Table of Content

25 January 2020, Volume 41 Issue 2
Food Chemistry
Physiochemical Characterization of Pickering Emulsions Stabilized by Anthocyanin and Soybean Protein Isolate Composite Nanoparticles
JU Mengnan, ZHU Gang, CHEN Hongyu, LAN Tian, DONG Yabo, WEN Jiayu, JIANG Lianzhou, SUI Xiaonan
2020, 41(2):  1-7.  doi:10.7506/spkx1002-6630-20190109-101
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In this paper, composite nanoparticles of soy protein isolate (SPI) and anthocyanin (ACN) were prepared by covalent binding and used to stabilize Pickering emulsions. We measured the surface hydrophobicity of nanoparticles with different concentrations of anthocyanins. The emulsifying activity index (EAI), emulsion stability index (ESI), rheological properties and microstructure of the resulting Pickering emulsions were measured via chemical and instrumental analysis. The results showed that as the volume fraction of anthocyanin increased from 0% to 0.15%, the surface hydrophobicity of nanoparticles decreased from 18 174 to 8 945; the EAI of Pickering emulsions increased 127 m2/g, and the ESI by nearly 100%, which was accompanied by a significant improvement in the distribution of lipid droplets. In addition, the Pickering emulsions exhibited solid-like properties and were a typical non-Newtonian pseudoplastic fluid. We also found that droplet bridging in SPI-ACN composite Pickering emulsions occurred with the addition of anthocyanins, which will lay a theoretical basis for developing new Pickering emulsions in the food industry.
Functional Properties, Structure and Anti-Glycosylation Activity of Polysaccharide from Blue Honeysuckle Fruit (Lonicera caerulea L.)
XU Yaqin, LIU Ningyue, LI Dalong, REN Yaoyu, DONG Xiaotong, YANG Yu, WANG Libo
2020, 41(2):  8-14.  doi:10.7506/spkx1002-6630-20190105-069
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In this study, an acidic heteropolysaccharide was isolated from the fruits of blue honeysuckle (Lonicera caerulea L.) through ultrasonic-assisted enzymatic extraction with an enzyme mixture followed by purification with D4006 macroporous resin. The functional properties, structural characteristics and anti-glycosylation activity of the polysaccharide were investigated. It turned out that the polysaccharide had good water- and oil-holding capacity, and exhibited great emulsifying property and emulsion stability. The polysaccharide exhibited typical shear-thinning behavior and viscoelastic properties. It might be used as a texture modifier or thickener for food and biomedicine. In addition, the polysaccharide showed desirable thermal stability, and thus it had the potential to be applied in the food industry as a functional additive. The polysaccharide was composed of galacturonic acid, rhamnose, arabinose, mannose, glucose, and galactose with a molar ratio of 2.84:10.02:15.47:1.00:2.48:36.12 by gas chromatography. Infrared and ultraviolet-visible spectra demonstrated that the polysaccharide had characteristic absorption peaks of polysaccharide, and nucleic acid, protein and anthocyanin were absent in it. Based on the analyses of congo red test, scanning electron microscopy, and X-ray diffraction, the polysaccharide had no triple helix structure, and exhibited an irregular flake-like structure. In addition, anti-glycosylation activities of the polysaccharide in vitro were investigated. The results showed that it exhibited good inhibitory activity on the formation of the three stages of glycosylation (Amadori products, dicarbonyl compounds and advanced glycosylation end products (AGEs)). At a concentration of 0.5 mg/mL, the maximum inhibitory rates for these stages were (35.24 ± 1.44)%, (33.41 ± 1.01)%, and (42.62 ± 0.70)%, respectively. This study provides a theoretical basis for the utilization of blue honeysuckle fruits.
Effects of Sodium Pyrophosphate on Transglutaminase Catalyzed Cross-Linking and Gel Properties of Oxidized Pork Myofibrillar Protein
SUN Yue, GENG Xiaoqian, ZHANG Yueshu, WANG Shi, SHI Rui, ZHAO Hongfei, LI Chunqiang
2020, 41(2):  15-21.  doi:10.7506/spkx1002-6630-20190312-151
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In this paper, the effects of sodium pyrophosphate (TSPP) on the degree of microbial transglutaminase (MTG)-induce cross-linking and gel properties of natural and oxidized pork myofibrillar protein were studied. Results showed that the oxidation degree of myofibrillar protein rose with the increase of H2O2 concentration. However, TSPP inhibited the attack of hydroxyl radicals on myofibrillar protein to some extent. Moreover, the cross-linking degree of TSPP-treated (+TSPP) samples was obviously higher than that of untreated (?TSPP) samples. Irrespective of TSPP treatment, the storage modulus (G’) and gel strength of protein gels were gradually reduced with increasing H2O2 concentration, but they later rebounded after MTG treatment and the increase was negatively correlated with increasing H2O2 concentration. Compared to the untreated counterpart, TSPP-treated unoxidized samples showed a higher increase in G’ and gel strength, but the increment decreased faster upon oxidation, suggesting that TSPP treatment helps MTG cross-linking enhance gel properties of myofibrillar protein despite having a detrimental effect upon oxidative stress.
Effect of Different Modified Starches on Gel Properties of Myofibrillar Protein
WU Xiang, LI Xinfu, LI Cong, YANG Ting, ZHOU Hui, DU Xianfeng, XU Baocai
2020, 41(2):  22-28.  doi:10.7506/spkx1002-6630-20190227-209
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Starch-protein composites were prepared by separately adding different levels (0%, 4%, 6%, 8%, 10%, and 12%) of native corn starch (NCS), acetylated distarch phosphate (ADP), acetylated distarch adipate (ADA) and starch acetate (SA) to myofibrillar protein (MP) solution, and their rheological properties, gel strength, water-holding capacity and nuclear magnetic resonance (NMR) water relaxation time were measured. The results showed that the addition of starches significantly increased the storage modulus (G′) of MP, which began to increase at around 42 ℃. At this time MP began to form a gel, and the addition of modified starches significantly delayed the denaturation of MP (43–46 ℃). The gel strength of starch-protein composites reached its maximum when the addition level of modified starches was 8%, while NCS had no significant effect on the gel strength of MP (P > 0.05). The WHC of starch-protein composite gels with modified starches was about 13% higher than that with NCS (P < 0.05), and the best WHC occurred with the addition of SA and ADA. NMR analysis showed that the T2 relaxation time decreased with increasing level of modified starches, and T22 moved in the direction of fast relaxation, which indicates that the addition of modified starches reduced the mobility of water molecules. Therefore, among the modified starches, ADA has the most significant effect on the rheological properties, gel strength, WHC and moisture migration of MP. An appropriate amount (no greater than 10%) of modified starches can significantly improve the G’, gel strength and WHC of MP and decrease the water migration rate.
Effect of Salt Addition on Lipid and Protein Oxidation and Volatile Compound Formation in Harbin Dry Sausages
WEN Rongxin, HU Yingying, YIN Xiaoyu, WANG Yan, Kong Baohua, Chen Qian
2020, 41(2):  29-36.  doi:10.7506/spkx1002-6630-20190203-020
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The effects of different levels of salt addition (2.5%, 2.0%, 1.5%, and 1.0%) on the oxidation of lipids and proteins in Harbin dry sausages during fermentation were investigated. The results showed that reducing salt addition level led to lower peroxidation values, carbonyl contents and surface hydrophobicity of myofibrillar and sarcoplasmic proteins, and higher sulfhydryl contents in dry sausages (P < 0.05), indicating that NaCl can promote the oxidation of lipids and proteins in dry sausages during fermentation. Additionally, the amounts of volatile compounds in all groups gradually increased during fermentation, and there was a significant influence of salt addition on the generation of most volatile compounds (P < 0.05). With the decrease in salt addition, the total concentration of aldehydes decreased, while the total concentrations of ketones, acids, esters, and alcohols increased. Compared with the control (2.5%), there were lower concentrations of aldehydes, alcohols and acids in the sausage prepared with 2.0% salt, which were generated from the oxidation of lipids and proteins, despite higher concentrations of ketones, alcohols, acids and esters, which came from microbial metabolism. The salt addition level in dry sausages can be reduced to 2.0% given improved overall flavor of dry sausages.
