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Table of Content

15 July 2021, Volume 42 Issue 13
Basic Research
Biofilm Inhibition Activity and Mechanism of Action of Sodium Hypochlorite against Salmonella Derby
YAN Yuqing, ZHANG Yimin, DONG Pengcheng, MAO Yanwei, LIANG Rongrong, ZHU Lixian, LUO Xin
2021, 42(13):  1-9.  doi:10.7506/spkx1002-6630-20200615-201
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Purpose: In order to control the contamination of Salmonella Derby during food processing, the inhibitory effect of different concentrations of sodium hypochlorite on the biofilm formation of Salmonella Derby was studied and the underlying mechanism was investigated. Methods: The crystal violet staining and plate counting methods were used to observe the potential of sodium hypochlorite to inhibit and eradicate Salmonella Derby biofilm, and the content of extracellular polymeric substances (EPS), biofilm metabolism, micromorphology and swimming mobility of Salmonella Derby in the presence of sodium hypochlorite at different concentrations were observed. Results: The minimum inhibitory concentration (MIC) of sodium hypochlorite was 0.08% (V/V), and the sub-MICs (0.04%, 0.02% and 0.01%) of sodium hypochlorite could inhibit the formation of Salmonella Derby biofilm, and also eradicate mature biofilms and the effect of sodium hypochlorite with different sub-MICs was significantly different (P < 0.05). Sodium hypochlorite could significantly reduce biofilm metabolism of Salmonella Derby and inhibit biofilm exopolysaccharide synthesis, and the effect of sodium hypochlorite with different concentrations was significantly different (P < 0.05). The results of confocal laser scanning microscopy (CLSM) showed that sodium hypochlorite treatment greatly reduced the thickness of the biofilm, reduced the number of live bacterial cells, increased the number of dead bacterial cells, and transform the biofilm cells from an aggregated state to a dispersed one. Conclusion: Sodium hypochlorite at different sub-MICs has a significant inhibitory effect on the formation of Salmonella Derby biofilms, possibly by interfering with bacterial growth, metabolism and extracellular polysaccharide secretion.
Antibacterial Mechanism of Eugenol-Containing Composite Preservatives against Shewanella putrefaciens
WANG Ming, ZHANG Jiatao, ZHOU Bin, DING Jie, XU Zhaomeng, SUN Tong
2021, 42(13):  10-16.  doi:10.7506/spkx1002-6630-20200831-409
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This work was undertaken in order to study the antibacterial activity and underlying mechanism of eugenol-containing composite preservatives on Shewanella putrefaciens as the dominant spoilage bacterium in aquatic products. The composite preservatives tested included binary mixtures of eugenol with thymol, lactic acid, lysozyme (food-grade, 18 U/mg) and eugenol/lysozyme (biological-grade, 20 000 U/mg), while these compounds were used individually as controls. The morphological changes of bacterial cells before and after treatment with single and composite preservatives were observed by field emission scanning electron microscope (SEM) and transmission electron microscope (TEM). The cell membrane integrity and permeability, the degree of cell membrane damage and the activities of Na+, K+-ATPase and AKPase in the cell membrane of S. putrefaciens were determined. The results showed that eugenol had good antibacterial properties against S. putrefaciens, and could cause distortion, shrinkage, collapse or even significant dissolution of the cell membrane. The cell membrane structure was damaged to a certain extent, resulting in poor membrane integrity, increased membrane permeability and decreased Na+, K+-ATPase/AKPase activities. In combination with thymol, lactic acid, food-grade lysozyme and biological-grade lysozyme, eugenol showed a synergistic antibacterial effect, causing more serious damage to bacterial cell structure and consequently leading to poorer membrane integrity, a greater increase in membrane permeability and a significant decrease in Na+, K+-ATPase/AKPase activities (P < 0.05). The knowledge obtained in this study can provide a reference for the research and development of new preservatives for aquatic products.
Effect of Degree of Doneness on Structural and Oxidation Properties of Beef Myofibrillar Protein
WAN Hongbing, LI Haipeng, LEI Yuanhua, XIE Peng, ZHANG Songshan, FENG Yonghong, LIU Xuan, WANG Huan, SUN Baozhong
2021, 42(13):  17-25.  doi:10.7506/spkx1002-6630-20200717-229
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This study aimed to compare the differences in myofibrillar protein aggregation, oxidation and structural properties among beef M. longissimus dorsi cooked to different degrees of doneness (control, rare, medium rare, medium, medium well, well done, and over cooked). The results showed that the cooking process significantly affected myofibrillar protein aggregation, oxidation and structural properties. As the degree of doneness increased, myofibrillar protein solutions gradually changed from an aggregated state to a cleaved one; the content of protein carbonyl increased gradually, and the surface hydrophobicity and sulfhydryl content increased first and then decreased; the fluorescence intensity of dityrosine and intrinsic fluorescence intensity increased first, then decreased and finally increased again. The results of attenuated total reflection Fourier transform infrared spectroscopy analysis showed that the degree of medium cooking was the turning point in the evolution of protein secondary structure. As the degree of doneness increased from control to medium, the β-sheet relative content decreased, while the α-helix relative content remained stable, the aggregation of protein was mainly through intramolecular interactions; as the degree of doneness further increased to over cooked, the β-sheet relative content increased gradually, the α-helix relative content increased first and then decreased, and the protein was mainly intermolecularly aggregated. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) studies indicated that myosin heavy chain, α-actin and actin were involved in the thermal aggregation of myofibrillar proteins. As the degree of doneness increased, the gray values of myosin heavy chain and actin increased first and then decreased, and the gray value of α-actin increased continuously. The exact mechanisms need further study. The results from this study can provide a theoretical basis for the optimization of the frying process and the quality control of steak.
Residual Pattern and Predicting Modeling of Florfenicol in Eggs and Body Tissues of Laying Hens
BAI Xue, CHEN Yu, ZHAO Lijun, ZHANG Jing
2021, 42(13):  26-33.  doi:10.7506/spkx1002-6630-20200701-010
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The veterinary drug florfenicol is used widely to treat bacterial infections in farmed animals. Long-term intake of foods with florfenicol residues can cause drug resistance, immune suppression and other adverse effects on the body. The aim of this study was to investigate the residual pattern of florfenicol and its metabolite florfenicol amine in the eggs and some body tissues of laying hen fed a diet containing different florfenicol levels, and further develop a predictive model for veterinary drug residues. A total of 250 Roman hens 350 days old and weighing (1.97 ± 0.07) kg at peak production were arbitrarily assigned to five treatments each containing 50 hens, fed a diet supplemented with 0, 30, 60, 120 and 240 mg/(kg mb·d) florfenicol for 5 days, respectively. Eggs were collected every day, and the birds were slaughtered at different times after the termination of drug administration. Egg yolk, egg white, yolk, muscle and liver were collected to measure florfenicol and florfenicol amine concentrations by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that egg production rate was significantly decreased in the 240 mg/(kg mb·d) group from days 1 to 3 after administration compared to the other dose groups (P < 0.05), and returned to that observed in the control group on day 4. The residual levels of florfenicol and florfenicol amine were ranked as follows: egg yolk > yolk > egg white > liver > muscle, and the depletion time was in the decreasing order of egg yolk > yolk > egg white > muscle > liver. The florfenicol dosage and the depletion time as well as the interaction between them had significant effects on the residual amounts of florfenicol and florfenicol amine (P < 0.001), which was depicted by a quadratic polynomial model (P < 0.001). When it was administered to laying hens within the dosage range of 40–60 mg/(kg mb·d) according to the Chinese Veterinary Pharmacopoeia (2015 Version), the depletion time of flurfenicol was 1 day for muscle and liver tissues, 13 days for eggs and 21 days for yolk .
Stability and in Vitro Simulated Gastrointestinal Digestion Properties of Natural Soybean and Rapeseed Oil Body Emulsions
HE Shenghua, DENG Qianchun
2021, 42(13):  34-42.  doi:10.7506/spkx1002-6630-20200609-130
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The aim of this study was to explore the stability and in vitro simulated gastrointestinal digestion properties of natural soybean and rapeseed oil body (OB) emulsions. The basic chemical compositions of soybean and rapeseed OB were analyzed. The particle size, viscosity and microstructure were analyzed with a laser scattering particle analyzer, a rotary rheometer and a confocal laser scanning microscope. Also, the stability of the two natural emulsions under various environmental stresses (pH, ion concentration and thermal treatment) was investigated, and changes in the protein profile and particle size during simulated gastrointestinal digestion were investigated. The results showed that the protein content of soybean OB was significantly higher (P < 0.05) than that of rapeseed OB while the lipid content was significantly lower (P < 0.05) than that of rapeseed OB. The particle sizes of the two emulsions decreased along with the increase in OB concentration, the particle size of soybean OB emulsion being significantly lower than that of rapeseed OB emulsion, as also demonstrated by the confocal laser scanning microscopic images. The droplet interface in soybean OB emulsion was covered with a large amount of oleosins. The viscosity of soybean OB emulsion was higher than that of rapeseed OB emulsion. Soybean OB emulsion showed large particle and was unstable at pH 4.0 and 100, 200 mmol/L NaCl concentration, whereas NaCl concentration caused little effect on the stability of rapeseed OB emulsion. Soybean OB emulsion was stable at 85 ℃ for 15 min, while rapeseed OB emulsion was sensitive to temperature. The two emulsions were consecutively treated with simulated gastric?fluid (SGF) and simulated intestinal fluid (SIF) for 180 minutes each.?The hydrolysis of protein in soybean OB emulsion was fast in the first 30 min of gastric digestion and then tended to level off. However, the protein of rapeseed OB emulsion was gradually hydrolyzed during the whole gastric digestion process. The particle size of the two emulsions was higher after the gastric digestion. The particle size of soybean OB emulsion was significantly reduced after the intestinal digestion, while the particle size of rapeseed OB emulsion showed no significant change.
