Volume 32,Issue 8,2016 Table of Contents

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  • 1  Composition of Different Phenolic Extracts from Rose Bee Pollen and Their Inhibitory Activity against B16 Melanoma Cells
    ZHUANG Yong-liang ZHANG Yan-xin TANG Yuan-long
    2016, 32(8):1-7. DOI: 10.13982/j.mfst.1673-9078.2016.8.001
    [Abstract](978) [HTML](0) [PDF 3.24 M](1750)
    Abstract:
    The content and composition of free and bound phenolic acids in rose bee pollen were studied in this paper. Their antioxidant activity was evaluated by three models: ferric reducing ability of plasma (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging capacities. Their inhibitory effects on mushroom tyrosinase activity were also determined, and their effects on cell proliferation, melanin content, and tyrosinase activity in B16 melanoma cells were studied. The content of free and bound total phenolics in rose bee pollen were 23.36 mg GAE/g dry weight (DW) and 1.47 mg GAE/g DW, respectively, and the content of free and bound total flavonoid were 19.12 and 2.42 mg RE/g DW, respectively. The phenolic compounds existed mainly in the free form, with high levels of quercetin and rutin. The content of ellagic acid and 3,4-dimethoxybenzoic acid were relatively high in the bound extract of rose pollen. Both free and bound polyphenolics showed good antioxidant activities in three models, and the half maximal inhibitory concentration (IC50) values against mushroom tyrosinase inhibitory activity were 26.34 μg/mL and 22.26 μg/mL, respectively, which were significantly better than that of Vc. Rose bee pollen phenolic extract also affected the cell proliferation and morphology of B16 cells to some extent, and pronouncedly reduced the relative melanin content and tyrosinase activity in B16 cells. The activities of different forms of phenolic extract from rose bee pollen were obviously related to the phenolic composition and content.
    2  Hepatoprotective Activity of Perna viridis Extracts Against CCl4-induced Liver Injury in Mice
    LIU Shu-ji PAN Yu-tian LIU Zhi-yu HUANG Jia-fu WU Xiao-mei SU Yong-chang CAI Yun-hui WANG Yin CHEN Jin-quan
    2016, 32(8):8-13. DOI: 10.13982/j.mfst.1673-9078.2016.8.002
    [Abstract](815) [HTML](0) [PDF 1.02 M](1205)
    Abstract:
    Here, the protective effect of Perna viridis extract against acute liver injury was explored. A carbon tetrachloride (CCl4)-induced mouse model of acute liver injury was established, and levels of serum aspartate aminotransferase (AST) and alanine transaminase (ALT), as well as the content of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione (GSH), tumor necrosis factor alpha (TNF-α), and interleukin 6 (IL-6) in hepatic tissues, were determined. Two-dimensional (2D) electrophoresis was used to analyze the differentially expressed proteins in the liver, and pathological damage in liver tissue was observed by pathological sectioning. The results showed that the groups treated with P. viridis extract at different doses showed a significant decrease in serum AST and ALT levels and the content of MDA, TNF-α, and IL-6, as well as a pronounced increase in the content of SOD, CAT, GSH-Px, and GSH (p<0.01) as compared with levels observed in the model group. The 2D-electrophoresis analysis showed 97 significantly deviating protein spots, four overexpressed proteins, and one protein exhibiting low expression in the model group, and three overexpressed proteins in the P. viridis-treated group. Additionally, microscopic pathologic examination revealed decreased liver damage in the P. viridis-treated group. These results suggested that the P. viridis extract exerted adequate protective effects against CCl4-induced acute liver injury.
    3  Antioxidant Activity of the Phenolics from Adinandra nitida Leaves and Their Antiproliferative Effect on HepG2 Cells
    CHEN Yong-sheng FU Xiong ZHOU Lin YOU Li-jun LIU Rui-hai
    2016, 32(8):14-20. DOI: 10.13982/j.mfst.1673-9078.2016.8.003
    [Abstract](1039) [HTML](0) [PDF 927.78 K](1496)
    Abstract:
    The antioxidant activity of phenolic compounds from Adinandra nitida leaves collected in spring and fall and their antiproliferative effects on HepG2 cells were studied. The free/bound polyphenolic contents and free/bound flavonoid contents in Adinandra nitida leaves were investigated by the Folin reagent method and sodium borohydride/chloranil-based assay (SBC), respectively. The in vitro antioxidant activities of free/bound phytochemicals in the extracts and the in vivo antioxidant activities of free phytochemicals in the extracts were measured through oxygen radical absorbance capacity (ORAC), peroxyl radical scavenging capacity (PSC), and cellular antioxidant activity (CAA) assays. The antiproliferative effect of free phytochemicals from Adinandra nitida leaf extracts was measured by the methylene blue colorimetric method. The free phenolic content and free flavonoid content from autumn Adinandra nitida leaves were high, and the values were 142.69 ? 0.58 mg GAE/g DW and 112.98 ? 0.37 CE/g DW, respectively. The ORAC, PSC, and CAA of free phytochemicals from leaf extracts were relatively strong, and the values were 1723.08 ± 109.27 μmol TE/g DW, 24.07 ± 1.98 μM VCE/g DW, and 900.84 ± 2.68 μmol QE/100 g, respectively. The free phytochemicals from autumn Adinandra nitida leaves showed a strong antiproliferative effect on HepG2 cells, with a half maximal effective concentration (EC50) value of 4.30 mg/mL. Adinandra nitida is rich in phytochemicals, and especially, autumn Adinandra nitida leaves are a new raw material for natural antioxidants.
    4  Preparation and Anti-aging Effect of Casein-g-glucose-PGG Nanocomplexes
    CHEN Yun-jiao LI Wei CHEN Hong-zhang HUANG Qing-rong CAO Yong
    2016, 32(8):21-27. DOI: 10.13982/j.mfst.1673-9078.2016.8.004
    [Abstract](992) [HTML](0) [PDF 811.23 K](1260)
    Abstract:
    A casein and glucose copolymer was prepared by Maillard reaction and its properties investigated by gel electrophoresis, Fourier transform infrared spectroscopy, and fluorescence spectroscopy. Casein-g-glucose-PGG nanocomplexes were prepared using the solvent evaporation method to improve the water solubility and anti-aging effects of PGG in Caenorhabditis elegans. The results showed that the molecular weight of the conjugate product (casein-g-glucose) was larger than 11 ku. The reducing end of the glucose was covalently linked with the amino group of the protein, and the sugar molecule introduced into the casein had a d-glucopyranose ring structure. The binding force between PGG and casein, or casein-g-glucose, was mainly hydrophobic interaction, which induced the self-assembly of PGG and casein-g-glucose to form casein-g-glucose-PGG nanocomplexes. The encapsulation efficiency of the nanocomplex reached up to 62.27%, the particle size of the nanocomplexes was 265 nm, and the nanocomplexes were light-yellow powders. Nanocomplexes showed good solubility in water at a concentration of 10 mg / mL. Compared with PGG treatment, treatment with the nanocomplexes could significantly extend the mean worm lifespan by 13.00%. In conclusion, the nanocomplex can effectively increase the anti-aging effect of PGG in C. elegans.
    5  Protective Effect of Lactic Acid-Fermented Beverage Prepared from the Peduncles of Hovenia dulcis on Alcohol-Induced Liver Damage in Mice
    WANG Nan DU Shuang-kui FENG Xian-chao YANG Zhi XUE Kai-li LI Zhi-xi
    2016, 32(8):28-33. DOI: 10.13982/j.mfst.1673-9078.2016.8.005
    [Abstract](883) [HTML](0) [PDF 740.95 K](1179)
    Abstract:
    A model of alcohol-induced liver damage was established in this study by administering 52° liquor to mice orally. A lactic acid-fermented beverage was prepared with the peduncles of Hovenia dulcis as the raw material, and was also administered to mice by gavage. The hepatoprotective effect of this lactic acid fermented beverage from the peduncles of Hovenia dulcis (LBPHD) was evaluated by measuring the specific enzyme activities in the serum and liver of the mice and liver histopathological analysis with microscopic sections. The results showed that the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were substantially elevated by the administration of alcohol, and were significantly decreased by the gavage administration of LBPHD. Compared with the model group, LBPHD could also increase the levels of superoxide dismutase (SOD), alcohol dehydrogenase (ADH), and glutathione (GSH), and decrease the level of malondialdehyde (MDA)-the oxidation product-in the liver tissues of mice. Liver histopathology results indicated that LBPHD could effectively alleviate hepatomegaly and steatosis in mice with alcohol-induced liver damage. These results demonstrate that LBPHD exhibits a significant hepatoprotective effect, which is comparable to that of biphenyldicarboxylate (the positive control). Therefore, LBPHD can be a healthy drink to counter the effect of alcohol and to protect liver tissue.