Effect of a Blend of Texturized Soy Protein and Soy Protein Hydrolyzate on Dough Properties and Noodle Quality
ZHANG Yingying, GUO Xingfeng, WANG Ruihong, SHI Changshuo, REN Cong
2020, 41(2):  37-42.  doi:10.7506/spkx1002-6630-20190306-063
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In order to reduce the weakening effect of soy protein hydrolyzate (SPH) on the gluten network in dough, texturized soy protein (TSP) and SPH (degree of hydrolysis of 4.54%) were blended and used to replace wheat flour at levels of 6.0% and 2.2%, respectively in dough preparation. Changes in noodle quality, gluten characteristics, farinographic properties, and dynamic rheological properties of dough were determined in comparison with control. Results showed that compared with control, the elasticity of the noodles with TSP-SPH decreased; the softening degree of the TSP-SPH incorporate dough decreased, while the farinographic evaluation score increased. The dry and wet gluten content decreased to 5.10% and 15.65%, respectively, while the gluten index increased to 89.24%. The storage modulus and loss modulus of the TSP-SPH incorporated dough increased, but the loss factor decreased. The content of glutenin macropolymer increased significantly. These results revealed that TSP-SPH promoted the formation of disulfide linkage between gluten proteins, thus lowering the weakening effect of SPH on the gluten network.
Effects of Phloretin on Rheological Properties, Antioxidant Activity and Microstructure of Low Ester Pectin under Acidic Conditions
ZHANG Shuyi, CHOU Shurui, CUI Huijun, WANG Hanchen, LIU Xuan, LI Bin
2020, 41(2):  43-49.  doi:10.7506/spkx1002-6630-20190128-356
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This study aimed to understand the effect of added phlorizin on the gel and functional properties of low ester pectin (LEP). A mixed system of phlorizin and LEP was prepared by adding 0.05% to 0.40% phlorizin and was adjusted to pH 4.2. The storage modulus (G’), loss modulus (G’’) and tanδ of phlorizin-LEP mixed systems were studied by rheological analysis. The antioxidant capacity was examined by hydrogen peroxide radical scavenging capacity, and the microstructure was observed by scanning electron microscopy (SEM). The results showed that adding phlorizin in the range of 0.05%–0.40% could effectively increase the gel strength and enhance the antioxidant activity of LEP. SEM observation showed that the microstructure of LEP-calcium gels with phlorizin added was more uniform and denser. The results provide theoretical data for the application of phlorizin-LEP mixed systems.
Effect of Citric Acid Soaking on Cadmium Content of Parboiled Rice during Milling and on Its Quality Attributes before and after Cooking
ZHOU Xianqing, ZHANG Pengju, ZHANG Yurong, PENG Chao
2020, 41(2):  50-57.  doi:10.7506/spkx1002-6630-20180920-213
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The purpose of this research was to understand the effect of citric acid on the milling characteristics of brown rice, the cadmium content during milling and the quality of parboiled rice, aiming to provide useful data for the utilization of rice contaminated by cadmium to a certain by processing it into parboiled rice. Two samples of Hunan-grown Indica rice with excessive cadmium content were selected for parboiled rice making. Brown rice derived from husking of paddy pretreated by citric acid soaking, steaming and drying was ground by a gradual milling method. The changes in cadmium content, as well as the milling characteristics and appearance quality of parboiled rice with different whitening times were measured, and the mineral composition and cooking characteristics of parboiled rice and the texture characteristics as well as the sensory evaluation of appearance and eating quality of cooked parboiled rice were determined. The results showed that after citric acid soaking, the husk of brown rice was more easily ground, and the degree of bran removal from parboiled rice per unit time was improved. However, citric acid had no significant effect on the percentage of broken kernels of parboiled rice after milling. Although citric acid made the color of parboiled brown rice more yellowish, it had no significant influence on the color of parboiled rice. The addition of citric acid promoted the migration of Cd, K, Ca and Al from endosperm to outer tissue, but had little effect on the migration of Mn and Cu. It also promoted the migration of Na, Mg, Fe and Zn from rice hull to endosperm, and increased the contents of Na, Mg and other elements. The water absorption rate, volume expansion rate, iodine blue value, pH value and hardness after cooking of parboiled rice were all significantly reduced after soaking with citric acid solution. The color of parboiled rice was significantly increased as well as taste and overall sensory score after cooking.
Structure and Heat-Induced Gelation Properties of Soybean 7S and 11S Proteins
FENG Fang, LIU Wenhao, CHEN Zhigang
2020, 41(2):  58-64.  doi:10.7506/spkx1002-6630-20190121-243
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The present study aimed to investigate the relationship between the structural, physicochemical and gelation properties of soybean 7S and 11S proteins. The secondary structures were explored by Fourier transform infrared (FT-IR) spectroscopy with Gaussian peak fitting. The fluorescent probe 1-anilino-naphthalene-8-sulfonate (ANS), Ellman’s reagent and a zeta potential meter were used to determine the surface hydrophobicity, sulfhydryl content and particle size of the proteins, respectively. The hardness, gumminess and springiness of the protein gels were analyzed with a texture analyzer. The results showed that the surface hydrophobicity decreased with increasing proportions of α-helix and β-sheet, but increased with increasing proportions of random coil and β-turn. Higher surface hydrophobicity was advantageous to the formation of gel network. The optimal gelation conditions for soybean 7S protein were determined as follows: protein concentration 0.12 g/mL, temperature 90 ℃, pH 6–8; and Na+ concentration 0.002 g/mL; and for 11S soybean: protein concentration 0.12 g/mL, temperature 95 ℃, pH 8–9, and Na+ concentration 0.002 g/mL. The secondary structures of the proteins determined their surface hydrophobicity, while the surface hydrophobicity affected the formation of gels. Meanwhile, the external factors of gel formation also affected the surface hydrophobicity of the proteins.
Effect of Binding to Pectin on the Stability of Anthocyanins from Aronia melanocarpa Berries
WEI Jingqi, LI Dongnan, MENG Xianjun
2020, 41(2):  65-72.  doi:10.7506/spkx1002-6630-20190125-329
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In this study, the factors influencing the binding rate of pectin to anthocyanins from the fruits of Aronia melanocarpa were identified by ultrafiltration and centrifugation, and the optimal conditions for binding were found. The interaction between them under the optimal conditions was analyzed by high performance liquid chromatography (HPLC). The stability and antioxidant activity of anthocyanins were compared with those of its conjugate with pectin. The results showed that pH and pectin addition had a great influence on the binding efficiency. The presence of Ca2+ had a negative effect, while the addition of Mg2+ and carbohydrate had no significant effect. The optimal binding conditions were as follows: pH 3, and ratio of anthocyanins to pectin 1:2. Anthocyanins with more hydroxyl groups or glycosyl groups in L(+) configuration were more easily combined with pectin. Binding to pectin enhanced anthocyanin stability in both hot and gastrointestinal environments; however, the scavenging capacity against hydroxyl and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical cation and the Fe3+ reduction capacity of the conjugate were detectable but lower than those of anthocyanins.
Effect of Polysaccharides from Hawthorn Leaves on the Quality and Antioxidant Activity of Fermented Milk
ZHAO Yanyan, ZHAO Shengming, LI Shuai, KANG Zhuangli, WANG Zhengrong, ZHU Mingming, ZHAO Lu, MA Hanjun, HE Hongju
2020, 41(2):  73-79.  doi:10.7506/spkx1002-6630-20181213-159
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The effects of adding different amounts of polysaccharides isolated from hawthorn leaves (HLP) on the quality parameters of fermented milk were investigated, including total viable count, water-holding capacity, titratable acidity, color, texture, rheological properties, antioxidant activity and sensory properties. The quality characteristics of fermented milk were measured with a texture analyzer, a rheometer and a color difference meter, and the antioxidant activity was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method, salicylic acid method and Fe3+ reducing power assay. The results indicated that HLP could stimulate the growth of lactic acid bacteria and acid production during the fermentation process. When HLP was added at 0.12%, the fermented milk had the highest water-holding capacity of 60.24%; at an addition level of 0.16%, the fermented milk had the highest hardness, viscosity and chewiness. Simultaneously, the maximum DPPH and hydroxyl radical scavenging rate and Fe3+ reducing ability of fermented milk with added HLP were 80.7%, 81.6% and 0.56, respectively. These were significantly higher than those of the blank control group (P < 0.05). The addition of a certain amount of HLP can effectively improve the quality and antioxidant capacity of fermented milk. This study provides a theoretical basis and technical support for the application of hawthorn leaf polysaccharides.