Effect of Preparation Methods on the Structural and Functional Properties of Whey Protein Isolate-Chlorogenic Acid Conjugates
CHEN Weijun, LIU Donghong, LI Yuncheng, MENG Fanbing, LIU Dayu
2021, 42(13):  43-50.  doi:10.7506/spkx1002-6630-20200922-269
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Objective: To evaluate the effect of preparation methods on the structural and functional properties of whey protein isolate (WPI)-chlorogenic acid (CA) conjugates. Methods: The methods tested were an alkali method, a free radical method and an enzymatic method. The reactive group content, CA amount of covalent binding, molecular structure, surface hydrophobicity, thermal stability, antioxidant activity and emulsion properties of WPI-CA conjugates were analyzed. Results: Free amino groups, tryptophan and sulfhydryl groups all participated in the grafting reaction with free amino group being the major reactive group. The CA amounts of covalent binding of the conjugates prepared by the alkali, free radical and enzymatic methods were (52.70 ± 1.81), (42.57 ± 1.85), and (63.75 ± 2.50) μmol/g, respectively. The conjugates showed less α-helix relative content, higher random coil relative content and lower fluorescence intensity than WPI. Covalent bonding of CA induced by the alkali and enzymatic methods decreased the surface hydrophobicity and increased the thermal stability of WPI, while the free radical method led to the opposite results. The emulsion properties and antioxidant activity of the conjugates were higher than that of WPI, and the antioxidant activity was positively proportional to the amount of bonded CA. Conclusion: The highest grafting efficiency was obtained by the enzymatic method, and the prepared conjugates showed best thermal stability and antioxidant activity. This study can provide a reference for the preparation and application of protein-polyphenol conjugates as antioxidant carrier materials.
Enhancement of Antioxidant Activity of Chinese Yam by Fermentation with Cordyceps militaris
LI Huixing, ZHOU Yongkang, FANG Peiqi, ZHENG Lilin, HA Haiyang, XU Bin
2021, 42(13):  51-56.  doi:10.7506/spkx1002-6630-20200419-245
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The enhancing effect of Chinese yam fermentation with Cordyceps militaris on its antioxidant activity was studied, and the underlying mechanism was analyzed. Fresh and fermented (with Cordyceps militaris and its metabolites) samples were compared for differences in their antioxidant activity in terms of scavenging of superoxide anion and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical. Moreover, fingerprinting analysis by high performance liquid chromatography (HPLC) was conducted as well as scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR). The result showed that free radical scavenging rates of the fermented sample were significantly higher than the fresh sample (P < 0.05). The contents of total phenol, total flavonoids, total saponins were significantly higher in the former than in the latter (P < 0.05). The fermented sample contained some compounds not found in the fresh one, and there were significant changes in the contents of the six shared compounds between them. The microstructure of Chinese yam could be broken down by Cordyceps militaris. Sugars in Chinese yam such as polysaccharide and cellulose could be metabolized as a carbon source by Cordyceps militaris into phenols and saponins. This study confirmed fermentation with Cordyceps militaris to be effective in enhancing the antioxidant activity of Chinese yam, which may be mainly ascribed to the changes in the types and contents of bioactive components as well as the microstructure.
Optimization by Response Surface Methodology of the Formulation of Seaweeds, Fruits and Vegetables Extracts to Assist in Reducing Blood Glucose and Lipid Levels
ZHOU Sainan, ZHANG Qing, WANG Fahe, WANG Xiaomei, LI Zhaojie, XUE Changhu, TANG Qingjuan
2021, 42(13):  57-63.  doi:10.7506/spkx1002-6630-20200611-152
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The formulation of Sargassum fusiforme, curcumin (a vegetable bioactive compound) and punicalagin (a fruit bioactive compound) for assisting in lowering blood glucose and lipid levels was optimized using one-factor-at-a-time method and response surface methodology based on median inhibition concentration (IC50) for α-glucosidase and pancreatic lipase. The results showed that the best ratio of the water extract of Sargassum fusiforme to curcumin to punicalagin was 150:6:3 (m/m/m). The inhibition rates of α-glucosidase and pancreatic lipase were (47.77 ± 2.15)% and (74.18 ± 0.46)% by the optimized formulation, respectively, which were close to the predicted values from the response surface regression equation, indicating that the model was reliable. The IC50 values for inhibition of α-glucosidase and pancreatic lipase by the formulation were (0.56 ± 0.04) and (0.210 0 ± 0.000 3) mg/mL, which accordingly could assist in reducing blood glucose and lipid levels. This study provides a scientific basis for the development of dietary supplements that can help reduce blood glucose and lipid levels, which will help improve the utilization rate of natural resources of seaweeds, fruits and vegetables.
Bioactive Ingredients and Microbial Diversity in the Manufacturing Process of Fuzhuan Tea from Eucommia ulmoides Leaves
ZENG Qiao, DUAN Jie, BIAN Wenwen, LIU Jing, YU Zhenglü, HU Xin, YANG Wenjuan, LÜ Shenghua
2021, 42(13):  64-71.  doi:10.7506/spkx1002-6630-20210125-281
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In order to investigate the bioactive ingredients and microbial diversity in the manufacturing process of Fuzhuan tea from Eucommia ulmoides leaves, we examined the bioactive ingredients content and the microbial community structure in samples collected from different steps of the manufacturing process using several analytic methods and high-throughput sequencing content technology, respectively. Meanwhile, we further performed a correlation analysis between the bioactive ingredients and the microbial community structure. The results showed that in the manufacturing process, the contents of all bioactive ingredients detected presented an overall decreasing trend. Aspergillus was the dominant fungus in the whole manufacturing process and its relative abundance decreased gradually from the raw material to the steaming and shaping stage, and increased rapidly after the beginning of the flowering stage. The relative abundance of Aspergillus reached 95.58% on day 4 of flowering, and was more than 99.99% on day 8 and in all subsequent stages, indicating Aspergillus to be the absolute dominant flora. The bacterial community in the manufacturing process?was abundant, which was subordinated?to?7 phyla and 47 genera, of which the dominant bacteria were Rhodococcus, Ralstonia and Burkholderia-caballeronia-Paraburkholderia. From the raw material to day 8 of the flowering stage, the bacterial community diversity was high, with Ralstonia being the dominant genus. Starting from day 12, the bacterial community diversity decreased and the structure tended to be stable, while the relative abundance of Rhodococcus increased significantly, which was the dominant genus in the late stage of flowering and the maturing stage. The correlation analysis between the bioactive ingredients content and the abundance of the major microbial genera indicated that polysaccharides, free amino acids, polyphenols, chlorogenic acid, geniposide and aucubin content were significantly negatively correlated with the abundance of Aspergillus (P < 0.05), while they were correlated positively with Apiotrichum (P < 0.05). The content of total flavonoids was significantly negatively correlated with the abundance of Aspergillus (P < 0.05) but positively with the abundance of Apiotrichum (P < 0.01). The abundance of Rhodococcus was significantly negatively correlated with the contents of water extract as well as polysaccharides, total flavonoids, free amino acids, polyphenols, chlorogenic acid and geniposide (P < 0.01), but negatively with the contents of geniposidic acid and aucubin (P < 0.05). This study broadens the understanding of the bioactive components and microbial diversity in the manufacturing process of Fuzhuan tea from Eucommia ulmoides leaves, which will provide a basis for the formation and improvement of the quality of Fuzhuan tea from Eucommia ulmoides leaves.
