Table of Content

15 June 2019, Volume 40 Issue 11
Basic Research
Changes in Amino Acids and Tryptic Peptides from Antarctic Krill Protein before and after Autolysis
HU Lingping, ZHANG Xiaomei, ZHANG Hongwei, SUN Weiwei, WEN Yunqi, LIN Liming, XUE Changhu, JIANG Xiaoming
2019, 40(11):  1-6.  doi:10.7506/spkx1002-6630-20180606-049
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Antarctic krill contains high endogenous protease activities that contribute to autolysis after its death, thus limiting its processing and utilization. In order to analyze the autolysis characteristics of Antarctic krill, the relative activity of autolytic enzymes was determined as a function of temperature and pH. It was shown that the optimum temperature of the autolytic enzymes was 55 ℃, and optimum pH 7.5; under these conditions, there was an increase in the amino nitrogen content of the autolysate. Furthermore, the changes in amino acids and tryptic peptides of Antarctic krill were analyzed before and after 3 h of autolysis at the optimum temperature and pH. The results showed that glycine and proline were the dominant amino acids of Antarctic krill, followed by glutamic acid and alanine. The contents of umami amino acids such as glutamic acid, glycine and alanine decreased, while the contents of bitter amino acids such as leucine, isoleucine, tyrosine and phenylalanine increased after the autolysis. The molecular mass distribution of the autolysate was shifted to smaller molecular mass. In conclusion, this study provides a theoretical basis for further exploring the autolysis characteristics of Antarctic krill.
Inhibitory Effect of Sodium Fumarate on Quorum Sensing and Spoilage Capacity of Pseudomonas fluorescens
SUN Xiaojia, LI Tingting, HE Binbin, MEI Yongchao, WANG Dangfeng, XIE Jing, LI Jianrong
2019, 40(11):  7-13.  doi:10.7506/spkx1002-6630-20180510-163
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In this paper, Chromobacterium violaceum CV026 strain was used as a test model to investigate the effect of sodium fumarate on quorum sensing and spoilage capacity of Pseudomonas fluorescens. The inhibitory effect of sodium fumarate on biofilm formation was evaluated with a microplate reader and optical microscopy, and its effect on the secretion of signal molecules in Pseudomonas fluorescens was determined by gas chromatography-mass spectrometry (GC-MS). The results showed that sodium fumarate could significantly reduce the production of violacein in strain CV026 at sub-minimum inhibitory concentrations. Violacein production was inhibited 50.95% by sodium fumarate at 2.0 mg/mL while not affecting the growth of CV026. Sodium fumarate could effectively inhibit spoilage characteristics of Pseudomonas fluorescens as reflected by biofilm formation, swarming and swimming motility, and extracellular protease activity and this effect was positively correlated with its concentration. By GC-MS analysis, we also found that sodium fumarate significantly inhibited the secretion of the signal molecules N-acylhomoserine lactones (AHLs). Therefore, sodium fumarate has great inhibitory activity and can be developed as a quorum sensing inhibitor for refrigerated storage and preservation of aquatic products.
Effect of Milk Clotting Enzyme from Bacillus methanolicus on the Processing Properties of Mozzarella Cheese
LI Liu, ZHENG Zhe, ZHAO Xiao, WU Fengyu, YANG Zhennai
2019, 40(11):  14-22.  doi:10.7506/spkx1002-6630-20180507-089
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In order to explore the application of milk clotting enzyme (MCE) from Bacillus methanolicus in Mozzarella cheese making, single B. methanolicus MCE and an enzyme mixture of 10% B. methanolicus MCE and 90% commercial rennet were used separately in the preparation of Mozzarella cheese, while that made with commercial rennet was used as the control. The proteolytic properties, texture, flavor and microstructure of the cheeses were determined during the ripening process. Results showed that there was no significant difference in pH (4.6–5.3) or microbial count (8.80–9.68 (lg(CFU/g))) between the three groups (P > 0.05). The moisture contents and cheese yields of the experimental groups ((43.21 ± 1.17)% and ((9.27 ± 0.17)% for single B. methanolicus MCE, and (46.15 ± 0.94)% and (9.46 ± 0.16)% for the enzyme mixture, respectively) were both significantly higher than those of the control group ((41.08 ± 1.04)% moisture content and (8.98 ± 0.13)% cheese yield) (P < 0.05). Moreover, the experimental cheeses were also better than the control in terms of the proteolytic properties (the content of pH 4.6 soluble protein, the degree of casein hydrolysis and the content of free amino acids) and the types and contents of flavor substances. However, the cheese made with single B. methanolicus MCE had relatively poor shape-preserving property together with low sensory score. The cheese made with the enzyme mixture was comparable to the control in terms of texture and sensory scores, indicating that MCE from B. methanolicus could be used as a partial substitute for commercial rennet in cheese production.
Effects of Dietary Supplementation of Allium mongolicum Regel and Its Extract on Fatty Acid Composition and Contents in Different Carcass Parts of Small-tailed Han Sheep
ZHANG Xiuyuan, WANG Cuifang, DING He, LI Shuyi, AO Changjin
2019, 40(11):  23-29.  doi:10.7506/spkx1002-6630-20180606-067
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The objective of this study was to investigate the effects of dietary supplementation of Allium mongolicum Regel (AMR) and its extract on the fatty acid composition and contents of lipids in different carcass tissues of small-tailed Han sheep. Healthy sheep were randomly divided into control, AMR polysaccharide, AMR and polysaccharide extraction residue groups. The control group was fed on a basal diet, while the rest were fed on a basal diet supplemented with 0.1% of AMR polysaccharide, 10 g of AMR and 10 g of AMR extraction residue per animal daily, respectively. The pre-experimental period lasted for 15 days, and the formal experimental period lasted for 60 days. At the end of the experiment, Longissimus dorsi, gluteal muscle and subcutaneous fats were collected to determine the composition and contents of fatty acids by gas chromatography-mass spectrometry (GC-MS). The results obtained showed that compared with the control group, the relative contents of C14:1, C16:1, C17:1 and midchain mutton odor fatty acid (MCMOFA) in Longissimus dorsi muscle of the AMR group, C22:6n3 in gluteus muscle of the three experimental groups, C18:1n9c in subcutaneous fat of the AMR group, C18:3n3 in subcutaneous fat of the extraction residue group and C18:3n6 of the polysaccharide and AMR groups were significantly decreased (P < 0.05), while the relative contents of C20:0 in gluteal muscle of the AMR and residue groups, C18:3n6 and C20:1 in gluteal muscle of the AMR group, C10:0, C23:0 and MCMOFA in gluteal muscle of the residue group, C17:0 in subcutaneous fat of the AMR and residue groups, C18:0 and C18:1n9t in subcutaneous fat of the AMR group and C15:1 in subcutaneous fat of the three experimental groups were significantly increased (P < 0.05). In addition, the contents of saturated fatty acid (SFA) and MCMOFA in Longissimus dorsi of the AMR group, polyunsaturated fatty acid (PUFA) in Longissimus dorsi of the three experimental groups, PUFA in the gluteal muscle of the extraction residue group and C18:0 in Longissimus dorsi of the AMR and extraction residue groups were significantly decreased (P < 0.05); the contents of total fatty acids (TFA) in Longissimus dorsi and gluteal muscle of the three experimental groups were decreased (P > 0.05); atherogenic index (AI) in each fatty tissue of the polysaccharide and AMR group, thrombosis index (TI) in Longissimus dorsi of the polysaccharide group were decreased (P > 0.05). Therefore, dietary supplementation of AMR polysaccharide, AMR and extraction residue can adjust fatty acid composition and contents in different carcass parts of sheep, thereby improving the flavor and nutritional value of mutton.
Identification and Analysis of Phosphoproteome in Chicken Egg White
YANG Ran, SONG Hongbo, HUANG Qun, LIU Lili, QIU Ning, MA Meihu
2019, 40(11):  30-35.  doi:10.7506/spkx1002-6630-20181217-195
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In order to systematically elucidate the structural and functional characteristics of phosphorylated proteins in egg white, the phosphoproteome in chicken egg white (CEW) was identified and analyzed with a proteomic strategy in this study. Chicken egg white was digested with trypsin, and phosphopeptides were enriched from the resulting hydrolysate by using immobilized metal-chelate affinity chromatography, and then identified by nano-liquid chromatography/tandem mass spectrometry. After searching against the protein databases, a total of 33 unique phosphorylated peptides were identified, including 41 phosphorylated sites, belonging to 25 egg white phosphorylated proteins. The motif analysis showed that “S-X-E” was the most over-represented. The results of gene ontology annotation and classification indicated that the identified phosphoproteins in chicken egg white were mainly involved in the processes of “biological regulation”, “stimulation reaction” and “development”, and associated with the functions of “binding” and “catalysis”. These results provide key structural information of phosphorylation modification of egg white proteins for future relevant research.
