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Table of Content

15 October 2019, Volume 40 Issue 19
Basic Research
Effect of Acid Stress on Biofilm Formation of Escherichia coli O157:H7
WANG Xianjing, DONG Chen, YU Jinlong, HU Jie, FU Wenjing, ZHANG Su, JIANG Yun
2019, 40(19):  1-7.  doi:10.7506/spkx1002-6630-20181018-193
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The aim of this study was to investigate the effect of long-term acid stress on biofilm formation (BF) of Escherichia coli O157:H7. Firstly, the adhesion capacities of different strains were compared by using microwell plate-crystal violet staining method and the BF curves of strains with different adhesion capacities were analyzed. Secondly, one representative strain was selected to investigate the effect of long-term acid stress on BF using plate-counting method. Finally, the changes in biofilm microstructure of the adhesive strains under acidic condition were observed using a confocal laser scanning microscope (CLSM). The results showed that adhesion capacity varied among 14 investigated strains. The BF curves of the adhesive strains were different although they all began to form biofilm after 2 h of cultivation. The results of acid stress showed that the BF of ATCC43895, a representative strain with medium adhesion ability, was inhibited by acid, the lower pH could result in lower BF, and the inhibitory effect of lactic acid on BF was significantly higher than that of hydrochloric acid (P < 0.05). CLSM results showed that weakly adhesive strain CICC21530 and strongly adhesive strain J29 were able to form biofilm under acidic and neutral conditions, and the latter had a higher biofilm production than did the former. Acidic condition inhibited the BF process. Our findings demonstrated the inhibitory effect of lactic acid on BF of E. coli O157:H7, which provides scientific evidence for the elimination of the biofilm formed by E. coli O157:H7 in food processing.
Preparation and Functional Properties of Food-Grade Flavonoid Microemulsion from Acanthopanax senticosus Leaves
YU Xinxin, ZHAO Duojia, ZHANG Po, SUN Guangmei, XU Xiaojuan, ZHANG Yinghua
2019, 40(19):  8-16.  doi:10.7506/spkx1002-6630-20181016-163
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Favonoids have low solubility, poor alkali resistance and photolysis resistance, and are very unstable in chemical properties, thereby limiting their application in foods. Microemulsion is a good carrier that can solve the problem that favonoids are difficult to utilize due to incompatibility and oxidization. By drawing pseudo-ternary phase diagrams using the titrimetric method, the influence of surfactants, cosurfactants, surfactant/cosurfactant ratio (Km, m/m), and oil phases on the formation of microemulsion was investigated in order to determine the best microemulsion formulation. The morphology and size distribution of microemulsions were explored by a transmission electron microscope (TEM) and a particle size analyzer. Furthermore, a microemulsion system containing flavoinoids from Acanthopanax senticosus leaves was prepared and its antioxidant capacity was evaluated by the scavenging activity against superoxide anion, hydroxyl and 1,1-diphenyl-2-picrylhydrazyl radicals. Its antibacterial activity was studied by measuring the diameter of the inhibition zones. Untreated flavoinoids were employed as control. The results showed that the greatest microemulsion area was obtained using isopropylmyristate as oil phase, Tween-80 as surfactant, and anhydrous alcohol as cosurfactant (Km = 2) . The average particle size of the microemulsion was about 18.3 nm. After high-speed centrifugation and standing for a long time, the system was still uniformed, transparent and without stratification. The antioxidant tests indicated that the antioxidant capacity of the flavonoid microemulsion was better than that of the control. In the antibacterial tests, the flavonoid microemulsion was more effective against Escherichia coli, Staphylococcus aureus, Salmonella and Pseudomonas fluorescens than the control.
Antimicrobial Mechanism of Antimicrobial Peptide P-1 from Bacillus pumilus HN-10 against Trichothecium roseum
GUO Juan, YUN Jianmin, DENG Zhanrui, AI Duiyuan, ZHANG Wenwei, ZHAO Fengyun
2019, 40(19):  17-22.  doi:10.7506/spkx1002-6630-20180830-347
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Antimicrobial peptide P-1 from Bacillus pumilus HN-10 has strong antifungal activity against Trichothecium roseum, but its mechanism of action remains unclear. In this study, we investigated this topic from the perspectives of cell membrane permeability, protein synthesis and nucleic acid synthesis. Firstly, the effect of antimicrobial peptide P-1 on the membrane permeability of T. roseum was studied by measuring the release of macromolecules and electrical conductivity. Secondly, the effect on protein synthesis was studied by measuring the expression of intracellular and intracellular proteins through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Finally, in order to prove whether nucleic acid synthesis was inhibited by antimicrobial peptide P-1, agarose gel retardation assay was performed and the competitive binding of antimicrobial peptide P-1 with ethidium bromide (EB) to T. roseum DNA and RNA contents were analyzed by fluorescence spectroscopy. The results showed that the antimicrobial peptide P-1 could increase the membrane permeability of T. roseum, leading to leakage of intracellular electrolytes and macromolecules. Meanwhile, T. roseum protein synthesis was inhibited, especially for proteins with molecular masses between 43.0 and 97.4 kDa. The antifungal peptide showed no DNA gel retardation, but it could compete with EB for binding to DNA and inhibit nucleic acid synthesis, resulting in fungal metabolism disorder and abnormal protein expression and eventually exerting antimicrobial activity.
Differences in Taste Characteristics of Sugar-Free Green Tea Beverages from Different Producing Areas
YE Qingqing, LIU Panpan, WANG Fang, WANG Jieqiong, XU Yongquan, YIN Junfeng, ZENG Liang
2019, 40(19):  23-31.  doi:10.7506/spkx1002-6630-20180824-260
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The taste quality and chemical composition of commercial sugar-free green tea beverages from different producing areas were comparatively analyzed with a view to clarifying the major taste components in sugar-free green tea beverages and the differences in taste characteristics among producing regions. The results showed that no obvious variation in the taste or color of green tea beverages was observed among producing regions, and the overall taste quality of Japanese green tea beverages was superior to the others. The concentrations of tea polyphenol, caffeine, flavonoids, soluble sugar, total catechins, total flavonoid glycosides and total cations in Japanese and Chinese Taiwanese green tea beverages were significantly higher than in the ones made in mainland China. Totally 13 chemical components showed high correlations with sensory scores. The concentrations of tea polyphphenols (0.910), flavonoids (0.917), and Mn2+ (0.912) were significantly positively correlated with the taste strength (P < 0.01). The concentration of caffeine (0.830) was significantly positively correlated with the bitterness (P < 0.01). The concentrations of vitexin-2’’-O-rhamnoside (Vit-rha) (0.862) and Al3+ (0.811) were significantly positively correlation with the astringency (P < 0.01). The dose-over-threshold (Dot) analysis showed that flavonoids and their glycosides contributed mainly to the astringency, including quercetin-3-O-rutinoside (Que-rut), kaempferol-3-O-rutinoside (Kae-rut), quercetin-3-O-galactoside (Que-gala), quercetin-3-O-glucoside (Que-glu), myricetin-3-O-galactoside (Myr-gala), Vit-rha, of which Que-rut had the highest Dot value; and caffeine played a major role in the bitterness of sugar-free green tea beverages.
Effect of Environmental Conditions on the Stability and Free Radical Scavenging Capacity of Lutein-Enriched Nanoemulsion
LI Jinan, HU Hao, WU Xuejiao, WU Yan
2019, 40(19):  32-39.  doi:10.7506/spkx1002-6630-20181028-322
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A lutein-enriched nanoemulsion stabilized by sodium caseinate was constructed by high-pressure homogenization, and its 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging capacity and oxygen radical absorbance capacity (ORAC) were investigated. The effects of environmental conditions on lutein stability and free radical scavenging capacity in the nanoemulsion were evaluated. The free radical scavenging capacity of lutein was improved significantly by incorporation into the emulsion system (P < 0.05). In addition, the free radical scavenging activity and lutein content of the nanoemulsion decreased to varying degrees when exposed to pH 2.0 as well as 50 and 100 mmol/L NaCl, but increased significantly after condensation treatment (P < 0.05); in contrast, thermal treatment (60, 80, 100 ℃) had little impact on the two parameters.
Kinetics of Rice Bran Oil Extraction with Isopropanol
YANG Huanyue, WANG Zhenhua, XU Duoxia, WANG Junhai, ZHANG Min,
2019, 40(19):  40-45.  doi:10.7506/spkx1002-6630-20181019-204
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Rice bran oil was extracted by solvent extraction method with three different solvents. The extraction process was kinetically analyzed, and oil yield was investigated as a function of solvent type, solid-to-solvent ratio, extraction temperature and auxiliary treatment methods. The results showed that the extraction process accorded with Fick’s second law, and the kinetic equation could accurately simulate it. Oil yield and the extraction rate varied greatly with the extraction conditions. Oil yield (Me) and mass transfer coefficient (k) of rice bran using isopropanol as the extraction solvent were higher than using anhydrous ethanol and n-hexane. Appropriately increased solvent dosage, increased extraction temperature, or dynamic treatment contributed to improving oil yield and mass transfer coefficient. Dynamic treatment increased the driving force for oil mass transfer, and oil yield was up to 90.12% under the conditions: isopropanol as the solvent, an extraction temperature of 50 ℃, solid-to-solvent ratio of 1:7.5 and use of dynamic treatment, which was 1.54 times higher than obtained with static treatment. In addition, the maximum effective diffusion coefficient was as high as 5.172 6 × 10-12 m2/s.