    6  Antioxidant Activity of Enteromorpha prolifera Polyphenols and Their Effect on Improving Insulin Resistance
    LI Feng CAI Zhen-hui CHEN Jin-mei GUO Yang-hao
    2016, 32(8):34-41. DOI: 10.13982/j.mfst.1673-9078.2016.8.006
    [Abstract](915) [HTML](0) [PDF 682.53 K](968)
    Abstract:
    Enteromorpha prolifera polyphenols (EPs) were extracted and separated, and their antioxidant activity and effect on insulin resistance (IR) were investigated in this paper. The 2,2-diphenyl-1-picrylhydrazyl (DPPH?) radical scavenging assay was used to evaluate the in vitro antioxidant capacities of EPs; the capability of EPs for reducing IR was evaluated in vitro by measuring the glucose consumption of IR-HepG2 cells. Experiments with diet-induced obese (DIO) mice were used to evaluate the in vivo antioxidant activities of EPs and their effects on IR in vivo. The results showed that the fraction EP1 had good DPPH? radical scavenging ability with an IC50 value of 1.08 mg/mL. Compared to the control group, EP1 significantly increased the liver SOD and CAT activities in mice by 25.04% and 36.28%, respectively, and decreased the serum malondialdehyde (MDA) level by 42.92%. EP1 improved IR states of HepG2 cells and DIO mice significantly (p<0.05), reduced the homeostatic model assessment (HOMA)-IR index by 16.8%, and decreased the degree of obesity and reduce the fat percentage in DIO mice significantly(p<0.05). On the other hand, EP2 was inferior to EP1 in terms of antioxidant activity and IR-improving effect. In summary, EP1 has good in vitro and in vivo antioxidant capacities, and can improve IR state significantly, which may be associated with its antioxidant activity by suppressing levels of reactive oxygen species (ROS).
    7  Hypoglycemic Effect of Grape Seed Proanthocyanidins in Diabetic Mice
    WU Tao HUANG Yun-xia ZHANG Min
    2016, 32(8):42-47. DOI: 10.13982/j.mfst.1673-9078.2016.8.007
    [Abstract](1822) [HTML](0) [PDF 691.71 K](1352)
    Abstract:
    The hypoglycemic effect of proanthocyanidins was investigated. A diabetic model was established by intraperitoneal injection of streptozotocin (STZ) in mice, and the effect of proanthocyanidins at doses of 50 mg/kg, 100 mg/kg, and 150 mg/kg on the weight of diabetic mice, fasting blood glucose (GLU), glucose tolerance, serum triglyceride (TG), total cholesterol (TC), superoxide dismutase (SOD), lipid peroxide malondialdehyde (MDA), and the concentration of short chain fatty acids was determined. The results revealed that low, medium, and high dose of proanthocyanidins reduced body weight of diabetic mice by 13.23 %,20.85 %, and 30.03 %, respectively; lowered fasting glucose by 10.96 %, 17.18 %, and 20.89 %, respectively, and improved glucose tolerance (p<0.01). High doses of proanthocyanidins effectively decreased serum TC, TG, and MDA by 18.03 %, 32.54 %, and 22.88 %, respectively, while increased the serum SOD activity by 30.28 %. All the three doses of proanthocyanidins significantly increased the levels of total short chain fatty acids (p<0.05 or p<0.01).Thus, proanthocyanidins could reduce the serum sugar level, reduce the free radical damage, inhibit lipid peroxidation, and improve sugar and lipid metabolism in diabetic mice. Proanthocyanidins may play an important role in human health.
    8  Hemolytic Activity of the Metabolites Produced by Vibrio parahaemolyticus ATCC33847 in Five Food Matrices and Their Toxicity toward Mice Organs
    WANG Run-dong SUN Li-jun WANG Ya-ling DENG Yi-jia GUO Mu-han DENG Qi LIU Ying XU De-feng
    2016, 32(8):48-53. DOI: 10.13982/j.mfst.1673-9078.2016.8.008
    [Abstract](901) [HTML](0) [PDF 516.99 K](1069)
    Abstract:
    The hemolytic activity of the metabolites produced by V. parahaemolyticus (Vp) in different food matrices and their toxicity on mice organs were analyzed. Shrimp, oyster, freshwater fish, beef, and egg-fried rice were inoculated with the ATCC33847 strain and incubated. After centrifugation and filtration, a plate hemolysis assay was used to detect the hemolytic activity of metabolites produced by Vp in food matrix filtrates, and mice were fed with different doses of the filtrates of the above food matrices by gavage. Mice were sacrificed, and organ coefficients (OC) and serum biochemical parameters were measured. The filtrate from egg-fried rice had the highest hemolytic activity, but did not produce greater toxicity to mice than other filtrates. In mice fed with the Vp-contaminated shrimp and oyster filtrates, the stomach and intestinal OC were significantly increased (p < 0.05) compared with other food matrix filtrates. The metabolites produced by Vp in five food matrices caused various degrees of changes in albumin (ALB), alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and blood urea nitrogen (BUN) (p < 0.05) in mice. The shrimp filtrate showed a stronger effect on the indicators of mouse liver function than other filtrates and had a stronger liver toxicity, while oyster and freshwater fish filtrates showed a greater toxicity to kidney. These results suggest that Vp may produce different virulence factors in different food matrices, therefore causing different toxic damage to the organs in mice.
    9  Metabolic Behavior and Transcriptomic Analysis of A Pediococcus pentosaceus Strain in Simulated Fish Sauce
    LI Meng-ru WANG Xiang-jun DUAN Shan WU Feng-ying
    2016, 32(8):54-63. DOI: 10.13982/j.mfst.1673-9078.2016.8.009
    [Abstract](1221) [HTML](0) [PDF 959.72 K](1297)
    Abstract:
    The influence of Pediococcus pentosaceus inoculation on the fermentation in a simulated fish sauce system was investigated by chemical analysis and transcriptomic sequencing technique in this paper. The results showed that P. pentosaceus remarkably increased the content of amino acids with an agreeable taste, including glutamic acid (Glu), glycine (Gly), alanine (Ala), serine (Ser), aspartic acid (Asp), and others, and reduced the content of amino acids with an unpleasant taste, including phenylalanine (Phe) and others. Additionally, after inoculation with P. pentosaceus, the volatile compound content changed significantly. The types and content of hydrocarbon and ester compounds were reduced dramatically; the types of aromatic compounds decreased but the total content was increased greatly; and the types and content of aldehydes, ketones, acids, and amines increased significantly. Sensory evaluation showed that P. pentosaceus remarkably improved the flavor and aroma of fish sauce. The results of transcriptomic sequencing indicated that carbohydrate and amino acid metabolism of P. pentosaceus in the simulated fish sauce were the most active. The content of the amino acids, which were involved in the most active pathways, showed the most significant changes in fish sauce. Additionally, P. pentosaceus had relatively strong protease and peptidase activities. The degradation of limonene and pinene was found to be a major pathway in P. pentosaceus and was associated with the formation of volatile compounds. In this study, the expression of various amino acid decarboxylases was not detected in P. pentosaceus during fermentation of the simulated fish sauce.