Dynamic Change of Major Taste Substances during Green Tea Processing and Its Impact on Green Tea Quality
XU Wei, PENG Yingqi, ZHANG Tuo, KONG Yingying, XIAO Wenjun
2019, 40(11):  36-41.  doi:10.7506/spkx1002-6630-20180518-275
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Green tea was made from the one bud two leaves in spring of ‘Bixiangzao’ tree plants by spreading, fixation, rolling and drying processes. The dynamic changes in water extract content and the contents of taste substances in the water extract of green tea such as tea polyphenols, amino acid, caffeine, soluble sugar and catechins were analyzed during the processing of green tea and the ratio of phenol to ammonia, the ratio of non-esterified to esterified catechins and sensory quality were measured. The aim of this study was evaluate the impact of the dynamic changes in taste substances during green tea processing on its taste quality. The results showed that overall the contents of water extract and all taste compounds gradually declined during all processing stages, while the contents of water extract, amino acids, caffeine and soluble sugar increased during the spreading process. Correspondingly, the ratio of phenol to ammonia dropped from 11.45 to 6.21 at the spreading stage, then increased up to 8.01 at the fixation stage, and finally tended to stable at the rolling and drying stages. The ratio of non-esterified to esterified catechins increased from 0.43 to 0.45 at the spreading stage, followed by a decrease from 0.47 to 0.44 at the fixation stage, and then gradually declined to 0.35 at the rolling and drying stages. At the same time, these taste substances were significantly associated with the taste quality of green tea. When the phenol/ammonia ratio was in the range of 5.5–6.5, and the ratio of non-esterified to esterified catechins was 0.3–0.5, the taste quality of green tea turned from light and bitter to mellow and refreshing.
Effects of Deep-Fat Frying Methods and Foodstuffs on Contents of 3-Monochloropropane-1,2-diol Esters and Glycidyl Esters in Frying Peanut Oil
LIU Yulan, LIU Hailan, HUANG Huina, MA Yuxiang, AN Jun, WANG Manyi
2019, 40(11):  42-48.  doi:10.7506/spkx1002-6630-20180504-042
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Different foodstuffs (deep-fried dough sticks, French fries, chicken wings, tofu and blank control) were subjected to different deep-fat frying methods: 32 h continuous frying and intermittent frying for a total of 15 h. Sampling was carried out during these processes for determination of the contents of polar components (PC), 3-monochloropropane-1,2-diol esters (3-MCPDE) and glycidyl esters (GEs) in the frying peanut oil. The purpose of this study was to investigate the effect of different frying methods and foodstuffs on the contents of 3-MCPDE and GE esters in the frying oil. The results showed that the content of 3-MCPDE in peanut oil when used for consecutive deep-fat frying of deep-fried dough sticks, French fries, chicken wings, tofu and blank control increased from an initial value of 0.84 to the maximum value of 2.08, 2.96, 17.45, 7.12 and 8.02 mg/kg after 12, 4, 12, 16 and 8 h, respectively, followed by a decrease afterwards, and the content of GEs increased from an initial level of 2.43 to 20.80, 7.20, 5.00, 2.10 and 66.34 mg/kg at the end of the 32 h frying period, respectively. When PC reached the national standard limit of 27%, the sum of 3-MCPDE and GEs in different frying oils followed the decreasing order of blank control (66.51 mg/kg) > deep-fried dough sticks (21.48 mg/kg) > tofu (12.93 mg/kg) > French fries (8.51 mg/kg) > chicken wings (6.60 mg/kg). The contents of 3-MCPDE in frying oils from French fries, chicken wings, tofu, deep-fried dough sticks and blank control increased to 9.96, 2.17, 4.60, 11.02 and 5.41 mg/kg over the first 3 h of intermittent frying, and were 3.51, 1.58, 12.88, 11.81 and 3.72 mg/kg, respectively at the end. The content of GEs increased from 2.43 to 46.47, 9.06, 9.00, 40.36 and 47.05 mg/kg over the 15 h intermittent frying period, respectively. After 15 h of intermittent frying, none of the five frying oils had a PC content exceeding the national standard limit, and the sum of 3-MCPDE and GEs was in the descending order of chicken wings (52.17 mg/kg) > blank control (50.87 mg/kg) > deep-fried dough sticks (49.98 mg/kg) > tofu (21.88 mg/kg) > French fries (10.64 mg/kg). The increase in the sum of 3-MCPDE, GEs and PC over the 32 h consecutive frying period was ranked in the decreasing order of blank control > deep-fried dough sticks > French fries > chicken wings > tofu, while that over the 15 h intermittent frying period in the decreasing order of chicken wings > deep-fried dough sticks > blank control > tofu > French fries. For each food stuff, the increase in the sum of 3-MCPDE, GEs and PC in the 16 h continuous frying oil was lower than that in the 15 h intermittent frying oil. In summary, the health risk of 3-MCPDE and GEs formed during deep-fat frying should be taken seriously.
Application of Zero-Inflated Models in Quantitative Exposure Assessment of Listeria monocytogenes in Bulk Cooked Meat
SUN Wanxia, JIN Yuqin, DAI Yingxiu, XIAO Jianwei, WANG Xiang, DONG Qingli
2019, 40(11):  49-54.  doi:10.7506/spkx1002-6630-20180429-380
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In many cases, measured contamination levels of Listeria monocytogenes in bulk cooked meat are characterized by zero-inflation and over-dispersion features. The effect of different left-censored data processing methods on quantitative exposure assessment was discussed in this work. The contamination level of L. monocytogenes in bulk cooked meat products was determined using 254 samples collected from supermarkets, farmers’ markets and catering links in a certain district of Shanghai from February to December 2017. As an illustration, traditional statistical distributions and their zero-inflated models were used to assess the concentration of L. monocytogenes in bulk cooked meat products. The models were compared and validated for their performance using R 2.0 software. The L. monocytogenes concentration data consisting of a considerable number of left-censored data could be appropriately represented by zero-inflated lognormal distribution or zero-inflated Poisson lognormal distribution. The parameter estimates of the zero-inflated models indicated that the prevalence of L. monocytogenes in bulk cooked meat products was 2%. This work provides a theoretical basis for the statistical analysis of left-censored L. monocytogenes concentration data and serves as the essential starting point for a complete risk assessment framework.
Effect of Light Quality on Tomato Fruit Quality and Volatile Compounds
YANG Junwei, LIANG Tingting, YAN Lulu, ZHANG Kejia, XI Linjie, ZOU Zhirong
2019, 40(11):  55-61.  doi:10.7506/spkx1002-6630-20180521-278
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This study investigated the effects of different red/blue light treatments (R, 2R1B, 1R1B, 1R2B and B) (white light as the control) on the individual fruit mass, major quality traits and volatile components of the tomato cultivar ‘Jinpeng chaoguan’. Results showed that 2R1B (red : blue = 2:1) treatment significantly enhanced individual fruit mass and the contents of soluble protein, ascorbic acid and lycopene. Under R (pure red) treatment, both soluble solids content and sugar/acids ratio were significantly higher than the control (P < 0.05). Headspace solid phase extraction and gas chromatography mass spectrometry were used to analyze the volatile components of tomato fruit under different light treatments. The content of total volatile components was significantly improved under R and 2R1B treatments when compared with other treatments. These results provide a theoretical rationale for the improvement of tomato fruit quality and flavor using different light qualities.
Fruit Quality Analysis of the New Wine Grape Variety ‘Pearl Noir’
PENG Wenting, WANG Wenran, YANG Hangyu, CHEN Weikai, YANG Zhe, HE Fei, WANG Jun
2019, 40(11):  62-69.  doi:10.7506/spkx1002-6630-20180518-255
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In order to study the wine-making characteristics of ‘Pearl Noir’ grape and its parental information, the compositions and the contents of anthocyanins and volatile compounds in ‘Pearl Noir’ grapes were analyzed using high performance liquid chromatography-mass spectrometry (HPLC-MS) and gas chromatography-mass spectrometry (GC-MS), respectively. HPLC-MS results showed that the content of total anthocyanins in ‘Pearl Noir’ skin was 2 774.76 mg/kg mf and the high proportion of diglucoside anthocyanin (71.2%) indicated that ‘Pearl Noir’ may have a potential genetic relationship with non-vinifera grapes. GC-MS results showed that a total of 123 volatile compounds in free and/or glycosidically-bound forms were detected in ‘Pearl Noir’ grapes. Simple sequence repeats (SSR) analysis showed that no parents of ‘Pearl Noir’ were found in all tested cultivars (‘Beta’, ‘Yan 73’ and ‘Kolor’). In the future, ‘Pearl Noir’ grapes can be used as a new variety to make wine with regional characteristics or to enhance wine color by blending with pale red wines due to the high content of anthocyanins in its skin and the deep color possessed by its varietal wines.