Metabolomic Analysis of Differences in Chemical Composition of Peanut Skins with Different Colors
JIA Cong, LU Xin, GAO Jinhong, SUN Qiang, ZHU Xiaopeng, WANG Qiang, HUANG Jinian,
2019, 40(19):  46-51.  doi:10.7506/spkx1002-6630-20190201-006
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With the aim of identifying the differential metabolic pathways in peanut skins of different varieties, non-targeted metabolomic analysis of peanut skins with different colors was performed by liquid chromatography-mass spectrometry. Principal component analysis (PCA) showed that there were significant metabolic differences in peanut skins with different colors. Totally 16 differential metabolites were separated according to the variable importance in the projection values from the orthogonal partial least squares discriminant analysis (OPLS-DA). The contents of kaempferol and catechin-(4α→8)-gallocatechin-(4α→8)-catechin as well as the contents of proanthocyanidins, myricetin and quercetin were significantly higher in peanut skins with a darker color (P < 0.05). The differential metabolites were enriched in four metabolic pathways. The flavone and flavonol biosynthesis pathways were the most significant among the metabolic pathways, in which kaempferol, quercetin, myricetin and rutin were involved. Kaempferol was actively metabolized in peanut skins with a darker color, while myricetin and quercetin were actively metabolized and synthesized in larger amounts in peanut skins with a lighter color.
Sensory Characteristics and Physicochemical Quality of Fresh and Preserved Pork from Several Chinese Local Pig Breeds
LIU Wenying, GAO Xinyue, LI Xiang, CHENG Xiaoyu, WANG Shouwei, QIAO Xiaoling
2019, 40(19):  52-59.  doi:10.7506/spkx1002-6630-20181225-292
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With the increase of consumer demand for high-quality pork, the local pig farming and meat processing industries in China are experiencing a rapid development. A comparative analysis of pork quality attributes of different Chinese local pig breeds was conducted in the present study. Duroc × (Landrace × Yorkshire)?(DLY) pork was used as the control sample and nutritional properties, physicochemical properties and sensory characteristics of the three-breed crossbred Longissimus dorsi muscle (TL) were evaluated and compared with those of Longissimus dorsi from Yihao native pigs (YL), Beijing black pigs (BL), Hunan village black pigs (HL), and Northeastern indigenous pigs (NL), with a larger market share. In addition, the induced oxidative stability of lipids in the middle layer of streaky pork from these five breeds was analyzed and Cantonese bacon prepared from TL, YL, BL, HL and NL (designated as TLP, YLP, BLP, HLP and NLP, respectively) were investigated for lipid oxidation as well as color, flavor and taste characteristics. The results showed that TL had the highest protein content, the lowest crude fat content and medium water content among the five breeds. The pH of YL and HL was the highest, the pH of TL was in the middle, and NL had the lowest pH, and. The redness value (a*) and yellowness value (b*) of TL were lower than those of the other breeds, and the brightness values (L*) of YL, BL and HL but not NL were higher than that of TL. The total antioxidant capacity (T-AOC) of YL, BL and NL but not HL was higher than that of TL, and YL had the highest T-AOC value. The oxidation induction time (OIT) of lard from Hunan village black pigs was the longest (P < 0.05), while the OIT of lard from the other breeds was very short. The L* values of NLP and HLP were lower than that of TLP (P > 0.05), and YLP had the highest L* value (P < 0.05), but had the lowest a* and b* values (P > 0.05). The thiobarbituric acid reactive substance (TBARS) value of YLP was the lowest, while the highest value was found in BLP (P < 0.05). The major flavor characteristics of the five Chinese bacon products were distinct, and principal component analysis (PCA) could be used to discriminate among them. The flavor of NLP was similar to that of TLP. The astringency value of the TLP was lower, but the acid taste, astringency aftertaste, umami taste, umami taste aftertaste and salty taste were all at a higher level. In conclusion, the protein content of TL was higher, and the taste characteristic value of TLP was also higher. PL had better color. YL fat had higher oxidation stability, and YLP had a better oxidation state. The physiochemical properties and sensory characteristics of different varieties of pork were different, and the sensory characteristics of processed meat products were dissimilar to that of fresh meat.
Antioxidant Activity of Crude Polysaccharides from Fomitopsis pinicola from Different Geographical Origins
NIE Linran, HAO Limin,, WANG Taotao, LIU Yang, ZHANG Liming, LU Jike, KANG Caicai, CUI Yan, HAN Peipei, JIA Shiru
2019, 40(19):  60-68.  doi:10.7506/spkx1002-6630-20190329-381
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The present work was undertaken to investigate the antioxidant activity of crude polysaccharides extracted from Fomitopsis pinicola fruiting bodies from different geographical origins: Jilin, Heilongjiang and Yunnan provinces (designated as JFPF, HFPF and YFPF, respectively), Fomitopsis pinicola mycelium (FPM) and its fermentation broth (FPFB). The antioxidant activity was evaluated by determining the scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydroxyl radicals and K3Fe(CN)6 reducing power, followed by the evaluation of the protective effects against ultraviolet (UV) radiation and H2O2-induced?oxidative damage in yeast cells. The results showed that the five crude polysaccharides had different antioxidant activities and significantly increased the survival rate of yeast cells under oxidative damage in a dose-dependent manner. The scavenging capacity against DPPH, ABTS and hydroxyl radicals, and the reducing power of YFPF polysaccharides were relatively stronger among these polysaccharides. At 5 mg/mL, the scavenging rates of DPPH, ABTS and hydroxyl radicals were 78.78%, 99.24% and 64.38%, respectively, and the reducing power was 0.84. In addition, the protective effect of FPM polysaccharides against oxidative damage was the strongest, as evidenced by significantly improved survival rate of yeast cells. At 20 mg/mL, the survival rates of yeast cells under UV and H2O2-induced oxidative damage were 75.48% and 48.38%, respectively. This study demonstrated that the antioxidant activity of crude polysaccharides from F. pinicola varied with geographical origin, which will provide a theoretical basis for the exploitation and utilization of F. pinicola.
Effect of Fermented Blueberry Juice on Oxidative Stability and Quality Characteristics of Frankfurters
ZHOU Hengyue, DENG Shaolin, ZHOU Changyu, ZHUANG Xinbo, ZHOU Guanghong
2019, 40(19):  69-76.  doi:10.7506/spkx1002-6630-20180824-226
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The objective of this study was to evaluate the effect of fermented blueberry juice (FBJ) on the oxidative stability and sensory analysis of frankfurters. The thiobarbituric acid reactive substances (TBARS) level, total protein carbonyl content, color, pH, texture properties and sensory evaluation of frankfurters with various amounts (2%, 4%, 6%) of FBJ were investigated. The results showed that the addition of FBJ could significantly inhibit the oxidation of lipids and proteins, and its effect was better than that of 0.05% sodium D-isoascorbate (P < 0.05) at the late storage stage. Frankfurters with FBJ had significantly higher a* and b* values but significantly reduced hardness when compared to the control (P < 0.05). Yet, there was no significant difference in elasticity (P > 0.05). Using electronic nose and sensory evaluation, the flavor of frankfurters with FBJ was clearly discriminated from that of the control; the sensory quality of frankfurters with FBJ was better than that of the control, and the highest sensory score was obtained with addition of 4% FBJ. This experiment confirmed that FBJ had good antioxidant properties, and could effectively inhibit the oxidation of lipids and proteins and improve the sensory quality of frankfurters.
Effect of Age on Nutritional Value and Antioxidant Activity of House-feeding Yak Meat
DONG Airong, MIAO Jianjun, PENG Zhongli, ZENG Yu, FU Yangyang, WANG Ding, GUO Chunhua
2019, 40(19):  77-82.  doi:10.7506/spkx1002-6630-20180831-374
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This study was conducted to investigate the effect of age on nutritional value and antioxidant activity of house-feeding yak meat, and to provide the guidance for the production of high-quality yak meat. The healthy Maiwa male yaks (n = 18) were allocated to three groups (1.5-year-old = ‘AGE1.5’, 2.5-year-old = ‘AGE2.5’ and 4.5-year-old = ‘AGE4.5’) by age, with 6 yaks in each group. Pre-experimental period was 15 days, and the trial period was 180 days. The results showed that: 1) the age had a significant effect on crude protein and crude ash of yak meat (P < 0.05). The content of crude protein in yak meat of AGE4.5 group was 23.50%, and the content of crude ash in yak meat of AGE2.5 group was 1.36%, which was the highest in three groups. 2) The ratio of essential amino acids to total amino acids (EAA/TAA) and essential amino acids to non-essential amino acids (EAA/NEAA) in different age groups were significantly different (P < 0.05), as followed by an order: AGE2.5 > AGE4.5 > AGE1.5. The ratio of flavor amino acids to total amino acids (FAA/TAA) in the AGE2.5 group was 42.88%, which was significantly lower than 43.49% in the AGE1.5 group and 43.43% in the AGE4.5 group (P < 0.05). 3) The effect of age on fatty acids in yak meat was relatively weak. The content of C21:0 in the AGE2.5 group was significantly higher than that of the AGE1.5 and AGE4.5 groups (P < 0.05), while the contents of other fatty acids were not significantly different (P > 0.05). The C22:0 and C20:2 were detected in the AGE1.5 group, but did not detected in the AGE2.5 and AGE4.5 groups. 4) As the extension of age, the content of malondialdehyde (MDA) gradually increased, with increase by 53.80% in the AGE4.5 group when compared with the AGE1.5 group. However, the contents of catalase (CAT), total superoxide dismutase (T-SOD), total antioxidant capacity (T-AOC) and glutathione peroxidase (GSH-Px) in yak meat from different age groups were not significant (P > 0.05). In conclusion, age can modify nutritional components of yak meat, but has no significant effect on its antioxidant property.