Effect of Exogenous γ-Aminobutyric Acid on the Accumulation of Phenolics and Antioxidant Capacity in Germinated Soybean
DING Yuxuan, WANG Yao, YAO Yi’an, LI Wanmei, WANG Mian, WANG Pei, GU Zhenxin, YANG Runqiang
2021, 42(13):  72-78.  doi:10.7506/spkx1002-6630-20200614-189
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During seed germination, γ-aminobutyric acid (GABA) and phenolics are both accumulated, and GABA may play a regulatory role in the accumulation of phenolics. In this study, the effect of exogenous GABA at doses of 0, 2.5, 5, 10 and 20 mmol/L was investigated on the growth indices, total phenolics and phenolic acid contents and antioxidant capacity of germinated soybean grown in hydroponics. The results showed that 2.5, 5 mmol/L exogenous GABA could significantly increase the sprout length, mass, growth (P < 0.05). With the increase in GABA concentration, the contents of total phenolics and free phenolic acid increased gradually. When the concentration of GABA was 20 mmol/L, the content of total phenolics was enhanced by 1.39 times relative to the control group. However, the content of bounded phenolic acid increased firstly and then decreased with the increase in GABA concentration, reaching the highest value at 2.5 mmol/L concentration, proving that bound phenolic acid was released gradually and transformed into a free form. In addition, GABA treatment also improved the scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl, 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) cation radical and the activities of peroxidase, catalase and ascorbic acid peroxidase. The above findings indicated that exogenous GABA significantly promoted the growth of germinated soybean, regulated the activity of phenylalanine ammonia lyase, induced the accumulation of phenolics, and enhanced the activity of antioxidant enzymes as well as the free radical scavenging capacity in vitro, which will provide a theoretical basis for the development of soybean sprouts rich in phenolics.
Food Engineering
Preparation and in Vivo and in Vitro Sustained-Release Characteristics of Egg White Peptide Liposomes by Ethanol Injection Combined with High-Pressure Homogenization
ZHANG Ting, WEN Hedi, SONG Jingyi, GE Huifang, WANG Minghua, CHEN Yan, LIU Boqun, LIU Jingbo
2021, 42(13):  79-86.  doi:10.7506/spkx1002-6630-20200624-331
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In order to improve the stability of egg white peptides, high-pressure homogenization-assisted ethanol injection was used to prepare egg white peptide liposomes. The optimum technological conditions were obtained by single factor experiments as follows: cholesterol 2 mg/mL, egg yolk lecithin 10 mg/mL, egg white peptides 50 mg/mL, core-to-wall ratio 3:5, 40 MPa high pressure homogenization for 7 minutes, and ultrasonic treatment at 100 W for 30 s. Under these conditions, egg white peptide liposomes with an encapsulation efficiency of (65.7 ± 3.6)% were obtained. Using 1% Tween-80 as a stabilizer, the liposomes had good storage stability for 30 days. In addition, the results of in vitro and in vivo release experiments demonstrated that the product had good slow-release properties, and the concentrations of six essential amino acids accumulated in the serum of mice gavaged with the liposomes to a maximum level significantly higher in that observed with egg white peptides. Particularly, tryptophan was released from the liposomes into the serum of mice 3.5 hours later and phenylalanine, valine and methionine were released 2 hours later than from egg white peptides. Among the six essential amino acids, the highest concentration of lysine increased the most (by 523.53%) in the serum of mice administered with the liposomes compared with mice given egg white peptides, while methionine concentration exhibited the least increase (by 109.31%). In this study, egg white peptide liposomes with stronger stability, higher entrapment rate and better sustained-release effect were obtained, which could potentially be a promising candidate for amino acid supplementation. The knowledge acquired in this study will provide potential technical support for the development of egg white peptide-based functional products.
Effect of Ultrahigh Pressure on the Structure of Scallop Adductor Muscle
GONG Xue, CHANG Jiang, LI Danting, SUN Zhihui
2021, 42(13):  87-93.  doi:10.7506/spkx1002-6630-20200623-314
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We undertook this study in order to determine the shelling efficiency of scallops with ultrahigh pressure (UHP) and its impact on the structure of scallop adductor muscle (the 2 mm thick segment contacting with the shell) as studied by Raman spectroscopy and scanning electron microscopy (SEM). It was found that the main-chain structure and side-chain conformations of adductor muscle protein were greatly affected by UHP treatment. Notably, at 200 and 300 MPa, the intensity of the characteristic peaks of adductor muscle protein was increased, but the degree of protein denaturation was not very obvious. When the pressure was greater than 200 MPa, the oxygen atoms of the hydroxyl group on the benzene ring of tyrosine residues were gradually transformed from a hydrogen bond donor to a hydrogen bond acceptor, I850 cm-1/I830 cm-1 ratio was decreased, the buried tryptophan residues were gradually exposed to a polar environment, and the conformation of the disulfide bond was reduced. In conclusion, UHP can impact on the structure of scallop adductor muscle, which will provide a theoretical basis and technical support for the industrial production of scallop products and even other shellfish products.
Effect of Far-Infrared Variable-Temperature Aroma Enhancement Technology on the Flavor Quality of Congou Black Tea
LIU Fei, WANG Yun, ZHANG Juan, YE Yang, YAN Linfeng, LIU Jun
2021, 42(13):  94-102.  doi:10.7506/spkx1002-6630-20200718-242
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Aroma enhancement is an important process to develop the flavor quality of tea. In this study, an L27 (36) orthogonal array design was employed to investigate the effect of far-infrared variable-temperature aroma enhancement technology on the flavor quality of Congou black tea as determined by sensory evaluation and analysis of flavor components. Results showed that the temperature in the third step, the temperature in the first step, the duration of the first step, the duration of the second step, the temperature in the second step, and the duration of the third step affected the overall sensory score of tea, ranked in decreasing order of importance. Under the optimized conditions: the first step lasted at 70 ℃ for 30 min, the second step lasted at 100 ℃ for 30 min, and the third step lasted at 115 ℃ for 10 min, the aroma and taste quality of raw tea were significantly improved (an increase in sensory scores by 4.66 and 5.00 points, respectively). The content of theaflavin was significantly increased from (0.70 ± 0.01)% to (0.81 ± 0.02)% (P < 0.05), whereas the contents of thearubigin and total polyphenols were significantly decreased to (6.81 ± 0.07)% and (14.79 ± 0.03)% (P < 0.05), respectively. A total of 40 aroma components in five black tea samples was detected, with alcohols being the most predominant, including 10 alcohol compounds (together accounting for 47.60% to 51.07% of the total aroma compounds). Compared to the sample without aroma enhancement, the contents of some aroma substances such as alcohols and aldehydes in Congou black tea were decreased after variable-temperature aroma enhancement, while the contents of olefines, ketones and esters were increased. Furthermore, linalool and its oxide (24.60%), geranol (13.16%), methyl salicylate (9.13%), phenylacetaldehyde (7.11%) and benzene ethanol (5.98%) were the major aroma components. Far-infrared variable-temperature aroma enhancement technology could greatly improve the flavor quality of black tea, which will provide a technical reference for improving the processing technology for Congou black tea.
Nutrition & Hygiene
Cyanidin-3-O-Glucoside Protects RAW264.7 Cells against Hydrogen Peroxide-Induced Oxidative Damage
XUE Hongkun, TAN Jiaqi, LI Qian, TANG Jintian
2021, 42(13):  103-113.  doi:10.7506/spkx1002-6630-20200622-299
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The aim of this study is to evaluate the cytoprotection and potential molecular mechanisms of cyanidin-3-O-glucoside (C3G) on hydrogen peroxide (H2O2)-induced oxidative damage in RAW264.7 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was conducted to determine the viability of RAW264.7 cells exposure to H2O2 or C3G. Meanwhile, we measured the antioxidant properties of C3G by determining the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), nitric oxide (NO) release and malondialdehyde (MDA) levels by enzyme-linked immunosorbent assay (ELISA). 2’,7’-dichlorofluorescin diacetate (DCFH-DA) was employed to evaluate the production of intracellular reactive oxygen species (ROS). Finally, the expression levels of related mRNA/protein were evaluated by reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. The results showed that the H2O2-induced decrease in the cell viability of RAW264.7 cells was remarkably suppressed C3G (6.25–25.00 μmol/L). C3G significantly inhibited the H2O2-induced of overproduction of intracellular ROS, NO release and MDA levels, but increased the activities of intracellular SOD and GSH-Px (P < 0.05). In addition, the relative mRNA and protein expression levels of Mst1, Mst2 and Keap1 were up-regulated, while the mRNA and protein relative expression levels of Nrf2 and HO-1 were down-regulated in the 400 μmol/L H2O2-treated group when compared to the vehicle-treated group. However, the above changes were reversed by intervention with C3G. C3G could exert a cytoprotective effect possibly by activating the Mst/Nrf2 signaling pathway and improving the activities of antioxidant enzymes.