Production of Calcium Lactate from Eggshell Fermentation by Enterococcus mundtii Cells Immobilized on Different Carriers
ZHAO Jingli, LIU Yuanyuan, MA Meihu
2020, 41(2):  80-86.  doi:10.7506/spkx1002-6630-20190630-421
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A large amount of eggshell is produced and discarded in China annually. In order to utilize this waste, Enterococcus mundtii was immobilized on sodium alginate (SA), sodium alginate-polyvinyl alcohol (SA-PVA) or sodium alginate-activated carbon (SA-C) and then used to convert eggshell to calcium lactate. The three immobilized cells were compared in their mechanical strength, mass transfer and calcium lactate production ability and the best one was characterized. The results showed that SA-C was found to be the optimum immobilization carrier that provided the maximum yield of calcium lactate of 101.02 g/L with a conversion rate of 82.43%. The yield of calcium lactate remained high after repeated fermentation for 18 times, and the fermentation cycle tended to be shortened by repeated use. The presence of residual eggshell in the fermentation broth effectively maintained the mechanical stability of the immobilized cells. Compared with the free cells, the operating stability as well as temperature, pH and storage stability of the immobilized cells were significantly improved in a certain range.
Optimization of Fermentation Conditions for γ-Aminobutyric Acid Production by Lactobacillus buchneri
SI Kuolin, XU Juanjuan, YUE Tianli, YUAN Yahong, GUO Chunfeng
2020, 41(2):  87-93.  doi:10.7506/spkx1002-6630-20181218-210
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Two Lactobacillus buchneri strains, S37 and J68, with great ability to produce γ-aminobutyric acid (GABA) had been isolated from Chinese traditional fermentable vegetables in our previous study. In this study, in order to further improve their GABA production ability, the fermentation conditions were optimized. The results showed that the optimal fermentation conditions for the two strains were as follows: time of 72 h, temperature of 35 ℃, L-monosodium glutamate (L-MSG) concentration of 400 mmol/L, and initial pH of 5.0. Under these conditions, the GABA yields for the two strains were 233.9 and 159.3 mmol/L, respectively, and the L-MSG conversion rates were 58.5% and 39.8%, respectively. The one-factor-at-a-time experiments demonstrated that folic acid, L-cysteine and manganese chloride significantly enhanced the GABA production of the two strains. The addition levels of these compounds were optimized to be 8.37 mg/L, 0.94 g/L and 0.60 g/L for strain S37, and 10.16 mg/L, 0.97 g/L and 0.60 g/L for strain J68, respectively by response surface methodology, resulting in GABA yields of 312.6 and 251.2 mmol/L and L-MSG conversion rates of 78.2% and 62.8%, respectively.
Effects of in Vitro Colonic Fermentation on Phenolic Content and Antioxidant Activity in Dietary Fiber from Highland Barley
ZOU Qingfei, YANG Shihua, LI Yongqiang, HUANG Yonghua, HUANG Jiaqi, LI Qing, LI Ziyu, HUANG Aixiang
2020, 41(2):  94-100.  doi:10.7506/spkx1002-6630-20181207-098
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In this study, changes in the phenolic content and antioxidant activity in soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) extracted from highland barley were determined during in vitro colonic fermentation for up to 48 h. The phenolic compounds in the fermentation broth were qualified and quantified by high performance liquid chromatography (HPLC). The results showed that the content of phenolic compounds in IDF increased gradually with the prolongation of fermentation time while that in SDF increased first and then decreased, reaching the highest level ((50.62 ± 2.45) μmol/g) after 30 h. The trend of antioxidant activity was similar to that of phenolic content for both IDF and SDF. A total of 18 phenolic compounds in the fermentation broths were identified, which were classified into three types: hydroxybenzoic acids, hydroxycinnamic acids and flavonoids. The contents of ferulic acid in both IDF and SDF increased first and then decreased during colonic fermentation, which reached the highest level after 24 h in IDF and after 5 h in SDF. This study showed that highland barley dietary fiber could slowly release bound phenolic compounds during colonic fermentation, thereby enhancing the content of free phenolics and antioxidant activity, indicating that highland barley dietary fiber possess potential health benefits.
Cryoprotective Effect of Acid-Cold Cross Stress on Lactobacillus fermentum
YANG Jie, GUO Jinfeng, LI Baokun, LU Shiling, WANG Qingling, DONG Juan, JIANG Caihong, JI Hua, WANG Tengbin
2020, 41(2):  101-106.  doi:10.7506/spkx1002-6630-20181228-343
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This study aimed to explore the protective effect of acid-cold stress treatment on Lactobacillus fermentum strain ATm during freeze-drying. We determined the survival rate, lag time and acidification curve of freeze-dried bacteria cells which had been subjected to acid-cold cross stress. Furthermore, the activities of lactate dehydrogenase (LDH) and ATPase and cell membrane integrity were determined. The results showed that the acid-cold cross stress (pH 4.5 and 4 ℃) significantly improved the survival rate (reaching 87.19%, which was higher than that observed with either treatment alone) and acidification rate of the freeze-dried cells. In conclusion, acid-cold cross stress could improve the freeze-drying survival rate of L. fermentum ATm, protect its viability, increase intracellular enzyme activities and preserve cell membrane integrity.
Screening for Ethanol-Degrading Strains and Evaluation of Antialcoholic Efficacy of Fermented Milk Product with Them
LIU Weiliang, MAO Ruixia, WANG Xuefeng, JI Yu, ZHAO Cunchao, WEI Guangqiang, HUANG Aixiang
2020, 41(2):  107-113.  doi:10.7506/spkx1002-6630-20190629-400
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In this experiment, 10 strains of lactic acid bacteria with good fermentation performance were screened for their ethanol tolerance and ethanol degradation ability, aiming to find strains with high ethanol degradation ability. Then the selected strains were used to develop fermented milk, and its antialcoholic efficacy was evaluated. The results indicated that Lactobacillus acidophilus was found to be the best strain to degrade ethanol. Under simulated gastrointestinal digestion conditions, the activation rates of ethanol dehydrogenase (ADH) in fermented milk with Lactobacillus acidophilus, Lactobacillus helveticus and Streptococcus thermophilus (2:1:1) were (36.87 ± 1.58)% and (33.64 ± 1.90)%, respectively; the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical cation scavenging abilities (glutathione equivalent) were (1 293.72 ± 4.12) and (729.98 ± 21.37) μmol/mL, and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging abilities (glutathione equivalent) were (16.14 ± 0.12) and (11.26 ± 0.10) μmol/mL, respectively. After intragastric administration of the fermented milk at different doses, blood alcohol levels in alcohol-drinking rats decreased, reaching 51.62 mg/100 mL at 3 h in the high dose group (P < 0.001). Additionally, the fermented milk reduced the serum activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) to different degrees in a dose-dependent way, and it had a potent protective effect on alcohol-induced liver injury. In summary, this study provides a scientific basis for developing antialcoholic products in the future.
Effects of Different Fermentation Conditions on Folate Synthesis of Lactobacillus plantarum
LI Qiangkun, LIU Chenjian, LUO Yiyong, YANG En, LI Xiaoran
2020, 41(2):  114-118.  doi:10.7506/spkx1002-6630-20181229-356
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In this study, Lactobacillus plantarum 4-3, producing folate at high yield, was investigated for the effects of natural pH and maintaining pH at 6.0 on its growth status and folate synthesis in skim milk or soybean milk. The results showed that strain 4-3 produced more folate when cultured in soybean milk. When the culture pH was controlled at 6.0, this strain could still maintain high cell density after the logarithmic growth phase and showed enhanced accumulation of folate. Real-time fluorescence quantitative polymerase chain reaction (qPCR) results showed that the expression levels of folate biosynthesis-related genes were higher at constant pH.
