was developed for the determination of capsanthin and capsaicin in chili peppers by using a three-phase salting-out extraction system (petroleum ether/acetonitrile/dipotassium hydrogen phosphate). The composition of the system was determined, and the effects of temperature, sonication time and mixing sequence on the separation of the target products were further investigated. Based on the yields of capsaicin and capsaicin, the optimal extraction conditions were determined by response surface methodology as follows: temperature 45 ℃, sonication time 10 min, distilled water 44%, dipotassium hydrogen phosphate 20%, acetonitrile 20%, and petroleum ether 16%. After the capsicum sample powder was treated by the three-phase mixed solvent, capsanthin and capsaicin were concentrated in the upper and middle phases, respectively, and the concentrations of the target products in either phase were analyzed by HPLC. The results showed that the highest yields of capsanthin and capsaicin under optimal conditions were 0.263 mg/g and 1.412 mg/g, respectively. The proposed method could extract both capsaicin and capsaicin from chili peppers quickly and efficiently. The contents of capsanthin and capsaicin in 33 different varieties of chili peppers were determined, and these varieties were evaluated by cluster analysis, aiming to provide a theoretical basis for the identification and cultivation of chili varieties.
Safety Detection
Rapid Screening of 234 Pesticide Residues in Vegetables and Fruits by Multi-plug Filtration Cleanup Method Combined with Gas Chromatography-Quadrupole Time of Flight Mass Spectrometry
MENG Zhijuan, HUANG Yunxia, DI Pengyue, ZHAO Limin, NIU Lisha, FAN Sufang, LI Qiang, ZHANG Yan
2020, 41(16):  272-285.  doi:10.7506/spkx1002-6630-20191227-328
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A new method for screening pesticide residues in vegetables and fruits by multi-plug filtration cleanup (m-PFC) method combined with gas chromatography-quadrupole time of flight mass spectrometry (GC-QTOF-MS) was developed. The samples were extracted with acetonitrile, purified by m-PFC, and detected by GC-QTOF-MS. Qualitative analysis was carried out by retention time and accurate mass measurements in full scan mode and quantitation was performed using matrix-matched standard calibration, which could effectively eliminate matrix interference. Twelve typical samples (Chinese cabbage, celery, tomato, cucumber, spinach, Chinese leek, pakchoi, tangerine, pear, apple, grape, and orange) were used to evaluate the method. Good linearity was achieved for 234 pesticides in the concentration range of 5 to 500 μg/kg with correlation coefficients greater than 0.990. The results showed that the limits of detection of this method were in the range of 5–20 μg/kg. The average recoveries at three spiked levels of 10, 50, and 100 μg/kg were in the range of 73.2%–124.8%, 75.5%–122.6% and 74.8%–121.7%, with relative standard deviations (RSDs) of 2.4%–13.2%, 2.8%–11.4% and 2.2%–10.5%, respectively. The method could effectively improve the detection efficiency of high-resolution mass spectrometry for high throughput screening of pesticide residues in vegetables and fruits, thereby having great potential for practical application.
Processing Technology
Optimization of Bioinformatics-Based Directional Preparation of Antioxidant Peptide from Caragana Seed Protein
JIE Yu, HU Jinling, ZHAO Hongfei, ZHANG Bolin
2020, 41(16):  278-284.  doi:10.7506/spkx1002-6630-20190822-224
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In order to determine the most suitable enzyme to prepare antioxidant peptide from Caragana seed protein, gluten was chosen as the bioinformatic template of Caragana seed protein for simulated hydrolysis by four different enzymes including papain, pepsin, trypsin and V-8 protease based on the BIOPEP database. Based on degree of hydrolysis and linoleic acid oxidation inhibitory rate, papain plus 10% V-8 protease was regarded as the best enzyme for hydrolyzing Caragana seed protein. Using one-factor-at-a-time and orthogonal array design methods, the optimal hydrolysis parameters were obtained as follows: temperature 45 ℃, hydrolysis time 2 h, pH 5.0, and enzyme dosage 1%. As a result, six antioxidant peptides were obtained whose sequences were identified by mass spectrometry. The inhibition rate of LDEPDPL against linoleic acid oxidation was 50.3%. In conclusion, the computer-assisted enzymatic hydrolysis provides a novel strategy for directional preparation of antioxidant peptide from Caragana seed protein.