Effects of (+)-Catechin and Epigallocatechin Gallate on Ethanol-Induced Lipid Accumulation and Oxidative Stress in HepG2 Cells
HU Boran, DING Jiancai, CAO Yang, TIAN Ying, GUO Fenghua, YUAN Jing
2021, 42(13):  114-120.  doi:10.7506/spkx1002-6630-20201009-051
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Objective: To compare in vitro effects of (+)-catechin (Cat) and epigallocatechin gallate (EGCG) on ethanol (ETOH)-induced aberrant lipid metabolism and oxidative stress in HepG2 cells. Methods: HepG2 cells were divided into six groups: normal, 200 μmol/L (+)-Cat, 200 μmol/L EGCG, 300 mmol/L ETOH treatment, 200 μmol/L (+)-Cat plus 300 mmol/L ETOH treatment, and 200 μmol/L EGCG plus 300 mmol/L ETOH treatment. All groups were cultured at 37 ℃ for 24 h. Thereafter, the contents of triglyceride and malondialdehyde (MDA) and superoxide dismutase (SOD) activity were determined. The morphology of lipid droplets in HepG2 cells in each group was observed by Oil Red O staining. The mRNA expression of sterol regulatory element binding protein 1 (SREBP-1), peroxisomal proliferators activate receptors α (PPARα), carnityltransferase 1 (CPT1) and diacylglyceryltransferase 2 (DGAT2) in HepG2 cells were measured by fluorescence quantitative polymerase chain reaction. Results: The level of oxidative stress and TG content in ETOH-treated cells were significantly higher than those in the normal, (+)-Cat and EGCG groups. The oxidative stress response in the (+)-Cat plus ETOH and EGCG plus ETOH groups was significantly improved, and TG content was significantly lower in the two groups than in the ETOH group (P < 0.05, P < 0.01). Moreover, the mRNA expression of SREBP-1 and DGAT2 was down-regulated (P < 0.05, P < 0.01) , and the mRNA expression of PPARα and CPT1 was up-regulated (P < 0.05, P < 0.01). Conclusion: Both (+)-Cat and EGCG can improve ETOH-induced oxidative stress and lipid metabolism disorders in HepG2 cells, and EGCG is more effective.
Protective Effect of Genistein on Aβ25-35-Induced Hippocampal Neuron Injury by Regulating Ca2+-CaMKIV Pathway
GAO Huawu, WANG Yan, ZHOU Peng, YE Shu, SONG Hang, WANG Guangyun, CAI Biao
2021, 42(13):  121-126.  doi:10.7506/spkx1002-6630-20200622-306
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Objective: To investigate if and how genistein can protect hippocampal neurons against Aβ25-35-induced injury by regulating the Ca2+-calmodulin-dependent protein kinase IV (CaMKIV) pathway. Methods: The hippocampal tissue was taken from neonatal SD rats within 24 h after birth for isolation, purification and culture of neurons as well as identification by immunofluorescence staining. The neuronal cells were randomly divided into four groups: blank control, model, and genistein treatment (50 μmol/L) and estradiol and valerate treatment (10 μmol/L). After being pretreated for 3 h, the hippocampal neurons in all groups except the blank control group were treated with Aβ25-35 to establish a cell injury model. The cell survival rate was detected by methylthiazolyl tetrazolium, the intracellular Ca2+ concentration was detected using a fluorescent probe, and the expression of calmodulin (CaM), calcium/calmodulin dependent protein kinase kinase (CaMKK), phosphorylation calmodulin-dependent protein kinase (p-CaMKIV) and p-Tau were detected by Western blot. Results: Immunofluorescence showed that the hippocampal neurons were successfully isolated. Compared with the blank control group, the survival rate of hippocampal neurons in the model group was significantly decreased (P < 0.01), and the intracellular concentration of Ca2+ was significantly increased as well as the protein expression of CaM, CaMKK, p-CaMKIV and p-Tau (P < 0.01). Compared with the model group, genistein significantly increased the survival rate of hippocampal neurons (P < 0.01), decreased the intracellular concentration of Ca2+ (P < 0.01), and down-regulated CaM, CaMKK, p-CaMKIV and p-Tau protein expression (P < 0.01). Conclusion: Genistein has an obvious protective effect on hippocampal neuron damage induced by Aβ25-35, which may be mediated by the Ca2+-CaMKIV signaling pathway.
Effect of Ginseng Water-Soluble Dietary Fiber on Glucolipid Metabolism, Oxidative Stress and Intestinal Health in Rats
HUA Mei, FAN Meiling, LI Zhiman, DONG Lina, LI Shanshan, SUN Yinshi
2021, 42(13):  127-135.  doi:10.7506/spkx1002-6630-20201013-119
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Purpose: To investigate the effect of ginseng water-soluble dietary fiber (GSDF) on glucolipid metabolism and intestinal health in rats. Methods: SD rats were gavaged with GSDF or an equal volume of normal saline as a control for 15 days, and they were evaluated for growth performance, metabolism level and intestinal flora structure. Results: GSDF could significantly increase the feed intake of rats (P < 0.01), but had no significant effect on percent body mass gain, feed utilization rate or visceral organ indexes (P > 0.05). Low-dose GSDF significantly increased fasting insulin level (P < 0.05), and decreased total cholesterol level (P < 0.05). High-dose GSDF significantly reduced fasting blood glucose (P < 0.05) and total triglyceride level (P < 0.01). GSDF significantly reduced serum malondialdehyde content (P < 0.01), and improved total antioxidant capacity (P < 0.01). Low-dose GSDF significantly reduced the inflammatory factor levels including tumor necrosis factor α (P < 0.01), interleukin (IL) 1β (P < 0.05) and IL-4 (P < 0.01), and increased fecal water content (P < 0.05). Moreover, GSDF increased the abundance of intestinal Firmicutes and Lactobacillus, changing the structure of intestinal flora in the direction of enriching probiotics and cellulose-degrading bacteria, and affected the functional gene expression of related metabolic pathways. Conclusion: GSDF exerts a positive effect on rats by regulating growth metabolism, oxidative stress status and intestinal flora structure.
Positive Regulation of Lactoferrin on Gut Micro-Ecology of Rats with Inflammatory Bowel Disease
ZHAO Xiao, XU Jinghan, CUI Dongying, XU Jinzhao, LIU Yang, TENG Guoxin, XU Xiaoxi
2021, 42(13):  136-142.  doi:10.7506/spkx1002-6630-20200715-210
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The effect of lactoferrin (LF) on the α-diversity and composition, as well as the abundance of KEGG signaling pathway-related operational taxonomic unit (OTU) in the colonic microbiota of rats with inflammatory bowel disease (IBD) induced by dextran sulphate sodium (DSS) was analyzed by high-throughput sequencing. The results showed that LF alleviated the reduction of α-diversity and the imbalance between the dominant phyla Firmicutes and Bacteroidetes caused by DSS stimulation. LF increased the abundance of Lactobacillaceae (12% vs. 40%) and Ruminococcaceae (17% vs. 27%), and decreased Bacteroides (28% vs. 8%) and Prevotellaceae (13% vs. 6%). LF administration reduced the abundance of OTUs associated with human diseases such as cancer and infectious diseases, immune system, cells and genetics-related signaling pathways in the gut microbiota in IBD rats. The results of this study indicated that LF can play a beneficial role in regulating the colonic micro-ecology of IBD rats and modulating the microbiota composition to be similar to that of healthy rats, thereby having the potential to reduce the risk of other concomitant diseases.
Regulatory Effects of Pea Oligopeptides on ACE Activity and Intestinal Flora in Diet-Induced Hypertensive Rats
CHEN Xuanhong, JI Wei, DONG Leichao, NAN Xijun, WANG Meng, SUN Wanting, WANG Sai, ZHOU Quancheng
2021, 42(13):  143-150.  doi:10.7506/spkx1002-6630-20200907-097
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Objective: This study aims to evaluate the regulatory effects of a pea oligopeptide (Val-Glu-Pro-Gln, VGPG) on diet-induced hypertension (HTN) and the underlying mechanism. Methods: The molecular docking between the oligopeptide and angiotensin-converting enzyme (ACE) was performed, and the regulatory effects of oral administration of the oligopeptide on the blood pressure, serum ACE activity, blood lipids and intestinal flora of hypertensive rats were studied. The relationship of VGPG with ACE activity and intestinal flora for the regulation of hypertension was explored. Results: The results indicated that VGPG had a notable regulatory effect on HTN and could alleviate diet-induced obesity. The underlying mechanism may be as follows: 1) through hydrogen bonding and Zn2+ coordination, VGPG combined with ACE active site to produce a competitive inhibition on ACE activity, thereby exerting a hypotensive effect; 2) by regulating the intestinal microenvironment, VGPG maintained the richness and diversity of the microbial community within the normal range, avoiding the adverse effects on blood pressure in rats associated with intestinal microbiota imbalance, and it improved the ability of intestinal bacteria to decompose carbohydrates, thus reducing the digestion and absorption of carbohydrates, controlling body mass, and finally reducing the possibility of blood pressure increase associated with overweight. VGPG with a purity of 98% at a concentration of 25 mg/mL had the best regulatory effect on hypertension without significant adverse effects on organs or the gastrointestinal environment when compared with antihypertensive drugs. Conclusion: VGPG has significant hypotensive effect on HTN. This study provides a theoretical basis for applying VGPG as a functional factor for regulating HTN and preparing relevant functional foods.