A Comparative Study on Functional Unsaturated Fatty Acids and Fat Globule Microstructure in Breast Milk and Goat Milk
ZHANG Yu, WANG Lina, ZHANG Hongda, LI Xiaodong, LIU Lu, LENG Youbin, GONG Yanni, JIANG Shilong
2019, 40(19):  83-88.  doi:10.7506/spkx1002-6630-20180718-227
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Gas chromatography-mass spectrometry (GC-MS) and microscopic observation were used to analyze the relative contents of major functional unsaturated fatty acids, physicochemical properties and microstructure of fat globules in breast milk and goat milk from different lactation periods, aiming at providing a theoretical basis for the study of breast milk lipids and the development of infant formula based on goat milk. The results showed that the fat contents of colostrum, transitional and mature breast milk were (26.7 ± 3.6), (33.7 ± 4.6) and (41.0 ± 6.8) g/L, respectively, increasing significantly with the prolongation of lactation (P < 0.05). The relative content of fat in goat milk ((42.1 ± 4.3) g/L) was significantly higher than in human colostrum and transitional milk (P < 0.05). However, the major functional fatty acids were significantly more abundant in breast milk than in goat milk (P < 0.05). Notably, the content of linoleic acid (LA) (the lowest in the transitional period, 19.76%) was significantly higher than that of goat milk (4.43%) (P < 0.05). In terms of physical properties, breast milk fat globules (MFG) had the maximum average particle size of (5.63 ± 0.51) μm and the minimum zeta potential of (?5.72 ± 0.21) mV, while the average particle size and potential of goat milk MFG were (3.63 ± 0.31) μm and (?13.69 ± 0.27) mV, respectively. Furthermore, MFG particle size and potential were significantly correlated with fat content (P < 0.05). The major functional fatty acids and MFG physical properties in breast milk at different lactation stages were different, which were significantly different from those in goat milk. The results of this experiment can be useful for further study of breast milk and goat milk products.
Effect of Modification on the Structure and Gel Properties of Porcine Myofibrillar Protein
JIANG Guochuan, WANG Liyan, LIU Yachun, SUN Hongrui, ZHANG Jialin, LIU Xuejun, YAN Xiaohui
2019, 40(19):  89-95.  doi:10.7506/spkx1002-6630-20181011-088
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In order to improve gel properties of porcine myofibrillar protein, we examined the effect of ultrasonic and/or transglutaminase (TG) treatment on gel strength, hardness, elasticity, water-holding capacity and chemical forces of heat-induced myofibrillar protein gels. We also investigated the effect on structural properties of?myofibrillar protein?by protein secondary structure analysis, differential scanning calorimetry and ultraviolet absorption spectroscopy. The results showed that the combined treatment could more significantly modify the properties of myofibrillar protein than either treatment alone. Compared with the control group, the content of sulfhydryl groups decreased, and water-holding capacity, whiteness value and hydrophobic interaction force increased; gel strength, hardness and elasticity values were enhanced by 3.57, 3.65 and 1.15 times in the combined treatment group, respectively. The results of structural analysis indicated that the combined treatment increased the thermal denaturation temperature of myofibrillar protein and resulted in a decrease in the relative content of alpha-helix with a simultaneous an increase in the relative contents of beta-sheet and beta-turn structure. In addition, this treatment increased the ultraviolet absorbance. The modified protein structure was conducive to improving the formation of myofibrillar protein gel. These results provide a theoretical basis for comprehensive utilization of myofibrillar protein.
Scavenging Effect of Alkyl Gallates on 1,2-Dicarbonyl Compounds in Foods
WANG Jiaqi, XIAO Liubang, WANG Xi, ZHANG Dingmin, ZHENG Tiesong, Lü Lishuang
2019, 40(19):  96-103.  doi:10.7506/spkx1002-6630-20181008-033
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In this study, gas chromatography (GC) was applied to investigate the scavenging effects of the food antioxidants alkyl gallates [propyl gallate (PG), octyl gallate (OG), and dodecyl gallate (DG)] on the highly active glycosylation factors 1,2-carbonyl compounds [glyoxal (GO) and methylglyoxal (MGO)] in foods, and we also evaluated how PG/OG/DG concentration, pH and reaction time influence the scavenging effect of these 1,2-carbonyl compounds. In addition, the scavenging mechanism was explored through high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The following findings were obtained: 1) The 1,2-carbonyl compounds were effectively scavenged by the three antioxidants and the effects decreased in the following order: PG > OG > DG. 2) The scavenging percentages of 1,2-carbonyl compounds by PG at 0.5 mmol/L were 70.5% for GO and 67.6% for MGO, while the scavenging percentages of GO and MGO were more than 50% by OG and DG at 0.5 mmol/L. 3) In an arginine-glucose system and cookies, the scavenging effects were positively proportional to scavenger concentration, pH, and reaction time. 4) In cookies, the mechanism may be that PG and OG captured one molecule of GO or MGO to form adducts, while DG captured one molecule of GO to form an adduct. We therefore conclude that alkyl gallates can scavenge exogenous 1,2-carbonyl compounds during food processing, thereby enhancing food safety.
Isolation, Identification and Antioxidant Activity of Polyphenols from Kiwifruits
ZHANG Yun, LIU Fang, BU Fanwen, LU Ying, XU Hai, TANG Jiale, YIN Chunfeng, LIN Wenli,
2019, 40(19):  104-112.  doi:10.7506/spkx1002-6630-20180815-153
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High-speed countercurrent chromatography (HSCCC) and preparative high performance liquid chromatography were used to separate polyphenols from kiwifruits (KPT). A total of 8 compounds were obtained and 7 of them were identified by spectroscopically: neochlorogenic acid (compound 1), caffeic acid-3-O-glucoside (compound 2), 2-O-caffeoylthreonic acid (compound 3), epicatechin (compound 5), procyanidin C1 (compound 6), malaxinic acid (compound 7), and quercitrin (compound 8). Compound 4 may be presumed to be a B-type proanthocyanidin dimer. Compounds 2, 5, 6 and 7 had effective scavenging effects on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cations in the decreasing order: proanthocyanidin C1 > epicatechin > caffeic acid-3-O-glucoside > malaxinic acid.
Effects of Processing Methods on Structure and Functional Properties of Mung Bean Protein
ZHANG Shu, WANG Changyuan,, SHENG Yanan, FENG Yuchao, FU Tianxin, LI Xue
2019, 40(19):  113-119.  doi:10.7506/spkx1002-6630-20190307-098
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Mung beans are rich in protein as well as a variety of amino acids, and are an excellent protein source with good processing suitability. In this experiment, mung beans were steamed or boiled in distilled water before being used for the preparation of mung bean protein by alkali extraction and acid precipitation. The structure and functional properties of mung bean protein were determined. Experimental results showed that the large subunits of steamed or boiled mung bean protein became lighter in color with the extension of heat treatment time evidencing reduced content of large proteins. The 57.5 kDa 8S globulin subunit band gradually disappeared, and a 35.4 kDa band was found in the boiled mung bean protein but not in the steam one. Either cooking treatment time-dependently improved the water-holding capacity, oil-holding capacity, and emulsifying capacity and emulsion stability of mung bean proteins, and steaming was better than boiling. The foaming capacity, foam stability and solubility increased first and then decreased with treatment time, reaching the maximum values of 25.6%, 77.1%, and 13.6% at 20–25 min, respectively. This study provides a theoretical basis for the modification of mung bean protein and is of guiding significance for improving the application of mung bean protein in the food industry and the intensive processing of mung bean products.
Functional Properties and Structure of Red Bean Protein Improved by Combined Ultrasound-Transglutaminase Treatment
ZHAO Chengbin, YIN Huanhuan, LIU Jingsheng, XU Xiuying, ZHANG Hao, WU Yuzhu, CAO Yong, QI Baokun, WU Fei
2019, 40(19):  120-127.  doi:10.7506/spkx1002-6630-20181008-052
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Red bean protein isolate (RBPI) was treated by ultrasound (US) combined with transglutaminase (TG), and analyzed for functional and structural characteristics. The relationship between structural modification and functional properties was explored. The results indicated that 5-min US treatment alone could improve the emulsifying activity and foaming ability of RBPI, but reduce the foam stability without affecting the emulsion stability, and it could also increase the surface hydrophobicity (H0) and free sulfhydryl content. TG alone was able to improve the emulsifying activity, emulsion stability and foam stability, but reduce foaming ability, H0 and free sulfhydryl content of RBPI. RBPI treated by US-TG had higher emulsifying activity and foam stability, and lower H0 and free sulfhydryl content. The gel induced by TG after US treatment for 5 min had a more uniform and compact microstructure with lower syneresis, and possessed increased hardness and adhesiveness. The absorption peak strength in the amide I band of RBPI treated by US-TG was enhanced, and more random coil structure was transformed into an ordered β-sheet structure, which may contribute to the improvement of functional properties. Treatment with US for 5 min combined with TG could significantly increase the peak temperature (Tp) and enthalpy (ΔH) (P < 0.05), thereby improving the thermal stability or tertiary structure stability of RBPI, which indicated that TG-induced cross-linking of RBPI was promoted by treatment with US and the combined treatment could facilitate the development of functional properties of proteins.