Safety Detection
Molecular Characteristics and Antimicrobial Susceptibility of Foodborne Methicillin-Resistant Staphylococcus aureus in Shanghai, China
ZHANG Pengfei, ZHANG Jie, LIU Xinyu, FU Xueting, ZHANG Meng, XU Xuebin, WU Congming, JI Hua, WANG Xin
2020, 41(16):  285-291.  doi:10.7506/spkx1002-6630-20190714-184
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Objective: To evaluate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains from different types of food in Shanghai, and investigate the molecular characteristics and antibiotic resistance of these strains. Methods: A total of 184 foodborne S. aureus strains were collected in Shanghai during 2011–2016 for this study. MRSA positive strains were identified by detection of the mecA gene using polymerase chain reaction (PCR) and were further characterized by staphylococcus protein A (spa) typing, multilocus sequence typing (MLST), and staphylococcal cassette chromosome mec (SCCmec) typing, and their antimicrobial susceptibility and virulence genes were also evaluated. Results: Nine (4.9%, 9/184) positive MRSA isolates were identified from the 184 strains, among them one strain was isolated from eggs, one strain from ready-to-eat salads, three strains from raw meat products and the remaining four strains from cooked meat products. All MRSA strains were multidrug-resistant (MDR), being most frequently resistant to ampicillin and penicillin (100%, 9/9), followed by cefoxitin and trimethoprim/sulfamethoxazole (88.9%, 8/9), erythromycin (55.6%, 5/9), amoxicillin/clavulanic acid (33.3%, 3/9), tetracyclines and oxacillin (22.2%, 2/9) and ciprofloxacin (11.1%, 1/9). The carrying rates of the hemolysin genes (hla, hlb and hld) and the panton-valentine leukocidin gene (pvl) were high, while the carrying rates of all enterotoxin genes were low. ST59-IVa-t437 (33.3%, 3/9) and ST88-III-t14340 (22.2%, 2/9) were the most predominant clones, followed by ST398-IVa-t034, ST630-III-t4549, ST5-II-t002 and ST4495-t10738 (11.1%, 1/9 each). Conclusion: Our findings indicated that the foodborne MRSA strains mainly contaminated animal products and artisanal foods at a low level in Shanghai. These foodborne MRSA strains shared the same molecular profiles as LA-MRSA, CA-MRSA and HA-MRSA. Despite the low contamination rate of the MRSA in food, there could be a potential risk of transmission through the food chain.
Geographical Origin Discrimination of Anhua Dark Tea by Elemental Fingerprint
YANG Chun, YAN Hongfei, LÜ Xiaoyuan, LU Jing, HE Peng
2020, 41(16):  286-291.  doi:10.7506/spkx1002-6630-20190304-033
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In this study, we discriminated the geographical origin of Hunan Anhua dark tea by using inductively coupled plasma mass spectrometry (ICP-MS) combined with chemometrics. Quantitative analysis of 48 elements such as B, Li and P was carried out in Hunan Anhua dark tea and those from other geographical origins by ICP-MS, and an elemental fingerprint for Anhua dark tea was obtained. The element distribution in dark teas from different geographical origins was evaluated by characteristic analysis, discriminant analysis, principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA). In the PCA and the PLS-DA score plots, Anhua dark tea was effectively discriminated from those from other regions. Nineteen elements including Li, Pb and Ga were significantly different between Anhua dark tea and those from other regions. Seven key elements (Li, Pb, Ga, Ce, Rb, Cs and Na) were introduced into?the discriminant?analysis?model. The correct discrimination rate of the mode was 100% and 98%?in back substitution and cross-validation test, respectively. The results showed that the elemental fingerprint could be used for the geographical origin discrimination of Anhua dark tea.
