• Volume 39,Issue 3,2021 Table of Contents
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    • >Special Edition
    • Research Progress of Lactic Acid Bacteria Genome-Scale Metabolic Models

      2021, 39(3):1-10. DOI: 10.12301/j.issn.2095-6002.2021.03.001

      Abstract (979) HTML (1752) PDF 7.63 M (1134) Comment (0) Favorites

      Abstract:Genome-scale metabolic models (GEMs/GSMM) are cellular biochemical reaction networks of the genomic scale, which can quantitatively describe the relationship between genes and phenotypes,and be widely used in systems biology, metabolic engineering, environmental science and other fields. Microbial GEMs are constructed based on physiological and biochemical knowledge bases of microbial genomes to simulate the physiological and biochemical reactions of targeted microorganism via mathematic model. Microbial GEMs have become important tools for studying the regulation of microbial metabolism. The work flows of GEMs reconstruction usually included four steps:draft reconstruction, refinement reconstruction, conversion of reconstruction, network evaluation. Based on the introduction of the development process of GEMs represented by model microorganisms (Escherichia coli, Bacillus subtilis, and Saccharomyces cerevisiae), the current research status of the lactic acid bacteria GEMs was focused. The reconstructed lactic acid bacteria GEMs and its application were systemically introduced. The development direction of the lactic acid bacteria GEMs was prospected. The future research on lactic acid bacteria GEMs was proposed to build higher-quality metabolic and macromolecular expression models and pan-genome models on the basis of existing models, so as to provide more efficient tools for the research of lactic acid bacteria.

    • >Expert Forum
    • Research Progress on Walnut Polysaccharide

      2021, 39(3):11-21. DOI: 10.12301/j.issn.2095-6002.2021.03.002

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      Abstract:Walnut is one of the four major dried fruits in the world with high nutrition and health care value. In recent years, the biological activity of plant polysaccharides has been widely concerned, and the research is also gradually deepened, however, there is few study focused on walnut kernel polysaccharides. Polysaccharides are distributed in all parts of walnut tissues, in order to better develop the nutritional and health effects of walnut polysaccharides, especially the extraction and utilization of walnut meal polysaccharides, the domestic and oversea literatures on the extraction, separation, purification, determination, molecular structure characteristics and biological activity of walnut polysaccharides in recent years had been comprehensively sorted and analyzed, a series of meaningful data and information for walnut polysaccharide research were obtained:ultrasonic and microwave-assisted hot water extraction process had good effect. High yield of polysaccharides was obtained under the extraction technology with temperature higher than 85℃ and 150min extraction time, and ethanol volume fraction more than 90%. After deproteinization by Sevag method, different molecular weight cutoffs and purification with DEAE-Sepharose and Sephadex could obtain multiple polysaccharides with molecular weights ranging from 7015 to 133021u. Walnut polysaccharides in different tissues all contained glucose, rhamnose, galactose, xylose, arabinose and mannose, which indicating that walnut polysaccharides were mainly acidic heteropolysaccharides, they also exhibited various biological activities such as anti-cancer, anti-oxidation, hypoglycemic, antibacterial, and prevention of Alzheimer's disease. The research on walnut polysaccharide might have important practical significance for improving the quality and efficiency of walnut industry chain.

    • Research Progress on Tea Flower Polysaccharide

      2021, 39(3):22-29. DOI: 10.12301/j.issn.2095-6002.2021.03.003

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      Abstract:Tea blossom and tea leaf hare the same root system, however, the tea blossom is often regarded as the waste of tea tree without well utilization, which results in the waste and loss of resources. Tea blossom is rich in active substances, and there are similar polysaccharides in tea blossom and tea, while the content of polysaccharides in tea blossom is significantly higher than that in fresh tea leaf. Tea flower polysaccharides have many functions, such as lowering blood sugar, antioxidant, immunomodulatory, anti-tumor, liver protection, anticoagulant and etc. It might be a very valuable new resource food. The main extraction methods of tea flower polysaccharides included solvent extraction, enzyme extraction, microwave-assisted extraction and ultrasonic assisted extraction. The purified tea flower polysaccharides were obtained via deproteinization, decolorization, chromatographic column classification and other purification processes from crude tea flower polysaccharides. At present, there was few report focused on tea flower polysaccharide, which is worthy of further study. Focusing on the new resource food of tea blossom, this paper expounded the functions, extraction methods, separation and purification methods of tea flower polysaccharides, and introduced its current research progress, so as to provide new research ideas for the development and utilization of tea flower polysaccharides and its active substances.