    10  Study on the Emulsifying and Antifungal Properties of Octenyl Succinic Anhydride Modified Inulin
    ZHANG Xiao-yun ZHANG Hong-yin DONG Ying YANG Qi-ya WANG Hai-ying DONG Man-jia ZHENG Li-bo DING Wen-hui
    2016, 32(8):64-69. DOI: 10.13982/j.mfst.1673-9078.2016.8.010
    [Abstract](994) [HTML](0) [PDF 1.47 M](1232)
    Abstract:
    The effect of degree of substitution (DS), concentration, and freeze-thaw on the emulsifying properties of inulin and octenyl succnic anhydride modified inulin (OSA-In) were studied. Furthermore, the inhibitory effects of OSA on the growth of hyphae, spore germination, and germ tube elongation of Penicillium expansum, Aspergillus niger, and Rhizopus nigricans were investigated. The results showed that OSA-In improved emulsifying properties compared to inulin, and its emulsifying ability increased with the increasing concentrations of DS. OSA-In (DS = 3.17 × 10-2) at a concentration of 2.5% exhibited good emulsification and freeze-thaw stability. The minimum inhibitory concentrations (MIC) of OSA-In were one, four, and two percent (m/V) for Penicillium expansum, Aspergillus niger, and Rhizopus nigricans, respectively. OSA-In inhibited the hyphal growth, spore germination, and germ-tube elongation of Penicillium expansum, Aspergillus niger, and Rhizopus nigricans in a dose-dependent manner. At sub-MIC levels of OSA-In, the inhibitory effect was highest on Penicillium expansum followed by Aspergillus niger and Rhizopus nigricans.
    11  Study of Quorum Sensing and Biofilm Formation of Hafnia alvei Separated from Turbot
    MA Yan LI Ting-ting CUI Fang-chao YANG Bing LIU Ming-huang LI Jian-rong
    2016, 32(8):70-76. DOI: 10.13982/j.mfst.1673-9078.2016.8.011
    [Abstract](874) [HTML](0) [PDF 866.03 K](1240)
    Abstract:
    One quorum-sensing (QS) strain separated from a spoiled turbot sample was used as the study object and determined as Hafnia alvei (Ha-01) according to physiological and biochemical tests and 16S rRNA analysis. The QS compounds [N-acyl-homoserine lactones (AHLs)] were detected by parallel-streak method using Chromobacterium violaceum CV026 and Agrobacterium tumefaciens A136. Additionally, the plate-diffusion method was used to study the kinetics of AHL secretion and the amount of biofilm produced in different growth phases, and exogenous signaling molecules were added to study the relationship between AHLs and biofilm formation. The results indicated that strain Ha-01 produced QS phenomena, and the number of AHLs produced by Ha-01 during cultivation exhibited a downward trend after the initial increase, reaching the maximum at 16 h. The amount of biofilm formed was positively correlated with incubation time and reached a maximum at 72 h, followed by gradual stabilization. The addition of exogenous AHL strands could promote the production of biofilm. These results indicated that strain Ha-01 was capable of producing QS phenomena and regulating biofilm formation.
    12  Composition and Antioxidant Activity of Different Forms of Phenolic Compounds from Sorghum Bran
    CHEN Hua-min WU Hui LAI Fu-rao CHEN Cai-wei TANG Yu-qian
    2016, 32(8):77-82. DOI: 10.13982/j.mfst.1673-9078.2016.8.012
    [Abstract](975) [HTML](0) [PDF 1.11 M](1315)
    Abstract:
    The different forms of phenols, including free, soluble esterified, soluble glycosidic, insoluble-bound esterified, and insoluble-bound glycosidic polyphenols were extracted from sorghum bran. The content of 15 phenolic compounds were determined by high performance liquid chromatography. The antioxidant activities of different forms of phenols were evaluated by measuring the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and superoxide (O2-) radical scavenging activities and Fe3+ reducing ability power. The results showed that the content of free, soluble esterified, soluble glycosidic, insoluble-bound esterified, and insoluble-bound glycosidic phenols in sorghum bran were 645.27, 138.57, 48.67, 118.92, and 176.06 mg GAE/100 g, respectively. The highest phenolic content were found in ferulic acid (39.04%) and salicylic acid (28.04%), while 3,4-dihydroxybenzoic acid showed the lowest phenolic content (0.09%). Ferulic acid was mainly found in insoluble-bound form, and the content of isochlorogenic acid was relatively high in the soluble phenolic compounds, while salicylic acid had the highest content among the free phenolic compounds. In different antioxidant systems, there were slight differences in the antioxidant activities of phenols in different forms. In general, soluble esterified, insoluble-bound esterified, and insoluble-bound glycosidic phenols possesses relatively high antioxidant activities, while free phenols have relatively low antioxidant activity, in spite of having the highest phenol content.
    13  Effect of REG1 Deletion with SNF1 Overexpression on the Fermentation of Industrial Baker’s Yeast in Lean Dough
    LIN Xue ZHANG Cui-ying BAI Xiao-wen XU Jia LIU Xiao-er XIAO Dong-guang
    2016, 32(8):83-89. DOI: 10.13982/j.mfst.1673-9078.2016.8.013
    [Abstract](1133) [HTML](0) [PDF 1.20 M](1406)
    Abstract:
    The effects of REG1 (regulatory subunits of protein phosphatase type 1 PP1) deletion with protein kinase gene SNF1 overexpression on the maltose metabolism and lean dough fermentation by industrial baker’s yeast were investigated by analysis of the MAL mRNA expression, maltase and maltose permease activities, maltose metabolism and leavening ability in lean dough. The basic growth characteristics of REG1 deletion with SNF1 overexpression strain BYKPS-R, the parental strain BY14α, and the REG1 deletion strain BYK-R were also studied. REG1 deletion with SNF1 overexpression had significant effects on increasing MAL gene expression and enzyme activity, and relieving glucose repression, thereby enhancing the maltose utilization efficiency (increase of 18.59% and 4.40% compared with the strains BY14α and BYK-R, respectively, at the point of glucose exhaustion), and lean dough leavening ability (12.51% and 3.22% increases compared with the strains BY14α and BYK-R, respectively). On the background of REG1 deletion, overexpression of SNF1 further improved maltose metabolism and leavening ability of industrial baker’s yeast in lean dough. Moreover, overexpression of SNF1 did not affect growth in REG1 deleted yeast. This strain has potential for application. This study lays a foundation for the breeding of fast-fermenting baker’s yeast.
    14  Effect of the Ca2+-binding Site on Thermal Activity and Stability of the Thermococcus kodakarensis Hyperthermophilic α-Amylase ApkA
    ZENG Jing GUO Jian-jun GU Bin-tao ZHANG Li-li XIONG Da-wei YUAN Lin
    2016, 32(8):90-95. DOI: 10.13982/j.mfst.1673-9078.2016.8.014
    [Abstract](872) [HTML](0) [PDF 890.54 K](1332)
    Abstract:
    The development of a thermostable α-amylase for use in starch liquefaction processes is urgently needed. Hyperthermophilic α-amylase possesses good activity at high temperature and thermal stability, and the study of the mechanism underlying the thermal adaptation of hyperthermophilic α-amylase could provide a theoretical basis and design concept for the construction of other thermally stable α-amylases. Based on the amino acid sequence of the α-amylase ApkA produced by the hyperthermophilic archaeon Thermococcus kodakarensis KOD1, a Ca2+-binding site mutant termed ApkAdsN110A/D155A/D164A was constructed. Enzymatic assays suggested that compared to wild-type ApkA, the mutant exhibited significantly reduced thermal activity and stability. The optimal reaction temperature of ApkA was 90 ℃ and the corresponding specific activity was 2946.75 U/mg, while the mutant had an optimal reaction temperature of 80°C with corresponding specific activity of 917.07 U/mg. The half-lives of ApkA and the mutant at 90 ℃ were 5 h and 2 h, respectively. The results suggest that the Ca2+-binding site plays an important role in the maintenance of thermal activity and stability of ApkA, and that Ala substitutions at Asn110, Asp155, and Asp164 lower the thermal activity and stability.