New Method for Stability Determination of Docosahexaenoic Acid (DHA)-Enriched Microalgae Oil Emulsion and Factors Influencing the Emulsion Stability
LIANG Jingrui, LI Wei, WANG Jian, WANG Fei, WANG Zhanyi, FENG Xiaohui, DU Jian
2019, 40(19):  128-135.  doi:10.7506/spkx1002-6630-20181014-122
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In this study, a new method was proposed to determine the stability of the emulsion formed during the microencapsulation of docosahexaenoic acid (DHA)-enriched microalgae oil and the factors influencing the emulsion stability was investigated. By comparing three different methods for determining the emulsion stability as well as by microscopic observation, we found that dilution of the emulsion with 0.1 g/100 mL sodium dodecyl sulfate (SDS) solution followed by measurement of the change in light transmittance at 600 nm at 24 h relative to that at 0 h was a convenient and accurate method. The emulsion stability and consequently the microcapsule quality were impacted considerably by wall material composition, core material proportion and total solids content. The quality of microencapsulated products prepared using a mixture of octenyl succinic anhydride modified starch and maltodextrin at a mass ratio of 2:3 as the wall material and 20% DHA-enriched microalgae oil and 33% of total solids concentrations as the core material was good and could meet the requirements of the national standards SC/T 3505—2006 Microcapsules of Fish Oil. The storage stability of DHA-enriched microalgae oil was significantly improved after being microencapsulated.
Total Phenols and Flavonoids and Antioxidant Activity of Artichoke (Cynara scolymus L.) Bud Juices before and after Gastrointestinal Digestion in Vitro
WANG Zhenshuai, CHEN Shanmin, XIN Siyue, SHENG Huaiyu, JIANG Heti
2019, 40(19):  136-142.  doi:10.7506/spkx1002-6630-20181015-147
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The contents of total phenols and flavonoids in artichoke bud juices prepared from receptacles and inner and outer bracts before and after gastrointestinal digestion in vitro were compared. Their antioxidant capacity was evaluated by four methods: total reducing power, and 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation and superoxide anion (O2-·) radical scavenging capacity. The results showed that the content of total phenols in receptacle juice was 2.46 mg/mL, which was 1.13 and 1.94 times higher than inner and outer bract juices, respectively. The content of total flavonoids in receptacle juice was 6.53 mg/mL, which was 1.15 and 2.06 folds increased relative to inner and outer bract juices. The antioxidant capacities of the three juices decreased in the following order: receptacle juice > inner bract juice > outer bract juice, and their radical scavenging capacity increased with phenolic concentration. After being treated with either simulated gastric juice or gastric acid, the antioxidant activity of receptacle juice was significantly enhanced (P < 0.05), whereas this was reversed by subsequent treatment with simulated intestinal juice. Therefore, pepsin, gastric acid, and trypsin could promote the release of antioxidant factors, thus improve antioxidant capacity.
Food Engineering
Effect of Dynamic High Pressure Microfluidization Treatment Sequence on the Structure and Properties of Pectin-Lactoferrin Complexes
LIANG Ruihong, HUA Hui, WANG Xuedong, LI Ya, LIU Chengmei, CHEN Jun
2019, 40(19):  143-148.  doi:10.7506/spkx1002-6630-20180929-331
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Three lactoferrin-pectin complexes (MLFP, MPLF and MLFP) were prepared by treatment with dynamic high pressure microfluidization (DHPM) in different sequences. MLFP was obtained by mixing lactoferrin (LF) pretreated by DHPM with pectin (P), MPLF was obtained by mixing pectin pretreated by DHPM with LF, and MLFP was obtained by mixing LF with pectin and then treating the mixture by DHPM. The present study was undertaken to explore the effect of DHPM treatment sequences on the properties and structure of LF-P complexes. The results showed that DHPM treatment increased the dispersibility, but reduced the emulsifying properties of LF-P complexes. Among the three complexes, MLFP had the highest dispersibility and emulsifying properties, while MLFP had the lowest dispersibility and emulsifying properties. This result was consistent with the results of interfacial tension measurement. The particle sizes of the complexes were significantly reduced compared to the control prepared without DHPM treatment (P < 0.05), in the increasing of MPLF < MLFP < MLFP < control. The formation of the complexes was driven by electrostatic interaction between pectin and LF, as confirmed by ζ-potential measurement and infrared spectroscopy, and DHPM treatment promoted this interaction. This study provides a theoretical basis for exploring the changes in the structure and properties of food components during food processing.
Characterization of Polyphenol Oxidase from Fresh Pear Juice after High Pressure Processing Activation
SHANG Haitao, XUAN Xiaoting, CUI Yan, LIN Xudong, YU Jingfen, LING Jiangang
2019, 40(19):  149-155.  doi:10.7506/spkx1002-6630-20180824-263
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This paper aimed to explore the mechanism by which high pressure processing (HPP) accelerates browning of pear juice. The effect of HPP, applied at 500 MPa treatment for 5 min on the color of fresh Cuiguan pear juice during its shelf life was investigated. Untreated samples were used as control. Dissolved oxygen concentration and total phenol concentration in the pear juice were measured before and after HPP treatment, together with enzymatic characteristics of polyphenol oxidase (PPO) such?as?optimal pH, optimal temperature, thermal stability, and Michaelis constant (Km). The results showed that obvious browning in the HPP-treated juice occurred at 6 h (ΔE = 1.61), while no browning was observed in the untreated juice at 24 h (ΔE = 0.56). In the fresh juice there were two forms of PPO: PPO1 (pH 5.0) and PPO2 (pH 7.0), and the accelerated browning of HPP-treated juice was associated with the activation of the two PPOs; the activity of PPO1 was increased from 6.5 to 14.1 U/mL, by 2.17 folds, and the activity of PPO2 from 2.6 to 25.5 U/mL, by 9.8 folds. The potential PPO activities themselves were very weak or even nearly zero, which could be activated by external factors such as HPP, sodium dodecyl sulfate (SDS) and heat treatment. The Km was decreased, and the substrate affinity of PPO was increased by HPP, thereby enhancing the rate of enzymatic reaction. The substrate affinity (1/Km) of PPO1 was increased from 2.353 to 46.909 L/mol, by 19.9 folds, and the substrate affinity of PPO2 from 2.852 to 62.857 L/mol, by 22.0 folds. The maximum reaction rate Vmax was decreased after HPP treatment. Inactivation will occur if the Vmax has a greater effect on the rate of enzymatic reaction than does the Km. To sum up, HPP treatment accelerates browning of fresh pear juice by activating potential PPO, and increasing the substrate affinity of PPO and consequently the enzymatic reaction rate.
Effect of Extrusion Stabilization of Wheat Bran and Embryo on the Properties of Whole Wheat Noodles
LIU Yanxiang, WANG Liping, TAN Bin, GAO Kun, QIAO Congcong, TIAN Xiaohong, SUN Yong, ZHENG Xianzhe, LIU Ming, WU Nana, ZHAI Xiaotong, LIU Jinming
2019, 40(19):  156-163.  doi:10.7506/spkx1002-6630-20181019-206
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In order to explore the effect of the extrusion stabilization of wheat bran and embryo on the properties of whole wheat foods, two kinds of 100% whole wheat noodles were prepared by addition of unextruded and extruded mixtures of wheat bran and embryo to wheat flour and they were compared for changes in quality characteristics such as nutrients, color, flavor and storage stability. The results showed no significant differences in multiple macronutrients and mineral elements between the two kinds of whole wheat noodles (P > 0.05). Some nutrient levels were changed by no more than 10%. Extrusion was conducive to the release of β-carotene, vitamin B2, and bioactive phytochemicals, but not to the maintenance of vitamin B6 and folic acid. Moreover, upon extrusion, the contents of linoleic acid, α-linolenic acid, C11:0, and total and some individual amino acids were increased significantly (P < 0.05), the color quality was improved, and the response values of the electronic nose were greatly decreased; the fatty acid and acidity values were significantly lowered (P < 0.05) and the storage quality was more stable. Compared with ordinary wheat noodles, the contents of macronutrients, vitamins (not including β-carotene), mineral elements and bioactive phytochemicals in whole wheat noodles with extruded mixtures of wheat bran and embryo were significantly increased (P < 0.05). Among them, a larger increase was seen in the contents of fat, ash, vitamin B1, vitamin B2, vitamin B6, niacin, folic acid, total phenols and total dietary fibers. The whole wheat noodles contained more unsaturated fatty acids, and showed a significant increase in the contents of total amino acids and all individual amino acids (P < 0.05) except glutamate, proline and cystine (P > 0.05). However, the color was deepened, the response values of the electronic nose were increased observably, and the fatty acid and acidity values were elevated significantly (P < 0.05). Conclusively, this study demonstrates that whole wheat noodles have a high nutritional value, a deeper color and increased contents of flavor components than ordinary wheat noodles. The extrusion stabilization of wheat bran and embryo can improve the quality and storage stability of whole wheat noodles.
