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25 October 2020, Volume 41 Issue 20
Food Chemistry
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(20):  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
CHENG Zhe, PAN Siyi
2020, 41(20):  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.
Effect of Fat Content on Texture, Rheology and Microstructure of Yak Milk Hard Cheese
SHI Yongqi, LIANG Qi, SONG Xuemei, ZHANG Yan
2020, 41(20):  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.
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(20):  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.
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(20):  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.
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(20):  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.
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(20):  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.
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(20):  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.
Yeast Glucan Pretreatment and Its Deodorization Effect for Silver Carp Mince
HUANG Jingjing, ZHANG Huimin, ZHAO Liyuan, XIONG Shanbai, HUANG Qilin
2020, 41(20):  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.
Isolation, Purification and Physicochemical Properties of Polysaccharides from Chlorella
SHI Ruiqin, LIANG Jingjing, LI Dawei, WANG Jie, GUO Shuxian, MA Yanli
2020, 41(20):  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.
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(20):  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.
Bioengineering
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(20):  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.
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(20):  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.
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(20):  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.
Effect of Starter Cultures on Protein Degradation and Antioxidant Capacity of Peptides from Fermented Sausages
FENG Meiqin, YU Di, SUN Jian
2020, 41(20):  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.
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(20):  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%).
Purification and Characterization of Bacteriocin Produced by Lactobacillus pentosus LS1
LI Zhiru, HAN Jianchun, LIU Rongxu, LIU Danyi, LIANG Junfeng
2020, 41(20):  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.
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(20):  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.
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(20):  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.
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(20):  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
Discrimination of Three Famous Teas in Jiangxi Using Gas Chromatography-Mass Spectrometry Combined with Chemometrics
XU Chunhui, WANG Yuanxing
2020, 41(20):  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.
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(20):  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.
Comparison of Volatile Components of Six Potato Cultivars Cooked by Three Different Methods
LI Kaifeng, ZHOU Yuanping, WANG Qiong, GUO Huachun
2020, 41(20):  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.
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(20):  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.
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(20):  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.
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(20):  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 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(20):  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.
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(20):  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.
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(20):  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.
Sensory Characteristics of Beijing Douzhi (Fermented Mung Bean Juice)
LIU Wenying, SUN Jiaqi, CHENG Xiaoyu, LI Xiang, JIA Xiaoyun, WANG Le
2020, 41(20):  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.
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(20):  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.
Taste Evaluation of Various Sweeteners by Electronic Tongue
HUANG Jiali, HUANG Baohua, ZUO Shanshan, GUO Chenglong, ZHOU Jinlin, LU Yujing
2020, 41(20):  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.
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(20):  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(20):  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.
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(20):  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.
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(20):  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.
Effects of Roasting, Steaming and Extrusion on the Flavor and Bitterness of Quinoa
ZHOU Yang, LI Lu, LÜ Ying
2020, 41(20):  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.
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(20):  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.
Optimization of Bioinformatics-Based Directional Preparation of Antioxidant Peptide from Caragana Seed Protein
JIE Yu, HU Jinling, ZHAO Hongfei, ZHANG Bolin
2020, 41(20):  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(20):  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.
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(20):  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.
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(20):  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.
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(20):  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.
Rapid Detection of Staphylococcus aureus in Foods Based on Metabolite Markers
HU Kaili, LI Yanmei, CHEN Juan, TANG Junni, MA Xinyue
2020, 41(20):  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.
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(20):  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.