    15  Construction of Single-stranded Oligonucleotide-mediated Homologous Recombination in Bacillus amyloliquefaciens
    LIAO Yu-ling PAN Li WANG Bin
    2016, 32(8):96-102. DOI: 10.13982/j.mfst.1673-9078.2016.8.015
    [Abstract](842) [HTML](0) [PDF 5.73 M](1816)
    Abstract:
    Bacillus amyloliquefaciens is an important industrial microorganism that has been widely used in agriculture, pharmaceutical, and food industries. In order to develop highly efficient genetic manipulation techniques in B. amyloliquefaciens, a single-stranded oligonucleotide (ssDNA)-mediated recombination method was introduced. First, the mutS gene involved in mismatch repair was knocked out, followed by introduction of the expression plasmid for the bet gene encoding the beta protein (a ssDNA-binding protein) into B. amyloliquefaciens, to construct the B. amyloliquefaciens XH7 host (mutS-,bet+), where the mutS gene was inactivated and the beta protein was expressed. Second, homologous recombination targeting the ropB gene was successfully achieved by designing an 88-bp ssDNA oligonucleotide and transforming it into the B. amyloliquefaciens XH7 host (mutS-,bet+) by electroporation, followed by antibiotic selection. The parameters for ssDNA-mediated recombination were optimized as follows: 75 μg ssDNA oligonucleotide and 6 h to 12 h of cell recovery from electroporation. Here, oligonucleotide-mediated recombination was successfully applied in B. amyloliquefaciens for the first time, providing a new approach for developing an effective genetic manipulation technique in B. amyloliquefaciens and other Bacillus spp. that are not naturally transformable.
    16  Influence of Cryoprotectants on the Metabolic Pathways of Lactobacillus plantarum
    ZHAO Yan-sheng XIAO Xiang ZHOU Xing-hua SU Ping DONG Ying
    2016, 32(8):103-108. DOI: 10.13982/j.mfst.1673-9078.2016.8.016
    [Abstract](928) [HTML](0) [PDF 736.62 K](1309)
    Abstract:
    The effects of different cryoprotectants on the metabolic pathways of freeze-dried Lactobacillus plantarum dy-1 (L. P dy-1) powder during fermentation were analyzed through a metabolomics study. The intracellular metabolites of L. P dy-1 were separated and analyzed by gas chromatography-mass spectrometry. The metabolites produced in the presence of the different cryoprotectantss were identified and analyzed by using pattern recognition and partial least squares methods, and were employed to reconstruct the metabolic pathways using the Kyoto Encyclopedia of Genes and Genomes database. The results indicated that 10% inulin, 22.4% inulin, inulin composite protective agent, or skim milk composite protective agent showed different impacts on the energy metabolism, amino acid metabolism, and fatty acid metabolism in the fermentation of freeze-dried L. P dy-1. When the inulin content was increased from 10% to 22.4%, the differences in metabolic characteristics between freeze-dried bacteria and directly activated bacterial cells decreased. The metabolic characteristics of freeze-dried L. P dy-1 were closer to those of directly activated bacterial cells when using the inulin composite protective agent than when using the skim milk composite protective agent. Storage temperature had a significant effect on the metabolism of the freeze-dried bacteria; storage at -20 ℃ was more beneficial than storage at 4 ℃ to maintain the normal metabolism of L. P dy-1 during fermentation.
    17  Study on the Fermentation Characteristics of Citric Acid by a Lactobacillus fermentum
    HU Li-yun YU Yuan-shan XU Yu-juan XIAO Geng-sheng WU Ji-jun FU Man-qin
    2016, 32(8):109-114. DOI: 10.13982/j.mfst.1673-9078.2016.8.017
    [Abstract](958) [HTML](0) [PDF 727.13 K](1373)
    Abstract:
    Fermentation characteristics by a Lactobacillus fermentum strain that can utilize citric acid in citrus fruits such as green plum were studied. Results showed that L. fermentum could grow in the basic culture medium with citric acid as the main source of carbon and energy. Citric acid metabolism yielded small amounts of acetic acid and lactic acid; hence, the total titratable acid content in the culture medium could be reduced by more than 50%. The strain has a high tolerance to ethanol, as ethanol concentration greater than nine percent (v/v) inhibits growth of the strain and citric acid metabolism. The strain is sensitive to sulfite; and the growth of the strain and citric acid metabolism are completely inhibited by 0.5 mM of sodium sulfite. Sucrose improved the growth of the strain and increased citric acid metabolism; however, no significant decrease in sucrose was observed during fermentation, indicating that the ability to utilize sucrose is low in the presence of citric acid.
    18  Purification and Identification of ACE Inhibitory Peptides from Porcine Skin Collagen
    ZHANG Ying WANG Hong-yan MA Liang HUANG Dan-dan LIU Yi ZHANG Yu-hao
    2016, 32(8):115-122. DOI: 10.13982/j.mfst.1673-9078.2016.8.018
    [Abstract](776) [HTML](0) [PDF 772.58 K](1260)
    Abstract:
    After being pretreated by ultrasound combined with dilute alkali, porcine skin underwent enzymatic hydrolysis for 30 min to produce hydrolysate with ACE inhibitory activity. This hydrolysate was used as raw material, and the collagen ACE inhibitory peptides were separated and purified using Sephadex G-15 semi-preparative high performance liquid chromatography. The results showed that the optimum separation conditions were as follows: sample concentration of 100 mg / mL; injection volume of 2 mL; flow rate of 2 mL / min; distilled water as the eluent; and a 1 m × 10 mm chromatography column. Under these separation conditions, the mixed peptides were divided into two fractions, AP-I and AP-II. The half maximal inhibitory concentration (IC50) values were 19.50 mg/mL and 1.01 mg/mL, for AP-I and AP-II, respectively. Fraction AP-II, with relatively strong ACE inhibitory activity, was further separated by semi-preparative high performance liquid chromatography, and eight peaks were obtained. The IC50 values of peaks two, five, and six were the lowest (0.44 mg / mL, 0.4 mg / mL, and 0.73 mg / mL, respectively). Based on the IC50 value and the weight of the samples collected from semi-preparative high performance liquid chromatographic separation, liquid chromatography tandem mass spectrometry sequence analysis was conducted for peaks two and six. The results showed that the peptide sequences of peaks two and six were QGPPGPAGPR and AGPPGPPGPA, respectively. Additionally, these sequences occupied amino acid positions 526-535 and 730-739 of the collagen α1 chain, respectively.
    19  Antibacterial Activity of Plant Essential Oils Against Common Harmful Microorganisms in Foods
    CHAI Xiang-hua DONG Yan WU Ke-gang CUI Qi-chang MA Hai-jie
    2016, 32(8):123-127. DOI: 10.13982/j.mfst.1673-9078.2016.8.019
    [Abstract](1060) [HTML](0) [PDF 434.05 K](2039)
    Abstract:
    The antibacterial effects of thirteen plant essential oils—extracted from basil, tea tree, thyme, clove, fennel, ylang-ylang, marjoram, cinnamon, eucalyptus, coriander seed, citronella, sage, and nard—against six common harmful microorganisms in food were studied using inhibition zone, fumigation, and other in vitro antibacterial experiments. The results showed that all thirteen essential oils had an inhibitory effect on the tested bacteria, fungi, and yeasts. Among them, thyme oil and cinnamon oil exhibited the strongest but different levels of antimicrobial activity; the inhibition zone diameter was >20 mm at a volume concentration of 300 μL/L of the oils. Combinations of cinnamon oil and thyme oil at different ratios did not show strong synergistic effects. However, some of the combinations showed significant additive effects, with the optimal antimicrobial effect noted for cinnamon oil/thyme oil at 80:20 (V/V).
    20  Isolation and Identification of Conjugated Linoleic Acid-producing Lactobacillus Strains from Fermented Pickle Brines
    WANG Wu ZHANG Li-xin PAN Jian
    2016, 32(8):128-133. DOI: 10.13982/j.mfst.1673-9078.2016.8.020
    [Abstract](925) [HTML](0) [PDF 1.12 M](1455)
    Abstract:
    Conjugated linoleic acid (CLA) has wide application potential in medicine, food, and health products, because of its anticancer, immune regulatory, anti-atherosclerosis, antiobesity, and antioxidant activities. Currently, commercial CLA is typically produced through alkali isomerisation using sunflower oil as raw material, generating a mixture of CLA with undesirable isomer by-products. Use of CLA for nutraceutical and medicinal purposes requires safe isomer-selective synthesis. Hence, CLA biosynthesis naturally attracted much attention because of its specificity and safety. The aim of the present study was to isolate and identify Lactobacillus strains from the fermented pickle brines, which can convert linoleic acid (LA) into CLA under aerobic conditions. Using serial dilutions and plate streaking in de Man Rogosa Sharpe (MRS) agar medium under aerobic conditions, 16 CLA-producing Lactobacillus strains were isolated, among which PC-3 exhibited the highest production of CLA. Based on analyses using SEM, API-50CHL, and 16S rRNA gene sequencing, PC-3 was identified as Lactobacillus plantarum. The 16S rDNA gene sequence(1460bp)was submitted to GenBank under the accession number JX270774.1.