    • Effect of Short-Time Micro-Flow Water Treatment on Flavor Quality of Grass Carp Fish Meat

      2021, 39(3):30-42, 51. DOI: 10.12301/j.issn.2095-6002.2021.03.004

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      Abstract:In order to improve the flavor quality of grass carp (Ctenopharyngodon idella) fish meat, the pond cultured grass carp was used as the research object, and the indoor micro-flow water system was used to treat the grass carp for 0, 1,4, 7d, respectively. Comprehensive two-dimensional gas chromatography-time of flight mass spectrometry technology was employed to screen out the key odor substances at different treatment time. And a metabolomics method based on liquid chromatography-mass spectrometry/mass spectrometry technology was used to study the effects of flavor components of micro-flow water treatment on grass carp. The results showed that the treatment time of micro-flow water had a significant effect on the contents and types of odor components in the meat of grass carp. With the extension of the treatment time, the relative contents of flavor precursors glutathione, oxidized glutathione and polyunsaturated fatty acids increased. The relative contents of the key unpleasant odor compounds of grass carp fish meat, such as grassy hexanal, fishy heptanal, green moldy (E)-2-pentenal and 1-heptanol were reduced. And the contents of umami and sweet amino acids and nucleotides in the flavor substances of grass carp fish meat were accumulated, the bitter amino acid content gradually decreased, thereby improving the texture of the grass carp meat and bringing a rich flavor.

    • Taste Changes of Pearl Gentian Grouper in Waterless Keep Alive Process

      2021, 39(3):43-51. DOI: 10.12301/j.issn.2095-6002.2021.03.005

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      Abstract:To explore the taste changes of pearl gentian grouper during the process of waterless keep alive, the taste changes of pearl gentian grouper after 0,3, 6,9, 12h waterless keep alive were studied through analysis results of electronic tongue and measuring indicators of nucleotides, organic acids and free amino acids. The results showed that in PCA analysis of electronic tongue, the cumulative contribution rate of PC1 and PC2 was 90.29%, which could reflect the overall characteristics of the samples. Compared with fresh samples, the umami and kokumi taste value increased significantly after waterless keep alive, reaching 3.52 and 5.00 at 12h, respectively. The nucleotide content increased first and then decreased. After 3h waterless keep alive, AMP and IMP reached the maximum values of 9.0mg/100g and 465.0mg/100g, respectively. The overall trend of organic acids was increasing. The lactic acid content of each treatment group was significantly different (P<0.05), and the maximum value of lactic acid was 158.70mg/g after 12h waterless keep alive. The TAV values of succinic acid, lactic acid and citric acid in all treatment groups were greater than 1, indicating that organic acids had an important contribution to the taste of grouper. Total free amino acids, umami amino acids and sweet amino acids all showed a trend of first increasing and then decreasing. After 3 h waterless keep alive, the maximum values of umami amino acids Glu and Asp were 41.50mg/100g and 7.29mg/100g, which were significantly higher than those of 8.54mg/100g and 0.60mg/100g in fresh samples, respectively. In conclusion, waterless keep alive could improve the taste of pearl gentian grouper and enhance the nutritional value of grouper protein.

    • Changes of Taste Substances of Litopenaeus vannamei During Hot Air-Microwave Combined Drying

      2021, 39(3):52-61. DOI: 10.12301/j.issn.2095-6002.2021.03.006

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      Abstract:To study the taste changes of Litopenaeus vannamei in the process of hot air-microwave combined drying (HAMD), the content of taste nucleotides and free amino acids and their changes of dry basis contents calculated by moisture content during HAMD of shrimp meat were determined, and equivalent umami concentration (EUC) was calculated. The results showed that the content of inosine monophosphate (IMP) was the highest in taste nucleotides during process of HAMD, and the content of IMP was 405.96mg/100g in dried shrimp meat. The content of IMP was always higher than the threshold value, which contributed significantly to the formation of umami taste in dried shrimp meat. Compared with those in fresh shrimp meat, the dry basis contents of IMP and AMP in dried shrimp meat decreased significantly. In the shrimp meat, glutamic acid contributed significantly to umami, glycine, alanine and arginine contributed to sweet, and phenylalaninie, lysine and histidine resulted in bitter taste. During the process of HAMD, the relative contents of umami and sweet amino acids increased from 3.77% to 4.29% and 17.03% to 35.84%, respectively. The total content of free amino acids in dry basis decreased. However, the contents of glycine, alanine, arginine and proline in dry basis increased which contribute to good taste. The content of myofibrillar protein and sarcoplasmic protein in dry basis of shrimp meat decreased continuously and some of them were decomposed into free amino acids. The EUC of shrimp meat showed a significant increasing trend, but it decreased significantly in the first 40 seconds of microwave drying process. The EUC of dried shrimp meat was 3.50g/100g and was much higher than that of fresh shrimp meat (0.53g/100g). In addition, the EUC of shrimp meat was always much higher than the threshold value during process of HAMD. In conclusion, this study indicated the water evaporation and substances changes caused by HAMD could promote the formation of Litopenaeus vannamei taste.