Knockout of ptsG and Co-Expression with Vitreoscilla Hemoglobin Enhance the Production of Serine Hydroxymethyltransferase in Escherichia coli
HAN Qin, XU Xinxing, WANG Ruxin, LI Xin, YAN Dazhong, WU Jing, LIU Jun
2020, 41(2):  119-125.  doi:10.7506/spkx1002-6630-20181114-165
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The phosphotransferase system G (ptsG)-deleted strain BL21(DE3)ΔptsG was obtained by Red homologous recombination. Recombinant plasmids pET-glyA and pET-SV were constructed and transformed separately into the host strain. As a result, the engineered strains BL21(DE3)/pET-glyA and BL21(DE3)ΔptsG/pET-glyA for expression of serine hydroxymethyltransferase (SHMT) from Escherichia coli were obtained as well as BL21(DE3)ΔptsG/pET-SV for co-expression of E. coli SHMT and Vitreoscilla hemoglobin (VHb). In LB medium, there was no significant difference between the growth of BL21(DE3)/pET-glyA and that of BL21(DE3)ΔptsG/pET-glyA, but in the stationary phase, the OD600 nm of BL21(DE3)ΔptsG/pET-SV increased by 21.3% compared to that of BL21(DE3)ΔptsG/pET-glyA. In LBG medium, the OD600 nm of BL21(DE3)ΔptsG/pET-glyA was 19.4% higher than that of BL21(DE3)/pET-glyA in the stationary phase, but was 21.5% lower than that of BL21(DE3)ΔptsG/pET-SV. In LBG medium, the SHMT activities produced by BL21(DE3)/pET-glyA, ΔptsG/pET-glyA and ΔptsG/pET-SV were 6.4, 7.7 and 9.6 times as high as that produced by the control strain, respectively. The results showed that knockout of the ptsG gene could increase the growth of E. coli in glucose-containing medium and SHMT expression, and this effect was enhanced by co-expression with VHb.
Analysis of Fungal Community Diversity during Fermentation and Drying of Hand-Made Fu Brick Tea by Illumina MiSeq Sequencing
CHEN Mengjuan, JIANG Liwen, XU Yuanhao, ZHOU Hongli, ZHOU Hui
2020, 41(2):  126-132.  doi:10.7506/spkx1002-6630-20181104-041
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In order to understand the changes in fungal species during the fermentation and drying of hand-made Fu brick tea, the fungal diversity at different times of fermentation (0, 4, 8 and 12 d) and drying (17 and 22 d) was analyzed using Illumina MiSeq high-throughput sequencing. The results showed that the fungal community was diverse during the early fermentation stage, but this diversity exhibited an overall declining trend as fermentation and drying proceeded?successively. After sequencing and data cleansing, a total of 990 522 valid Tags were obtained. After clustering, there were 186 operational taxonomic units (OTUs), which were annotated to 5 phyla, 14 classes, 29 orders, 47 families and 65 genera. Among all time points, the highest diversity of fungi was observed on fermentation day 0, and Aspergillus showed the highest relative abundance (40.59%), followed by Debaryomyces, Eurotium and Penicillium. However, Eurotium was the absolutely dominant genus at the other five time points. Its relative abundance reached 97.27% on fermentation day 4, and the average relative abundance of these five time points was 98.81%. In this study, accurate and detailed nalysis of the changes in the bacterial community structure and diversity during the fermentation and drying of hand-made Fu brick tea was achieved using Illumina MiSeq sequencing, which will provide a new idea for improving the processing of hand-made Fu brick tea and for understanding the underlying mechanism.
Effect of Thermal Pretreatment on Enzymatic Hydrolysis of Clam (Aloididae aloidi) and Flavor Characteristics of Hydrolysates
LI Xuepeng, LIU Yanwei, XIE Xiaoxia, ZHU Wenhui, LI Jianrong, ZHANG Yuyu, LI Tingting, YU Jianyang, MU Weili
2020, 41(2):  133-140.  doi:10.7506/spkx1002-6630-20181206-086
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In this study, the effects of different heating pretreatment conditions (temperatures of 50, 70, 90, 100 and 121 ℃, and time durations of 5, 10, 15, 20, 25 and 30 min) before enzymatic hydrolysis on the hydrolysis characteristics of Aloididae aloidi and the flavor characteristics of the hydrolysates were investigated by determining the degree of hydrolysis, the concentrations of soluble peptides, flavor nucleotides and glutamic acid content, and taste profile (analyzed by electronic tongue). Our aim was to provide a rationale for innovative preparation of marine shellfish-flavored seasonings. The results showed a 2:1 mixture of neutral protease and flavourzyme was found to be the enzyme of choice to hydrolyze A. aloidi protein, and that the resulting hydrolysate had good taste characteristics. With the increase of pretreatment temperature, the degree of hydrolysis, the concentrations of soluble peptides, taste nucleotides and glutamic acid and umami taste first decreased and then increased, while the bitterness value showed a fluctuating trend. The prolongation of thermal pretreatment time was detrimental to the hydrolysis of A. aloidi protein and the accumulation of taste substances, but it was beneficial to reduce the bitterness value. To a certain extent, the heating pretreatment could improve the flavor and color of A. aloidi hydrolysates. The optimal pretreatment conditions were 70 ℃ and 10 min.
Inhibition Mechanism and Application of Lactic Acid Bacteria on N-Nitrosamine Formation
LI Xiuming, LIU Jingjing, YAN Lijuan, YANG Hua, WANG Yang, MA Lizhen
2020, 41(2):  141-147.  doi:10.7506/spkx1002-6630-20181202-014
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This study aimed to explore the inhibition mechanism of Lactobacillus starter culture PRO-MIX5 (containing Staphylococcus xylosus + Lactobacillus sake + Lactobacillus paraplantarum), which had been obtained in our previous study and found to effectively inhibit the formation of N-nitrosamines in Harbin red sausage, on the formation of N-nitrosamines. PRO-MIX5 was cultured in both minced meat medium and MRS medium for stepwise screening using nitrite degradation system and N-nitrosodimethylamine (NDMA) generation system. As a result, we found that the cell debris but not the metabolites, intracellular enzymes or whole cells could inhibit NDMA formation. Furthermore, the effect of the type of inducer added to MRS medium and the amount of cell debris added on the inhibition of NDMA formation was investigated. Finally, confirmation experiments were conducted by adding the cell debris obtained under optimized conditions at levels of 0.05%, 0.25% and 0.5% (on a wet mass basis) to Harbin red sausage and bacon. The results showed that the cell debris of PRO-MIX5 inhibited NDMA formation. A good inhibition effect was observed by culturing PRO-MIX5 in MRS medium containing 9 N-nitrosamines at a concentration of 0.04 μg/mL. Among the three addition levels, the cell debris at 0.05% showed the highest inhibition effect on the formation of the N-nitrosamines in both Harbin red sausage and bacon with inhibition percentages of 41.04% and 13.83%, respectively, and therefore its application could give good results.
Selection of Indigenous Saccharomyces cerevisiae Strains from Spontaneous Fermentation of Vidal Icewine in Huanren Region and Evaluation of Their Oenological Properties
SHEN Jingyun, ZHANG Boqin, DUAN Changqing, YAN Guoliang
2020, 41(2):  148-157.  doi:10.7506/spkx1002-6630-20180903-022
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To obtain suitable yeast for Vidal icewine production, a rapid selection procedure was proposed in this study. Nine Saccharomyces cerevisiae strains were selected from spontaneous fermentation of Vidal icewine in Huanren region by determining their tolerance to ethanol and SO2. The oenological evaluation in a flask and a fermenter showed that all the isolates could complete the alcoholic fermentation of Vidal icewine and produced different aroma profiles as compared to the commercial strain DV10 as evidenced by principal component analysis (PCA). SC42 and SC45, isolated at the final stage of spontaneous fermentation, were finally selected for their high fermentation activity. SC42 produced higher amounts of higher alcohol and esters along with a lower amount of acetic acid, while SC45 generated higher levels of glycerol, esters, trans-rose oxide and β-damascenone. Our present results proved the feasibility of this simple method to select suitable yeast strains for icewine industrial production, and also suggested that using indigenous Saccharomyces strains is a feasible way to improve the aroma quality and diversity of icewine products.
Isolation, Identification and Enzymatic Characteristics of Kluyveromyces marxianus Producing β-D-Galactosidase
ZHENG Yi, ZHANG Jian, CAO Yongqiang, ZHAO Xiao, YU Zhijian, CHEN Chao, YANG Zhennai
2020, 41(2):  158-165.  doi:10.7506/spkx1002-6630-20181120-226
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A strain, named ZX-5, with the ability to produce a high yield of β-D-galactosidase was isolated from traditional Tibetan kefir, and identified as Kluyveromyces marxianus by DNA internal transcribed spacer (ITS) sequence analysis. We found 2.0% galactose and 1.0% tryptone to be the optimal carbon and nitrogen sources, respectively. The optimal fermentation conditions were determined as follows: temperature 30 ℃, initial medium pH 6.5, medium volume 30%, shaking speed 100 r/min, inoculum size 2.0% and fermentation time 36 h. The activity of β-D-galactosidase produced under these conditions was 2.60 U/mL. Furthermore, the crude enzyme solution was purified by ammonium sulfate fractionation and DEAE-Sepharose fast flow ion-exchange chromatography to a specific activity of 157.35 U/mg. The purified β-D-galactosidase exhibited the maximum catalytic activity at 35 ℃ and pH 6.0, and had good stability at 20–40 ℃ and pH 5.0–7.0. Mn2+ could promote the enzyme activity. When the β-D-galactosidase produced by strain ZX-5 was used to decompose lactose and produce galacto-oligosaccharide under the conditions of 35 ℃, lactose concentration of 60 g/100 mL and enzyme concentration of 1.0 U/mL, the hydrolysis rate of lactose was 68.34% (after 50 h) and the yield of galacto-oligosaccharide was 34.70% (after 40 h), showing good potential application prospects.