    21  Effect of Collagen Hydrolysate on the Properties of Dialdehyde Starch-gelatin Films
    CHEN Shu-lin WANG Yan-xia YE Yan-jun CHEN Jun LIU Jian-zhan HAO Geng-xin WENG Wu-yin TANG Lan-lan
    2016, 32(8):134-139. DOI: 10.13982/j.mfst.1673-9078.2016.8.021
    [Abstract](946) [HTML](0) [PDF 968.16 K](1282)
    Abstract:
    The effect of tilapia skin collagen hydrolysate (TSCH) on the physicochemical properties of dialdehyde starch (DAS) cross-linked gelatin films was investigated, and the biocompatibility of these films with the human skin keratinocyte (HaCat) cell was also studied. When the TSCH content in the DAS-gelatin films was increased from 0 to 16%, the tensile strength (TS) of films decreased from 55.00 MPa to 24.85 MPa, while the elongation at break (EAB) showed a downward trend after the initial increase with increasing amount of added TSCH. The solubility of DAS cross-linked gelatin films in water at 30 ℃ was 33.10%, and at TSCH concentration higher than four percent, it increased to 100%. However, TSCH from films was released into water after 240 min irrespective of the amount of added TSCH. The results of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that the addition of TSCH in the DAS cross-linked gelatin film could hinder the interaction between the protein molecules of gelatin. On the other hand, when HaCat cell was cultured on the surface of DAS cross-linked gelatin films, the cell activity of HaCat cells was 11.39%. When the DAS cross-linked gelatin film contained 8% TSCH, the HaCat cell activity reached up to 108.2%. Based on the above results, the DAS-gelatin films containing TSCH have potential applications in the cosmetic industry.
    22  Effect of Wheat Gluten Content on Buckwheat Dough and its Mechanism of Action
    WANG Jie-qiong QIAN Hai-feng WANG Li ZHAGN Hui QI Xi-guang
    2016, 32(8):140-147. DOI: 10.13982/j.mfst.1673-9078.2016.8.022
    [Abstract](877) [HTML](0) [PDF 3.63 M](1595)
    Abstract:
    The effect of different wheat gluten content (5%, 10%, and 15%) on the rheological properties of high content (50% wheat flour replacement rate) buckwheat dough and the quality of Chinese steamed bread (CSB) were comprehensively studied in this paper. Based on mixed dough with 10% wheat gluten and the reference (pure wheat flour) dough, the mechanism of the action of wheat gluten on the improvement of the rheological properties of mixed dough and CSB quality was further studied using scanning electron microscopy and Fourier transform infrared (FT-IR) spectroscopy as well as by analyzing chemical interactions in the dough. The results indicated that the addition of 10% wheat gluten increased the disulfide bond content of buckwheat-wheat dough, changed the chemical interactions (ionic bond and hydrogen bond content and hydrophobic forces), changed the gluten protein conformation, and improved the microstructure of mixed dough. Consequently, the pasting properties of mixed flour, the farinograph and extensograph properties of dough, the specific volume and springiness of CSB, and the pore structure of CSB core were improved, but the quality was still not equal to the quality of pure wheat steamed bread, suggesting that the addition of high levels of buckwheat flour does not merely dilute the gluten protein.
    23  Effect of Moisture Content on the Physicochemical Properties of Porous Starch during Heat-moisture Treatment
    ZHANG Jing LIU Qing-qing CHEN Bing LIU Xiong
    2016, 32(8):148-155. DOI: 10.13982/j.mfst.1673-9078.2016.8.023
    [Abstract](888) [HTML](0) [PDF 1.88 M](1645)
    Abstract:
    The moisture content of porous starch was controlled at 10%, 15%, and 20%, and heat-moisture treatment was performed at 115 ℃ for 1 h to study the effect of heat-moisture treatment on the structure and properties of porous starch. The results indicated that heat-moisture treatment partially destroyed the porous structure of porous starch and reduced its absorptive capacity. The crystal structure of porous starch exhibited no obvious change; however, the degree of crystallinity decreased. Additionally, following heat-moisture treatment, the solubility, swelling capacity, and light transmittance of the porous starch decreased, but the freeze-thaw stability increased and presented a corresponding trend with increases in water content. Heat-moisture treatment increased the pasting temperature, retrogradation, and hot-paste stability of porous-starch paste, whereas decrease the peak viscosity. After heat-moisture treatment, the content of resistant starch in porous starch was altered. When the moisture content was 15%, the content of resistant starch in the resultant porous starch was relatively high (27.67%). Heat-moisture treatment exhibited clear effects on the relevant properties of porous starch, with the changes depending on moisture content during treatment.
    24  Fabrication of Cinnamon Essential Oil-based Composite Microemulsions and Their Applications in Braised Beef
    ZHANG Yun-bin LI Wei-di WANG Yi-fei LUO Ning-ning ZHENG Feng WEI Meng-yue
    2016, 32(8):156-162. DOI: 10.13982/j.mfst.1673-9078.2016.8.024
    [Abstract](843) [HTML](0) [PDF 1.05 M](1417)
    Abstract:
    To study the phase behavior of an oil-in-water cinnamon essential oil-based microemulsion system, Tween -80 and ethanol were selected as the surfactant and co-surfactant, respectively, and 0.5% nisin, 0.5% sodium phytate, or 0.5% ε-poly-L-lysine?hydrochloride (HCl) was used as the aqueous phase. The pH value, viscosity, electric conductivity, particle size, and other physical properties of the microemulsion system were analyzed, the most stable water-soluble microemulsion formulations were optimized, and the minimum inhibitory concentrations (MICs) of the microemulsions for Escherichia coli and Staphylococcus aureus were determined. Braised beef samples were treated with composite microemulsions containing different preservatives, and the performances of the microemulsions on the preservation of braised beef during cold storage based on total volatile base nitrogen and microbial characteristics were analyzed. The results showed that the three food preservatives had no significant influence on the water solubility of the microemulsionss but affected the pH, electric conductivity, etc. The microemulsions containing ε-poly-L-lysine?HCl (MEP) had the lowest MIC for E. coli (16 mg/ml), and MEP and the microemulsions containing nisin showed the lowest MIC for S. aureus (8 mg/ml). Treatment with the microemulsions delayed beef spoilage, reduced the content of total volatile basic nitrogen in the braised beef during cold storage, and significantly lowered the growth of total bacterial count and coliform bacteria.
    25  Nitrite Infusion and Thermal Stability of Roasted Chicken Wings during Processing
    LI Bian-sheng HUANG Zhi-jun GU Miao-qing RUAN Zheng GUO Wei-bo LIN Guang-ming YANG Huan-bin
    2016, 32(8):163-170. DOI: 10.13982/j.mfst.1673-9078.2016.8.025
    [Abstract](855) [HTML](0) [PDF 1.13 M](1087)
    Abstract:
    The effects of nitrite infusion during vacuum tumbling and static standing at low temperature and of different amounts of nitrite and processing parameters on the thermal stability of the nitrite during hot-air drying and high-temperature roasting of chicken wing roots were analyzed. The results showed that nitrite accumulated exponentially in the chicken wing roots with increasing time during tumbling, and penetration throughout the chicken wing root increased with the amount of nitrite added. Static standing resulted in a slight loss of nitrite, with a sharp decrease during hot-air drying and roasting at high temperature. After roasting, only 5.92–7.87% of nitrite was detected as NO2- and nitrite residuals were below the national standard (30 mg/kg). The amount of nitrite added, tumbling time, static standing time, drying temperature, and roasting temperature had significant (P<0.05) effects on the nitrite content of the chicken wing roots during processing. Higher temperatures increased the rate of nitrite degradation.