    • Effect of Frozen Storage on Flavor Characteristics of Aqueous and Enzymolysis Extract from Pinctada martensii

      2021, 39(3):62-72. DOI: 10.12301/j.issn.2095-6002.2021.03.007

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      Abstract:In order to explore the effect of frozen storage on the content and characteristics of flavor substances of aquatic products, the fresh and frozen meat of Pinctada martensii was used, and the Pinctada martensii extracts were prepared by boiled water extraction method and enzymatic hydrolysis, respectively. And then the flavor characteristics of different extracts were evaluated by electronic tongue and sensory evaluation system, the contents of basic components, free amino acids, flavor nucleotides, organic acids and organic bases of different extracts were determined and their contributions to the flavor were assessed by taste activity value. Taste characteristics results of the electronic tongue showed that the aqueous extract from fresh meat exhibited the strongest sweetness, which was stronger than the aqueous extract from frozen meat. Umami, sweetness and richness were the important flavor characteristics of the enzymolysis extract of fresh meat. Sweetness and richness were higher than those of frozen meat. The principal component analysis results of electronic tongue revealed that the enzymolysis extract of fresh meat taste characteristics were close to those of sodium glutamate. The results of artificial sensory evaluation showed that the sweetness and umami of frozen meat extract were weaker than those of fresh meat extract, and the sourness was more prominent with irritation. Compared with those in the aqueous extract of frozen meat, the determination results of flavor substances showed that the aqueous extract of fresh meat contents of glycine and 5′-monophosphate increased by 19.30g/kg and 302.60mg/100g, respectively. The enzymolysis extract from fresh meat had higher contents of glutamic of 27.60g/kg and succinic acid of 1352.70mg/100g, which were significantly higher than those of enzymolysis extract from frozen meat (P<0.05). Therefore, frozen storage treatment could reduce the content of umami and sweetness substances in Pinctada martensii meat extract, increase the content of bitter substances, and weaken the delicious taste of the extract.

    • >Foundational Research
    • Effect of Salt Preadaptation on High Salinity Stress Resistance of Zygosacchromyces rouxi

      2021, 39(3):73-79, 128. DOI: 10.12301/j.issn.2095-6002.2021.03.008

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      Abstract:In order to further improve the resistance of Zygosacchromyces rouxii (Z. rouxii) to high salinity stress, the effect of salt preadaptation on the high salinity stress resistance of Z. rouxii was studied.The results indicated that after preadaptation with 60,120, 180g/L NaCl for 90min, the survival rate of cells under 350g/L saturated NaCl increased to 2.05,2.53 and 1.92 folds than treatment before, respectively. The effect of 120g/L NaCl preadaptation for 90min on physiological characterization of Z.rouxii was further analyzed. The results showed that during salt preadaptation, intracellular pH level and Na+/K+-ATPase activity were higher than those without preadaptation. The relative contents of saturated fatty acids (palmitic acid C16:0, stearic acid C18:0) decreased to 93% and 60% than treatment before, the unsaturated fatty acids (palmitoleic acid C16:1, oleic acid C18:1 and linoleic acid C18:2) increased to 2.55,1.78 and 1.39 times than treatment before, and the unsaturation degree increased to 2.28 times than treatment before. The intracellular free serine, threonine and lysine contents also increased significantly. This study might be helpful to understand the resistance mechanisms of Z. rouxii to high salinity stress, and provide theoretical guidance for the improvement of stress resistance and industrial application of Z. rouxii.