Functional Properties of High Hydrostatic Pressure Modified Wheat Bran
MIAO Ziye, YAO Yaya, LIU Yangxingyue, TIAN Boyu, LI Xiaoyang, LI Huijing
2019, 40(19):  164-171.  doi:10.7506/spkx1002-6630-20180929-333
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In this experiment, wheat bran was ground and suspended in distilled water before being treated by high hydrostatic pressure (HHP) in an effort to explore the effects of pressure, holding time, particle size, and wheat bran concentration on functional properties of wheat bran, and the ultrastructure and functional groups of wheat bran before and after modification were analyzed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Under the conditions of pressure 400 MPa, holding time 20 min, particle size 40 meshes, and wheat bran concentration 20%, modified wheat bran had the highest soluble dietary fiber (SDF) content and cation exchange capacity and the lowest lipase activity. Under the conditions of pressure 400 MPa, holding time 15 min, particle size 50 meshes, and wheat bran concentration 20%, the water-holding capacity and oil-holding capacity were higher. Under the conditions of pressure 300 MPa, holding time 25 min, particle size 40 meshes, and wheat bran concentration 15%, the nitrite scavenging ability was stronger. Under the conditions of pressure 500 MPa, holding time 25 min, particle size 50 meshes, and wheat bran concentration 25%, the cholesterol adsorption capacity was stronger. SEM results showed that HHP destroyed the structure of dietary fiber in wheat bran and made its structure loose. FTIR measurement confirmed that HHP could destroy intermolecular covalent bonds and consequently degrade cellulose and convert insoluble dietary fiber (IDF) to SDF. The modified wheat bran has good functional properties and is promising in the future.
Effect of Ultra-High Pressure Treatment on Sensory Quality of Skim Milk
ZHAO Xufei, HU Zhihe, XUE Lu, LU Dingqiang, JIA Lingyun, CHENG Kaili
2019, 40(19):  172-184.  doi:10.7506/spkx1002-6630-20190415-198
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The effects of ultra-high pressure (UHP) treatment (0.1–700 MPa for 10–30 min) on the sensory quality of fresh skim milk were studied. Changes in the light transmittance and average particle size were measured, and changes in the color, odor and taste were detected as well by electronic eyes, electronic nose and electronic tongue, respectively. The results showed that when the pressure was more than 200 MPa, the light transmittance was increased while the average particle size was decreased. In addition, UHP treatment caused changes in the sensory characteristics, and the major color number (3002 and 3018) gradually disappeared and some new color numbers (2183 and 2200) were obtained with the increase of pressure; the major odor component acetone did not change greatly after 10 min treatment in the range of 0.1–700 MPa but decreased when the holding time was 20–30 min, while acetaldehyde disappeared after treatment at 700 MPa for 10 min or at 200 MPa for 20 or 30 min. Meanwhile, some new components such as 2-methylthiophene and ethanol could be observed, with no significant difference (recognition index < 80) among UHP treatments. The intensity of sour, salty and umami taste were weakened, whereas sweetness and bitterness increased after 20–30 min treatment. Therefore, HUP treatment has little effect on the odor of skim milk, but can alter the color, taste, light transmittance and average particle size.
Nutrition & Hygiene
Influence of Swinging on the Metabolome of Pu-erh Tea Theabrownins in Rats Fed with High-Fat, High-Sugar, High-Salt Diet
WU Enkai, ZHANG Tingting, PENG Chunxiu, WANG Qiuping, TAN Chao, GONG Jiashun
2019, 40(19):  185-195.  doi:10.7506/spkx1002-6630-20180818-189
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The swinging-induced metabolomic changes of theabrownins (TB) extracted from Pu-erh tea in the serum of rats fed with a high-fat, high-sugar, high-salt diet were investigated by 1H-nuclear magnetic resonance (1H-NMR). An NMR-based metabolomic approach was used to analyze the NMR spectra of sera from 14 rat groups. Orthogonal partial least squares-discriminant analysis (OPLS-DA) was used to analyze the obtained metabolites in the comparison of chemical constitutes from different groups. The results showed that before swinging, the relative contents of isoleucine, leucine, valine and 3- hydroxybutyrate decreased significantly in serum from the metabolic syndrome (MS) model group (P < 0.05) compared with the normal control group, while the relative contents of alanine, N-acetyl-glycoprotein, glutamic acid, dimethylglycine (DMG), betaine, taurine, arginine, glycogen, glycerol increased significantly (P < 0.05). After swinging, compared with the MS model group, the relative content of 3-hydroxybutyrate in the high-dose TB group increased significantly (P < 0.05), while low density lipoprotein/very low density lipoprotein (LDL/VLDL) ratio and the relative contents of lactic acid, alanine and arginine decreased significantly (P < 0.05). After swinging, the relative contents of serum HDL, isoleucine and 3-hydroxybutyrate in the normal control group significantly increased (P < 0.05), while the relative contents of dimethylglycine (DMG), arginine, glycogen, and α-glucose were significantly decreased (P < 0.05). For the MS model group, LDL/VLDL ratio and the relative content of isoleucine in serum decreased significantly (P < 0.05) after swinging, while the relative contents of alanine and lactic acid increased significantly (P < 0.05). The metabolomic results demonstrated that swinging could significantly reduce the level of serum LDL/VLDL ratio and increase HDL level, and effectively promote blood glucose metabolism. Swinging and TB have a synergistic effect in rats with MS, and have great potential in the prevention of metabolic syndromes and cardiovascular diseases.
Effect of Bama Characteristic Dietary Patterns on Exercise Capacity and Antianxiety Level of D-Galactose-Induced Aging Mice
LAN Haijing, YANG Boning, HUANG Lianli, SUN Hui, SONG Qi, HUANG Yanting, HE Qianzu, LI Meng, LI Quanyang
2019, 40(19):  196-203.  doi:10.7506/spkx1002-6630-20180727-338
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In order to explore the anti-aging effects of new dietary patterns, an aging mouse model was established by subcutaneous injection of 100 g/L D-galactose solution for 9 weeks, and starting from the 9th week, the mice were fed with Bama dietary patterns and simultaneously administered orally with a mixture of two probiotics, Lactobacillus casei LT-L614 and Lactobacillus fermentans LT-P132 (1:1, V/V) with a viable cell count of 109 CFU/mL at a dose of 0.2 mL/20 g body mass for another 9 weeks. The locomotor activity, sensorimotor capacity, neuromuscular coordination and anxiety status of the mice were measured by the open field test and the tight-rope test in week 18. The results showed that in the open field test, compared with the aging model group, Bama characteristic dietary pattern II significantly increased the number of hind limb stand by 131.91% (P < 0.05) and the number of squares crossed by 19.71% (P > 0.05), and prolonged the total activity time to (273.72 ± 8.78) s (P < 0.05). Bama characteristic dietary patterns II and III increased the time spent in the center of the open field by 73.46% and 116.60% (P < 0.05), respectively. In the tight-rope test, compared with the control group, Bama characteristic dietary patterns II and III extended the suspension time up to (58.90 ± 4.74) and (57.67 ± 6.28) s (P > 0.05), respectively, and the conversion score by 43.66% and 39.33% (P < 0.05). Compared with the aging model group, the suspension time was prolonged by 51.92% and 48.75% (P < 0.05), respectively, and the conversion score by 154.47% and 146.79% (P < 0.05), respectively. Conclusion: The Bama characteristic dietary patterns can effectively improve the movement coordination ability and antianxiety ability of aging mice. Among them, dietary patterns II and III are the most effective, and can significantly reverse the decline of exercise capacity of D-galactose-induced aging mice.
Release of β-Casomorphin-7 and β-Casomorphin-5 and Opiate Activity from Yogurt in Vitro Digestion Model
NING Yaru, LI Qi, LIU Xiaoyu, ZHI Tongxin, LIU Xiaohan, SANG Yaxin
2019, 40(19):  204-209.  doi:10.7506/spkx1002-6630-20180731-380
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Yogurt can be digested in the gastrointestinal tract of humans to produce β-casomorphin (β-CM), which is believed to be able to relieves emotional tensions. In order to explore its release in the gastrointestinal tract and biological activity, an in vitro digestion model was used to simulate the digestion of yogurt in the body. The release of β-CM-7 and β-CM-5 was monitored by high performance liquid chromatography (HPLC); the opiate activity was measured by NG108-15 neurohybridoma cell in vitro assay and mouse behavioral test. After digestion in simulated gastric and pancreatic juices, the concentrations of β-CM-7 released were 40.24 and 47.81 μg/mL, respectively; the concentrations of β-CM-5 released were 88.00 and 82.04 μg/mL, respectively. Both digests could reduce the intracellular cAMP level in NG108-15 cells, which could be reversed by naloxone, reflecting the opiate activity of β-CM. The mouse experiments showed that the strongest analgesic activity was achieved at 30 minutes after injection of the gastric digest, giving an increase in pain threshold of 59.80%. Ingestion of the high-dose purified gastric digest prolonged the average swimming time of mice by 18.94 min, indicating good anti-fatigue effect. The experimental results show that β-CM with opiate activity and analgesic and anti-fatigue effects is produced from yogurt when ingested into in the body.