Inhibition Kinetics and Mechanisms of Resveratrol on α-Glucosidase
JIANG Lili, ZHANG Zhongmin, CHEN Daoyu, WANG Zhen, XUE Hongyu, LIU Yong
2019, 40(11):  70-74.  doi:10.7506/spkx1002-6630-20180503-031
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Due to its extensive biological activities such as hypoglycemic effects, resveratrol has gained much attention. Besides, α-glucosidase inhibitors can decrease hyperglycemia, which is closely related to the treatment of type-2 diabetes. In the present study, enzyme-inhibitory kinetics and computer simulation were applied to investigate the effect of resveratrol on the activity of α-glucosidase. The activity of α-glucosidase was measured by spectrophotometry, the inhibition kinetics was investigated using Lineweaver-Burk method, and the binding mechanisms between resveratrol and α-glucosidase were explored using molecular docking simulation. The results indicated that resveratrol was a stronger inhibitor (half maximal inhibitory concentration (IC50) = 5.047 μmol/L) than acarbose (IC50 = 632.6 μmol/L). The inhibition type was noncompetitive, and the value of Ki was 5.743 μmol/L. Molecular docking results demonstrated that the existence of multiple binding modes between resveratrol and α-glucosidase did not affect the binding interaction between acarbose and α-glucosidase. Therefore, resveratrol had potent inhibitory activity against α-glucosidase, and thus had the potential to be developed as an antidiabetic drug or as a dietary supplement in a synergetic manner with acarbose for the treatment of diabetes.
Separation and Enrichment of Casein Phosphopeptides Using SiO2@TiO2 Composite
LIU Zhenzhen, LI Rong, TANG Shuhua, HUANG Xianyong, ZHANG Wanjing, LI Yongjie, JIANG Zitao
2019, 40(11):  75-81.  doi:10.7506/spkx1002-6630-20180606-063
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Titania can selectively adsorb phosphopeptides. In order to obtain TiO2 with high specific surface area and improve the separation and enrichment of phosphopeptide, a SiO2@TiO2 composite was prepared by layer-by-layer selfassembly method. The specific surface area and average pore diameter of SiO2@TiO2 are 116.26 m2/g and 8.42 nm, respectively. The core-shell composite was used in the separation and enrichment of casein phosphopeptides (CPPs). The adsorption rate of CPPs was determined to be 93.0% by high performance liquid chromatography (HPLC), and the desorption rate was 81.5%. The sequence of the five phosphopeptides present in the eluent was identified as PS*H, PS*PR, S*SRS*E, PHS* and PS*SRS*EP by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOFMS ), respectively. The contents of CPPs in commercial CPPs product, calcium tablets and infant formula were determined by HPLC with theophylline as the internal standard, and the results showed that average recoveries of CPPS were 92.5%–95.1%. It can be concluded that the core-shell SiO2@TiO2 composite had excellent properties and allowed efficient separation and enrichment of CPPs, and the proposed method was accurate and reliable to determine CPPs in real samples.
Effect of Aroma Enhancement Methods on the Quality of Congou Black Tea
QIU Fangfang, ZENG Weichao, QU Fengfeng, YU Zhi, CHEN Yuqiong, ZHENG Shibing, NI Dejiang
2019, 40(11):  82-87.  doi:10.7506/spkx1002-6630-20180515-211
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The effects of different aroma enhancement treatments (hot air, far-infrared, microwave, light wave and microwave + light wave (microwave : light wave = 67%:33%)) on the sensory evaluation, physicochemical properties and aroma composition of Yihong black tea were studied. Sensory evaluation results showed that each of the treatments especially far-infrared and microwave irradiation could significantly strengthen the sweet aroma and fresh taste of black tea. Physicochemical analysis indicated that the different treatments had little effect on the content of water extractable substances in black tea, but greatly affected the composition of amino acids, aromatic compounds and catechins, and the contents of soluble sugar, tea polyphenols and theaflavins. Compared with the control, all these treatments could increase the content of theaflavins, and their effects followed the descending order: light wave (0.96 mg/g) > microwave (0.86 mg/g) > far-infrared (0.85 mg/g) > hot air (0.82 mg/g). The results also revealed that the treatments could decrease the amounts of linalool and benzyl alcohol and increase the amounts of benzaldehyde, (E)-β-lonone and (E)-trans-nerolidol, as well as lead to the formation of new heterocyclic compounds responsible for roasted aroma such as pyrazine and pyrimidine. Changes in each of the aromatic substances contributed to the sweet aroma of black tea. Furthermore, the contents of ketones, esters, ethers and aromatic components after hot air, far-infrared, and microwave treatments were significantly higher than in those subjected to any other treatments. Overall, far-infrared and microwave treatments were considered to be more suitable for aroma enhancement of Congou black tea.
Effects of Different Extraction Methods on the Release of Flavor Substances from Grifola frondosa
XU Rui, XU Xiaodong, SONG Ze, JIA Qian, FENG Tao, SONG Shiqing
2019, 40(11):  88-94.  doi:10.7506/spkx1002-6630-20180515-210
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Purpose: To study the effects of different treatment methods (enzymatic hydrolysis, high pressure cooking and flash extraction) on the release of flavor substances from Grifola frondosa. Methods: Soluble sugar, organic acid, free amino acid composition and molecular mass distribution were analyzed by high performance liquid chromatography. The flavor characteristics of the edible mushroom were analyzed using an electronic tongue. Principal component analysis (PCA) was used for statistical analysis of the products prepared by different extraction methods. Results: The total amount of soluble sugar in the aqueous extract of Grifola frondosa (untreated control) was significantly decreased by all treatments (P < 0.05), especially high-pressure cooking after flash extraction. On the contrary, the total amount of organic acids was significantly increased by enzymatic hydrolysis and high pressure cooking (P < 0.05) and was increased by flash extraction pretreatment for both the control and treatment groups. The total amount of amino acids was increased by sequential two-step enzymatic hydrolysis but was decreased by high-pressure cooking. The amounts of umami, sweet and bitter amino acids were increased significantly by sequential enzymatic hydrolysis (P < 0.05) and the resulting hydrolysate was dominated by peptides smaller than 3 000 Da. The content of these peptides was decreased by flash extraction pretreatment, which indicates that flash extraction is unfavorable for the retention of free amino acids. PCA analysis showed that the taste and taste substances were significantly different from the control after enzymatic hydrolysis and high-pressure cooking, and also changed significantly after flash extraction. Conclusion: The taste characteristics of Grifola frondosa are closely related to its specific taste substances and efficient preparation of taste substances depends on the treatment method used. Therefore, this study provides a theoretical basis for the development of Grifola frondosa seasonings and the preparation of taste peptides.
Food Engineering
Effect of Freeze-Thaw Cycles on Changes in Functional and Structural Properties of Myofibrillar Protein from Mirror Carp (Cyprinus carpio var. specularis)
DENG Siyang, WANG Bo, LI Haijing, ZHONG Qiang, DONG Chunhui, XIA Xiufang
2019, 40(11):  95-101.  doi:10.7506/spkx1002-6630-20180606-079
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The effect of freeze-thaw cycles on the functional and structural properties of myofibrillar protein from mirror carp (Cyprinus carpio var. specularis) was investigated by measuring the changes in the emulsifying properties, solubility, δ-potential, surface hydrophobicity and content of sulfydryl, free amino acids, dityrosine, surface hydrophobicity and α-helix. The results indicated that the solubility, emulsifying activity and emulsion stability of myofibrillar protein decreased to 62.85%, 20.67 m2/g and 34.83%, respectively after five freeze-thaw cycles (P < 0.05). The δ-potential, surface hydrophobicity and dityrosine content increased constantly with the increase of freeze-thaw cycles, while the sulfydryl, free amino acid and α-helical contents decreased gradually. These changes suggested that freeze-thaw cycles damaged the structural integrity and functional properties of fish myofibrillar protein.
Kinetics and Energy Consumption Analysis of Cell Disruption of Chlorella sp. for Carotenoid Extraction by Bead Beating
LU Kongyong, XIE Youping, ZHAO Xurui, HE Shixin, CHEN Jianfeng
2019, 40(11):  102-108.  doi:10.7506/spkx1002-6630-20180515-214
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The bead beating method was used to disrupt the lyophilized and wet cells of Chlorella sp.. The kinetics and specific energy consumption of cell disruption were investigated in order to determine the effect of the degree of cell disruption (as reflected by the amount of released chlorophyll) on carotenoid extraction. The results showed that the first-order dynamic equation could well describe the cell disruption process. The maximum extraction efficiencies of carotenoid of 6.38 and 6.26 mg/g were obtained when the percentage disruption of lyophilized and wet cells were 70% and 90%, respectively. It was found that the energy consumption required for disruption of wet cells was higher than that required for lyophilized cells. Consistent results were observed from the disruption of lyophilized cells in the concentration range of 40–160 g/L and carotenoid extraction using the same specific energy consumption. For wet cells at 80 g/L, higher cell disruption and carotenoid extraction efficiencies could be obtained even at lower specific energy consumption. The results of this study can provide both theoretical and experimental evidence for the cell disruption of Chlorella sp., and the development and utilization of its effective components.