Determination of 121 Pesticide Residues in Houttuynia cordata Thunb. by QuEChERS-Gas Chromatography Tandem Mass Spectrometry
GOU Yan, GAO Chi, DENG Jingjing, GENG Zhao, YUAN Jun, LI Min, ZHOU Juan, GUO Li, BAO Xiaoming
2020, 41(16):  292-299.  doi:10.7506/spkx1002-6630-20190509-081
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A multi-residue analysis method was developed for the determination of 121 pesticides in Houttuynia cordata Thunb. by the QuEChERS extraction procedure (the abbreviation of quick, easy, cheap, effective, rugged and safe) coupled with gas chromatography-tandem mass spectrometry (QuEChERS-GC-MS/MS). This method was applied for screening of 68 sample batches. The pesticide residues from the samples were extracted with acetonitrile and purified by a modified QuEChERS method before being detected by GC-MS/MS in the multiple reaction monitoring mode. The results showed that all 121 pesticides exhibited good linearity in certain ranges with correlation coefficients (r) higher than 0.997 3. The recoveries of more than 90.9% pesticides ranged from 60% to 140% at three spiked concentration levels, with relative standard deviations of less than 15% for 86.8% of the pesticides. The limits of detection (RSN = 3) of this method ranged from 0.000 1 to 0.1 mg/kg, below 0.01 mg/kg for most of the selected pesticides. A total of 27 pesticide residues were detected from the 68 sample batches. This simple, sensitive and accurate method proved to be suitable for the fast screening and detection of pesticide residues in H. cordata Thunb. in order to provide?a?basis for the cultivation and circulation supervision of H. cordata Thunb..
Establishment of a Risk Prediction Model for Adulterated Beef and Lamb Kebabs in Beijing by Data Mining
FAN Wei, GAO Xiaoyue, DONG Yuxin, LI Henan, WANG Lin, GUO Wenping
2020, 41(16):  292-299.  doi:10.7506/spkx1002-6630-20200316-245
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In order to establish a food safety risk prediction model based on data mining, we monitored whether samples of beef and lamb kebabs sold in Beijing in 2019 are adulterated. A total of 200 samples were collected from 100 sales agencies via 10 different sales channels. Pork-, cattle-, sheep-, chicken- and duck-derived ingredients in these samples were detected by real-time polymerase chain reaction (PCR) to judge whether they were adulterated. Based on the detection indexes and the sample information, back propagation (BP) neural network algorithm was used to build the risk prediction model for adulteration of beef and lamb kebabs. The results showed that the reporting limit (Ct value) of meat from each of the animal species tested obtained with the quality control samples was 28.0. On this basis, the non-acceptance rate of the 200 samples tested was 17.5% (35/200), the non-acceptance rate of the beef and lamb kebabs being 14% (14/100) and 21% (21/100), respectively. Meat adulteration with pork and/or duck was prevalent. In addition, based on the above survey data, a three-layer BP neural network prediction model was constructed by sequential data preparation, model generation, data training and verification, and parameter optimization. This model was 95.7% accurate in predicting the unaccepted samples, which could meet the purpose of risk prediction. The established model will provide the basis for the prevention and control of food safety risk.
Geographical Origin Traceability of Songjiang Rice Based on Mineral Elements Fingerprints
SHI Chunhong, CAO Meiping, HU Guixia
2020, 41(16):  300-306.  doi:10.7506/spkx1002-6630-20190827-284
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The contents of 40 mineral elements in 180 Songjiang and non-Songjiang rice samples were determined by inductively coupled plasma mass spectrometry (ICP-MS). The mineral elements fingerprints were characterized by multivariate statistics including analysis of variance (ANOVA), correlation analysis, principal component analysis (PCA) and discriminant analysis, and a discriminant model for geographical origin traceability of Songjiang and non-Songjiang rice samples was developed. The results showed that the samples from different geographical origins displayed significantly different mineral profiles with significant correlations among mineral elements. Sixteen of these 40 mineral elements were selected for dimensionality reduction. As a result, the first five PCA factors were obtained. The geographical origins of rice samples were accurately discriminated from each other by a score plot of the first three PCA factors. The discriminant model based on the eight characteristic mineral elements B, Na, Fe, Co, Ni, Zn, As and Se constructed by linear discriminant analysis gave an overall correct discrimination rate of 93.0% to the training set. Besides, the discrimination accuracy was 95.2% (sensitivity) for Songjiang rice samples and 86.8% (specificity) for non-Songjiang rice samples. The cross-validation accuracy of discrimination was 84.2%–95.2% in the training set. The overall discrimination accuracy, sensitivity and specificity for the validation set was 92.1%, 96.0% and 84.6% in back substitution test, respectively. The overall discrimination accuracy for the validation set agreed with that for the test set, proving that the established model had good discrimination accuracy, sensitivity, specificity and stability and therefore, it was feasible to discriminate Songjiang rice from non-Songjiang rice.