    • Preparation of Natural Equivalent Ester Aromas with Lipase Catalysis of Fusel Oil

      2021, 39(3):80-88. DOI: 10.12301/j.issn.2095-6002.2021.03.009

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      Abstract:The influence factors of ester aromas with lipase catalysis of fusel oil in non-aqueous media system were studied via screening suitable lipase, optimizing the conditions of enzymatic conversion, and the effect of ultrasonic processing on enzymatic conversion was also studied. The results showed that the esterification activity of immobilized lipase Novozym 435FG was high and easy to recycle, and the yield of isoamyl acetate was 92.62%. The addition of dehydrating agent molecular sieve promoted the esterification reaction. The yield of ester aromas was affected by addition times and time interval of acetic acid, reaction temperature, reaction time, shaking speed, and ultrasonic field intensity. The optimized conditions by orthogonal test design were as follows:1.5mL acetic acid added in six times, the interval time of 3h, the reaction time of 36h, the molecular sieve of 2g, the fusel oil of 3mL, the lipase of 70mg, the reaction temperature of 45℃, the shaking speed of 140r/min, and the yield of isoamyl acetate, isobutyl acetate and propyl acetate reached (89.2±0.7)%, (89.3±0.6)% and (76.8±0.9)%, respectively, which closed to ester yield in hexane reaction system. At the ultrasonic frequency of 50Hz and ultrasonic power of 0.5W/cm2 for 6h, the yield of ester aromas reached 85%. It indicated that proper ultrasonic treatment could greatly accelerate the reaction process and shorten the reaction time. However, the ultimate production and yield after ultrasonic treatment did not increase, and long-time ultrasonic cavitation led to changing the microenvironment of the system and reducing the stability and use frequency of immobilized enzyme.

    • Analysis of Aroma Active Compounds of Ejiao

      2021, 39(3):89-100. DOI: 10.12301/j.issn.2095-6002.2021.03.010

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      Abstract:Sensory analysis was applied to establish the flavor profile of Ejiao. In order to further explore the flavor attributes, both solid-phase micro-extraction (SPME) and solvent assisted flavor evaporation (SAFE) were used to extract volatile compounds from Ejiao, respectively. Subsequently, gas chromatography-olfactometry (GC-O) and aroma activity value (OAV) were both used to determine the aroma active compounds. The attributes contributed to the profile were mainly fishy, scorched and meat flavor of Ejiao. 44 and 52 volatile compounds were identified by SPME and SAFE, respectively. 34 aroma active substances were identified by SPME including 23 substances identified by GC-O and 24 substances by OAV method. Additionally, 41 aroma active compounds were identified by SAFE including 29 compounds by GC-O and 26 compounds by OAV method. The key aroma active compounds of Ejiao were hexanal, 2-ethyl-6-methylpyrazine, 2,3,5-trimethylpyrazine, 3-ethyl-2,5-dimethyl pyrazine, 2,5-dimethylpyrazine, 2-ethyl-5-methylpyrazine, dimethyl trisulfide, decyl alcohol, phenylethyl alcohol, butyric acid, 4-methyl valeric acid, isoprene acid, caproic acid, octanoic acid, citric acid and γ-decalactone. In general, pyrazines, acids and sulfur-containing compounds were the most valuable components contributed to the flavor profile of Ejiao.

    • Effect of Compound Modified Areca Taro Starch with Ball Milling and Esterification on Formation of Pickering Emulsions

      2021, 39(3):101-110. DOI: 10.12301/j.issn.2095-6002.2021.03.011

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      Abstract:To improve the emulsifying capacity of starch particles, soybean oil-in-water Pickering emulsions were prepared using compound modified areca taro starch with ball milling and esterification. The appearance, droplet size, microscopic morphology, and dynamic rheological properties of Pickering emulsions were characterized using laser scattering analyzer, research-grade upright microscope, rheometer, etc. The effects of starch particle mass concentration (1,5, 10,20, 30mg/mL) and oil phase volume fraction (10%, 20%, 30%, 40%, 50%) on stability and rheological properties of emulsion were investigated. Results indicated that the increment of the particle concentration increased the emulsified phase volume and decreased the droplet size. The emulsified phase volume and droplet size of Pickering emulsions increased with the increase of the oil phase volume fraction. When the particle mass concentration was 20mg/mL, and the oil phase volume fraction was 40%, the Pickering emulsion exhibited a great improvement in separation of emulsion. Compound modified areca taro starch particles were adsorbed at the oil/water interface and effectively resisted droplet coalescence, which led to good stability of the emulsion after 30 d storage. The rheological properties indicated that there was an elasticity-dominated gel-like network structure at inside of the emulsion. With the increasing of particle mass concentration and oil phase volume fraction, the emulsion droplets might pack in a denser manner, which increased the emulsion viscosity and gel-like strength, and enhanced its resistance to deformation. These findings demonstrated that compound modified areca taro starch with ball milling and esterification exhibited good potential as a stabilizer for Pickering emulsion stabilizer.