Effect of High-Energy Ball Milling on Particle Size and Rheological Properties of Whole Pulp of Gannan Navel Orange
YANG Ying, SHAN Yang, DING Shenghua, PAN Zhaoping, ZHANG Mengling, FU Fuhua
2019, 40(11):  109-115.  doi:10.7506/spkx1002-6630-20180521-291
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Crude whole navel orange pulp was subjected to ball milling treatment to develop whole fruit products with reduced particle size and improved rheological properties. The whole fruit paste of Gannan navel orange was ball milled for different durations (0, 30, 60, 90, 120, 150, and 180 min). Changes in its particle size and rheological properties were examined. The results showed that ball milling could effectively reduce the particle size of the whole fruit pulp. The average particle diameter decreased from 110.00 to 56.53 μm after ball milling for 180 min, by 49% overall. The whole fruit pulp became more and more delicate and uniform without aggregation with the increase of milling time. The shear strength increased with the increase of shear rate, while the apparent viscosity decreased. Shear thinning occurred in the fruit pulp, which was a typical pseudoplastic fluid with good viscoelasticity. Compared with the unmilled pulp, the whole pulp ball milled for 60 min showed the highest viscosity and the most stable gel-like state and was suitable for the processing of jam products with higher viscosity, whereas the pulp system ball milled for 30 min exhibited the lowest viscosity but the best fluidity and was suitable for the processing of juices with better fluidity. This study provide a rationale for the processing of whole citrus fruit products.
Effect of Fermentation and Processing on Antioxidant and Hypoglycemic Activity of Mulberry Fruit
LONG Xiaoshan, HU Tenggen, ZOU Yuxiao, LIAO Sentai, WANG Siyuan, LIN Guangyue, LI Erna, LIU Fan, LI Qian
2019, 40(11):  116-123.  doi:10.7506/spkx1002-6630-20180504-049
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Objective: To study the effect of fermentation and processing on the antioxidant and hypoglycemic activity of mulberry fruit. Methods: The monosaccharide content, microbial populations and scavenging capacity against 2,2’-azinobis- (3-ethylbenzthiazoline-6-sulphonate) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals, ferrous ion chelating power and alpha-glucosidase inhibitory activity of mulberry powder (MP), fermented mulberry (FM), freeze-dried fermented mulberry (D (FM)) and freeze-dried fermented mulberry mixed with soybean (D (FM + S)) were determined. Results: After fermentation and freeze-drying of mulberry, its fructose and glucose levels decreased to zero. The survival rates of Leuconstoc mesenteroides and Saccharomyces cerevisiae in D (FM) were 54.77% and 53.40%, respectively, while those in D (FM + S) were both more than 90%, implying that the presence of soybean resulted in reduced loss of probiotics during the freeze drying process. The ABTS radical scavenging capacity of these samples followed the decreasing order of D (FM) > D (FM + S) > MP > FM. Consistent trends were observed for DPPH and hydroxyl radical scavenging capacity and ferrous ion chelating power. Both D (FM) and D (FM + S) were ranked the highest, followed by MP, and FM was the weakest. The IC50 values for inhibition of alpha-glucosidase by MP, FM, D (FM) and D (FM + S) were 0.58, 0.53, 0.19 and 0.31 mg/mL, respectively, which indicates that the inhibitory effect of D (FM) and D (FM + S) was better than that of the other samples. Conclusion: Frozen-dried fermented mulberry mixed with soybean has stronger antioxidant and hypoglycemic effects than both fermented and unfermented mulberry.
Effect of Steam Explosion Pretreatment on Quality of Tea Seed (Camellia oleifera Abel.) Oil Obtained by Aqueous Extraction
ZHANG Shanying, ZHENG Lili, AI Binling, ZHENG Xiaoyan, YANG Yang, PAN Yonggui, SHENG Zhanwu
2019, 40(11):  124-130.  doi:10.7506/spkx1002-6630-20180614-272
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Steam explosion pretreatment was employed for Camellia oleifera seeds, and the effects of different steam pressure levels and holding time on the yield, physicochemical properties, bioactive substance contents of tea seed oil were explored, as well as the internal factors that affect the change in tea oil quality. The results showed that the oil yield increased with steam pressure up to 1.6 MPa and then decreased. The maximum extraction efficiency was obtained when the pressure holding time was 30 s. Therefore, 1.6 MPa and pressure holding time of 30 s could be considered as the optimal steam explosion conditions for tea seeds. Steam explosion pretreatment reduced the acid, peroxide value of tea seed oil, and increased iodine value and the contents of polyphenols, squalene and vitamin E. Scanning electron microscopy revealed that steam explosion pretreatment made the surface of tea seeds rougher and destroyed the cell structure, thereby promoting the release of oil and bioactive substances. In addition, steam explosion accelerated the Maillard reaction of tea seed oil. Therefore, steam explosion could be an effective method for the extraction of tea seed oil and the release of bioactive substances.
Effect of Variable Low Temperature Combined with High-Humidity Thawing on Physicochemical Characteristics, Thermal Denaturation and Rheological Properties of Pork
ZHU Mingming, PENG Zeyu, ZHAO Hekai, KANG Zhuangli, ZHAO Shengming, WANG Zhengrong, HE Hongju, MA Hanjun
2019, 40(11):  131-138.  doi:10.7506/spkx1002-6630-20180606-056
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This study was conducted to analyze the effects of thawing at different relative humidity (RH 80%, 85%, 90% and 95%) and viable low temperature (2 ℃ → 6 ℃ → 2 ℃) on the quality characteristics of pork by using fresh pork and conventional low temperature thawing (4 ℃, RH 65%–73%) as the controls. The changes in thawing rate, physicochemical characteristics including water-holding capacity (WHC), color, tenderness and freshness, protein thermal denaturation and rheological properties were examined. The results showed that compared with conventional low temperature thawing, variable low temperature, high humidity thawing could improve the thawing efficiency (P < 0.05), maintain the WHC, color and tenderness of pork, and inhibit lipid oxidation significantly (P < 0.05). The thawing efficiency at RH of 90% and 95% was higher than at RH of 85% and 80%. In addition, viable low temperature thawing at RH of 90% and 95% allowed better maintenance of WHC, color and tenderness (close to fresh pork), reduced lipid oxidation and increased protein solubility. The degree of protein denaturation in the thawed pork at RH of 90% and 95% was significantly lower than at RH of 80% and 85% (P < 0.05) as measured by differential scanning calorimetry (DSC). Also, the thawing at RH of 90% and 95% maintained the G′ value better. However, total bacterial count (3.97(lg(CFU/g))) and TVB-N content (1.40 mg/100 g) in the thawed pork at 95% RH were significantly higher than other thawed samples. Moreover, greater humidity could require higher energy consumption. Therefore, variable low temperature combined with 90% relative humidity thawing was more suitable for frozen pork .
Nutrition & Hygiene
Composition and in Vitro Immunostimulatory Activity of Low-Molecular-Mass Fractions of Chemically Degraded Ascophyllan from Ascophyllum nodosum
HE Pingping, WEI Jingliuyi, JIANG Zedong, ZHU Yanbing, NI Hui, LI Qingbiao
2019, 40(11):  139-145.  doi:10.7506/spkx1002-6630-20180610-122
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Objective: To separate and purify low-molecular-mass fractions from the chemical degradation products of the sulfated polysaccharide ascophyllan extracted from the brown seaweed Ascophyllum nodosum and to analyze the monosaccharide composition and in vitro immunostimulatory activity of each of these fractions for the purpose of providing useful information for the studies on the biological activities and structural characteristics of ascophyllan and other seaweed polysaccharides. Methods: The degraded products of ascophyllan, prepared separately by treatment with hydrochloric acid or hydrogen peroxide, were fractionated sequentially by ultrafiltration and Sephadex G-50 gel filtration chromatography into four low-molecular-mass fractions (HCl-F1, HCl-F2, H2O2-F1 and H2O2-F2). The monosaccharide composition of each fraction was determined by high-performance liquid chromatography (HPLC) with pre-column ethyl-p-aminobenzoate (ABEE) derivatization and some of their chemical groups were analyzed. Their weight-average molecular masses were evaluated by high-performance size exclusion chromatography (HPSEC), and their in vitro immunostimulatory activities were investigated by using mouse RAW264.7 macrophages as a model. Results: All these compounds were heteropolysaccharides with significant differences in their monosaccharide composition and sulfation level. The weight-average molecular masses of HCl-F1, HCl-F2, H2O2-F1 and H2O2-F2 were estimated to be 4.80, 4.20, 5.30 and 2.30 kDa, respectively. The in vitro immunomodulatory activity revealed that HCl-F1, HCl-F2, and H2O2-F2 significantly induced the activation of RAW264.7 macrophages to produce immune factors such as nitric oxide (NO) and tumor necrosis factor-a (TNF-a) in the test concentration range (0–200 mg/mL), whereas the ability of H2O2-F1 to induce the production of NO and TNF-a in RAW264.7 cells was significantly lower than that of any other polysaccharide fraction. Conclusion: All the low-molecular-mass polysaccharide fractions (HCl-F1, HCl-F2 and H2O2-F2) derived from ascophyllan possessed potent immunostimulatory activity, with HCl-F1 and H2O2-F2 being much stronger than ascophyllan. Taken together, the immunostimulatory activity is likely determined by a combination of monosaccharide composition and sulfate content.