Inhibition Effects and Mechanisms of Curcumin on Hydrogen Peroxide-Induced Platelet Apoptosis
YA Fuli, XIN Yu, ZHANG Chunmei, CHEN Binlin, LI Weiqi, MA Yongjie
2021, 42(13):  151-157.  doi:10.7506/spkx1002-6630-20200714-187
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Objective: Platelet apoptosis plays an important role in the development and progression of cardiovascular diseases. Curcumin (Cur), a polyphenol compound enriched in the rhizomes of turmeric (Curcuma longa), exerts a wide range of biological activities. Whether Cur acts on platelet apoptosis has not been reported. We therefore sought to investigate the effects of Cur on platelet apoptosis induced by H2O2 as well as to clarify the underlying mechanisms in vitro. Methods: Gel-filtered human platelets were pre-incubated with different concentrations of Cur (0, 1, 10 and 100 μmol/L) for 30 min, followed by intervention with H2O2 (100 μmol/L) for 60 min. The levels of platelet phosphatidylserine (PS) exposure and mitochondrial membrane potential (ΔΨm) depolarization were determined by flow cytometry. Enzyme linked immunosorbent assay was used to measure caspase-3 and caspase-9 activation, and reactive oxygen species (ROS) and superoxide generation. The expression of Bax, Bak and cytochrome c were evaluated by Western blot. Results: H2O2-induced platelet PS exposure and ΔΨm depolarization were significantly attenuated by 10、100 μmol/L Cur treatment when compared with the control group (P < 0.05). Moreover, Cur significantly down-regulated Bax, Bak and cytochrome c expression in platelets treated with H2O2 (P < 0.05). H2O2-induced platelet caspase-3 and caspase-9 activation were significantly inhibited by 10、100 μmol/L Cur (P < 0.05). Additionally, the levels of intracellular total ROS and superoxide were significantly increased in H2O2-treated platelets, which were attenuated by Cur intervention (P < 0.05). Conclusion: Cur can inhibit H2O2-induced platelet apoptosis in vitro.
Packaging & Storage
Effect of Glycine Betaine Treatment on Chilling Injury and Ascorbic Acid-Glutathione Cycle Metabolism in Peach Fruit
WANG Yi, HOU Yuanyuan, MA Yuqing, ZHU Xuan, ZHENG Yonghua, JIN Peng
2021, 42(13):  158-165.  doi:10.7506/spkx1002-6630-20200818-242
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The effects of 10 mmol/L glycine betaine dipping treatment on chilling injury and ascorbic acid-glutathione (AsA-GSH) cycle metabolism in peach fruit (Prunus persica Batsch cv. ‘Hujingmilu’) stored at (0 ± 1) ℃ were investigated. The results indicated that glycine betaine treatment could significantly inhibit the incidence of chilling injury in peach fruit and delay the increase in relative electric conductivity, malondialdehyde (MDA) content and hydrogen peroxide content. In addition, glycine betaine treatment could improve the activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase, induce the up-regulation of PpAPX, PpGR, PpMDHAR and PpDHAR gene expression and maintain high levels of ascorbic acid, glutathione, ascorbic acid/dehydroascorbate ratio and glutathione/oxidized glutathione ratio. It is suggested that exogenous glycine betaine can effectively remove excessive hydrogen peroxide in cells and relieve the oxidative damage to the cell membrane caused by low temperature stress by regulating the AsA-GSH cycle, thereby reducing chilling injury symptoms in peach fruit during cold storage.
Effect of Packaging Atmospheres on Microbial Counts and Succession in Beef Steaks during Storage
YANG Hongbo, YANG Xiaoyin, ZHANG Yimin, LIANG Rongrong, LUO Xin, WANG Fangfang, MAO Yanwei
2021, 42(13):  166-173.  doi:10.7506/spkx1002-6630-20200519-217
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In order to investigate the effect of different packaging methods on meat quality, microbial counts and microbial community succession in beef steaks during storage, meat samples were stored in modified atmosphere (50% O2 + 30% CO2 + 20% N2) or vacuum at 0-4 ℃ and evaluated for pH, meat color, microbial counts and bacterial diversity after 0, 3, 7, 14 and 21 days. The results showed that modified atmosphere packaging (MAP) maintained meat color better than vacuum packaging (VP). On day 21, the total viable count, lactic acid bacterial count and Pseudomonas spp. count in the MAP group decreased as compared to those in the VP group. The microbial diversity in both groups increased at first and then decreased as storage time was extended, being more complex in the VP group than in the MAP group. The initial bacterial community in steaks was dominated by Acinetobacter, Ochrobactrum, Thermus and Chryseobacterium, and then Carnobacterium gradually became the dominant microorganism in the VP group, while Brochothrix, Serratia and Lactobacillus eventually became the dominant microorganisms in the MAP group. The storage time from day 7 to 14 was the critical period for the changes in microbial species in beef steaks. Higher protein and lower carbohydrate metabolism levels in the MAP group were found compared with the VP group. The results from this study may provide a reference for targeted inhibition of microorganisms in beef steaks and prolonging the shelf life.
Improved Properties of Polysaccharide-Based Edible Films Incorporated with Egg White Protein and Apple Polyphenols and Application to Quality Preservation of Cashews during Storage
LIU Xixin, CHI Yujie, ZHANG Hong, WANG Lechuan, ZHANG Huajiang, XIA Ning, Ahmed M. RAYAN, CHEN Hui, Amro ABDELAZEZ
2021, 42(13):  174-184.  doi:10.7506/spkx1002-6630-20200917-224
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Sodium alginate (SA) and κ-carrageenan (κ-C) are often used as natural non-toxic materials in edible packaging films due to their good film-forming ability. However, the formed polysaccharide films have some disadvantages, such as strong hydrophilicity, poor mechanical properties and low antioxidant activity. This study aimed to enhance the packaging performance of natural edible composite films and impart antioxidant activity to it by adding egg white powder (EWP) and apple polyphenols (AP) into SA/κ-C-based film-forming matrix with calcium lactate added as a cross-linking agent. The film was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron microscopy (SEM) and ultraviolet (UV) spectroscopy, and the interactions among the components were analyzed. The edible composite film was applied to the preservation of cashew nuts. The results indicated that the composite edible film with AP and EWP showed good packaging performance and antioxidant properties. The mechanical properties and barrier properties of the edible film were significantly improved by Ca2+ cross-linking. With the addition of egg white powder, the elongation at break of the film increased from 7.99% to 20.81%, the water vapor permeability decreased by 28.84%, and the oxygen permeability decreased by 27.07%. AP increased the tensile strength of the film from 18.58 MPa to 30.23 MPa, decreased the water vapor permeability and oxygen permeability by 42.35% and 34.13%, respectively, and significantly improved the light barrier performance. The AP/EWP/SA/κ-C edible film could inhibit the increase in the water activity, water content, peroxide value and acid value of cashew nuts during storage, thereby effectively inhibiting the oxidative rancidity of cashew nuts. The findings of this study can provide a reference for the preparation and application of polysaccharide/protein-based edible composite packaging films.
Effect of Chitosan-Nanocrystal Cellulose Composite Coating on the Preservation of Shatangju Mandarin
LI Baoxiang, YU Yilin, HE Yue, GUO Lirong, REN Dan, XU Dan
2021, 42(13):  185-192.  doi:10.7506/spkx1002-6630-20200822-303
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In order to investigate the influence of nanocrystal cellulose (NCC) addition to chitosan coating on its effect on the preservation of Shatangju mandarin (Citrus reticulata cv. Shatangju), the fruit were treated with chitosan solution (CS) and chitosan composite solutions containing 2% and 4% of NCC (CS-2% NCC and CS-4% NCC) in this study, separately. In addition, a prochloraz-treated group (PCZ group) and an untreated group (CK group) were set up. The mass loss rate, decay incidence, nutritional quality, malondialdehyde (MDA) content in the fruit peels and antioxidase activities in each group were determined regularly during storage, and the microscopic morphology of the peel surface was also observed. The results showed that the composite coating could not reduce fruit mass loss, but its inhibitory effect on the decay incidence was better than that of CS and PCZ. Compared with CK, the decay incidence of CS-4% NCC was reduced by 50% on day 24 of storage; meanwhile, the contents of titratable acid, soluble solid, total phenol and soluble protein were effectively maintained by chitosan coating. The content of peel MDA in CS-4% NCC was the lowest among all groups, and the activities of peroxidase (POD) and catalase (CAT) could be maintained at relatively high levels in this group during storage, which indicated that CS-4% NCC composite coating could significantly delay membrane lipid peroxidation, thus maintaining the anti-aging capacity of fruit. It was observed from the surface micromorphology of peels that micropores appeared on the coated fruit on the first day of storage, while addition of 4% NCC enhanced the structural stability of the coating, thereby helping in reducing the appearance of micropores. These results indicated that addition of NCC was able to stabilize the structure and improve the properties of CS coating, thus enhancing its preservation effect on fruits. The effect of 4% NCC composite coating on inhibiting fruit decay and maintaining fruit quality was similar to that of prochloraz treatment. Therefore, the composite coating could replace chemical preservatives for citrus fruits such as Shatangju mandarin.