Effect and Mechanism of Mulberry Leaf Alkaloids on the Improvement of High-Fat Diet Induced Liver Injury in Mice
WANG Zuwen, YANG Zhongmin, YANG Min, HUANG Xianzhi, DING Xiaowen
2019, 40(19):  210-216.  doi:10.7506/spkx1002-6630-20180910-096
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Objective: Our aim was to study the effect and underlying mechanism of mulberry leaf alkaloids on the improvement of liver injury induced by a high-fat diet in mice for the purpose of providing a basis for the reasonable use of mulberry leaves. Methods: Mice were fed with a high-fat diet and administered by gavage with three doses of mulberry leaf alkaloids for 16 weeks. After 4, 8, 12 and 16 weeks of administration, liver index and the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity in plasma were detected, histopathological characteristics of liver tissue were observed by hematoxylin and eosin staining and the expression of tumor necrosis factor-α (TNF-α), interleukin (IL)-10, Bax and Bcl-2 mRNA in liver tissue was also detected by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Results: Compared with the high-fat diet control group, liver index and plasma ALT and AST activity were decreased significantly (P < 0.05), lipid deposition and steatosis in the liver were ameliorated, the mRNA expression levels of IL-10 and Bcl-2 were increased significantly (P < 0.05), and the mRNA expression levels of TNF-α and Bax were decreased significantly by administration of the alkaloids in a dose- and time-dependent manner (P < 0.05). The indexes altered by liver injury returned to normal after administration of the alkaloids at a dose of 200 mg/kg mb for 16 weeks. Conclusion: Mulberry leaf alkaloids significantly improve high-fat-induced liver injury in mice and its mechanism may be related to the regulated mRNA expression of TNF-α, IL-10, Bcl-2 and Bax.
Anthocyanins from the Fruits of Nitraria tangutorun Bobr. Improve Nonalcoholic Fatty Liver Injury Induced by High-Fat Diet in Mice
LI Bing, LIU Kang, ZHANG Jin, LI Cuiqin,
2019, 40(19):  217-223.  doi:10.7506/spkx1002-6630-20180913-138
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Objective: To investigate the effect of anthocyanins from Nitraria tangutorun Bobr. fruits on nonalcoholic fatty liver injury induced by high-fat diet (HFD) in C57BL/6J mice and its underlying mechanism. Methods: Male C57BL/6J mice were randomly divided into control, model and anthocyanin treatment groups. The feeding period lasted for 14 weeks. Routine physiological parameters (body mass, abdominal fat mass, body fat index, visceral fat mass, body length and Lee’s index) were measured in each mouse. Serum samples were collected to detect the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and the concentrations of total cholesterol (TC), total triglyceride (TG), low density lipoprotein (LDL) and high density lipoprotein (HDL). Besides, liver samples were collected to detect oxidative stress-related indicators such as malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and the expression of liver lipid metabolism-related proteins such as acetyl coenzyme A carboxylase (ACC), liver X receptor-alpha (LXR-α), fatty acid translocase (CD36) and peroxisome proliferator-activated receptor-alpha (PPAR-α). Results: Compared with the high-fat model group, the anthocyanins from N. tangutorun Bobr. significantly reduced body mass, abdominal fat mass, body fat index, visceral fat mass and Lee’s index. The levels of serum AST, ALT, TC, TG and LDL were significantly reduced and HDL level in high-fat diet-fed mice was significantly increased after administration with the anthocyanins. In addition, the anthocyanins significantly decreased MDA content and SOD activity and increased GSH-Px activity, as well as significantly downregulated the expression of ACC, LXR-α and CD36 and upregulated the expression of PPAR-α in liver tissue. Conclusion: The anthocyanins from N. tangutorun Bobr. can ameliorate HFD-induced NAFLD in mice by regulating oxidative stress and lipid metabolism in hepatocytes.
Mechanism of HeLa Cell Proliferation and Apoptosis Induced by Bitter Substances in Citrus
BI Jingying, LI Hua, WANG Hua
2019, 40(19):  224-230.  doi:10.7506/spkx1002-6630-20181008-027
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Purpose: To investigate how three bitter substances (limonin, nomilin and naringin) extracted from the seeds and peel of ‘Gaotai’ honey pomelo (Citrus grandis L.) impact the proliferation and apoptosis of HeLa cells. Methods: The substances were obtained and purified by ultrasonic-assisted organic solvent extraction and recrystallization and were detected by ultra-performance liquid chromatography (UPLC) using an Acquity UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm). Cell counting kit-8 (CCK-8) assay, cell scratch assay and reverse transcription-polymerase chain reaction (RT-PCR) were used to verify the anti-cancer effect of these substances at 50 μmol/L. Results: The extraction yields of limonoid and naringin were 5.21 and 7.72 mg/g, respectively. The purity of limonin, nomilin and naringin were up to 94.08%, 93.91% and 93.39%, respectively. The anti-cancer tests confirmed that the inhibition of HeLa cell growth by these bitter substances was closely related to the inhibition of cancer cell proliferation and migration.
Flavonoids from Sonchus oleraceus L. Exert a Hepatoprotective Effect in Hyperlipidemic Mice by Regulating Blood Lipid Metabolism
SHAN Kekai, WANG Hongfei, XU Feng, LUO Jie, LI Yanxia, HAN Airu, SHAO Xingfeng, WEI Yingying
2019, 40(19):  231-236.  doi:10.7506/spkx1002-6630-20181010-087
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The aim of the present study was to observe the effect of flavonoids from Sonchus oleraceus L. (FSOL) on blood lipid metabolism and to further evaluate the hepatoprotective efficacy in hyperlipidemic mice. Sixty male ICR mice were randomly and equally divided into six groups: normal control group, high fat model group, positive control group (simvastatin, 10 mg/kg), and low-, middle- and high-dose FSOL (50, 100, and 200 mg/kg) groups. The mice in the normal control group were fed a basic diet, while those in the other groups were fed a high-fat diet. After 5 weeks of feeding, serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), alanine aminotransferase (ALT), aspartate aminotransferase (AST), malondialdehyde (MDA), superoxide dismutase (SOD) and liver TC, TG, MDA and SOD were determined, and morphological changes in the liver of mice were observed. The results showed that FSOL could inhibit body mass gain in high-fat diet-fed mice, and reduce serum TC, TG, LDL-C, ALT, AST and MDA and atherosclerosis index (AI) levels as well as hepatic TC, TG and MDA and liver index. In addition, it could increase the levels of HDL-C and SOD to varying degrees. These findings indicated that FSOL has potent hypolipidemic and hepatoprotective effects in hyperlipidemic mice, and the underlying mechanism may be related to the improvement of liver lipid metabolism and the enhancement of antioxidant function. This study provides a theoretical basis for the development and utilization of FSOL.
Effect of Lactobacillus rhamnosus on the Toxicity of Tetrodotoxin in the Liver of Puffer Fish
DING Jie, WANG Mengmeng, WANG Liping, LU Ying
2019, 40(19):  237-241.  doi:10.7506/spkx1002-6630-20180816-164
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The efficacy of active and thermally inactivated Lactobacillus rhamnosus in reducing the toxicity of tetrodotoxin (TTX) in the liver of wild puffer fish was evaluated by enzyme-linked immunosorbent assay (ELISA), chromatographic strip test and mouse bioassay. Changes in the contents of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the liver after incubation with this strain were analyzed by gas chromatography-mass spectrometry (GC-MS). The competitive ELISA results showed that thermally inactivated and active Lactobacillus rhamnosus reduced TTX by 82.16% and 70.05%, indicating that better efficacy could be obtained after heat inactivation. In addition, TTX in the liver of wild puffer fish was reduced by 93.27% after 7 days of fermentation by Lactobacillus rhamnosus, and the contents of EPA and DHA in the liver were decreased by 11.93% and 22.50%, respectively. In summary, Lactobacillus rhamnosus can reduce TTX in the liver of puffer fish, and better effect can be obtained after fermentation with Lactobacillus rhamnosus. This study provides a basis for the toxicity reduction of puffer visceral tissues.
Packaging & Storage
Effect of Preharvest Spraying of Diethyl Aminoethyl Hexanoate on Metabolism of Reactive Oxygen Species in Longan Fruit Pericarp during Postharvest Storage
LIN Yixiong, LIN Hetong,, CHEN Yihui, WANG Hui, LIN Yifen,
2019, 40(19):  242-248.  doi:10.7506/spkx1002-6630-20181121-236
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We studied effects of preharvest spraying of diethyl aminoethyl hexanoate (DA-6) on the metabolism of reactive oxygen species (ROS) in longan fruit pericarp during postharvest storage. Fruit of ‘Fuyan’ longan (Dimocarpus longan Lour. cv. Fuyan) were sprayed with 10 mg/kg DA-6 or distilled water (as control) at 70, 90 and 110 days after full bloom. The fruit were harvested at 120 days, cleaned and naturally dried prior to packaging in 0.015 mm thick polyethylene bags (50 fruits per bag) and subsequent storage at (28 ± 1) ℃ and 85% relative humidity. During storage, superoxide anion radical production rate, malondialdehyde (MDA) content, the contents of endogenous antioxidant substances such as ascorbic acid (AsA) and glutathione (GSH), the activity of ROS scavenging enzymes including superoxidase dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and reducing power were determined daily. The results showed that compared with the control fruit, pre-harvest spraying of DA-6 could increase the activities of SOD, CAT, APX and GR, delay the decrease in AsA and GSH contents, maintain higher levels of DPPH radical scavenging activity and reducing power, lower superoxide anion radical production rate, and reduce the content of MDA in longan fruit pericarp, thereby improving fruit storability. This effect may be due to reduced ROS metabolism in the pericarp of harvested longan fruit during storage.