    26  PCR-DGGE-based Analysis of the Microbial Community in Sichuan Bran Vinegar during Solid-state Fermentation
    PENG Yang ZHANG Nai-ying HE Li CHEN Shu-juan AO Xiao-lin LIU Shu-liang
    2016, 32(8):171-177. DOI: 10.13982/j.mfst.1673-9078.2016.8.026
    [Abstract](927) [HTML](0) [PDF 3.86 M](1298)
    Abstract:
    To profile the changes in the microbial community during Sichuan bran vinegar fermentation, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was employed to analyze the diversity of bacteria and fungi during the solid-state fermentation process. The results showed that during the fermentation, the dominant fungi were Saccharomyces cerevisiae, Saccharomycopsis fibuligera, Issatchenkia hanoiensis, Aspergillus niger, Penicillium oxalicum, and uncultured fungus, and the main bacteria were Lactobacillus acidophilus, Gluconacetobacter obediens, Acetobacter pasteurianus, Acidomonas methanolica, uncultured bacterium, uncultured Bacillus sp., and uncultured Lactobacillus sp. Thus, the PCR-DGGE technique allowed identifying a variety of uncultured microorganisms in the fermentation substrate. The microbial flora during the fermentation was complex, with different microorganisms dominating at different phases of the process; however, the overall microbial structure did not change significantly during the fermentation process.
    27  Application of Surface AcylatedNanocrystalline Cellulose in Polylactic Acid Based Composite Membranes
    LIN Dan ZHAO Guang-lei HE Bei-hai LI Xiao-feng
    2016, 32(8):178-182. DOI: 10.13982/j.mfst.1673-9078.2016.8.027
    [Abstract](865) [HTML](0) [PDF 986.55 K](1223)
    Abstract:
    Using nanocrystalline cellulose (NCC) and surface acylated NCC were used as strengthening agents, a newpolylactic acid (PLA) based composite membranes were prepared which can be used as biodegradable food packaging materials. The performance of the composite membranes were tested to investigate the effects of acylation modification on the composite membranes.NCC do have reinforce barrier properties on PLA, but not so obviously because of its bad dispensionin PLA, the reunion of NCC also resulting in the reduction of mechanical properties of composite membrane. After hydrophobically modified, NCC ester can be dispersed well in organic solvent, thus has little effect on the transparency of composite films, due to the stronger interfacial bonding force between polylactic acid and NCC ester, the mechanical and barrier properties of the composite films were promoted. As a new kind of degradable food packaging materials, the composite membranes showed great application potential in food realted industries.
    28  Changes in Total Colony Count during Production of Chilled Chicken Breasts: On-site Tests and Establishment of Shelf-life Prediction Model
    DONG Sa-shuang LI Chuan-ling ZHAO Gai-ming WANG Yu-dong GAO Xiao-ping LIU bin SUN Mei-ying LIN Liu-tao LI Miao-yun HUANG Xian-qing
    2016, 32(8):183-190. DOI: 10.13982/j.mfst.1673-9078.2016.8.028
    [Abstract](1130) [HTML](0) [PDF 832.41 K](1199)
    Abstract:
    The processing of chicken in plants is a source of potential contamination. The effects of the production line and the processes used to cut chilled chicken on the total colony count of chilled chicken breasts were examined. The changes in the total colony count of chilled chicken breasts at storage temperatures of 0, 4, 7, 10, 15, 20, and 25 ℃ were explored. Correlation analysis was conducted on the total colony count, pseudomonas count, pH, total volatile basic nitrogen, and sensory quality to determine putrefaction limitation. Logistic first-order kinetic models and Belehradek secondary square-root models were used to build shelf-life prediction model for chilled chicken breasts under differing temperatures. The results showed that chilled chicken breasts carried a small number of microbes and that secondary pollution was the main reason for the increase in the number of microbes. The limit of total colony count when predicting putrefaction of chilled chicken breasts was 5.78 log(cfu/g). The maximum specific growth rate of the microorganisms in chilled chicken breasts showed a linear relationship with lag time and storage temperature; the R2 value and absolute residue value of the models were above 0.94 and below 0.06, respectively. The shelf-life prediction model of chilled chicken breasts stored at 4, 7, and 10 ℃ were validated, and the relative error was approximately 10%, indicating that this model can accurately predict the remaining shelf-life of chilled chicken breasts.
    29  Effect of Different Heating Approaches on the Sterilization Rate and Tenderness of Beef
    GAO Wen-hong WANG Jun-cui TANG Xiang-wei HAN Zhong
    2016, 32(8):191-196. DOI: 10.13982/j.mfst.1673-9078.2016.8.029
    [Abstract](872) [HTML](0) [PDF 777.21 K](1762)
    Abstract:
    The effects of two low-temperature heating methods including inverter microwave heating and water bath heating on the tenderness, water-holding capacity, and sterilization rate of beef during heating were investigated in this study. The beef topside muscle was used as the experimental material, and all indicators of the meat products were determined after the treatments were carried out using two low-temperature heating methods at different temperatures and durations. The results showed that heating time using an inverter microwave was short. For every 5 ℃ reduction in microwave heating, the heating time was shortened and the electricity consumption could be saved by 10~15%. The drip loss of beef upon microwave heating was significantly less than drip loss upon water bath heating. Both shear forces of beef for the two heating methods showed a wavy trend with increasing temperature; the maximum shear force was reached when the heating temperature was 60 ℃, and the minimum shear force was reached when the heating temperature continuously increased to 65 ℃. The shear force of beef upon microwave heating was less than the shear force after water bath heating. When the beef sample was microwave-heated at 65 ℃ for four to six minutes, the shear force of beef was relatively low. The water holding capacity of beef was closely related to its drip loss, and this relationship could be expressed by the linear equation y = -0.323x + 99.49 (R2 = 0.927). In both heating methods, over 99% of microorganisms could be eliminated when the heating temperature was over 60 ℃. In conclusion, good beef quality could be obtained after 42 (±2) g of beef was heated by a 500 W-inverter microwave at 65 ℃ for four to six minutes.
    30  Effect of Different Drying Conditions on Color and Texture of Citrus Peels
    XU Ming-yue ZHONG Yao-guang BI Jin-feng ZHOU Mo HAN Dan-dan ZHENG Jin-kai
    2016, 32(8):197-203. DOI: 10.13982/j.mfst.1673-9078.2016.8.030
    [Abstract](826) [HTML](0) [PDF 3.09 M](1440)
    Abstract:
    Citrus peels have significant economic and medicinal values. To realize the full utilization of citrus fruits, a comparative study was carried out to illustrate the color and textural property of citrus peels dried by freeze drying, hot-air drying, and mid- and short-wave infrared radiation drying. Different drying conditions significantly affected the color and textural property of citrus peels (p < 0.05). The browning reaction caused △E changes in citrus peels, and the degradation of carotenoid led to a decrease in b value. When the drying temperature was in the range of 60 ℃ to 90 ℃, L value, a value, b value, and total carotenoid content of dried citrus peels decreased with increasing temperatures, and △E value and browning index were elevated. The variation of microstructure provided a theoretical basis to further study the crude fiber, textural parameters, drying efficiency, and rehydration of citrus peels. If the microstructure was loose, undamaged, and regular, the dried citrus peels had high crude fiber content, suitable hardness and crispness, and good rehydration. The mid- and short-wave infrared radiation drying at relatively low drying temperatures (60 ℃~70 ℃) gave better color and structural quality compared to that by freeze-drying and hot-air drying. This study provides an important theoretical basis for the industrial production of dried citrus peels.