Effect of Fat Ratio in Raw Meat on Safety Indictors during Processing of Bacon
JIANG Hao, CHEN Yuanyuan, YANG Lu, XU Wenyi, YANG Hua, MA Lizhen
2020, 41(16):  300-306.  doi:10.7506/spkx1002-6630-20190605-048
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In order to understand the effect of different proportions of fat in raw meat on safety indicators of bacon during processing, bacons with 0 (F0 group), 10% (F10 group), 20% (F20 group) and 30% (F30 group) fat were processed by sequential mincing, curing, molding, cooking, drying, smoking and roasting, and sampling was performed at the end of cooking, 3 h and 7 h of smoking, and the end of roasting to measure pH value, nitrite residue, thiobarbituric acid reactive substances (TBARS) value, biogenic amine and N-nitrosamines (NAs). The effects of different fat ratios on the changes in these physicochemical indicators during the processing of bacon were analyzed. The results showed that the pH, nitrite residue, thiobarbituric acid reactive substances (TBARS) value and NAs content of bacon were significantly increased with the increase in fat content in raw meat (P < 0.05), and each value in the four groups of bacon was in the decreasing order F30 > F20 > F10 > F0. During the processes of cooking and smoking, nitrite residue and TBARS value showed a decreasing trend, whereas the contents of biogenic amines and NAs significantly increased (P < 0.05). Among all tested NAs, N-nitrosodimethylamine (NDMA) changed most significantly, reaching the highest value at 7 h of smoking for all four groups. After roasting, the total amount of NAs decreased, but the content of N-nitrosopyrrolidine (NPYR) still increased. In particular, NPYR contents in the F20 and F30 groups reached the highest values ??(1.27 and 1.85 μg/kg, respectively). Correlation analysis showed that there was a high correlation coefficient between the fat ratio of raw meat and the amount of NAs formed after smoking for 7 h or after roasting. The results from this study show that controlling appropriate fat to lean ratio of raw meat used for the processing of bacon is particularly important for the safety of bacon products.
Simultaneous Determination of 41 Organochlorine and Pyrethroid Pesticide Residues in Lijiang-Grown Maca by Solid Phase Extraction-Gas Chromatography-Tandem Mass Spectrometry
HUANG Shaojun, DU Ping, YANG Jun, SUN Hui, ZHU Yanqin, SUN Xiaodong, QIU Lisha, CUI Xiuming, YANG Ye
2020, 41(16):  307-313.  doi:10.7506/spkx1002-6630-20190517-205
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A method of gas chromatography-tandem mass spectrometry was established for simultaneous detection of 41 organochlorine and pyrethroid pesticide residues in Lijiang-grown maca. Pesticide residues were extracted from the crushed samples with acetonitrile-sodium chloride saturated aqueous solution (5:4, V/V) with the aid of ultrasonic stirring. Then the extracts were purified with a graphitized carbon/amino composite column and eluted with a mixed solvent of acetonitrile and toluene (3:1, V/V). The purified extracts were separated with a medium-polar stationary phase (50% phenyl-methylpolysiloxane) capillary column. Finally, the analytes were detected by triple quadrupole mass spectrometry in the full scan mode, and quantified in the multiple reaction monitoring mode by an external standard method. The results showed that good linearity was observed for all analytes in the concentration range of 0.02–10 μg/mL or 0.04–20 μg/mL with a correlation coefficient (R2) over 0.99. The limits of detection (LODs) ranged from 0.01 to 2.38 μg/kg, and the average recovery rates of spiked samples varied from 90.2% to 108.8% with relative standard deviation between 2.1% and 10.9%. In summary, the proposed method proved to be simple, rapid, accurate, sensitive, economical and suitable for the screening and quantitative detection of organochlorine and pyrethroid pesticide residues in large batches of maca samples.