Effects of Saccharomyces cerevisiae Strains with Different Killer Activities on Yeast Diversity during Inoculated Fermentation of Cabernet Sauvignon
SUN Yue, ZHANG Fangfang, CHU Suixing, LI Jiaxing, SHAO Shuai, ZHANG Junxiang
2020, 41(2):  166-172.  doi:10.7506/spkx1002-6630-20190109-100
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In this study, Cabernet Sauvignon was inoculated with different strains of Saccharomyces cerevisiae, NXU17-26 (natural strain), UCD522 (sensitive strain) and UCD2610 (killer strain), or naturally fermented (control) in order to investigate the effects of these yeast strains on the fermentation performance and yeast diversity during the fermentation process. The results showed that the inoculated strains initiated fermentation more rapidly and exhibited a higher fermentation rate compared to spontaneous fermentation. A total of 480 yeast isolates were classified into 7 phenotypes by using Wallerstein Laboratory Nutrient (WLN) agar. In addition, 26S rDNA D1/D2 domain sequence analysis found that they belonged to 5 species in 4 genera: Hanseniaspora uvarum, Pichia kluyveri, Hyphopichia burtonii, S. cerevisiae and Pichia kudriavzevii. All of the yeast species were found in the spontaneous fermentation, while the yeasts isolated from the inoculated fermentations were H. uvarum and S. cerevisiae. Interdelta fingerprints showed that the inoculated yeasts were the dominant strains in the corresponding fermentations. The natural strain NXU17-26 accounted for 63.46% of the S. cerevisiae strains isolated from the fermentation inoculated with NXU17-26. In the fermentation inoculated with it, the sensitive strain UCD522 accounted for 44.68% of the S. cerevisiae strains isolated, while the indigenous S. cerevisiae NXU18-15 showed strong competitiveness with a percentage of 34.04%. The killer strain UCD2610 accounted for 62.74% of the S. cerevisiae strains during the corresponding fermentation. According to UPGMA cluster analysis, the genetic diversity among S. cerevisiae strains isolated from the same fermentation was small, while the genetic diversity between S. cerevisiae strains isolated from different fermentations was large.
Screening for Antioxidant Probiotics and Their Protective Effect on Oxidative Damage Induced by Acrylamide in Intestinal Epithelial Cells
LI Tong, WU Siqi, CAO Xin, SONG Jingyi, ZHANG Hongxing, XIE Yuanhong, JIN Junhua
2020, 41(2):  173-180.  doi:10.7506/spkx1002-6630-20181120-225
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Objectives: To screen for lactobacilli with high antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals in vitro and to evaluate their tolerance to simulated gastrointestinal environment and their protective effect against oxidative injury induced by acrylamide in intestinal epithelial cells. Methods: Lactobacillus GBE17 and GBE29, which were found to have strong antioxidant potential, were identified by were identified by 16S rDNA sequencing. The protective effect of the viable cells and cell-free culture supernatant of either strain on acrylamide-induced oxidative injury in Caco-2 cells was assessed by morphological observation and measurement of antioxidant compounds contents and enzyme activities in the cell culture supernatants and lysates. Changes in the viable cell count after 1–4 h of exposure to different pHs (3.0 and 2.5) and different bile salt concentrations (0.05% and 0.1%) were monitored. Results: The scavenging percentages of DPPH radical by the culture supernatants of L. plantarum GBE17 and L. salivarius GBE29 were 89.44% and 79.24%, respectively. Both treatment and prevention with GBE17 as well as prevention with GBE29 could increase cell viability by decreasing lactate dehydrogenase activity and increasing the activities of superoxide dismutase and catalase in Caco-2 cells. For both strains, the number of cells surviving pH 3.0 and 0.1% bile salt environments for 4 h was higher than 7.0 (lg(CFU/mL)). Conclusion: L. plantarum GBE17 and L. salivarius GBE29 have stress tolerance and show a protective effect against acrylamide-induced oxidative damage in Caco-2 cells by increasing intracellular antioxidant enzymes activities.
Optimization of Medium Components for Large-Scale Production of Intracellular Polysaccharides from Dictyophora indusiata in Submerged Fermentation
FENG Jie, FENG Na, LIU Yanfang, TANG Qingjiu, ZHOU Shuai, LIU Fang, ZHANG Jingsong, YANG Yan
2020, 41(2):  181-187.  doi:10.7506/spkx1002-6630-20181101-014
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The main purpose of this study was to increase the yield of mycelial polysaccharides from Dictyophora indusiata using a large-scale production process. Using a combination of one-factor-at-a-time method and response surface methodology with Box-Behnken design, the optimum medium formulation for the submerged fermentation of D. indusiata was determined as follows: glucose 32.3 g/L, yeast powder 4.5 g/L, potassium dihydrogen phosphate 2.1 g/L, and magnesium sulfate 2.5 g/L. The predicted yield of intracellular polysaccharides was 1.23 g/L, which was close to the experimental value from shake flask fermentation (1.19 g/L). The yields of intracellular polysaccharides in 5-, 30- and 50-L fermentors were 1.43, 1.28 and 1.26 g/L, respectively, which were 16.26%, 4.06% and 2.43% higher than the predicted values, respectively. In this study, the optimized fermentation process gave a high yield of intracellular polysaccharides. Thus, this process provides a good basis for the large-scale production of D. indusiata mycelial polysaccharides.
Bacterial Community Structure and Diversity in Different Stacking Fermentation Rounds in Mechanized Maotai-Flavor Liquor Brewing
WANG Huan, XI Dezhou, HUANG Yongguang, CAO Wentao, YOU Xiaolong, CHENG Pingyan, HU Feng
2020, 41(2):  188-195.  doi:10.7506/spkx1002-6630-20181218-202
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In this study, the 16S rDNA fragments of bacteria in fermented grains from seven rounds of stacking fermentation in Maotai-flavor liquor mechanized brewing were sequenced and analyzed by high-throughput sequencing technology. The results showed that a total of 14 phyla and 456 genera were detected in the seven rounds. Proteobacteria, Actinobacteria, and Firmicutes were the dominant phyla. The core bacteria were Acinetobacter, Bacillus, Caulobacter, Kroppenstedtia, Lactobacillus, Lentibacillus, Oceanobacillus, Pediococcus, Rhodococcus, Sphingomonas, Thermoactinomyces and Weissella. Both Caulobacter and Rhodococcus were the unique genera of bacteria in the process of mechanized brewing, which may come from the mechanical equipment or environment. The core microorganisms were interrelated to each other, including the symbiotic bacteria Bacillus, Lactobacillus, Thermoactinomyces, Lentibacillus, Kroppenstedtia, Weissella, Pediococcus and Oceanobacillus, while Acinetobacter, Caulobacter and Philingomonas were negatively correlated with the other nine genera. Among the fermentation environmental factors, moisture, acidity and starch content had great influence on the microbial community structure. Bacillus, Thermoactinomyces and Pediococcus were positively correlated with starch content and negatively correlated with moisture and acidity. Caulobacter and Sphingomonas were negatively correlated with starch content and positively correlated with moisture, and Sphingomonas was also positively correlated with acidity. The core bacterial community in the process of mechanized fermentation of Maotai-flavor liquor revealed in this study lays a scientific foundation for further theoretical research and engineering application of mechanized fermentation of Maotai-flavor liquor.