    • Effect of Different Heating Conditions on Fatty Acids Content in ω-3 Eggs

      2021, 39(3):111-121. DOI: 10.12301/j.issn.2095-6002.2021.03.012

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      Abstract:fatty acids exhibit instability due to their unsaturated double bonds and are easily oxidized during storage and processing. Egg as carrier, ω-3 egg is a new type of nutritional fortification food enriched with ω-3 fatty acids. The purpose of this research was to study the changes of ω-3 fatty acids in egg under heating conditions, so as to provide reference for the cooking and eating of ω-3 eggs. Whole shell ω-3 egg and whole egg liquid were used as experimental objects, which were processed into hot spring egg, soft boiled egg, and well-cooked egg, respectively. The content of fatty acids in eggs was determined by gas chromatography, and the effects of different heating conditions on the content of fatty acids in eggs were analyzed and compared. Due to multiple differences such as fortification methods and breeding methods, the fatty acids content in eggs of different brands varied greatly. Due to the differences between individual of whole shell eggs were still obvious after heating treatment, the final experimental results were based on the treatment of whole egg liquid. Compared with fresh whole egg liquid, the effect of heating process on fatty acid content of hot spring egg was the smallest. The content of PUFA, EFA and DHA in hot spring egg were decreased by 0.08%, 0.14% and 1.15%, respectively, which were decreased by 1.01%, 0.55% and 4.23% in soft boiled egg and 1.22%, 1.29% and 5.77% in well-boiled egg, respectively. During heating, the fatty acids in ω-3 eggs will be lost to a certain extent. With the increase of maturity, the loss of fatty acids in eggs will gradually increase, but the total loss was relatively small, indicating that the effect of heating process on the content of fatty acid in ω-3 eggs was not significant.

    • Effects of Oxidized Milk Protein Intaking During Gestation and Lactation on Redox Status in Offspring Mice

      2021, 39(3):122-128. DOI: 10.12301/j.issn.2095-6002.2021.03.013

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      Abstract:To study the effects of intaking oxidized milk protein with different fat content during pregnancy and lactation on the redox status of offspring mice, the whole milk and low-fat milk were oxidized by heat, then the contents of carbonyl and free thiol group were analyzed. Post-coital female mice were fed with daily ration containing oxidized milk protein, offspring mice were weaned at 3-week old and the indexes of oxidative injury were measured. The results showed that in comparison with those in corresponding milk without modification, the carbonyl content was increased and free thiol group content was decreased in oxidized whole milk and low-fat milk groups. Compared with those in low-fat milk group, the carbonyl content was increased and free thiol group was decreased in whole milk group. The activity of anti-oxidant enzymes (CAT and SOD) was significantly decreased and the accumulation of lipid peroxide MDA, HNE was increased in offspring mice fed oxidized milk protein than those fed normal milk protein. In comparison with those fed low-fat milk, the activity of anti-oxidant enzymes (CAT and SOD) was decreased and content of lipid peroxide MDA and HNE was increased in offspring mice fed whole milk. All results indicated that intake of whole or low-fat milk with oxidized milk protein during gestation and lactation affected the redox status of offspring mice. The anti-oxidant capacity of offspring mice was decreased with the increasing fat content and oxidation degree of milk protein in milk.

    • >Applied Technology
    • Discriminant Analysis of Physicochemical Indexes Related to Quality of Dry Red Wines from Northwest China