Effects of Different Solvent Extracts from Schisandra chinensis Bee Pollen on Hepatic Lipid Peroxidation and DNA Oxidative Damage
CHEN Sinan, WANG Xinyi, LI Mengting, HE Liangliang, WANG Qilei, WANG Guojiao, WANG Weidong, CAO Wei, CHENG Ni
2019, 40(11):  146-151.  doi:10.7506/spkx1002-6630-20180423-285
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Schisandra chinensis bee pollen has strong antioxidant activity. In order to explore the distribution of antioxidant components in it, the 75% ethanol extract of S. chinensis bee pollen was fractionated by successive extraction with petroleum ether, ethyl acetate and n-butanol. The active ingredients and antioxidant activity in vitro of the fractions were evaluated as well as the inhibitory effect on lipid peroxidation of liver homogenate and the protective effect on DNA oxidative damage. The results showed that the fractions differed significantly with respect to their antioxidant activity, inhibitory effect on lipid peroxidation and protective effect on oxidative DNA damage (P < 0.05), in the decreasing order: n-butanol extract > ethyl acetate extract > petroleum ether extract. The n-butanol extract had the highest total phenolic content (26.11 g/100 g), and its total flavonoid content was 27.90 g/100 g. This extract had strong Fe2+ chelating power, reducing power, and 1,1-diphenyl- 2-picrylhydrazyl scavenging capacity. Moreover, 85% of lipid peroxidation was inhibited by 0.2 mg/mL of the n-butanol extract. This study provides a basis for the separation and purification of powerfully antioxidant phenolics from S. chinensis bee pollen and for the development of antioxidant foods.
Effect of Soybean Oligopeptides on Blood Pressure and Plasma Angiotensin in Spontaneously Hypertensive Rats
LI Wenhui, ZHANG Jian, YING Xin, WANG Yong, ZHANG Lianhui, LI He, LIU Xinqi
2019, 40(11):  152-158.  doi:10.7506/spkx1002-6630-20181017-184
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Purpose: To investigate the effect of soybean oligopeptides on blood pressure and plasma angiotensin levels in rats. Methods: Soybean oligopeptides were prepared by enzymatic treatment, and its angiotensin I converting enzyme (ACE) inhibitory activity was evaluated both in vitro and in vivo experiments. Rats were divided into six groups: normal control (Wistar-Kyoto (WKY) rats with normal blood pressure rats fed high-dose soybean oligopeptides), negative control (spontaneously hypertensive (SHR) rats), positive control (SHR rats fed captopril), low, medium and high-dose groups (SHR rats fed 0.90, 1.80, 4.50 g/kg soybean oligopeptides). The feeding experiment lasted for 30 days. The changes in blood pressure, heart rate, urinary protein content and plasma angiotensin II concentration were determined during the experimental period. Results: The optimal conditions for enzymatic hydrolysis of soybean protein were found to be hydrolysis at 50 ℃ for 4 h with a mixture of alkaline protease and neutral protease at a dosage of 0.1% each. The percentage inhibition of ACE activity by soybean oligopeptides at 10 mg/mL prepared using the optimized conditions was up to 71.2%. After 30 days of feeding, there was no significant difference in blood pressure of WKY rats (P > 0.05), while the blood pressure of SHR rats had a decreasing trend in all dose groups of soybean oligopeptides. High-dose soybean oligopeptides significantly reduced blood pressure and mass concentration of angiotensin II in SHR rats at the end of the fourth week (P < 0.05), but had no significant effect on rat heart rate or urinary protein content (P > 0.05). Conclusion: Compared with soybean protein, soybean oligopeptides had better inhibitory effect on ACE activity, and could reduce blood pressure and plasma angiotensin II levels in SHR rats but without significant effect on blood pressure in normal rats. Therefore, soybean oligopeptides can exert antihypertensive effect perhaps by inhibiting ACE activity.
Antarctic Krill Oil Enhances Fracture Healing in Osteoporotic Mouse Model
LI Yuanyuan, MAO Xiangzhao, TANG Penghao, LI Cailong, YU Peng, WANG Jingfeng
2019, 40(11):  159-166.  doi:10.7506/spkx1002-6630-20180223-182
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Objective: To investigate the effect of Antarctic krill oil (AKO) on fracture healing in an osteoporotic mouse model. Methods: Female C57BL/6J mice were ovariectomized to establish the animal model of osteoporosis. Then the mice were subjected to open fracture operation on the right tibial and randomly divided into four groups: control, osteoporotic fracture model, positive control and AKO groups. We dynamically observed the effect of AKO on serum biochemical indicators and callus histomorphology, microstructure and biomechanical properties at 5, 11, 24, 35 and 56 days post-fracture. In addition, we also investigated the effect of AKO on the expression of key genes involved in endochondrial ossification. Results: The results of enzyme-linked immunosorbent assay showed that AKO could significantly increase the serum levels of vascular endothelial growth factor (VEGF) and bone alkaline phosphatase. The HE staining and micro-computed tomography results showed that AKO could promote the transformation of cartilaginous callus into osseous callus, improved the microstructure of callus and accelerated callus remodeling. AKO could enhance biomechanical properties of bony callus. The quantitative real time polymerase chain reaction results showed that AKO significantly increased the mRNA expression of angiogenesis factors (VEGF, platelet derived growth factor and angiotensin 1) (P < 0.05), and decreased the expression of the genes associated with chondrocyte proliferation and hypertrophy (Aggrecan and Col10a) (P < 0.05). Furthermore, AKO significantly increased the mRNA expression of MMP-13 and osteogenesis-related genes (Col1a, OCN and bone morphogenetic protein (BMP-2)) (P < 0.05). These results suggested that AKO could accelerate the process of cartilage ossification and promote fracture healing by regulating the expression of key genes related to endochondral ossification. Conclusion: AKO can accelerate osteoporotic fracture healing and improve healing quality by promoting the process of cartilage ossification and callus remodeling.
Enzymatic Preparation of Peptide from Cyclina sinensis Proteins and Its Inhibitory Activity toward Prostate Cancer DU-145 Cells
ZHANG Yaru, YAN Haiqiang, YANG Zuisu, YU Fangmiao, DING Guofang, GONG Jianfang
2019, 40(11):  167-174.  doi:10.7506/spkx1002-6630-20180421-281
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The purpose of this study was to investigate the enzymatic preparation of peptide from Cyclina sinensis proteins and to evaluate its activity against prostate cancer DU-145 cells. Different proteases were screened to increase the amino nitrogen content of hydrolysates and the hydrolysis conditions were optimized using orthogonal array experiments. An active peptide was purified from the hydrolysates through ultrafiltration, gel chromatography and preparative high performance liquid chromatography. The amino acid sequence of the purified peptide was identified as Ile-Leu-Tyr-Met-Pro. The antiproliferative activity of this peptide against DU-145 cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay and the morphologic change of DU-145 cells was observed by using an inverted microscope, Hoechst 33258 staining and transmission electron microscopy. A fluorescence method was used to detect the generation of intracellular reactive oxygen species (ROS). Cell apoptosis was evaluated by determination of mitochondrial membrane potential using flow cytometry. Furthermore, the expression of nm23H1 was detected by an immunohistochemical method. Our results showed that papain was the optimal protease for hydrolyzing Cyclina sinensis proteins and the optimum hydrolysis conditions were determined as follows: solid-to-solvent ratio 1:4, pH 7.0, enzyme dosage 1 500 U/g, temperature 45 ℃ and hydrolysis time 4 h. The purified peptide had a significant inhibitory effect on DU-145 cells in a time- and dosedependent manner. The treated cells exhibited apoptotic morphological characteristics. The concentration of the peptide was positively correlated with the generation of ROS in cells. Flow cytometry revealed that the percentage of cells with decreased mitochondrial membrane potential was increased from 4.22% to 25.07%. Immunohistochemical results indicated that the expression of nm23H1 was increased. Therefore, the enzymatic peptide from Cyclina sinensis could significantly inhibit the proliferation of DU-145 cells by inducing apoptosis.
Pu-erh Tea Inhibits Body Mass Gain and Modulates Cytokine Profiles of Nutritionally Obese Sprague-Dawley Rats
FENG Wei, WANG Xueqing, CHEN Pei, AN Wenwen, ZHANG Chaoying, LI Shengying, YAN Qiang, WANG Pengji, BAI Xiaoli, LI Changwen
2019, 40(11):  175-181.  doi:10.7506/spkx1002-6630-20180305-051
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In order to explore the antiobesity mechanism and health benefits of Pu-erh tea, SD rats with normal body mass were used as the normal control group, and nutritionally induced obese SD rats were randomly divided into five groups of 8 rats each: obese model group, sibutramine positive control group, and low-, middle-, and high-dose Pu-erh tea groups. The rats were administered with Pu-erh tea by gavage for 42 successive days, and their body masses were measured once a week. Glucose (Glu), insulin, leptin, adiponectin, tumor necrosis factor-alpha (TNF-α), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), interleukin-1 alpha/beta (IL-1α/β) and vascular endothelial growth factor (VEGF) levels were determined in the serum of rats in each group after 24 h fasting. Compared with the obese control, the body mass in the low-, middle-, and high-dose Pu-erh tea groups decreased by 24.8%, 26.59% and 27.62% (P < 0.05), respectively, serum Glu by 57.3%, 67.1% and 72.7% (P < 0.01), LDL-C by 7.11%, 9.11% and 25.74% (P < 0.05), insulin by 8.6%, 17.2% and 41.7%, leptin by 68.6%, 66.8%, 64.6% (P < 0.01), VEGF by 45.3%, 44.6%, 40.5% (P < 0.01), and TNF-α by 25.0%, 27.8%, 33.3% (P < 0.01); whereas HDL-C significantly increased by 20.4%, 22.2% and 25.0% (P < 0.05), and adiponectin by 5.9%, 7.6% and 9.7% (P < 0.05), respectively. Moreover, Pu-erh tea increased IL-1α and reduced IL-1β, thereby modulating the ratio of IL-1α to IL-1β. Therefore, Pu-erh tea obviously reduces body mass gain and modulates cytokine profiles in high-fat diet-induced obese rats.