Diversities of Culturable Yeast and Bacillus and Their Relationship with Process Parameters during the Production of Sichuan Luzhou-Flavor Daqu
XIANG Huiping, LIN Yijin, GUAN Tongwei, ZHANG Jiaxu, SHANG Hongguang, ZHAO Xiaolin, JIAO Shirong, FENG Xu, YANG Yang
2020, 41(2):  196-201.  doi:10.7506/spkx1002-6630-20181217-179
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This study was aimed at investigating the diversities of culturable yeast and Bacillus during the production of Sichuan Luzhou-flavor Daqu and at analyzing their relationship with process parameters (physicochemical and quality indexes). The process parameters were monitored according to the national light industry standard QB/T 4257-2011, and the selective isolation of yeast and Bacillus from 11 samples was performed by using pure culture technique. A total of 194 yeast strains were obtained and after molecular biological identification, they were assigned to nine genera that belong to the phyla Ascomycota and Basidiomycota, seven of which were clustered into the order Saccharomycetales. A total of 148 strains of Bacillus were obtained and identified as 8 species, with Bacillus subtilis being the dominant one. In addition, the best usage time of Sichuan Luzhou-flavor Daqu was between day 90 and 180 of the production process, and the quality of Daqu decreased greatly with the prolongation of storage period. Redundancy (RDA) analysis showed that physicochemical indexes were mainly negatively correlated with the diversities of yeast and Bacillus. There were six key species contributing to the quality of Daqu, including Kazachstania exigua, Candida tropicalis, Wickerhamomyces anomalus, B. subtilis, B. horneckiae and B. megaterium. There were abundant species diversities of yeast and Bacillus during the production process, and they were not only regulated by the physicochemical indexes during the production process, but also affected the quality of Daqu.
Metabolic Engineering of Escherichia coli for Production of trans-4-Hydroxy-L-Proline
LI Qiang, HAN Yakun, JIANG Shuai, ZHANG Yue, WU Heyun, XU Qingyang, XIE Xixian
2020, 41(2):  202-207.  doi:10.7506/spkx1002-6630-20181105-056
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In this study, we obtained a novel L-proline-4-hydroxylase with high activity from Micromonospora sp. CNB394. Then we successfully constructed a trans-4-hydroxy-L-proline-producing strain named HYP15 by enhancing the L-proline synthesis pathway and introducing the high-activity L-proline-4-hydroxylase into Escherichia coli using clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR-Cas9)-mediated gene editing. The strain could efficiently produce trans-4-hydroxy-L-proline utilizing glucose as the carbon source. HYP15 produced 13.6 g/L trans-4-hydroxy-L-proline after 30 h of fermentation in shake flasks and produced 48.6 g/L trans-4-hydroxy-L-proline with conversion ratio of sugar to acid of 21.6% and average productivity of 1.22 g/(L·h) after 40 h of fed-batch fermentation in a 5-L bioreactor and, therefore, could be promising for industrial application.
Isolation of Bacillus subtilis natto from Chinese Traditional Fermented Soybean Foods and Their Use in Fermentation of Natto
LIU Yanmin, SHEN Lu, WANG Kang, YAN Jinping, CHAGAN Irbis
2020, 41(2):  208-214.  doi:10.7506/spkx1002-6630-20181116-186
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In this study, 8 strains of Bacillus subtilis were isolated from Chinese traditional fermented soybean food and straw samples, which were found to have similar properties to B. subtilis natto based on protease and nattokinase activities, poly-L-glutamic acid (γ-PGA) production ability and biotin-dependent properties. Phylogenetic analysis of the isolated strains was performed using the 16S–23S rRNA internal transcribed spacer (ITS) sequence. The results showed that these strains shared high similarity (93%–97%) to the reported strains of B. subtilis natto and they were clustered into one cluster, independent of other strains of B. subtili. The nattokinase activities of natto prepared from strains TC100 and TC103 were the highest, which were 550 and 519 U/mL, respectively. The natto products fermented by strains HN48 and TC100 scored the highest (19 points) in sensory evaluation. In summary, all these strains were identified as B. subtilis natto according to their morphology and the phylogenetic analysis based on the ITS sequence. They could be promising as an industrial strain for natto production.
Differences between Huangshui from Old and Young Mud Pits of Chinese Strong-Flavor Liquor and Effect of Static Culture on It
ZHANG Huimin, MENG Yajing, WANG Yanli, LI Anjun, LIU Guoying, YUAN Zhiqiang, ZHANG Yan, XING Xinhui
2020, 41(2):  215-222.  doi:10.7506/spkx1002-6630-20190531-382
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In this study, the physicochemical properties and bacterial compositions of fresh and statically-cultured Huangshui (HS) from old and young strong-flavor-liquor pits were analyzed. Compared with young-pit fresh HSs, the contents of organic acids, such as butyric acid, caproic acid, valeric acid and acetic acid, and ammonium nitrogen in old-pit fresh HSs were higher. After 5 months of closed static culture, the values of starch, reducing sugar and acidity were decreased in both bit HSs, while the content of ammonium nitrogen was increased. In addition, in old-pit HSs, the contents of caproic acid and valeric acid were significantly decreased; in young-pit HSs, the content of alcohol was significantly decreased, while the contents of butyric acid and acetic acid were significantly increased. The bacterial compositions in old/young-pit fresh HSs were similar to each other, and in both fresh HSs Lactobacillus occupied absolute advantage with abundance of > 95%. After closed static culture, the abundance of Lactobacillus was reduced to 52.5% and 68.55%, respectively, while the abundance of some other aerobic/anaerobic bacteria was increased, including many pit mud (PM)-benefiting anaerobic bacteria. The cluster analysis indicated that static culture had a greater influence on the bacterial communities of HSs as compared with cellar age. The redundancy analysis (RDA) indicated that the reducing sugar showed the highest degree of interpretation of the correlation in RDA analysis, up to 65%. This study preliminarily proved the aging function of closed static culture on the bacteria in HSs, which would make it possible future targeted HS culture to promote the bacterial aging in new PM.
Component Analysis
Effects of Potato Flour on Baking Properties and Flavor Compounds of Bread
MENG Ning, SUN Ying, LIU Ming, ZHANG Peiyin, LIU Yanxiang, TAN Bin
2020, 41(2):  223-229.  doi:10.7506/spkx1002-6630-20190225-177
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The effects of adding 15% potato flour on the baking characteristics of bread were studied using pure wheat bread as the control, and the profile of volatile flavor compounds in potato incorporated bread was analyzed by electronic nose and headspace solid phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS). The results showed that the addition of potato flour had a significant impact on the quality of bread. Potato flour increased the specific volume to 4.12 mL/g and moisture content by 7%, reduced the hardness by 6 N, decreased the water activity, significantly enhanced the color and overall acceptability, and effectively improved the shelf-life and baking quality of bread. The main flavor components identified by electronic nose contributed to 97.3% of the total variance, indicating that the flavor of pure wheat bread could be distinguished from that of potato incorporated bread. SPME-GC-MS analysis showed that the main volatile components of the two breads were esters. The relative content of each of these volatile components was changed by adding potato flour. Mint ketone, p-menth-3-ene, 1-methyl-4-(1-methylethylidene)-cyclohexene were exclusively detected in potato incorporated bread, which showed an obvious increase in the number and amount of olefins.
Effect of Main Ingredients on Flavor Quality of Xinjiang Spicy Chicken Seasoning
GENG Qiuyue, TIAN Honglei, ZHAN Ping, WANG Peng, XI Jiapei, JI Yunyun, WANG Yongxiao
2020, 41(2):  230-237.  doi:10.7506/spkx1002-6630-20190126-335
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Gas chromatography-mass spectrometry (GC-MS) was used in this study to detect the volatile substances of several formulations of Xinjiang spicy chicken seasoning with different proportions of Sichuan pepper (Zanthoxylum bungeanum) oil, chili oil and chicken broth. Meanwhile, quantitative descriptive analysis (QDA) in terms of six sensory attributes namely, chicken-like flavor, sourness, slight numbing sensation, spiciness, kokumi and degree of simulation (DS) was performed on these formulations. It was shown that adding Sichuan pepper oil, chili oil and chicken broth had significant effects on the contents of flavor components. The QDA results indicated that Sichuan pepper oil had a greater contribution to the overall flavor than the other ingredients. The partial least squares regression (PLSR) analysis revealed that sabinene, myrcene, cinene and linalool had a significantly positive correlation with the DS and numbing flavor, terpinolene, 1-octen-3-ol, pentanal, furfural and 2-acetylpyrrole were significantly correlated with the spiciness, and 2-pinene, terpinolene, 1-octen-3-ol, (E,E)-2,4-decadienal, carvone and piperiton were significantly correlated with the chicken-like flavor.