Preparation and Properties of Lysozyme and ε-Polylysine Hydrochloride Composite Coating
LI Qiuying, ZHANG Dongdong, WANG Siwen, ZHONG Keli, XU Yongxia, LI Yingchang, SUN Tong, LI Jianrong
2019, 40(19):  249-255.  doi:10.7506/spkx1002-6630-20181017-183
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In the present study, a chitosan-pullulan composite coating (CS-PUL-A) containing antibacterial agents (3 mg/mL lysozyme and 1.8 mg/mL ε-polylysine hydrochloride) was prepared, and its properties were compared with those of its counterpart without antibacterial agents (CS-PUL). The results showed that addition of antibacterial agents improved the toughness and gas and water vapor barrier properties but had little effect on the tensile strength and light transmission of the composite coating. In addition, CS-PUL-A had stronger antibacterial activity against Pseudomonas fluorescens (one of the dominant specific spoilage organisms in fish) than did CS-PUL, and the activity appeared after cultivation for 12 h. Compared with CS-PUL, CS-PUL-A could result in increased leakage of intracellular nucleotides and electrolytes and subsequently higher conductivity of the cell suspension, indicating that CS-PUL-A more severely damaged the cell membrane integrity and permeability. The coating treatment also reduced the activity of alkaline phosphatase in the suspension. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that CS-PUL mainly affected small proteins, while CS-PUL-A affected both small and large proteins. Scanning electron microscopy further confirmed the damage to bacterial cells caused by CS-PUL-A. In summary, CS-PUL-A exerted better physicochemical properties and antibacterial properties than CS-PUL and could be potentially used in food preservation.
Effect of Antimicrobial Peptide Jelleine-I on the Control of Citrus Postharvest Green Mold
LI Xindan, WANG Wenjun, DENG Lili, YAO Shixiang, ZENG Kaifang,
2019, 40(19):  256-262.  doi:10.7506/spkx1002-6630-20190318-222
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In this study, the effect of peptide Jelleine-I (antimicrobial peptide derived from royal jelly) on the growth of Penicillium digitatum and its possible mode of action were investigated. Meanwhile its effect on the control of postharvest green mold induced by stab inoculation in citrus fruit was evaluated. The results showed that Jelleine-I could significantly inhibit the growth of P. digitatum. The minimal inhibitory concentration and minimal fungicidal concentration were 6.25 and 12.5 μmol/L, respectively. Jelleine-I could significantly decrease the incidence of green mold of citrus fruit. After being treated with Jelleine-I, the membrane permeability of P. digitatum hyphae increased and the intercellular membrane was damaged. The intracellular green SYTOX Green fluorescence increased and the intercellular blue Calcofluor White fluorescence decreased. In addition, Jelleine-I significantly increased the extracellular conductivity and the intracellular leakage of nucleic acid (P < 0.05). Therefore, Jelleine-I could effectively control citrus postharvest green mold by damaging the membrane structural integrity and consequently causing intracellular material leakage and accelerating the death of P. digitatum.
Effect of Different Packaging Treatments Combined with Eugenol-Loaded Diatomite on Storage Quality of Strawberry
LIAO Li, ZHANG Lihui, HU Yang, SHI Defang, CHEN Xueling, WANG Lan, WANG Chao, QIAO Yu
2019, 40(19):  263-271.  doi:10.7506/spkx1002-6630-20181008-048
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Strawberry fruit were packaged with polyethylene (PE), polyvinylidene chloride (PVDC), low-density polyethylene (LDPE), linear low-density polyethylene (L-LDPE) or modified atmosphere packaging (MAP) combined with eugenol-loaded diatomite treatment. The quality changes were monitored during subsequent storage at 4 ℃. The results showed that all four treatments could inhibit strawberry decay and mass loss in varying degrees, retard the loss of soluble solids, titratable acids, reducing sugar and VC, and suppress the increase of malondialdehyde (MDA) content and the decline of superoxide dismutase (SOD) and peroxidase (POD) activity. Among them, MAP combined with eugenol-loaded diatomite treatment was the most effective, followed by PVDC combined with eugenol-loaded diatomite treatment, which could prolong the shelf life of strawberry to 15 and 12 days, respectively. The results of this experiment can be useful for the preservation of strawberry fruit.
Effect of Modified Atmosphere Packaging on Shelf Life and Microbial Diversity of Roast Duck Legs
ZHAO Jiayue, LUO Xin, YANG Xiaoyin, MAO Yanwei, LIANG Rongrong, DONG Pengcheng, ZHU Lixian, ZHANG Yimin, LIU Guoxing, GAO Hejiang
2019, 40(19):  272-280.  doi:10.7506/spkx1002-6630-20181015-126
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The aim of this study was to extend the shelf life of roast duck legs, and to maintain its eating quality and to clarify the microbial community dynamics during storage. This experiment investigated the effects of different modified atmosphere packaging (MAP) (100% N2, 50% CO2 + 50% N2) on microbial counts (total viable counts, lactic acid bacteria and Enterobacteriaceae), thiobarbituric acid reactive substance (TBARS) level and sensory evaluation during storage at 0-4 ℃, with tray packaging as the control. High-throughput sequencing was also used to analyze microbial diversity. Compared with MAP with 100% N2 and the control, MAP with 50% CO2 + 50% N2 extended the shelf life up to 21 d by inhibiting the growth of bacteria (P < 0.05); meanwhile, this package method decreased lipid oxidation (P < 0.05) and maintained the quality and sensory characteristics of roast duck legs. Storage time and packaging had a significant effect on bacterial community compositions at the late storage stage. Pantoea spp., Myroides spp., Pseudomonas spp. and Acinetobacter spp. were the dominant bacteria in the 50% CO2 + 50% N2 group, while Brochothrix spp., Pantoea spp., Pseudomonas spp., Carnobacterium spp. and Leuconostoc spp. were the dominant bacteria in the 100% N2 group. The difference in the predominant bacteria may greatly contribute to the difference in shelf life among packaging treatments.
Application of Rabbit Skin Gelatin/Rosmarinic Acid Composite Film in Pork Quality Preservation during Cold Storage
LI Yuan, ZHANG Xiaojie, MA Liang, GUO Ting, YU Yong, DAI Hongjie, ZHOU Hongyuan, ZHANG Yuhao,
2019, 40(19):  281-287.  doi:10.7506/spkx1002-6630-20180930-339
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Rabbit skin gelatin films incorporated with different concentrations (0, 0.3, 0.5 and 0.8 g/L) of rosmarinic acid (RosA) were prepared and fresh pork was packaged using gelatin film alone, or gelatin film as an inner package coupled with polyethylene (PE) film as an outer package. This study showed that the composite films effectively inhibited the increase of total volatile basic nitrogen (TVB-N) content, total colony number and pH during refrigeration and also inhibited lipid oxidation. This effect was positively correlated with RosA concentration within the range used in this study. Compared with the control group, 0.8 g/L RosA-gelatin film packaging and PE packaging extended the shelf life of pork from 4 to 8 and 6 days, respectively, and PE/0.8 g/L RosA-gelatin film extended the shelf life to 10 days. In addition, by measuring the color, hardness and other indicators as well as visual observation of pork, it was found that PE/RosA-gelatin film better maintained the texture quality and color of pork compared with RosA-gelatin film. Therefore, PE/RosA-gelatin film can be used as an effective packaging for the preservation of meat quality during cold storage.
Quality Preservation of Tilapia Fillets Using Slightly Acidic Electrolyzed Water Ice
CEN Jianwei, YU Futian, YANG Xianqing, LI Laihao, HUANG Hui, WEI Ya, ZHAO Yongqiang, HAO Shuxian, LIN Zhi
2019, 40(19):  288-293.  doi:10.7506/spkx1002-6630-20181009-060
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The objective of this study was to investigate the effectiveness of slightly acidic electrolyzed water ice (SAEWI) in preserving the quality of tilapia fillets. Tilapia fillets were stored in SAEWI or tap water ice (TWI) and evaluated for changes in total volatile basic nitrogen (TVB-N) content, K value, pH, total colony number and sensory quality. The results showed that compared to TWI, SAEWI could inhibit the increase of total bacterial count, TVB-N content and K value during storage at 1 ℃, and imparted higher sensory scores to tilapia fillets. Overall, the shelf life of tilapia fillets treated with SAEWI could be prolonged by 3 to 4 days, and the quality of tilapia fillets was maintained more effectively. This study provides a theoretical basis for the application of SAEWI to preserve aquatic products during circulation.