Development of an Electrochemical Immunosensor for Rapid Quantification of Florfenicol in Animal-Derived Foods
LIU Weihua, YANG Xi, LIU Minxuan, YU Wenlong, WANG Xianghong
2020, 41(16):  307-313.  doi:10.7506/spkx1002-6630-20190612-127
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An electrochemical immunosensor based on graphene-chitosan composites was established to detect florfenicol residues in animal-derived foods. A linear relationship between the peak current and the concentration of florfenicol was observed in the range of 1–1 000 ng/mL and the detection limit (RSN = 3) was 0.08 ng/mL. The immunosensor displayed good selectivity, specificity and stability. The average recoveries from pork, beef, chicken and egg samples spiked at concentration levels of 10, 100 and 1 000 μg/kg ranged from 76.90% to 94.30%. The reliability of the electrochemical method was confirmed by a high correlation between it and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The established immunosensor method was accurate and reliable and could be applied to the on-site detection of massive samples.
Determination and Risk Assessment of Veterinary Drugs in Pork Meat and Viscera during Slaughter, Pre-cooling and Sale
MA Ning, WANG Jie, PEI Fei, FANG Yong, YANG Wenjian, HU Qiuhui
2020, 41(16):  314-319.  doi:10.7506/spkx1002-6630-20190606-068
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The distribution of veterinary drug residues in pork meat during slaughter and pre-cooling was evaluated in this experiment. A total of 240 samples of pork and viscera were randomly collected according to sampling method specified in the Sampling operating specification for the livestock and poultry and their products in slaughtering enterprises (NY/T 1897-2010), and they were analyzed for 43 veterinary drug residues by enhanced matrix removal lipid (EMR-L) cleanup followed by ultra-high performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS). Meanwhile, risk assessment of veterinary drug residues was carried out based on food safety index (IFS). The results showed that sulfamethazine, difloxacin and enrofloxacin were detected in the 240 samples. The detection rate of the 43 veterinary drugs was 5% at levels ranging from 2.43 to 19.94 μg/kg. The difference between the detection results after rigor mortis and maturation was not significant, indicating that there was no secondary pollution of the 43 veterinary drugs during slaughter and processing. At the same time, pork samples sold in Nanjing were collected and veterinary drug residues were detected in these samples with a detection rate of 4.4%. The IFS and values were found to be much less than 1, indicating that the levels of 43 veterinary drugs residues in pork products in Nanjing were acceptable.
Rapid Detection of Staphylococcus aureus in Foods Based on Metabolite Markers
HU Kaili, LI Yanmei, CHEN Juan, TANG Junni, MA Xinyue
2020, 41(16):  314-324.  doi:10.7506/spkx1002-6630-20190829-321
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In this study, headspace-solid phase micro-extraction followed by gas chromatography-mass spectrometry (HS-SPME/GC-MS) was employed to detect the volatile metabolites of Staphylococcus aureus. The specificity, stability and practical application of 3-methyl-butanal and 3-methyl-butyric acid as candidate metabolite markers to detect S. aureus were investigated. The results showed that S. aureus produced 3-methyl-butyric acid as its specific metabolite but not 3-methyl-butanal when cultured in 7.5% NaCl broth. The release of 3-methyl-butyric acid was not affected either by different S. aureus strains or by Escherichia coli O157:H7 and/or Salmonella enteritidis co-cultured with S. aureus indicating good stability. For raw pork, raw milk and cooked rice samples, the volatile metabolite markers-based method was highly consistent with the traditional culture method and the PCR assay. The method proposed in this study was simple to operate and could be expected to be a promising candidate for the detection of viable S. aureus.