    31  Effects of Ultra-high Pressure Treatment on Flavor Substances in Grass Carp
    MA Hai-jian SHI Wen-zheng SONG Jie DIAO Yu-duan WANG Zhi-he
    2016, 32(8):204-212. DOI: 10.13982/j.mfst.1673-9078.2016.8.031
    [Abstract](933) [HTML](0) [PDF 1.02 M](1164)
    Abstract:
    Grass carp was used as the raw material in this study to investigate the changes in the content of flavor nucleotides, free amino acids, and volatile compounds after treatment at various pressures (0.1, 100, 200, 300, 400, and 500 MPa for 10 min). The results showed that the content of adenosine monophosphate (AMP) in grass carp treated at 100, 400, or 500 MPa was increased significantly (p < 0.05), and decreased significantly after treatment at 200 or 300 MPa. Meanwhile, the content of inosine monophosphate (IMP) in the samples treated at 100 or 300 MPa was markedly improved, and was significantly reduced after the treatment at 200, 400, or 500 MPa. The effects of different pressures on free amino acids varied; treatment at 100, 300, and 400 MPa had a relatively small impact on the free amino acid content of grass carp, and the total free amino acid content of the samples treated at 200 or 500 MPa was decreased significantly. Among the six groups of samples, 32, 31, 35, 41, 44, and 40 types of volatile compounds were detected, respectively, and aldehydes, ketones and alcohols were the main compounds present. After ultra-high pressure (UHP) treatment, the relative content of alcohols was reduced, while the aldehyde and ketone content was increased significantly. Additionally, the number of aldehydes and ketones was increased when pressure exceeded 200 MPa.
    32  Microwave Vacuum Drying Characteristics of Lotus Seeds and the Fractal Characteristics of Their Microstructures
    ZHAO Ying-ting WANG Wei-wei ZHUANG Wei-jing ZHENG Bao-dong TIAN Yu-ting
    2016, 32(8):213-218. DOI: 10.13982/j.mfst.1673-9078.2016.8.032
    [Abstract](959) [HTML](0) [PDF 5.98 M](1557)
    Abstract:
    Lotus seeds are dried for storage. The effects of microwave vacuum drying (MVD) on lotus seeds were assessed. The effects of different drying parameters (microwave power density and degree of vacuum) on the drying characteristics, microstructure, and physical properties (shrinkage and rehydration) of lotus seeds were studied. A box counting method (BCM) was used to quantitatively describe the fractal characteristics of the microstructure of dried lotus seeds. The normalized change of the fractal dimension (ΔFD/FD0) was used to construct the functional relationship between physical properties, including shrinkage and rehydration, and the microstructure of lotus seeds dried by MVD. The results indicated that the time required for lotus seeds to be dried to equilibrium moisture content decreased with increasing microwave power density or degree of vacuum. With increasing microwave power density, the shrinkage of lotus seeds initially decreased but subsequently increased. Additionally, the rehydration of lotus seeds initially increased but subsequently decreased. The shrinkage of lotus seeds decreased gradually with an increase in the degree of vacuum (from -60 kPa to -90 kPa). However, the rehydration of lotus seeds initially increased and subsequently decreased. The analysis of dimension could qualitatively describe the microstructure of the lotus seeds dried by MVD. Shrinkage and rehydration of lotus seeds increased with an increase in ΔFD/FD0. The higher the fractal dimension, the higher the degrees of lotus seed shrinkage and rehydration. Furthermore, a linear relationship was observed between ΔFD/FD0 and shrinkage/rehydration, and the fractal dimension analysis could be used to predict the physical properties of lotus seeds.
    33  Effects of Enzymatic Hydrolysis Assisted by High Hydrostatic Pressure Processing on the Allergenicity of Proteins from Ginkgo Seeds
    ZHOU Hao WANG Cheng-zhang CAO Fu-Liang YE Jian-zhong LI Wen-jun CHEN Hong-xia TAO Ran
    2016, 32(8):219-224. DOI: 10.13982/j.mfst.1673-9078.2016.8.033
    [Abstract](805) [HTML](0) [PDF 2.42 M](1076)
    Abstract:
    The purpose of this paper was to study the combined effect of high hydrostatic pressure (HHP) and enzymatic hydrolysis treatments on the allergenicity of ginkgo seed proteins (GSP). Four food-grade proteases (papain, alcalase, pepsin, and neutrase) were used to hydrolyze GSP after pre-treatment with HHP (200, 300, or 400 MPa). The extent of hydrolysis and molecular weights of the hydrolysates were measured by the o-phthaldialdehyde (OPA) method and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and the allergenicity was assessed by western blotting and enzyme-linked immunosorbent assay (ELISA). The results showed that HHP could significantly improve the extent of proteolysis and reduce the antigenicity of GSP when the hydrolase was papain, alcalase, or pepsin, whereas neutrase showed a low degree of proteolysis and poor anti-allergenicity on GSP, and no significant improvement was observed upon high-pressure treatment. The highest degree of proteolysis and the optimal anti-allergenicity were obtained with papain or alcalase hydrolysis combined with HHPtreatment at 300 MPa or with pepsin hydrolysis combined with HHP treatment at 400 MPa. Under the above conditions, GSP could be hydrolyzed into polypeptides with molecular weights lower than 15 ku, the antigenicity was reduced over 95%, and all immunoreactive bands disappeared in the hydrolysates obtained. These results suggest that HHP can improve the degree of hydrolysis of GSP and reduce the residual antigenicity of hydrolysates, but the effects are dependent on the protease used and the magnitude of processing pressure.
    34  Changes of Physicochemical Property during Liuyang Douchi Fermentation
    XIE Jing JIANG Li-wen GONG Cai-jiao ZHOU Hui ZHOU Hong-li
    2016, 32(8):225-232. DOI: 10.13982/j.mfst.1673-9078.2016.8.034
    [Abstract](790) [HTML](0) [PDF 1.45 M](1195)
    Abstract:
    Dynamic changes in physicochemical indexes, microbiological indicators, and flavor during natural fermentation of Liuyang douchi were studied. Samples were obtained from the Liuyang Tianmashan Lobster Sauce Factory. Culture-based methods were used to determine changes in the bacterial and fungal counts, and total acid, amino acid nitrogen, protein, and water content were measured. The results indicated that during the production of Liuyang douchi, the total bacterial count reached a maximum (3.8×1011 CFU/g) on the fourth day, and the maximum fungal count was 1.5×105 CFU/g. Changes in total acid and amino acid nitrogen showed similar trends, and the content of total acid and amino acid nitrogen in the finished product were 2.15% and 1.37%, respectively. The total nitrogen content changed slightly during the fermentation process. The protein content in the finished product was 40.08%. The moisture content showed a downward trend during the fermentation and reached 14.30% in the finished product. Principal component analysis of the data obtained using an electronic nose could distinguish samples taken at different stages of the fermentation process. The electronic tongue could stably and efficiently detect differences in taste of the lobster sauce at various stages of the fermentation, mainly reflected in the bitterness, umami, richness and saltiness. The maximum intensities of bitterness and umami were found after 17 d of fermentation, and the maximum intensities of saltiness and richness were found after four days of fermentation.
    35  Fresh-keeping Effects of Different Packaging Treatment on Tuna (Thunnus thynnus)
    LEI Zhi-fang XIE Jing LI Yan-ni DENG Tian LIU Ai-fang
    2016, 32(8):233-239. DOI: 10.13982/j.mfst.1673-9078.2016.8.035
    [Abstract](789) [HTML](0) [PDF 756.58 K](1536)
    Abstract:
    To slow browning, reduce drip loss, and extend shelf life during cold storage of tuna (Thunnus obesus), fresh-keeping experiments were conducted during cold storage (0±1 ℃) involving air packaging (control), vacuum packaging, modified atmosphere packaging (MAP; 60% CO2+10% O2+30% N2), and biological antioxidants combined with MAP (60% CO2+10% O2+30% N2). Sensory evaluation was conducted, and the values of redness (a*), metmyoglobin content, drip loss, K-value, total volatile base nitrogen (TVB-N), 2-thiobarbituric acid, and total viable count (TVC) were measured. Results indicated that the biological antioxidants combined with MAP maintained tuna quality better than the other methods. After 8 d of storage, the TVC and TVB-N values were 3.74 log CFU/g and 21.3 mg/100 g, respectively, which were still lower than the limit for eating raw tuna. Compared with other MAP groups, biological antioxidants combined with MAP were capable of effectively delaying browning and reducing drip loss, thereby extending the shelf life of tuna during storage at 0±1 ℃.