Comparative Analysis of Non-Salt Taste Compounds in Featured Smoked Chickens from Different Regions
LIU Dengyong, ZHAO Zhinan, WU Jincheng, ZOU Yufeng, QU Wenna, LI Yan
2020, 41(2):  238-243.  doi:10.7506/spkx1002-6630-20190105-070
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In order to find out the difference in taste among commercial smoked chickens, we carried out a comprehensive evaluation of the taste compounds of featured smoked chicken products from different regions in China. Six representative brands of featured smoked chickens were selected for analysis of free amino acids (FAA) and nucleotides. The taste activity value (TAV) and equivalent umami concentration (EUC) were used to evaluate the taste and umami intensity of the taste compounds. Taste profile was determined using an electronic tongue and compared among samples. The results showed that there were significant regional differences in free amino acid and nucleotide contents of smoked chicken (P < 0.05). Glutamate (Glu) and 5’-inosinic acid (5’-IMP) were found to be the main umami compounds of smoked chicken. The EUCs of the six smoked chickens were in the range of 0.56%–16.08%. The results of electronic tongue demonstrated that umami and richness were the important taste characteristics of smoked chicken. Among these tested samples, Liaocheng smoked chicken had the strongest richness, while Tengqiao smoked chicken had the strongest umami. In summary, Glu and 5’-IMP are the main umami compounds, and umami is the most important taste characteristic of smoked chicken; the difference in umami compounds may be related to local food cultures and consumption habits.
Analysis of Key Odorants Responsible for Different Chestnut-Like Aromas of Green Teas Based on Headspace Solid-Phase Microextraction Coupled with Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry and Odor Activity Value
ZHANG Mingming, YIN Hongxu, DENG Yuliang, YAO Yuefeng, JIANG Yongwen, HUA Jinjie, YUAN Haibo, YANG Yanqin
2020, 41(2):  244-252.  doi:10.7506/spkx1002-6630-20190126-337
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The volatile components of green tea samples with three different typical chestnut-like aromas were investigated using headspace solid phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOFMS). The key odorants responsible for chestnut-like aroma were identified based on their odor activity values (OAV). The results showed that a total of 79 compounds were identified as common components among the three chestnut-like aromas, the majority of which were terpenes, while aldehydes showed the highest content. Moreover, 12 compounds with OAV ≥ 1 were identified as the key odorants responsible for the chestnut-like aromas, among which hexanal, 1-octen-3-one and trans-β-ionone exhibited higher OAV (≥ 10). Notably, 1-octen-3-one showed the highest OAV ( > 100) in all three chestnut-like aroma types. In addition, based on the OAV results, the key aroma components added at the same concentrations and ratios to the simulation system for aroma reconstitution. The cosine values of reconstituted samples and standard references for the three typical chestnut-like aromas were all above 0.97. The contribution of 12 key aroma components to the characteristic aroma of chestnut-like green teas were preliminarily confirmed, and the reliability was further confirmed by aroma reconstitution experiments. The results provide theoretical support for qualitatively and quantitatively evaluating green tea aroma compounds.
Nutritional Evaluation and Analysis of Volatile Flavor Components of Plain Mayonnaise
ZHANG Caixia, XI Yinci, YANAGISAWA Takuya, ZHOU Fen, YIN Mingyu, NIU Chen, WANG Xichang
2020, 41(2):  253-258.  doi:10.7506/spkx1002-6630-20190305-055
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To determine its nutritional and flavor quality, plain mayonnaise was analyzed for nutrient composition by conventional analysis method and for volatile components, headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). Based on their sensory threshold and relative odor activity values the contribution of the volatile flavor components to the overall flavor was evaluated. The results showed that the moisture, ash, crude protein and crude fat content of plain mayonnaise were 17.70%, 1.77%, 2.67% and 76.26%, respectively; it contained abundant essential amino acid (accounting for 34.58% of the total amino acids) with an essential amino acid index of 0.77, indicating that the mayonnaise is a valuable food protein source. The most prominent fatty acid in plain mayonnaise was oleic acid, which was rich in unsaturated fatty acids. The umami amino acids were mainly glutamic acid and aspartic acid, accounting for 63.94% of the total amino acids. The most abundant mineral element was Na (7.56 mg/g). A total of 35 volatiles were detected in the mayonnaise. The key flavor components identified included acetic acid, benzeneacetaldehyde, nonanal, undecanal, tetradecanal, ethyl acetate, and isobutyl isothiocyanate.
Pattern of Variations in Volatile Substances and Formation Mechanism of Characteristic Aroma Substances in Pixian Broad-Bean Paste
LIN Hongbin, BI Xiaopeng, FANG Jiaxing, LIU Yan, LIU Ping, DING Wenwu, CHE Zhenming, HE Qiang
2020, 41(2):  259-266.  doi:10.7506/spkx1002-6630-20190104-050
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Gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and electronic nose (E-nose) were used to study the changes in the aroma compounds in Pixian broad-bean Paste during its production process. The changes in aroma compounds were analyzed from the raw material to the starter-making, fermentation at constant temperature, and post-fermentation stages. The formation mechanism of characteristic aroma substances was explored, and correlation analysis was carried out on the aroma substances at different stages. The results showed that the number of volatile substances increased initially and then decreased during the fermentation process. Benzaldehyde was mainly converted from benzyl alcohol; furfural was mainly derived from the degradation of sugars; soamyl alcohol was produced by leucine conversion; 4-ethylphenol and 4-ethyl-2-methoxyphenol were mainly derived from fermented hot pepper; 2,3,5,6-tetramethylpyrazine was derived from board beans; phenylethanol and phenylacetaldehyde were mainly derived from microbial metabolism. Moreover, the degradation of methionine may be responsible for 3-methionyl propanal. The starter-making stage contributed minimally to the aroma, which accumulated mostly during the constant-temperature fermentation stage. Fermented hot pepper made a large contribution to the aroma at the early stage of fermentation but resulted in reduced aroma concentration at the late stage. During the first six months of post-fermentation, the concentration of aroma compounds changed slowly, but dramatically from month 6 to 12; however, it gradually reduced after 1 year. The correlation analysis showed that the aroma substances at the early stage of fermentation were significantly different from those at the late stage.
Processing Technology
Preparation and Stability Evaluation of Anthocyanin Microcapsules by Emulsification/Internal Gelation with Optimized Spray Drying
MAO Ying, SHUAI Xiaoyan, WANG Huiling, ZHOU Lan, LI Jia, LI Man, YANG Ning, HE Jingren
2020, 41(2):  267-275.  doi:10.7506/spkx1002-6630-20181228-330
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Spray-dried microencapsulated anthocyanins were prepared by emulsification/internal gelation with sodium alginate as the wall material. The drying process was optimized. The particle size and morphology of anthocyanin microcapsules were investigated. The stability of native and microencapsulated anthocyanins against light, temperature and gastrointestinal digestion was also evaluated. The optimal process parameters were determined as follows: heater temperature of 120 ℃, feeding rate of 12 r/min, and vacuum pressure of 0.03 MPa, giving a microencapsulation rate of 75.12% and an average particle size of 558.2 nm. The preservation rates of free and microencapsulated anthocyanins were 63.7% and 82.1%, respectively, after being kept for 5 h in light compared to 78.6% and 91.4% in darkness. The half-life of free anthocyanins was 2.54 h at 90 ℃ while that of anthocyanin microcapsules was 6.39 h. After gastric digestion for 2 h, the retention rates of free and microencapsulated anthocyanins were 45.3% and 83.7%, respectively; the retention rate of free anthocyanins was only 0.9% after intestinal digestion for 4 h while that of anthocyanin microcapsules was as high as 24.4%. These results demonstrated that the anthocyanin microcapsules were more stable against light, temperature and gastrointestinal digestion than the free ones.
Effect of Cooking on the Quality of Fenneropenaeus chinensis
GU Saiqi, DAI Wangli, BAO Rongbin, CHEN Yuan, ZHOU Xuxia, DING Yuting,
2020, 41(2):  276-283.  doi:10.7506/spkx1002-6630-20190605-041
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This study investigated the effect of different cooking conditions (citric acid concentration and cooking time) on the quality of Fenneropenaeus chinensis as evaluated in term of relative activity of polyphenol oxidase, moisture, water-holding capacity, astaxanthin content, protein content and extraction yield, color, texture, sensory evaluation, and scanning electron micrograph. The results showed that the complete inactivation time of polyphenol oxidase in shrimp head was gradually shortened with the increase of citric acid concentration. However, too high citric acid concentration was not conducive to the taste of shrimp, and therefore the optimal concentration was determined to be 4 g/L. With prolonging cooking time, the moisture and water-holding capacity of shrimp muscle decreased gradually, the astaxanthin content increased first and then decreased, and the total protein content declined continuously. Myofibrillar and sarcoplasmic proteins were mostly denatured after 2 min of cooking. During the cooking process, L* and a* values increased first and then decreased, while b* values increased continuously. Hardness, cohesiveness and chewiness increased continuously, while the opposite trend was observed for elasticity. Sensory evaluation results showed that shrimps cooked for 4 min scored highest in sensory scores for each quality attribute and in overall sensory scores. Scanning electron microscopy (SEM) results showed that shrimp muscle fibers were gradually denatured by heating, resulting in a decrease in regularity, an increase in the gap between muscle fibers and aggravation of dimensional breakage. Taken together, the optimum cooking time was determined to be 4 min. The results of this study can provide a theoretical basis for shrimp product enterprises to optimize the production process and to improve product quality in the future.