Reviews
A Review of the Application of Dielectric Spectroscopy in Food Field
ZHAO Kongshuang, LIU Yuan
2019, 40(19):  294-306.  doi:10.7506/spkx1002-6630-20190329-383
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This article mainly reviews the progress that has been made in recent years in the application of dielectric spectroscopy (DS) in various food systems (fruits/vegetables, edible oil, meat/fish, milk and its products, eggs, honey, and alcoholic drinks). We describe the advantages and limitations of dielectric heating in food processing. We also set forth the feasibility of applying DS in quality detection of various food systems. In order to utilize this technology effectively, the differences in the advantages of DS in various foods are provided specially. Besides, the possible roles and future trends of DS in food-related fields are discussed.
Recent Progress in Prevalence and Detection Methods of Foodborne Hepatitis A Virus and Norovirus in Berries
FENG Huawei, AI Haixin, YANG Tianzhou, QI Mengyuan, TAN Yanni, MA Lidan, LIU Hongsheng,
2019, 40(19):  307-317.  doi:10.7506/spkx1002-6630-20181008-030
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Berries are important vectors for the spread of foodborne hepatitis A virus (HAV) and norovirus (NoV), and have received worldwide attention. In order to identify the presence of foodborne viruses in berry products in a timely manner, sensitive methods are therefore needed. Due to the low concentration of HAV and NoV in contaminated berries that are weak in texture and contain a large amount of reverse transcription-polymerase chain reaction (RT-PCR) inhibitors such as pectin, polyphenols, polysaccharides and pigments, false-negative results easily occur, thereby making it difficult to monitor foodborne viruses. Based on an extensive review of the literature, the prevalence of foodborne HAV and NoV in berries is summarized, and future directions for the improvement of the existing detection methods for the two viruses in berries are proposed. Moreover, the applications of three types of process control, such as whole process controls, molecular process controls and RT-PCR controls are also discussed in the detection of HAV and NoV. In conclusion, this review provides a methodological basis for strengthening the surveillance capability of HAV and NoV in berries.
Recent Progress in Prolamines as a Food Nutrient Carrier
HUANG Hui, LI Xueyan, WANG Junwen, WU Wenhui, GUO Ruihua, YU Qingmei, ZHANG Chaoyan,
2019, 40(19):  318-325.  doi:10.7506/spkx1002-6630-20181008-049
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Prolamines, a group of naturally occurring polymers found in plants including zein, gliadin, hordein and kafirin, have a good biocompatibility and degradability. Prolamines can be used as a good carrier for functional components of foods. The structure and properties of the four prolamin proteins as well as the methods used to prepare their microparticles are reviewed in this paper. Meanwhile, the applications of prolamines as carriers to load nutrients such as polyphenols, oils and probiotics are also discussed.
Recent Progress in the Application of Flavonoids in the Intervention of Diabetic Retinopathy
HUANG Yongjie, LI Feng, LI Dapeng
2019, 40(19):  326-333.  doi:10.7506/spkx1002-6630-20181004-009
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Diabetic retinopathy is the most common microvascular complication in diabetic patients, and it is also one of the leading causes of blindness worldwide. It is evidenced that oxidative damage induced by excessive reactive oxygen species in the body is the major pathogenesis of diabetic retinopathy. Flavonoids, present ubiquitously in plant diets, have many pharmacological functions such as antioxidant, anti-inflammatory, hypoglycemic and free radical scavenging activities. Recently, increasing evidence has shown the significant role of flavonoids in preventing and treating diabetic retinopathy. In this paper, recent progress in the study of the anti-diabetic retinopathy potential of flavonoids is summarized with the aim of providing a theoretical basis and new ideas for further development and application of flavonoids.
Recent Progress in Understanding the Substance Basis for the Regulation of Cholesterol Metabolism by Lactic Acid Bacteria
TIAN Jianjun, ZHANG Kaiping, LI Quanwei, ZHAO Yanhong, JIN Ye
2019, 40(19):  334-339.  doi:10.7506/spkx1002-6630-20181014-114
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Cholesterol is essential for the growth and development of mammalian cells, but excessively high serum cholesterol can cause many diseases. Lactic acid bacteria have received extensive attention because of their ability to regulate serum cholesterol level in recent years. Cholesterol metabolism in vivo is a complex process where multiple factors, levels, proteins and genes are involved. At present, the regulatory mechanism of lactic acid bacteria on cholesterol metabolism is unclear yet. Most studies just focus on single or a few metabolic enzymes or proteins, and lack systematicness. This paper summarizes current studies on cholesterol metabolism and the substance basis for the regulation of cholesterol metabolism by lactic acid bacteria, and it discusses the applications of differential proteomics and polymerase chain reaction array to analyze the differentially expressed proteins in liver lipoprotein, plasma and liver of different mouse models and genes involved in the cholesterol metabolism pathways, with the aim of providing evidence for exploring the active substance basis and mechanism for the cholesterol-lowering effect of lactic acid bacteria.
Recent Progress in Understanding the Mechanism of the Interaction between Calcium and Milk Proteins and Its Influence on Functional Properties of Milk Proteins
LI Xiangying, ZHAO Xuan, QIN Yusi, CHEN Di, WANG Cunfang
2019, 40(19):  340-345.  doi:10.7506/spkx1002-6630-20180927-288
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Calcium is widely used in dairy products as an important material for the growth of human bone and the regulation of physiological functions. Calcium interacts with milk proteins, such as αs-casein, β-casein, κ-casein, α-lactalbumin and β-lactoglobulin, thus affecting the structural stability and changing thermal stability, emulsifying characteristics, solubility, foaming characteristics and gelation properties of milk proteins. In this paper, the interaction mechanism between calcium and various milk proteins and the effects of calcium on their functional properties are reviewed in light of their importance for systematically understanding the binding between calcium and milk proteins. This review is expected to provide a theoretical basis for further studies on calcium-containing functional dairy products and their industrial production.
Progress in the Improvement of Lycopene Bioavailability
YU Ying, ZHANG Wei, XIE Fan, GU Xinzhe, WU Jinhong, WANG Zhengwu
2019, 40(19):  346-352.  doi:10.7506/spkx1002-6630-20181011-094
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Lycopene bioavailability is a key determinant for its nutritional benefits. Naturally occurring lycopene has a low bioavailability. Meanwhile, lycopene isomerization, food dispersion, and the interaction between lycopene and other food components play an important role in lycopene bioavailability. In recent years, new food processing technologies and emulsions or co-digestive systems have been increasingly applied to improve lycopene bioavailability, which has become a hot topic. In this article, the absorption mechanism of lycopene, the factors affecting lycopene bioavailability, and the methods to improve and evaluate lycopene bioavailability are summarized. In addition, future research trends are presented.
Recent Advances in Understanding the Safety of Polycyclic Aromatic Hydrocarbons in Foods
LIU Yiqi, HU Changying
2019, 40(19):  353-362.  doi:10.7506/spkx1002-6630-20181008-053
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In recent years, consumers and the government have paid growing attention to food safety, and the presence of polycyclic aromatic hydrocarbons (PAHs) with carcinogenic and teratogenic potential in foods has become an increasing concern. In this article, the current available data on the contents of PAHs in different foods and the safety evaluation of their margins of exposure (MOE) and lifetime cancer risk (ILCR) are reviewed. It is believed that more attention should be paid to the food safety for vulnerable groups such as infants. Meanwhile, the influence of different processing methods and processing conditions on the formation of PAHs in foods is summarized, and some measures to reduce PAHs are presented with a view to providing useful information for consumers to reduce dietary risk and providing an impetus for studies on the formation mechanism and toxicology of PAHs.
Progress in Research on Structure-Function Relationship of Lentinan
WANG Jiateng, WANG Hecong, LIU Lei
2019, 40(19):  363-369.  doi:10.7506/spkx1002-6630-20181016-162
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Lentinan is one of the major functional components in Lentinus edodes and is often used in medicine and foods. Lentinan, whose backbone is composed of β-D-(1→3)-Glc, has been reported to have various bioactivities such as antioxidant, immunomodulatory, antitumor, antivirus and antibacterial functions. In this article, the current status of studies on structure characteristics, functions and structure-activity relationship of lentinan is summarized. Meanwhile, the existing problems and future development directions are discussed.
Legal Regulation of Recycling of Food Contact Plastic Packaging Materials in China: A Case Study on Polyethylene Terephthalate (PET) Beverage Bottles
YU Yangyao, LIN Lusuo
2019, 40(19):  370-377.  doi:10.7506/spkx1002-6630-20190510-099
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Recycling of plastic food packaging is a development trend in the future. There are currently no clear legal provisions on this issue in China. The legal regulation of recycling of food contact plastic packaging materials in China should focus on food safety while taking into account environmental protection, recycling economy and green consumption, which will not just promote the food packaging recycling industry’s development, but also will promote waste plastic management and environmental protection, thereby realizing the resource recycling and consumption upgrading under the premise of food safety. Based on the general situation of legal regulation in China, this article discusses the necessity and feasibility of legal regulation. Meanwhile, drawing on foreign experience, it proposes that the legal status of plastic food packaging recycling be defined, national food safety standards for recycled polyethylene terephthalate (PET) materials be formulated, market access for recycled food contact packaging materials be improved, and a social co-governance pattern for food packaging recycling be constructed.