Pre-harvest Spraying with Benzothiadiazole Inhibited Softening of Harvested Agaricus bisporus
WEI Yanan, Esrat Mahmud SILVY, PENG Hui, YANG Qian, WANG Ting, YUN Jianming, BI Yang
2021, 42(13):  193-199.  doi:10.7506/spkx1002-6630-20210131-369
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Objective: To investigate the effect of preharvest benzothiadiazole (BTH) spraying on the softening of harvested Agaricus bisporus during cool storage, and to explore the underlying mechanism. Methods: A. bisporus (cv. A15) was sprayed with BTH at 200 mg/L at the primordia stage and evaluated for texture properties and mass loss rate, the contents of chitin, cellulose and protein and related enzyme activities during postharvest cool storage. Results: Pre-harvest BTH spraying significantly reduced the mass loss of A. bisporus during cool storage, by 34.22% relative to the control group on day 8. BTH spraying significantly improved the firmness, flexibility, chewiness and gumminess of A. bisporus, decreased the activities of chitinase and cellulose, increased the contents of chitin and cellulose, reduced the activities of neutral, alkaline and acid proteinase at harvest and during cool storage (P < 0.05). In addition, BTH spraying delayed the degradation of protein. Correlation analysis indicated that the firmness, flexibility, chewiness and gumminess were significantly positively correlated with the contents of chitin, cellulose and protein, but significantly negatively correlated with the mass loss rate of A. bisporus (P < 0.01). Conclusion: Preharvest BTH spraying can significantly inhibit the softening of A. bisporus during cool storage, and the underlying mechanism may be closely related to reducing the activity of cell wall-degrading enzymes and postharvest mass loss rate.
Effect of Storage Temperature on Functional Properties of Rice Protein
ZHAO Qingyu, LIN Jiahui, SHEN Qun
2021, 42(13):  200-207.  doi:10.7506/spkx1002-6630-20200720-256
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‘Daohuaxiang 2’, ‘Liaoxing’ and ‘Yanfeng’ rice stored at 4, 30, and 70 ℃ were selected to investigate the effects of storage temperature on the functional properties of rice protein like protein solubility, water-holding capacity, oil-holding capacity, foaming properties, and emulsifying properties. The results showed that for each storage temperature, the water-holding capacity and foaming activity of rice protein generally decreased, while the oil-holding capacity generally increased with storage time. The foam stability of ‘Daohuaxiang 2’ and ‘Liaoxing’ rice proteins increased generally during storage. However, ‘Yanfeng’ rice protein showed a downward trend. During storage at 4 ℃, the emulsion stability of all three rice proteins decreased. The solubility and emulsifying activity of ‘Daohuaxiang 2’ and ‘Liaoxing’ proteins showed a downward trend, while those of ‘Yanfeng’ rice protein increased significantly (P < 0.05). The solubility of all three rice proteins decreased, while the emulsifying activity and emulsion stability increased significantly during storage at 30 ℃ (P < 0.05). During storage at 70 ℃, the solubility of all three rice proteins and the emulsion stability of ‘Liaoxing’ rice protein decreased significantly (P < 0.05), while the emulsifying activity of ‘Daohuaxiang 2’ rice protein showed an overall upward trend. Collectively, The functional properties of proteins in the three rice cultivars changed significantly during storage at different temperatures.
Effects of Syrup Characteristics on Texture of Canned Yellow Peach during Storage
LÜ Jian, YU Xiaoyan, BI Jinfeng, WANG Fengzhao, XIE Jin, ZHANG Siwei, GUO Chongting
2021, 42(13):  208-214.  doi:10.7506/spkx1002-6630-20200715-202
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In order to explore the effect of syrup properties on the texture of canned yellow peach (cv. ‘Goldbaby 5’), changes in the syrup characteristics including pH, total soluble solid (TSS) content, turbidity, color, apparent viscosity, osmotic pressure, and water soluble pectin in syrup (SWSP) content were measured during storage. Scanning electron microscope (SEM) and light microscope (LM) were applied to observe the microstructure of the fruit flesh. At the same storage times syrup samples from different locations (the upper, middle and lower layers) did not show a significant difference in pH or TSS content, illustrating that the mass transfer between the syrup and the flesh cells was uniform. The syrup pH did not change obviously with storage time. On the other hand, the syrup presented a decrease in TSS content, L* value and a* value, and an increase in turbidity, b* value, osmotic pressure, SWSP content. These parameters tended to stable at the late stage of storage. Deformation or even collapse of the flesh cells was observed by SEM and LM, macroscopically manifested by flesh softening, namely a significant decrease in hardness and chewiness (P < 0.05). A significant negative correlation between texture properties (hardness, resilience, cohesiveness and chewiness) and b* value, turbidity, osmotic pressure and SWSP content was found (P < 0.05) as well as a significant positive correlation of hardness and chewiness with L* value and a* value (P < 0.05). From these findings, it was clear that the texture of canned yellow peaches could be significantly affected by the syrup properties during storage and consequently could be improved by regulating them.
Effect of Polysaccharide from Flammulina velutipes on the Quality of Whole Fish and Fillets of Large Yellow Croaker (Pseudosciaena crocea) during Superchilled Storage
XIE Chen, XIONG Zeyu, LI Hui, JIN Sulaiman, CHEN Baike, BAO Hairong
2021, 42(13):  215-222.  doi:10.7506/spkx1002-6630-20200713-171
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In order to investigate the effect of pretreatment with polysaccharide from Flammulina velutipes (FVP) on the water distribution and chemical and rheological properties of myofibrillar proteins in whole fish and fillets of large yellow croaker during superchilled storage, FVP was used at three concentrations of 0.03, 0.06 and 0.09 g/L FVP, while sterile water was used as a control. The sensory evaluation, total volatile basic nitrogen (TVB-N) content, total sulfhydryl content, Ca2+-ATPase activity, rheological properties of myofibrillar protein and water migration of the samples during storage were analyzed. The results showed that FVP could effectively inhibit the increase in the TVB-N content and the decrease in the sensory score of whole fish, slow down the decrease in the total sulfhydryl content and Ca2+-ATPase activity of whole fish and fillets, and improve the water-holding capacity. In addition, FVP could retard the weakening of the gel-forming capacity of myofibrillar proteins in spoiled fish. In the concentration range used in this experiment, FVP treatment at 0.09 g/L had the best preservation effect on fish, which may provide a theoretical reference for the application of FVP in the quality preservation of aquatic products during storage and transportation.
Effect of Storage Temperature on Peel Wax Content and Chemical Composition of Citrus Cultivars with Different Storability
XU Chengxiang, ZHENG Fuqing, MA Yanping, ZHANG Shaoping, CHEN Xiaoting, YE Simin
2021, 42(13):  223-232.  doi:10.7506/spkx1002-6630-20190617-167
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To investigate the relationship between the peel wax and storability of citrus fruits, freshly harvested fruits of ‘Gonggan’ mandarin (Citrus reticulata ‘Gonggan’) and ‘Shatangju’ mandarin (Citrus reticulata ‘Shatangju’), both endemic to the Xijiang River Basin in southwest China’s Guangdong, were packaged in plastic bags and stored at (14.2 ± 2.8) ℃ (control) and (6.5 ± 0.5) ℃ (cold storage) for 90 days, separately. Changes in mass loss rate, decay incidence, peel structure and peel wax content and its chemical composition were analyzed periodically during storage. The results showed that mass loss rate and decay incidence in the citrus fruits significantly increased with increasing storage time for both storage temperatures (P < 0.05), accompanied by alternations in peel structure and a significant decrease in peel wax content and the contents of the main components (long-chain fatty aldehydes, long-chain fatty acids and long-chain aliphatic hydrocarbons, and long-chain aliphatic primary alcohols) in peel wax. Cold storage inhibited these changes and consequently maintained fruit quality better as compared to room temperature storage. Both fruit mass loss and decay incidence were significantly correlated with peel wax content and the contents of the four main wax components (P < 0.01). During storage, these wax components decreased to different extents. Among them, the contents of long-chain fatty acids and long-chain aliphatic primary alcohols showed the biggest and smallest decrease in ‘Gonggan’ mandarin with strong storability, respectively, while the opposite result was observed in ‘Shatangju’ mandarin with poor storability. Small-molecular-mass branched alkanes, alkenes and alkenals were all sensitive to storage temperature, implicating that the storability of the two citrus fruits was closely related to peel wax content and its components.