      2021, 39(3):129-139. DOI: 10.12301/j.issn.2095-6002.2021.03.014

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      Abstract:The discriminant functions of physiochemical indexes related to the quality of dry red wines from Northwest China were evaluated. In this study, 27 dry red wines originated in Xinjiang, Ningxia and Wuhai regions of Inner Mongolia were selected. The physiochemical indexes related to color, taste and aroma quality such as the anthocyanins, tannins, and tartaric acid esters were analyzed using spectrophotometric method, and aroma attributes were also quantified by quantitative sensory analysis. Statistical analysis of the data showed that the first two principal components (PC) of the color indexes, such as CIELab parameters and anthocyanins, accounted for 71.08% of the total variance in principal component analysis (PCA), which had good effect on identifying wine vintage, while had no obvious effect on identifying variety and producing area. The first two PCs of the taste indexes, such as tannin and polyphenols, accounted for 65.93% of the total variance, which had good effect on identifying producing area and vintage, while had no effect on variety. The first two PCs of aroma indices, such as tartaric esters, acid and aroma attributes, accounted for 83.10% of the total variance, showing a good effect on identifying producing area and variety, while had no effect on vintage. A total of 20 physicochemical indexes related to color, taste and aroma showed better effect on identifying wine region, variety and vintage in PCA, the first two PCs accounted for 67.32% of the total variance. Cluster analysis could classify wine regions into 3 kinds with an accuracy rate over 90%. The big data of color-flavor physicochemical indexes based on spectrophotometry had potential application prospects for identifying the region, variety and vintage of dry red wine in Northwest China.

    • Effects of Exogenous Abscisic Acid Treatment on Antioxidants in Grapes and Wines

      2021, 39(3):140-150. DOI: 10.12301/j.issn.2095-6002.2021.03.015

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      Abstract:In this study, Vitis vinifera cvs. Merlot and Cabernet Sauvignon in Jixian of Tianjin were used as research grape cultivars, the effects of exogenous abscisic acid (ABA) on phenolic characteristics of grapes and wines were systematically investigated. Grape clusters were treated with exogenous ABA (200mg/L) at early, middle and late of veraison, respectively. The total contents and antioxidant capacities of phenolic compounds were determined with spectrophotometry. The contents and compositions of anthocyanins were analyzed by high performance liquid chromatography-tandem mass spectrometry technology. The results indicated that exogenous ABA treatment at veraison had no significant effects on berry weights, soluble solids, titratable acids, pH, and the total contents and antioxidant activities of phenolic in grape seeds, but had a significant effect on phenolic characteristics of grape skins and wines. Exogenous ABA treatment before the middle veraison (30%-50% berries turned color) significantly improved the total contents of phenolics, anthocyanins and antioxidant activities of grape skins and wines. Exogenous ABA treatment increased the total contents of phenolics in grape berries of Merlot and Cabernet Sauvignon by 14%-39% and 73%-172%, respectively, and contents and antioxidant activities of anthocyanins increased by 18%-143% and 88%-178%, respectively. And the three indexes (total phenolic contents, anthocyanin contents, and antioxidant activity) of wines increased by 17%-69%, 18%-36% and 21%-46%, respectively, which could offer opportunities to effectively improve the organoleptic properties and nutritional value of wines. The precise control during the treatment period of exogenous ABA can increase the phenolic contents and antioxidant activity in wine grapes and wines, thereby improving wine quality and nutritional value.

    • Effect of Pre-Harvest Exogenous Phytohormone and Post-Harvest 1-MCP Treatment on Storage Quality of Sugar-Core Apples

      2021, 39(3):151-159. DOI: 10.12301/j.issn.2095-6002.2021.03.016

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      Abstract:In order to solve the problem of rapid deterioration of sugar core quality in sugar-core apples and improve the storage quality of fruits after harvest, sugar-core apples in Aksu was used as the material to investigate the effects of combined treatment with three exogenous phytohormones before harvest and 1- methylcyclopropene (1-MCP) after harvest on the storage quality of sugar-core apples. The results showed that all the three treatments could improve the storage quality of sugar-core apples. Among them, treatment with gibberellin and 1-MCP could effectively promote the formation of sugar core and delay its disappearance, which still had a large proportion of sugar core after 180d storage. The abscisic acid or gibberellin combined with 1-MCP treatment could effectively improve the vividness of fruit appearance. And best control effect in comprehensive quality was observed after auxin and 1-MCP treatment. During 6 months of low temperature storage, the color properties of apple peel and flesh were well maintained. The hue angle of apple peel was effectively reduced by 3.43%, the L* value of apple flesh was increased by 1.47%, the respiratory intensity was effectively inhibited by 6.53%-9.21% and the respiratory peak was delayed for 30d. The rates of fruit weight loss and decay were decreased by 3.49% and 1.12%, respectively. The contents of soluble solids and vitamine were increased by 1.32% and 10.72%, respectively. In addition, after auxin and 1-MCP treatment, the fruit firmness was increased by 3.25%, the water-soluble pectin content was decreased by 19.23%, and the polygalacturonase activity was always remained at a low level, which effectively delayed the postharvest softening process of the apple fruit. Therefore, auxin and 1-MCP synergistic treatment might be a safe and effective new preservative technology for sugar-core apples, which has a broad application prospect.