Protective Effect of Insulin-Like Growth Factor-I on Acetylsalicylic Acid-Induced Damage of Intestinal Epithelial Cells
WANG Yuexin, ZHANG Ligang, AN Jingjing, MA Ming, LIU Ning
2019, 40(11):  182-187.  doi:10.7506/spkx1002-6630-20180312-122
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The present study was designed to investigate the repairing effect of insulin-like growth factors-I (IGF-I) on acetylsalicylic acid (ASA)-induced damage of intestinal epithelial cells (IEC-6). The cell damage model was induced by ASA. The CCK-8 assay was used to evaluate the proliferation of IEC-6. After being treated with ASA and IGF-I, the cells were collected for determining the activities of lactate dehydrogenase (LDH) and alkaline phosphatase (ALP), and the culture supernatant for analysis of Na+,K+-ATPase and alkaline phosphatase (ALP) and the contents of total protein and malondialdelyde (MDA). We found that compared with the control group, IGF-I at all concentrations tested promoted cell proliferation (P < 0.05). IGF-I increased the cell survival rate, decreased the LDH activity in the culture supernatant and reduced the ALP activity and MDA content in the cells, as well as elevated the total protein content and Na+,K+-ATPase activity. According to our results, IGF-I can promote the proliferation of IEC-6 damaged by ASA, inhibit membrane lipid peroxidation, maintain the morphological integrity and consequently repair cell damage.
Walnut (Juglans regia) Kernel Can Prevent Scopolamine-Induced Memory Impairment in Mice
NAI Yifan, FENG Li, LIAO Jianqiao, MA Qi, BO Jifang, LI Mei*, XU Huaide
2019, 40(11):  188-194.  doi:10.7506/spkx1002-6630-20180424-321
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We undertook this study in order to investigate the effect of dietary supplementation of walnut (Juglans regia) kernel on learning and memory capacity in a mouse model of memory impairment induced by scopolamine (SCOP). The experimental mice were fed a diet containing 9% ( high-dose treatment and prevention groups) or 6% walnut kernel (low-dose and low-dose prevention groups) while those in the other groups (control, model and positive control) were fed a normal diet. After 8 weeks of feeding, the Morris water maze (MWM) was used to evaluate the learning and memory capacity of mice. Meanwhile, brain tissues were harvested to measure the levels of malondialdehyde (MDA) and glutathione (GSH), and the activities of total superoxide dismutase (T-SOD) and acetylcholinesterase (AChE). Results showed that in the MWM trial, the escape latency of the mice in the high-dose prevention group was significantly shortened on the fourth day (P < 0.01) while the number of punctures increased (P < 0.05) and the time spent and percentage distance traveled in the target quadrant were increased (P < 0.05) when compared with the model group. Besides, AChE activity and MDA content were decreased to (0.94 ± 0.08) U/mg and (11.64 ± 0.58) nmol/mg, respectively (P < 0.05); in contrast, GSH content and T-SOD activity were increased (69.53 ± 2.11) mg/g and (93.36 ± 4.94) U/mg, respectively (P < 0.05) in brain tissue. These findings suggest that dietary supplementation of walnut kernel could inhibit oxidative damage in the brain mice, enhance cholinergic function, prevent SCOP-induced memory impairment and improve learning and memory capacity.
Packaging & Storage
Relationship of Energy Metabolism and Storage Quality of Broccoli Head under O2/CO2 Controlled Atmospheres
WANG Liang, CHEN Yong, GUO Yanyin, YUAN Liping, LIU Shasha, ZHANG Yuxiao, ZHANG Xinhua
2019, 40(11):  195-200.  doi:10.7506/spkx1002-6630-20180604-030
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Energy plays an essential role in the postharvest senescence of fruits and vegetables. In order to study the effect of O2/CO2 controlled atmosphere packaging on the energy metabolism and storage quality of broccoli at 10 ℃, different controlled atmospheres: 20% O2 + 80% CO2, 50% O2 + 50% CO2, and 80% O2 + 20% CO2 were employed as the experimental groups while natural air was used as the control. pH, the activities of pyruvate dehydrogenase (PDH), succinate dehydrogenase (SDH) and cytochrome c oxidase (CCO), energy charge, ascorbic acid, color value (hue, H) and water content were periodically measured during storage. The results showed that compared with the 50% O2 + 50% CO2 treatment, excessive proportion of CO2 such as 20% O2 + 80% CO2 significantly decreased the pH, PDH, SDH and CCO activities, and energy charge, and finally resulted in a decrease of VC content, H value and water content in broccoli during storage. Excessive proportion of O2 such as 80% O2 + 20% CO2 increased the activities of PDH, SDH and CCO during the early storage period followed by a rapid drop during the later storage period, which hindered the establishment of a stable and continuous energy supply system. Appropriate controlled atmosphere with 50% O2 + 50% CO2 regulated the pH and respiratory key enzyme activity in broccoli during the whole storage period to establish a sustainable and stable energy supply system, and consequently ensure the quality maintenance of broccoli during storage. The correlation analysis showed a highly positive correlation between energy charge and VC, energy charge and H value, and energy charge and water content, with the highest correlation coefficient of 0.996. Therefore, energy charge can be used as an important indicator in measuring and optimizing the storage conditions for broccoli.
Microbial, Physical and Chemical Changes of Low-Salt Chinese Bacon during Storage
CHAI Zihui, LI Hongjun, LI Shaobo, ZHANG Dong, LI Ranran, HE Zhifei
2019, 40(11):  201-206.  doi:10.7506/spkx1002-6630-20180615-309
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This study was undertaken in order to explore the changes in the microbial and physicochemical quality of low-salt Chinese bacon during storage. High-salt Chinese bacon was prepared under the same conditions and used as a control. pH, water content, water activity, salt content and thiobarbituric acid reactive substances (TBARS) value were measured on the two samples. Meanwhile, total bacteria, lactic acid bacteria, Micrococcus, Staphylococcus and coliform bacteria were isolated and counted. The results showed that the two samples exhibited similar trends in each of the parameters examined. Concretely, water content, water activity and the number of lactic acid bacteria all decreased with storage time, while salt content, TBARS value, Micrococcus and Staphylococcus counts increased. The total number of colonies increased first and then decreased. Water content and total bacterial count of low-salt cured meat were higher than those of the control group, resulting in a decrease in shelf life. These results showed that reducing the salt content of Chinese bacon could cause changes in the quality and microflora during storage, while the salt content of low-salt Chinese bacon was 31.41% lower than that of the control group after the same storage period (90 days).
Effect of a Natural Preservative Combination Containing Chitosan on Changes in Muscle Proteins from Grass Carp during Cold Storage
CHEN Sai, LIU Yongle, YU Jian, LI Xianghong, HUANG Yiqun, WANG Jianhui, WANG Faxiang
2019, 40(11):  207-213.  doi:10.7506/spkx1002-6630-20190127-348
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Changes in the physicochemical properties of muscle proteins are among the leading causes of quality deterioration during the storage of freshwater fish. The effect of preservative treatment on changes in the physicochemical properties of muscle proteins from freshwater fish is not yet well understood nowadays. Therefore, in this study, two groups of grass carp fillets treated separately with a natural preservative combination of 10 mg/mL chitosan + 5 mg/mL tea polyphenol + 2 000 U/mL lysozyme and sterile water (control group) were analyzed and compared for changes in total volatile basic nitrogen (total volatile basic nitrogen (TVB-N) content, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) pattern, molecular mass distribution, active sulfhydryl group content and surface hydrophobicity, with the aim of evaluating the effectiveness of the mixed preservative for preventing changes in fish muscle proteins. The results showed that the preservative treatment group exhibited lesser changes in any of the protein properties than did the control group, especially from Day 6 to 9 of cold storage. The preservative treatment prevented the increase in TVB-N content and the decrease in active sulfhydryl group content as well as the change in surface hydrophobicity, indicating reduced protein breakdown, oxidation and denaturation. The slower change in SDS-PAGE and size exclusion-high-performance liquid chromatography profiles provided further evidence supporting the role of the preservative treatment in inhibiting protein degradation and structural change. These results provided evidence that the mixed preservative can stabilize the structure and properties of grass fish muscle proteins to a certain extent and consequently prevent quality deterioration.