Determination of 6 Eugenol Residues in Aquatic Products by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry
WU Shaoming, CAI Xiaoming, ZHOU Peng, CAI Huiqin, LIANG Min, CHEN Yankai, LI Yanping, FENG Lifeng, LIN Haoxue, HUANG Yuan
2020, 41(16):  320-326.  doi:10.7506/spkx1002-6630-20190826-280
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A new method for simultaneous determination of eugenol, isoeugenol, methyl eugenol, methyl isoeugenol, aceteugenol and lsoeugenyl acetate residues in aquatic products by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed. The samples were extracted with acetonitrile and purified on an HLB solid phase extraction (SPE) column. Chromatographic separation was achieved on a Shim-pack GIST column (2.1 mm × 50 mm, 2 μm) by linear gradient elution using methanol/water as the mobile phase before analysis by UPLC-MS/MS. The method validation showed that good linearity (R > 0.999) was observed in the range of 1.00–500 ng/mL for the 6 eugenols. The limits of detection (LODs) were between 0.1 and 0.3 μg/kg, and the limits of quantification (LOQs) were between 0.3 and 1.0 μg/kg. The recoveries ranged between 83.9% and 105.4% at three spiked levels (2.00, 5.00, and 10.0 μg/kg) with relative standard deviations (n = 6) between 1.8% and 6.9%. This method proved to be simple, accurate, sensitive, and suitable for the quantitative determination of six eugenol residues in aquatic products.
Analysis of Microbial Contamination and Community Structure of Bee Pollen
TANG Biao, LUO Yi, LI Rui, ZHOU Xiunan, ZHANG Ling, QIAN Mingrong, DAI Xianjun, XIA Xiaodong, YANG Hua
2020, 41(16):  325-331.  doi:10.7506/spkx1002-6630-20190527-329
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In order to investigate the microbial contamination and community structure of bee pollen, the bacterial and fungal colony counts (colony forming unit, CFU) of fresh and commercial bee pollen samples from different botanical sources collected from some regions of Zhejiang province were determined as well as their water contents using methods specified in the National Standard of the People’s Republic of China. The bacterial and fungal community structures of camellia bee pollen and lotus bee pollen were analyzed by 16S rDNA and internal transcribed spacer (ITS) amplicon sequencing, respectively. The results showed that fresh bee pollen had higher water content (> 18%) and lower microbial contamination than bee pollen during storage and transportation. The count of culturable fungal colonies in bee pollen was significantly higher than the count of culturable bacterial colonies. Cyanobacteria, Enterobacteriaceae and Lactobacillus were the most abundant bacteria in lotus bee pollen and camellia bee pollen, and Davidiellaceae, Aspergillus, Penicillium and Fusarium accounted for a higher proportion of the total fungal community. The diversities of fungal community of these two bee pollens were significantly different. We compared the microbial contamination of fresh and stored bee pollen. This study is the first to report a comparison of the bacterial and fungal communities of lotus bee pollen and camellia bee pollen. In general, the diversity of fungal community in bee pollen is high, and based on this, we can predict the presence of abundant mycotoxin-producing fungi and food safety risks. This study can provide a basis for the safety evaluation of bee pollen.
Determination of Fipronil and Four Metabolites in Animal-Derived Foods by Gas Chromatography-Negative Chemical Ionization-Tandem Mass Spectrometry
HAN Chao, HU Beizhen, JIN Na, LIU Bin, SHEN Yan, JIN Jianchang, CHEN Shubing,
2020, 41(16):  327-331.  doi:10.7506/spkx1002-6630-20200302-028
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A gas chromatography-negative chemical ionization-tandem mass spectrometry (GC-NCI-MS/MS) method for the determination of the residues of fipronil and its four metabolites (fipronil desulfinyl, fipronil sulfone, fipronil sulfide, and fipronil carboxamide) in animal-derived foods (egg, chicken, and chicken liver) was established. The samples were extracted with acetonitrile (saturated with n-hexane), and the extract was cleaned up using the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method before being detected by GC-NCI-MS/MS in the multi-reaction monitoring (MRM) mode. The matrix matched standard curve method was used for quantitation. Results showed that there was a good linearity for all analytes in the range of 1–100 μg/L with correlation coefficient (r2) higher than 0.999 0. The limit of quantitation (LOQ, RSN ≥ 10) of the method was 0.5 μg/kg for fipronil disulfonyl, fipronil, fipronil sulfide and 1.0 μg/kg for fipronil sulfone and fipronil carboxamide. The average recoveries at three spiked concentration levels (2.0, 10.0, and 20.0 μg/kg) were 80.2%–108.7% with relative standard deviations (RSDs) of 3.8%–10.2%. This method exhibited high sensitivity and accuracy, and could be used for the determination of the residues of fipronil and its four metabolites in animal-derived foods.