Potential Relationship between Endogenous Antioxidant Components and Egg Yolk Oxidation Process during Hen Egg Storage
YUAN Huchuan, LIU Yu, RAN Lidan, YANG Chuan, LUO Keyu, REN Xudong, WANG Qingling
2021, 42(13):  233-240.  doi:10.7506/spkx1002-6630-20200604-063
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In order to confirm the regulation of endogenous antioxidant components in egg yolk on the oxidation process of eggs, fresh eggs were stored at 22 ℃ and 65% relative humidity for 50 days. The extent of egg yolk lipid oxidation, and the antioxidant capacity of lipophilic antioxidant component (LAC) and hydrophilic antioxidant component (HAC) were characterized during the storage period. The experimental results showed that egg yolk proteins were significantly degraded during storage, resulting in a decrease in the mean value of total sulfhydryl content by 29.69%, and an increase in the mean value of carbonyl content by 2.2 times. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the degradation of phosvitin, high-density lipoprotein, and other proteins during egg storage, leading to a significant increase in conjugated diene (CD) value and malondialdehyde (MDA) content (P < 0.05). The free radical scavenging capacity of LAC was greater than that of HAC during egg storage. Compared with phospholipids in LAC, carotenoids in it had a relatively higher free radical scavenging capacity. Correlation analysis showed that the degree of egg yolk lipid oxidation was negatively correlated with the antioxidant capacity of phospholipids and carotenoids in egg yolk (P < 0.05), and the antioxidant capacity of phospholipids was positively correlated with that of carotenoids (P < 0.05). Compared with egg yolk proteins, LAC had a more significant regulatory effect on egg yolk lipid oxidation during egg storage, and there may be synergistic effects between the antioxidant components.
Effects of Vacuum Precooling and Different Circulation Modes on the Shelf Quality of Pakchoi (Brassica rapa L. ssp. chinensis)
AN Ronghui, ZHOU Hongsheng, LUO Shufen, ZHANG Yingtong, ZHANG Leigang, HU Huali, LI Pengxia
2021, 42(13):  241-248.  doi:10.7506/spkx1002-6630-20200609-119
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In order to investigate the effects of vacuum precooling and different circulation modes on the shelf quality of pakchoi, we simulated the circulation of the vegetable at room temperature (20 ± 1) ℃ or low temperature (4 ± 1) ℃ directly (as a control) or after vacuum precooling, and then simulated its storage at room temperature (20 ± 1) ℃ on shelves. The appearance quality and chlorophyll, carotenoids, lutein, ascorbic acid, titratable acid, soluble protein, soluble sugar, folic acid and nitrite contents of pakchoi during circulation and shelf storage were measured. The results showed that vacuum precooling could well maintain the shelf quality of pakchoi. Compared with room temperature circulation, low temperature circulation could significantly slow down the decrease in the contents of chlorophyll, carotenoids, lutein, ascorbic acid, titratable acid, soluble protein, soluble sugar and folic acid, and inhibit the accumulation of nitrite. To sum up, vacuum precooling combined with low temperature circulation can more effectively maintain the quality of pakchoi during circulation and shelf storage and inhibit the accumulation of nitrite, consequently extending the shelf life.
Reviews
Advances in Understanding the Formation Mechanism of Terpenoids during Winemaking and Factors Influencing It
ZHANG Huimin, PAN Qiuhong
2021, 42(13):  249-258.  doi:10.7506/spkx1002-6630-20200802-024
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Terpenoids are important aroma components in wine, and exist in both free and bound forms in wine grape berries. Grape-derived terpenoids undergo a series of changes during winemaking, mainly including the conversion of glycosidically bound terpenoids into free forms through acidic or enzymic hydrolysis, and molecular rearrangements of some terpenoids in the acidic environment of wine. The transformation and rearrangement of terpenoids and ultimately wine aroma are significantly affected by the winemaking process. The present paper summarizes the recent advances in research on the reactions involved in the transformation of terpenoids during winemaking, the mechanism underlying the phenomenon, and the factors regulating it. Meanwhile, future research directions are discussed.
Molecular Regulation of Biofilm Formation of Salmonella spp.: A Review
WANG Huhu, HE Shuwen, HU Haijing, BAI Yun, SHAO Liangting, XU Xinglian
2021, 42(13):  259-264.  doi:10.7506/spkx1002-6630-20200719-251
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Salmonella spp. is a major foodborne pathogen that poses a hazard to global public health. There are ten millions of people suffering from food poisoning caused by Salmonella spp. every year globally. The biofilm adhered to food contact surfaces during food processing is the source of Salmonella cross-contamination. It has a strong resistance to sanitizers used in food processing, which can cause large-scale food poisoning and food recalls. In this review, the exact contributions of fimbriae and flagella together with extracellular polymeric substances (EPS) to biofilm formation, and the regulatory mechanisms at the transcriptional level are discussed firstly. Then, this review concentrates on small non-coding small RNA (sRNA), a regulatory factor at the post-transcriptional level, and its regulatory mechanism on the core mRNA pathways including motility and EPS. In addition, the four modes of action of sRNA in regulating Salmonella biofilm formation are summarized. Finally, we conclude with an outlook on the future of this field. We expect that this review can provide a reference for sparking new research ideas, improving the scientific theory of Salmonella biofilm formation, and developing effective control technologies against Salmonella biofilm.
Progress in Understanding the Interaction between Bioactive Components of Soybean and Gut Microbiota
WU Xuejiao, ZHAO Lichao, FANG Xiang, GUO Yingyu, LIANG Wen’ou, MA Yuhao, WANG Li
2021, 42(13):  265-272.  doi:10.7506/spkx1002-6630-20200623-313
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At present, the interaction between food components and gut microbiota as well as its effect on health is a research hotspot in the field of diet and health. The gut microbiota of humans plays an important role in the catabolism, transformation and absorption of bioactive components from soybean, and bioactive components of soybean can be biotransformed by the gut microbiota, causing structural changes to form new bioactive ingredients, which can benefit human health. Moreover, metabolites generated by the gut microbiota from bioactive components of soybean can regulate the structure of the gut microbiota, protect the intestinal mucosa barrier, and maintain the intestinal microecological balance. In this paper, how soybean bioactive components are biotransformed by the gut microbiota, how the abundance and community structure of gut microbiota under exogenous disturbances are regulated, and the health benefits of metabolites generated by the gut microbiota from soybean bioactive components are reviewed, in order to provide a basis for in-depth research on the mechanism underlying the health benefits of soybean bioactive ingredients.
Progress toward Understanding the Effect of Low-Oxygen Storage on the Flavor of Postharvest Fruits
CHEN Jingxin, ZHANG Demei, LI Yongxin, LÜ Jingyi, ZHU Danshi, LI Jianrong, MI Hongbo, GE Yonghong
2021, 42(13):  273-280.  doi:10.7506/spkx1002-6630-20200621-285
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Hypoxia is one of the major measures applied in the conventional controlled atmosphere storage technology, which can remarkably prolong the storage period of fruits and alleviate the symptoms of postharvest physiological disorders. In a controlled atmosphere, hypoxia can lower fruit respiration rate and ethylene production, delay fruit ripening and senescence, and well maintain fruit quality attributes including firmness, soluble solid content, titratable acidity and ascorbic acid content. However, low levels of oxygen are generally considered to be a negative factor for the flavor quality of fruits. This paper reviews the effects of low oxygen in controlled atmosphere storage on the biosynthesis of major sugars, organic acids and volatile aroma components in fruits, and their underlying biochemical and molecular mechanisms, so as to provide a theoretical reference for improving the flavor of fruits under controlled atmosphere storage.
Mechanisms for and Control Strategies against the Flocculation of Protein-Stabilized Emulsion Based on Oil-Water Interface Behavior: A Review
JI Xuehua, DU Qiwei, SU Qihao, CHEN Yufeng, DING Yuting, ZHOU Xuxia
2021, 42(13):  281-288.  doi:10.7506/spkx1002-6630-20200601-005
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Flocculation is a ubiquitous phenomenon in emulsion systems possibly affecting the emulsification, appearance and rheology of protein-stabilized oil-in-water emulsions. This paper analyzes protein concentration, ionic strength, pH and other important factors that affect the flocculation of an emulsion, interprets the adsorption behavior of protein at the oil-water interface of a protein-stabilized emulsion from an interfacial rheological perspective, and further explains the stability mechanism of the emulsion. Next, this article summarizes the strategies currently available to control the flocculation of protein-stabilized emulsions by optimizing the characteristics of the interfacial adsorption layer, and reviews the mechanism by which binary and ternary complexes formed between protein and polysaccharide and/or polyphenol could improve the emulsion stability. This review is expected to provide a theoretical reference for the preparation of protein-stabilized emulsions with improved stability.
A Review of the Biofilm Formation and Transfer of Listeria monocytogenes in the Food Environment and Prevention and Control Measures for It
SUN Linjun, ZHANG Hongzhi, FANG Taisong, WANG Yuan, LIU Yangtai, WANG Xiang, LI Hongmei, LI Daixi, DONG Qingli
2021, 42(13):  289-299.  doi:10.7506/spkx1002-6630-20200525-288
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Listeria monocytogenes is a major foodborne pathogenic bacterium. Currently, there is a widespread concern over the issue that the formation and transfer of L. monocytogenes biofilm in the food environment can pollute food. Prevention and control of L. monocytogenes biofilm to prevent the food environment from biofilm contamination is important for guaranteeing food safety. In this article, the biofilm formation ability of L. monocytogenes sampled from the food environment is summarized. Moreover, the factors contributing to L. monocytogenes biofilm formation and transfer are reviewed. Finally, this review also gives an overview of the approaches currently available for the prevention and control of L. monocytogenes biofilm formation. We believe that further studies should be carried out by using more representative L. monocytogenes strains and simulating more realistic cases in order to better understand biofilm formation and transfer and to provide a theoretical basis for easier elimination of L. monocytogenes biofilm. Furthermore, the formation mechanism of L. monocytogenes biofilm, as well as the mechanism by which the relevant factors affect L. monocytogenes biofilm, should also be studied in order to provide a basis for the implementation of efficient prevention and control measures for L. monocytogenes biofilm.