Preparation and Application of Composite Antibacterial Pullulan Coating in the Preservation of Eggs
ZHANG Yuanchao, GUO Shengnan, ZHANG Bingqian, MA Meihu, CAI Zhaoxia, HUANG Xi, FU Xing
2019, 40(11):  213-219.  doi:10.7506/spkx1002-6630-20180315-188
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To extend the shelf life of eggs, an edible composite coating with antibacterial activity was made from pullulan with added glycerin, gum arabic, lysozyme and chitinase by ultrasonic treatment. The effects of film-forming agent composition and concentration, drying time, drying temperature and ultrasonic time on film performance were evaluated in terms of water vapor transmission coefficient and peroxide value. The results showed the film formed from a 3:1:2 mixture of pullulan, glycerol and gum arabic at a concentration of 3.0–3.3 g/100 mL with a 1:3 mixture of lysozyme and chitinase added at 0.75 g/100 mL subjected to ultrasonic treatment for 15 min at 150 W and drying at 60 ℃ for 90 min exhibited the best performance. The coating could effectively inhibit the growth of Escherichia coli, Staphylococcus aureus, Salmonella sp., Mucor sp. and Aspergillus sp.. After 28 d of storage at 25 ℃, the mass loss rate of eggs treated with the coating was 6.16%, the egg yolk index was 0.31, the Haugh unit decreased to 67.18 and the pH of egg white increased from 7.61 to 8.47; the quality of eggs in the experimental group remained at Level A. In summary, the composite pullulan coating can effectively inhibit the growth of spoilage bacteria and fungi and therefore have a good preservative effect.
CaCl2 Enhances the Biocontrol Efficacy of Candida oleophila against Inoculated Penicillium expansum on Postharvest Apples
CAI Mengxuan, DENG Lili, YAO Shixiang, ZENG Kaifang
2019, 40(11):  220-226.  doi:10.7506/spkx1002-6630-20180530-427
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The effect and underlying mechanism of Candida oleophila combined with CaCl2 on the biocontrol efficiency of Penicillium expansum inoculated onto postharvest apples were studied in this paper. The results showed that the effect of combined treatment with 1 × 107 CFU/mL C. oleophila and 10 g/L CaCl2 on the control of Penicillium expansum was significantly better than that of C. oleophila. When cultured at 25 ℃, C. oleophila could quickly colonize and grow on wounded apples and maintain a high population. The treatment with 10 g/L CaCl2 could significantly enhance the growth of C. oleophila. Moreover, under the combined treatment, the activities of chitinase and β-1,3-glucanase were significantly induced; meanwhile, the accumulation of lignin, total phenols and flavonoids as metabolites was promoted.
Recent Progress in Technologies for Non-destructive Detection of Fruit Diseases and Pests
QIAO Shicheng, TIAN Youwen, HE Kuan, YAO Ping, GU Wenjun, WANG Jianping
2019, 40(11):  227-234.  doi:10.7506/spkx1002-6630-20180529-399
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Diseases and pests are important factors affecting fruit quality grading. During the process of growth, processing, storage and transportation, fruit are susceptible to pathogens and pests, reducing fruit quality and causing adverse effects on food safety. Recent progress in the application of X-ray imaging, computer vision, nuclear magnetic resonance, spectroscopy and emerging sensors for the non-destructive detection of fruit diseases and pests is summarized in this article. Furthermore, the advantages and disadvantages of each technology are also analyzed, and particular focus is placed on the application of hyperspectral imaging technique in this field. Finally, existing problems and future directions are proposed in order to provide useful information for further research.
Recent Progress in Research on Toxicity Mechanism and Microbial Detoxification of Aflatoxin B1
ZHAO Meng, GAO Jing, CHU Huashuo, LIANG Zhihong
2019, 40(11):  235-245.  doi:10.7506/spkx1002-6630-20180502-001
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Aflatoxin B1 (AFB1) is a threat to human and animal health. AFB1 detoxification by microorganisms has become the focus of current research due to its safety and high efficiency. However, there are still bottlenecks such as long action period, unstable detoxification function, and difficulties in separation and purification. Therefore, efficient removal of AFB1 is great significance to ensure food safety. This paper summarizes the molecular mechanisms of AFB1 toxicity, including the mechanisms of action at the gene and protein levels and the toxicity sites. It focuses on recent progress in the microbial detoxification of AFB1 by adsorption and degradation, including bacteria, fungi and their metabolite, as well as the discovery and mechanisms of action of detoxification enzymes. In addition, the prospects of AFB1 detoxification technology with high efficiency and without pollution are also highlighted.
Recent Progress in Protective Effect of Flavonoids against Skin Photodamage
PENG Ziyao, JIANG Xinwei, SUN Jianxia, LI Xusheng, HU Yunfeng, TIAN Lingmin, BAI Weibin
2019, 40(11):  246-253.  doi:10.7506/spkx1002-6630-20180504-057
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Long-term excessive ultraviolet radiation can cause a series of skin diseases, including photoaging, nonmelanoma and melanoma. Flavonoids, such as hesperidin, baicalin, cyanidin-3-O-glucoside, and silybin, are a group of polyphenols widely present in plants. Flavonoids have been shown to prevent ultraviolet-induced photodamage effectively. This review focuses on the protective effects of flavonoids on ultraviolet-induced photodamage through preventing inflammation, oxidative stress, DNA damage and imbalanced extracellular matrix synthesis and degradation, and discusses the underlying mechanism. We hope that this review will provide a useful basis for the prevention of skin photodamage and the development of sunscreen products with flavonoids.
Recent Progress in Understanding of Hypoglycemic Effect and Underlying Mechanism of Plant Polysaccharides
XIAO Ruixi, CHEN Huaguo, ZHOU Xin
2019, 40(11):  254-260.  doi:10.7506/spkx1002-6630-20180429-385
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Diabetes is one of the clinical manifestations of hyperglycemia, and various complications may be caused by long-term diabetes. At present, no therapy has been found to cure diabetes and the treatment of this disease using western medicine is prevalent. However, western medicine has serious side effects. For this reason, natural substances with high potential to lower blood glucose, low toxicity and few side effects have gained much attention. Plant polysaccharides, widely distributed in nature, have been reported for their good hypoglycemic effect. As natural bioactive substances, they have the characteristics of low toxicity and small side effects making them a research hotspot in the fields of medicinal and health foods. The types of plant polysaccharides with hypoglycemic effects that have been researched worldwide in recent years and the underlying mechanisms are summarized in this article.
Recent Progress in the Study of Homoserine O-Acyltransferase, the Key Enzyme in the Methionine Biosynthesis Pathway
LIU Shimeng, HAN Caijing, GAO Yunna, ZHAO Lan, LU Hongyan, MIN Weihong
2019, 40(11):  261-267.  doi:10.7506/spkx1002-6630-20180511-169
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The first step in methionine synthesis is homoserine acylation catalyzed by homoserine acyltransferase to generate acylhomoserine. Homoserine O-acyltransferase, the key enzyme for methionine biosynthesis, is feedback inhibited or feedback repressed by the end products methionine and S-adenosylmethionine, and is easily inactivated at high temperatures, thus seriously affecting the flow of carbon toward methionine. In this context, studying and modifying homoserine O-acyltransferase are of great significance. However, there are few reports in the literature on studies and modification of homoserine O-acyltransferase. In the microbial metabolic pathways, inadequate carbon flow toward the methionine synthesis pathway can restrict microbial accumulation of methionine, and consequently hinder the industrial fermentation of methionine. In this paper, the role of homoserine O-acyltransferase in the methionine biosynthetic pathway is briefly described. Based on the structure catalytic mechanism of the enzyme as well as a review of recent studies on it, molecular modification strategies for feedback inhibition regulation and stability improvement are proposed.
Food Nutritional Evaluation: Caenorhabditis elegans as a Model Organism
YANG Fan, XIA Chengcheng, ZHONG Xiaoling, LI Qin, LI Xi, ZHANG Zhiyuan, SHI Wenbo, XU Ning, WU Qian, HU Yong, LIU Zhijie, WANG Chao, ZHOU Mengzhou
2019, 40(11):  268-276.  doi:10.7506/spkx1002-6630-20180424-317
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Food nutrition is always a research focus and hotspot in the field of food science. The consumption of functional foods has increased year by year. Model organisms are essential in the evaluation of food functionalities. Caenorhabditis elegans, a small free-living soil nematode, has been extensively used as an experimental in vivo system for biological studies due to its small size, short generation time, and suitability for genetic analysis. In this article, we summarize and review the homology of signaling pathways between C. elegans and humans, the classification and evaluation of functional food factors, and recent progress in the application of C. elegans in food nutritional evaluation, with the aim of providing a basis for food nutrition research and the development of functional foods.
Recent Advances in Identification Techniques for Fish Adulteration
WANG Zhiying, LI Tingting, ZHANG Guilan, LIU Rui, CHEN Ailiang
2019, 40(11):  277-288.  doi:10.7506/spkx1002-6630-20180405-059
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Due to the large number of fish species, large consumption and the quality and price gap between fish products from closely related species, adulteration and mislabeling of fish products and other types of fraud have occurred one by one, which damage the interest of consumers and even their health. The traditional sensory-directed identification has certain limitations, which highlights the requirement for faster and more accurate techniques to identify seafood adulteration. In this article, several kinds of common adulterated fish products are summarized, and the technologies used to identify adulterated fish products are reviewed, including non-destructive testing technologies (spectroscopy and mass spectrometry), protein analysis (enzyme-linked immunosorbent assay) and nucleic acid analysis (polymerase chain reaction). Meanwhile, the application and characteristics of these technologies are reviewed, and future development trends are also discussed in an effort to provide technical support for the identification of adulterated fish products.