Effect of Baking on Zeaxanthin Content in Corn Flour
WANG Jiaojiao, ZHENG Mingzhu, LIU Meihong, XIE Jiahan, WU Xi, JIN Zhibo, LIU Huimin, LIU Jingsheng
2020, 41(2):  284-290.  doi:10.7506/spkx1002-6630-20181227-321
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In this research, the effect of baking on the content of zeaxanthin in corn flour was analyzed. First of all, we explored the effect of baking temperature, baking time and water addition on zeaxanthin content using one-factor-at-a-time method. Next, the three factors were optimized using response surface methodology. The optimized conditions were as follows: baking temperature 190 ℃, baking time 30 min, and water addition at 75%. In three parallel experiments performed under these conditions, the zeaxanthin content in baked corn dough was 306.79 μg/100 g.
Ultrasound and Microwave-Assisted Synthesis of Linoleyl β-Sitosterol
YUAN Chuanxun, ZHANG Xueru, XU Yun, GUO Yuhua, JIN Risheng
2020, 41(2):  291-297.  doi:10.7506/spkx1002-6630-20181227-304
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Linoleyl β-sitosterol was synthesized by sequential microwave and ultrasonic treatment. Qualitative and quantitative analysis of the synthetic product was carried out. Single factor and orthogonal array design experiments were conducted to examine the effect of molar ratio of acid to alcohol, microwave heating time, number of microwave heating cycles and ultrasound irradiation time on the esterification rate in order to optimize the four conditions. The synthetic product was purified by solvent extraction and was analyzed by high performance liquid chromatography (HPLC), infrared spectroscopy, an element analyzer and nuclear magnetic resonance (NMR), and its oil solubility was studied. The results showed that the optimum conditions were as follows: molar ratio of acid to alcohol 2.2:1, microwave heating time 5 min, and 4 microwave heating cycles with 90 s ultrasonic irradiation apart, giving an esterification rate of up to 89.56%. The synthesized substance was identified as linoleyl β-sitosterol with a purity of up to 98.36%. The solubility of the linoleyl β-sitosterol in tea seed oil at different temperatures (-5, 4, 25 and 40 ℃) was more than 25 times higher than that of β-sitosterol under the same conditions.
Safety Detection
Potential Assessment of Stable Isotopes and Mineral Elements for Geographic Origin Identification of Eriocheir sinensis
LUO Renjun, JIANG Tao, CHEN Xiubao, XUE Junren, LIU Hongbo, YANG Jian
2020, 41(2):  298-305.  doi:10.7506/spkx1002-6630-20190109-108
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In the present study, chemometrics profiles of mineral elements and stable isotopes for Chinese mitten crabs (Eriocheir sinensis) from three geographic origins in China: the Yellow River (one location) and Liaohe River (two locations) were analyzed and compared with each other to assess the potential of the mineral elements and stable isotopes for geographic origin identification. The results showed that significant (P < 0.05) or highly significant (P < 0.01) differences in the contents of 7 elements (Na, Mg, Al, K, Zn, Sr, and Ba) and two stable isotopes (δ13C and δ15N) in crabs were found among locations, despite no significant differences (P > 0.05) in the contents of Ca, Mn and Cu. Nevertheless, the self-organizing map analysis of the mineral elements and stable isotope profiles visually clustered the two locations of Liaohe River into one group, which was distinguished from the remaining group of crabs from Dongying, located on the estuary of the Yellow River. Linear discriminant analysis showed that the accuracies of initial verification with the mineral elements alone and in combination with the stable isotopes were both higher than 95%, and, moreover, the combination of mineral elements and stable isotopes had an even higher potential for geographic origin identification.
Rapid Detection of Carminic Acid in Yogurt and Lactobacillus-Containing Beverage by Al3+ -Based Fluorescence Enhancement
LIU Lanxiang, YI Guandong, LI Kai, MA Jinju, XU Juan, SUN Yanlin, ZHANG Hong
2020, 41(2):  306-314.  doi:10.7506/spkx1002-6630-20190625-316
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The effects of solvents, carminic acid concentration, pH and metal ions on the fluorescence properties of carminic acid were systematically studied. The fluorescent intensity of carminic acid was the strongest at a concentration of 2.0 × 10-4 mol/L in an aqueous solution at pH 4. The selectivity of carminic acid to metal ions indicated that the addition of Al3+ could significantly enhance the fluorescence intensity of carminic acid thus improving the sensitivity of detection. A 2.0 × 10-3 mol/L aqueous solution of Al3+ (at) was used as the standard solution. The ?uorescence intensity of carminic acid was linear with its concentration ranging from 1.0× 10-5 to 8.0× 10-5 mol/L, and the limit of detection (LOD) was 5.0 × 10-6 mol/L. When the fluorescence method was applied to determine carminic acid in yogurts and Lactobacillus-containing beverages, the recoveries ranged from 96.6% to 110.5%, relative standard deviation (RSD) no more than 5.9%. This study provides an effective approach to rapidly and quantitatively detect carminic acid in foods.
A New Non-targeted Screening Method for Milk Powder Safety Based on Improved Spectral Angle Mapping
ZONG Jing, HUANG Zhixuan, CHEN Xiaoyu, CHEN Da
2020, 41(2):  315-320.  doi:10.7506/spkx1002-6630-20190625-313
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In this paper, a moving window spectral angle mapping-based Raman hyperspectral imaging method (MWSAM-RHIM) was proposed for non-targeted screening for milk powder safety, which could effectively compensate for the shortcomings of traditional targeted detection methods. In MWSAM-RHIM, an improved spectral angle mapping algorithm was used to calculate the spectral similarity of unknown samples. The pixels beyond the threshold were marked as adulterated to generate a visual binary image. The results showed that the recognition rates of negative and positive samples by MWSAM-RHIM method both reached 93.3%, indicating that this method can meet the needs of non-targeted screening for safety of dairy products and provide a new idea for rapid screening of other food samples.
Determination of Oxidized Triacylglycerol Polymers in Oils and Fats by High Performance Liquid Chromatography with Two Sequential Columns
DENG Qi, YUAN Zhong’an, HUANG Xuesong
2020, 41(2):  321-326.  doi:10.7506/spkx1002-6630-20190311-140
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This study aimed to establish a simple, rapid and accurate analytical method for the determination of oxidized triacylglycerol polymers (TGP) in oils and fats. Non-polar components (Non-PC) and polar components (PC), including oxidized triacylglycerol oligomers (TGO), oxidized triacylglycerol dimers (TGD), oxidized triacylglycerol monomers (ox-TGM), diacylglycerls (DG) and free fatty acids (FFA), were separated by high performance liquid chromatography with two sequential columns (silica gel column connected to Phenogel column) and detected by an evaporative light scattering detector. The peak area normalization method was used to quantitate TGP using DG as external standard. The eluent used was a gradient mixture of petroleum ether (A) and tetrahydrofuran (B). Elution was performed at a solvent flow rate of 0.7 mL/min in the following linear gradient mode: 0 min, 5% B; 20 min, 15% B; 30 min, 30% B; and 35 min, 5% B, and the analytical time was 50 min. The results showed that good separation of the above compounds was achieved. The method exhibited a good linearity with a correlation coefficient (R2) of 0.999 5. The limit of detection (LOD) of TGD was 156 mg/L, and the limit of quantitation (LOQ) was 267 mg/L. The recoveries of DG spiked samples were between 95% and 99% with relative standard deviation (RSD) of less than 2%. Moreover, the method presented good repeatability with RSD of less than 3%. This method could allow accurate quantification of TGP in oils and fats within 1 h with simple operation and without using extra experimental materials.