Recent Progress in the Types and Applications of Polyphenol-Based Composite Materials
JIANG Nan, YAO Weirong, GAO Yuan, WANG Meng
2021, 42(13):  300-308.  doi:10.7506/spkx1002-6630-20200527-328
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Polyphenol-based composite materials are a new type of complex that is synthesized by the interaction of polyphenol with a variety of compounds or elements through covalent or non-covalent bonds, mainly including the biomacromolecules polysaccharide, protein and phospholipid as well as metal elements. The poor aqueous solubility, stability and bioavailability of some natural polyphenols can be improved by synthesizing composite materials to enhance the targeted release of the polyphenols as oral nutraceuticals or drugs. The polyphenol-based composite materials can also be applied as plant antimicrobials. This practice can greatly expand the application of polyphenols in the fields of food, medicine and agricultural product quality and safety. On the basis of an extensive literature review, this paper summarizes the types, structural characteristics and functional properties of polyphenol composites as well as the current status of the application of polyphenol composites. Finally, we conclude some reasonable suggestions to solve the problems existing in the current research and for key research directions in the future.
Recent Advances in Analytical Techniques for the Traceability of Commercial Sea Cucumber
JIANG Bingxue, ZHANG Xiaomei, HE Xiaoxia, ZHANG Jiukai, ZHANG Hongwei, LI Zhaojie, XUE Changhu, FENG Tingyu, JIANG Xiaoming,
2021, 42(13):  309-318.  doi:10.7506/spkx1002-6630-20200630-386
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As a nutritious seafood, commercial sea cucumbers are loved by consumers, but its high price has led to frequent occurrence of food frauds. Driven by economic profits, illegal operators may produce counterfeit or adulterated sea cucumber products. This highlights the paramount importance of tracing the species, geographic origin and production process of commercial sea cucumbers. In light of the current status of the adulteration of commercial sea cucumber products, the analytical techniques for the traceability of sea cucumbers including DNA analysis, elemental analysis, stable isotope analysis and omics methodologies (lipidomics, proteomics and glycomics) are reviewed, and an outlook on future trends is given.
Progress in Understanding the Relationship between Human Milk Oligosaccharides and Infant Gut Microbiota
YUAN Huizhi, XUN Yiping, PU Xiaolu, ZHU Hong, WANG Shijie
2021, 42(13):  319-325.  doi:10.7506/spkx1002-6630-20200605-072
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Breast milk is rich in human milk oligosaccharides (HMOs), which are prebiotics that can stimulate the growth of beneficial bacteria in the neonatal intestine. At present, the oligosaccharides allowed to be added to infant formula in China are structurally different from HMOs so that they cannot simulate some structure-specific effects of HMOs. This review describes the composition, structure and content of HMOs in breast milk, focusing on the relationship between HMOs as well as their metabolites and the infant intestinal microbiota. Finally, the beneficial effects of feeding infant formula with HMOs on the infant intestinal flora are discussed, which will provide theoretical support for promoting the application of HMOs in infant formula foods.
Progress in Biotransformation of Red Algal Polysaccharides for Industrial Utilization
ZHOU Feng, TAN Huanghong, SUN Huimin, ZHENG Zhaojuan, OUYANG Jia
2021, 42(13):  326-334.  doi:10.7506/spkx1002-6630-20200607-098
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Compared with terrestrial biomass, marine biomass, called the third generation of biomass resources, has attracted more and more attention due to its higher photosynthetic efficiency, faster growth speed, higher carbohydrate content and zero lignin content. Red algae are typical large seaweeds enriched with polysaccharides in the cell wall. In this paper, the geographical distribution and chemical composition of red algae are described with a special focus on recent progress in the biotransformation of red algal polysaccharides for the enzymatic preparation of agar oligosaccharide and 3,6-anhydro-L-galactose and the microbial production of ethanol and organic acids. Moreover, future directions for the utilization of red algal biomass are discussed.
Progress in Bioactive Properties and Applications of Fish By-product Protein Hydrolysates
ZHANG Xiaodi, DAI Zhiyuan
2021, 42(13):  335-343.  doi:10.7506/spkx1002-6630-20200523-271
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Fish by-product is rich in protein and has high nutritional value, but its degree of comprehensive utilization is low, which causes a waste of resources, but also induces environmental problems. It has been shown that enzymatic hydrolysates of fish by-product mainly including small peptide hydrolysates could be used as potential food additives and nutritional supplements because of their functional properties such as antioxidant, antifreeze, antibacterial and antihypertensive activity. The aim of this article is to review the preparation, bioactive properties and applications of fish by-product protein hydrolysates and summarize the problems existing in the production of fish by-product protein hydrolysates and future trends, which could provide a reference for the research and application of fish by-product protein hydrolysates.
Design Principles of Food Gel Structures Based on Mixed Polysaccharide and Protein Solutions
LI Anqi, SHANG Jing, LI Qianjin, GUO Chuo, YANG Xi, GUO Yurong
2021, 42(13):  344-352.  doi:10.7506/spkx1002-6630-20200606-092
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With the rapid development of the modern food industry and gradually increased public awareness about a healthy diet, gel-based food products are increasingly favored by consumers due to their high water content, low calorie, appealing taste, and unique texture. Polysaccharides and proteins, natural biopolymers that are widely present in food systems, represent good raw materials for designing food gel structures. It has been recently suggested that the phase behavior of mixed polysaccharide and protein systems is the main factor governing the microstructural characteristics and physical properties of the final mixed gels. This paper clarifies the phase behavior of mixed binary systems of polysaccharide and protein and the factors influencing it and summarizes the design principles of food gels based on mixed polysaccharide and protein systems. Finally, it exemplifies the practical applications of mixed systems of whey protein and several common polysaccharides in building gel structures, highlighting their great potential in designing food gel structures.
Progress in Research on Camellia kucha (Chang et Wang) Chang and Its Special Constituent Theacrine
QIN Dandan, WANG Qiushuang, LI Hongjian, FANG Kaixing, JIANG Xiaohui, PAN Chendong, WANG Qing, LI Bo, WU Hualing
2021, 42(13):  353-359.  doi:10.7506/spkx1002-6630-20200617-231
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Camellia kucha (Chang et Wang) Chang is a wild tea germplasm resource endemic to China, whose buds taste extremely bitter and contain abundant theacrine (1,3,7,9-tetramethyluric acid) as a special purine alkaloid. Due to its health benefits such as antioxidant, anti-depression, anti-inflammatory effects, theacrine has received much attention in recent years. However, the scarcity of this plant and the difficulty in obtaining theacrine have limited the research and application of Camellia kucha (Chang et Wang) Chang and its theacrine. The present paper aims to introduce the botanical classification and geographical distribution of Camellia kucha (Chang et Wang) Chang as well as the major characteristics of some biochemical components. Furthermore, the biosynthetic pathways of theacrine as a special biochemical constituent in this plant, the methods currently available to prepare theacrine and recent progress in understanding the pharmacological activities of theacrine are reviewed. Additionally, the advantages and disadvantages of naturally occurring and synthetic theacrine are highlighted. Finally, future prospects for the application of Camellia kucha (Chang et Wang) Chang and theacrine are discussed. Hopefully, this review will provide a theoretical reference for the research and utilization of Camellia kucha (Chang et Wang) Chang resources and theacrine.
Analysis of Legal Issues on Collaborative Management of Health Food Safety in China
LI Wenhua
2021, 42(13):  360-369.  doi:10.7506/spkx1002-6630-20210401-004
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In view of the frequent occurrence of problems in the field of health food safety in China, the author analyzes the necessity of collaborative management of health food safety, and points out that there exist problems in China’s coordinative management mechanism for health foods, including the facts that the measures for supervision over and law enforcement on health food industries need to be improved, and the education and protection mechanism for health food consumers are imperfect. Moreover, the author puts forward some suggestions to improve these problems. First, the mechanism of supervision over non-compliance activities, such as false claims and pyramid scheme in the field of health food marketing should be improved by establishing a comprehensive compliance supervision system for health food enterprises, and introducing an administrative settlement system into the collaborative governance mechanism of health food safety. Second, a sound education and protection mechanism for health food consumers should be established. More specifically, firstly, the major supervision departments should take solid action in the work of consumer education through their official media channels; secondly, the proceeds from an administrative settlement should be wholly or partially used to compensate injured consumers and people who expose non-compliance activities of health food enterprises; thirdly, the class action system should be introduced into the field of health food safety civil procedure to form a health food safety collaborative governance mechanism in which all parties actively participate.