Recent Advances in the Studies on the Ca2+ Signaling Pathway Regulating Muscle Fiber Type Transformation
HOU Puxin, HOU Yanru, BAI Yanping, SU Lin, ZHAO Lihua, JIN Ye
2019, 40(11):  289-294.  doi:10.7506/spkx1002-6630-20180525-354
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The Ca2+ signaling pathway include two Ca2+-dependent signaling pathways, calcineurin (CaN) and calmodulin kinase (CaMK), whose activation can promote the transition from fast to slow muscle fibers. This review summarizes the structures and mechanism of action of the CaN and CaMK signaling pathways, the major factors affecting the regulation of the Ca2+ signaling pathway, the role of the Ca2+ signaling pathway in the transformation of muscle fiber types and its relationship with meat quality. Future research directions are also proposed. Hopefully, this review will provide a theoretical basis for improving meat quality through genetic and nutritional approaches.
Application of Edible Fish Byproducts in Restructured Fish Products
ZHOU Fen, ZHANG Yanxia, ZHANG Long, HOU Chunyu, ZHANG Caixia, TAO Ningping, WANG Xichang
2019, 40(11):  295-302.  doi:10.7506/spkx1002-6630-20180508-117
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During fish processing, great amounts of byproducts are generated, including a variety of bioactive substances, such as collagen, gelatin, chitin, lipase, protease and bioactive peptides. This paper describes the nutritional and health benefits and flavor characteristics of fish byproducts and outlines the nutritional composition and amino acid composition of common byproducts. The bioactive components of some specific fish byproducts are summarized and the classification of restructured fish products and fish restructuring technology are presented. Furthermore, the current status of the application of fish byproducts in restructured fish products is illustrated and future prospects for the development and application of fish byproducts are discussed. This review is expected to provide useful information for the development and utilization of fish byproducts.
Recent Progress in the Dissociation-Association Behavior of 11S Glycinin during Heat Treatment
ZENG Jianhua, YANG Yang, LIU Linlin, SHI Yanguo, ZHANG Na, ZHU Xiuqing
2019, 40(11):  303-312.  doi:10.7506/spkx1002-6630-20180614-274
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The dissociation-association reaction of soybean proteins is the process of depolymerization or polymerization of their higher order structures that is influenced by external factors and is currently a research hotspot of plant proteins. The ideal functional properties of soybean proteins can be obtained by subjecting them to heat treatment, which contributes to conformational changes in soybean proteins by dissociation-association reaction. 11S glycinin is one of the major components of soybean protein. Therefore, the post-processing characteristics, quality and application range of soybean products are determined to a certain extent by the thermal dissociation-association behavior of 11S glycinin. In this paper, the latest progress in the understanding of the fundamental structure of 11S globulin is summarized. Considering that the colloidal properties and dissociation-association behavior of 11S glycinin vary during heating process, depending upon its concentration, the effects of ionic strength, pH, 7S β-conglycinin and soybean lipoprotein on the dissociation-association behavior of 11S glycinin are elucidated, and the underlying mechanism is interpreted. This review hopes to provide theoretical support for controlling the dissociation-association reaction of soybean proteins within the expected range and hence obtaining high-quality soybean protein products.
A Review of Current Research on the Effect of Active Packaging on the Quality and Shelf-Life of Meat Products
LI Molin, LUO Xin, LIU Guoxing, MAO Yanwei, ZHANG Yimin
2019, 40(11):  313-320.  doi:10.7506/spkx1002-6630-20180627-497
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Active packaging is a new technology that can effectively reduce microbial contamination in foods and inhibit the oxidation of proteins and lipids, thereby allowing a better maintenance of food quality and extending the shelf life. In this paper, the active substances commonly used in active packaging and the underlying mechanism are described. Recent progress in understanding the effect of active packaging on the quality and shelf life of meat products is summarized. This review is expected to provide a theoretical basis for the application of active packaging in meat products, and provide useful guidance for relevant research in the future.
Recent Progress in Understanding the Regulation of Gut Microbiota by Several Different Kinds of Food
NIE Qixing, HU Jielun, ZHONG Yadong, NIE Shaoping
2019, 40(11):  321-330.  doi:10.7506/spkx1002-6630-20180113-171
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The gut microbiota is an important part in human body and plays an important role in the metabolism and health state of the host. The structure of the gut microbiota can be influenced by host status, genes, dietary habits, age and the environment. Diet is the most important and prompt factor for the structure and function of the gut microbiota. Minor cereals, legumes, fruits and vegetables are common food resources in our daily life, and their dietary fiber and polyphenols have been demonstrated to have important roles in regulating the gut microbiota. Dietary fiber can be fermented by the gut microbiota to produce vitamins and short chain fatty acids, and can selectively enhance the abundance of some beneficial bacteria to improve the health state of the host. In addition, the majority of phenols can be metabolized by the gut microbiota to enhance their bioavailability and consequently improve the host physiological state. In this paper, we review recent progress in our understanding of the regulation of the gut microbiota by minor cereals, legumes, fruits and vegetables commonly consumed by humans and discuss future prospects of the gut microbiota as a target in the prevention and treatment of metabolic diseases or dietary intervention.
Recent Progress in Research on Patatin, the Major Potato Tuber Protein
LIU Yaotong, SUN Wei, DONG Mosi, JI Yingxin, LI Tuoping, LI Suhong
2019, 40(11):  331-337.  doi:10.7506/spkx1002-6630-20180606-047
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Potato is rich in nutrients, and China is now the world’s biggest potato consumer and producer. Along with the development of the potato processing industry, understanding the nutritional and functional properties of potato proteins has continued to advance. Patatin is the major storage protein of potato tubers. In this paper, the advantages and disadvantages of the different methods for the separation and purification of patatin are described, and the molecular mass, structural characteristics, physicochemical properties and functional properties of patatin are presented. We hope that this review will provide a rationale for further research and application of patatin in the food processing area.
Recent Progress in Research on Probiotics Effect on Nervous System Diseases
WANG Nana, HUO Guicheng, LI Chun, LU Jingjing, LI Aili
2019, 40(11):  338-342.  doi:10.7506/spkx1002-6630-20180507-110
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The gut microbiome in humans consists of a vast and diverse population of microbes that is involved in many physiological processes. Many studies have demonstrated that the gut microbiome regulates the development and behavior of human brain through the microbiota-gut-brain axis. Probiotics are a group of live microorganisms that are beneficial to the human body by regulating the micro-ecological balance in the human intestinal tract. Clinical studies have shown that probiotics are highly effective in the prevention and treatment of autism spectrum disorders, Alzheimer’s disease, Parkinson’s disease, depression and multiple sclerosis and other neurological diseases. In this article, recent progress understanding in the mechanism of action of probiotics on nervous system diseases in China and abroad is reviewed in order to provide a new idea for the intervention and treatment of diseases using probiotics.
Recent Progress in Food Safety Assessment and Regulation of Genetically Modified Plants
WANG Guoyi, HE Xiaoyun, XU Wentao, LUO Yunbo
2019, 40(11):  343-350.  doi:10.7506/spkx1002-6630-20180507-092
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Genetically modified plants (GMPs) have been commercially produced for 20 years, and have brought great agricultural, economic and social benefits to farmers and even the whole society. However, the safety of GMPs especially when consumed as foodstuffs has been a major concern for the public. In this article, the food safety assessment of GMPs is reviewed from the viewpoints of key component analysis, nutritional assessment, toxicological studies, and allergenicity assessment. In addition, the current status of the GMPs industry and the safety assessment and regulation of GMPs worldwide are also discussed in the hope of providing useful guidance for the safety assessment and regulation of GMPs in China.
Recent Progress in Structural Modification and Physiological Activity of Anthocyanins
YOU Lu, SUI Qianqian, ZHAO Yanxue, LIU Suwen
2019, 40(11):  351-359.  doi:10.7506/spkx1002-6630-20180423-289
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Anthocyanins are the most ubiquitous and diverse class of natural pigments in the plant kingdom and are the main color substances of plant materials, and they exist in nature mostly as glycosides of anthocyanidins and have many important physiological functions and biological activities. Anthocyanins have poor structural stability due to their structures containing phenolic hydroxyls and are susceptible to external conditions such as pH, temperature, light, oxygen, metal ions and enzyme. These compounds can be easily decomposed during food processing, leading to loss of the bright color. The poor stability of anthocyanins restricts their storage and application in food processing. Modified anthocyanins can show improved stability to external environments and during food processing, and offer good color in a wide pH range. This article summarizes the different types of anthocyanin modification such as acylation, esterification and formation of pyranoanthocyanins as well as the structural characteristics and physiological activities of the modified anthocyanins, with the aim of providing a useful rationale for further studies on the structural stability and biological activity of anthocyanins and their application in agricultural products and food processing.