    • Effect of Combined Drying on Cell Breakage and Anthocyanin Content of Purple Sweet Potato Granules

      2021, 39(3):160-166. DOI: 10.12301/j.issn.2095-6002.2021.03.017

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      Abstract:Fresh purple sweet potatoes (PSP) were used as raw material. The effect of combined drying on the free starch content of PSP granules was studied using the indexes of iodine blue value and anthocyanin content. And the correlation of combined drying on cell breakage and anthocyanin content was explored to reflex the effect of combined drying on cell breakage of PSP granules. The single factor experiment and response surface methodology were used to optimize the process parameters of the combined drying of PSP granules. It was concluded that the optimal process parameters of combined drying were hot air drying temperature of 70℃, intermediate conversion moisture content of 25%, and freeze-drying time of 7hours. The PSP granules prepared according to the optimal parameters had an iodine blue value of 10.25 and anthocyanin content of 16.23mg/100g. At this time, the PSP granules had the lowest iodine blue value, and the anthocyanin retention was better, which was higher than the anthocyanin content of PSP granules at the optimal level of single factor. It indicated that the combined drying could reduce the free starch content of PSP granules and avoid huge losses of anthocyanins, and proved that combined drying could prevent the cell breakage of PSP granules, and better maintain the cell integrity of PSP granules.

    • >Safety Supervision
    • Comparison of Domestic and Foreign Meat Safety Supervision Pattern

      2021, 39(3):167-175. DOI: 10.12301/j.issn.2095-6002.2021.03.018

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      Abstract:In recent years, the proportion of meat products consumption in global food consumption has been increasing, and the international trade of meat products rapidly increased. As the developing country, there are obvious differences in food safety supervisory system between China and other developed countries and regions, which results in the emergence of Technical Barriers to Trade in the form of non-tariff barrier among China and United States, European Union (EU) and Japan. This has increasingly affected the international food trade, and significantly impeded the Chinese meat exportation. This report briefly introduced the meat regulation and standards in United States, EU, Australia and New Zealand, Japan, Association of Southeast Asian Nations and analyzed the commonness, differences and characteristics of legislation, supervision and management and operation in various countries and regions. Depending on the basic national conditions, China's technical regulations focused on the food safety requirements, such as microbial limitations, pesticide and veterinary drug residues, while developed countries and regions mainly payed attention to the quality characteristics for livestock or poultry and their processed products. The food safety supervision of China placed special emphasis on final product inspection. However, most of developed countries and regions had realized effective process supervision and implemented the “from farm to table” system. China's social credit system should be set up and perfected with reference to some countries such as United States, United Kingdoms and Japan, striving to achieve nationwide participation and eliminating the unspoken rules of the industry. A feasible and effective traceability system could be established to truly realize the whole food chain safety supervision from farm to table, and to control the food adulteration from the source of meat products.

    • Determination of Seven N-Nitrosamines in Ready-to-Eat Fish Products by GC-MS/MS with Alkali-Treatment Coupled Salt-Assisted Dispersive Liquid-Liquid Microextraction

      2021, 39(3):176-182. DOI: 10.12301/j.issn.2095-6002.2021.03.019

      Abstract (510) HTML (581) PDF 5.29 M (599) Comment (0) Favorites

      Abstract:To improve the detection efficiency, a new method for the determination of 7 N-nitrosamines in ready-to-eat fish products was developed by GC-MS/MS with alkali treatment coupled salt-assisted dispersive liquid-liquid microextraction (SADLLME). The sample was heated with barium hydroxide solution to transfer N-nitrosamines into the water based solution. Then SADLLME was carried out with dichloromethane as extractant and nearly saturated sodium sulfate as assisted salt, and the analytes extracted were determination by GC-MS/MS. The limits of detection and limits of quantitation were 0.10-0.19μg/kg and 0.28-0.56μg/kg, respectively. The recoveries were 79.19%-117.40% with relative standard deviations of 1.06%-10.30% at 1,5 and 10μg/kg spiking levels. The results showed that the method was sensitive,reliable and good selective with simple sample pretreatment and it could meet the needs of monitoring of N-nitrosamines in related foods.

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