    36  Effect of Sodium Alginate-based Antimicrobial Composite Coating Treatment on the Preservation of Chilled Duck
    TANG Qiu-ye PAN Dao-dong SUN Yang-ying CAO Jin-xuan WANG Guang-feng SHEN Jian-liang
    2016, 32(8):240-245. DOI: 10.13982/j.mfst.1673-9078.2016.8.036
    [Abstract](1022) [HTML](0) [PDF 849.68 K](1243)
    Abstract:
    ε-Poly-L-lysine (ε-PL) was used as biological antibacterial agent, and grapefruit peel microcrystalline cellulose (MCC) was used as reinforcing agent, to study the effects of the sodium alginate composite coating on the preservation of chilled duck during refrigerated storage. The microstructures of the composite films were characterized by scanning electron microscopy (SEM) analysis, and the effects of composite coating on the pH, total volatile basic nitrogen (TVB-N), water loss, microbiological indicators, and changes in the color difference of chilled duck during storage were studied. The results indicated that the antibacterial properties of composite coating was improved effectively with the addition of ε-PL, and the stable and ordered internal network structure of the composite film was formed by the addition of MCC, which improved the dispersion and stability of ε-PL. The sodium alginate coating containing 1% (m/V) of ε-PLcould effectively suppressed the increase in TVB-N of the chilled duck during the storage and significantly reduced the total number of colonies and the number of Escherichia coli colonies (p < 0.05). The sodium alginate coating containing 1% (m/V) of ε-PL and 0.1% (m/V) of MCC could significantly reduce the loss of water (p < 0.05) and maintain the red color of chilled duck meat, compared with co ntrol group and the sodium alginate coating group. The results obtained in this study can provide a new reference on the application of antimicrobial sodium alginate-based composite coating in the preservation of chilled duck.
    37  Effect of Reduced Glutathione-composite Preservatives on the Quality of Metapenaeus ensis
    HAN Shi-lei DAN Shu
    2016, 32(8):246-251. DOI: 10.13982/j.mfst.1673-9078.2016.8.037
    [Abstract](833) [HTML](0) [PDF 691.73 K](1141)
    Abstract:
    Metapenaeus ensis was used as the material to study the inhibitory effect of reduced glutathione (GSH) on polyphenol oxidase (PPO) activity, with optimal inhibitory effect on PPO activity determined at a GSH concentration of 4 g/L and a treatment time of 30 min. PPO activity, total volatile basic nitrogen (TVB-N) content, whiteness, salt-soluble muscle protein, and sensory evaluation were used as indicators to study the effect of different reduced GSH-composite preservatives on the quality of M. ensis during frozen storage at -18 ℃. Our results showed that 4 g/L GSH effectively inhibited PPO activity and decreased melanin accumulation. The preservatives prepared from 4 g/L GSH+10 g/L sorbitol and 4 g/L GSH+5 g/L citric acid reduced the generation of TVB-N and decreased the degradation rate of salt-soluble protein during storage. Shrimp treated with the preservative composed of 4 g/L GSH+10 g/L sorbitol+5 g/L citric acid possessed the highest sensory evaluation score. These findings suggested that the preservative composed of 4 g/L GSH+10 g/L sorbitol+5 g/L citric acid exhibited the best fresh-keeping effect for the storage of M. ensis.
    38  Lipolysis and Lipid Oxidation During the Process of Chinese Traditional Bacon Development
    LI Lin WANG Ya-na WANG Xiao-jun SHANG Yong-biao
    2016, 32(8):252-258. DOI: 10.13982/j.mfst.1673-9078.2016.8.038
    [Abstract](1025) [HTML](0) [PDF 537.51 K](1366)
    Abstract:
    Here, modified Chongqing Chengkou bacon was studied using samples collected before and after salting, roasting via electric heat, and smoking for 5, 10, and 15 h to assess changes in lipolysis and lipid oxidation during the processing by measuring acid value (AV), peroxide value (POV), thiobarbituric acid (TBA), lipase activities, and fatty acid composition. The results showed that AV increased sharply after salting, but exhibited slow changes during other phases of processing. TBA and POV values increased markedly after roasting with electric heat, with POV exhibiting a downward trend and insignificant changes in TBA during the smoking phase. Lipase activities were significantly enhanced after salting before a continuous decline during roasting with electric heat. The compositions of phospholipids and free fatty acids varied considerably during the early stage of smoking due to the influence of lipase activity. Changes in the content and fatty acid composition of phospholipids showed opposite trends from those of free fatty acids, especially, polyunsaturated fatty acids; however, the content of triacylglycerols and the relative content of their fatty acids was stable, suggesting that phospholipids play an important role in hydrolysis duringthe processing, and that phospholipid hydrolysis may be the main source of free fatty acids.
    39  Study on Enzymatic Hydrolysis Process and Stability of Walnut Milk
    YAO Kui-zhang Qi Bing LU Min XIA Jun-xia ZHAO Hui-bo LI Xi-ceng
    2016, 32(8):259-264. DOI: 10.13982/j.mfst.1673-9078.2016.8.039
    [Abstract](798) [HTML](0) [PDF 1.10 M](1311)
    Abstract:
    Walnut milk was hydrolyzed by trypsin, and the stability of the enzymatic prepared walnut milk was studied. The most optimal conditions for enzymatic hydrolysis were as follows: walnut slurry concentration 9% (m/m), trypsin amount 0.4‰ (m/m), pH 9.0, reaction time 1h and temperature 55 ℃. Under these conditions, the degree of hydrolysis (DH) reached 13.67 ± 0.41%. The stability of three hydrolysates with DH of 13.70%, 10.20% and 7.01%compared to the non-hydrolytic process were investigated by Turbiscan. Back scattering curve showed that the height of water separating layer from bottom was reduced from 0~10 mm to 0~5 mm by using the technique of enzymatic hydrolysis. The bottom stability indices of the hydrolysates were lower than the non-hydrolytic sample, and the higher the DH, the lower the stability index. . Compared with the non-hydrolytic process, the stability index curves of the hydrolytic process samples were smoother with unobvious inflection points. All the results indicated that the stability of the enzymatic hydrolysis process was better than the non-hydrolytic process.
    40  Shelf-life of Vacuum-packaged Refrigerated Turbot Fillets and the Quorum Sensing Profile of Dominant Spoilage Bacteria
    ZHANG Cai-li ZHU Su-qin SUN Xiu-jiao PAN Yu-rong ZENG Ming-yong
    2016, 32(8):265-270. DOI: 10.13982/j.mfst.1673-9078.2016.8.040
    [Abstract](848) [HTML](0) [PDF 849.87 K](1022)
    Abstract:
    Vacuum-packaged refrigerated turbot fillets were used as the study object, and their shelf-life was determined by sensory evaluation, microbiological and chemical indicators, and the distributions of microflora at the beginning and end of the storage period using a 16S rDNA method. Moreover, two types of quorum sensing signaling molecules (N-acyl homoserine lactones (AHLs) and autoinducer-2 (AI-2)) during the storage of turbot fillets were also detected using reporter strains, and the quorum sensing characteristics of dominant spoilage bacteria were examined. The refrigerated turbot fillets packaged under vacuum conditions could be stored for nine days, and the total viable counts and the total volatile basic nitrogen (TVB-N) value reached 6.87 log( CFU/g) and 28.70 mg/100 g, respectively. The changes in the microbial species over the storage period were examined, and the predominant spoilage bacterium was Shewanella spp., followed by Enterobacteriaceae. The content of quorum sensing signaling molecules (AHLs and AI-2) increased with increasing storage time. All the isolated Shewanella spp. strains were capable of secreting AI-2, while the secretion capacity varied by strains. The luxS gene responsible for AI-2 production was also present, indicating that luxS was relatively conserved in AI-2-producing bacterial strains and AI-2 production may be involved in the spoilage process of Shewanella spp.
    41  Drug Resistance of Escherichia coli Isolated from Different Foods in Xinjiang
    LUO Juan JI Hua WANG Qing-ling ZHOU Hong CHENG Xu-lin DANG Ya-jie LIU Wen-sheng
    2016, 32(8):271-277. DOI: 10.13982/j.mfst.1673-9078.2016.8.041
    [Abstract](906) [HTML](0) [PDF 720.05 K](941)
    Abstract:
    Escherichia coli strains were isolated from meat products, vegetables, dairy products, and instant foods in farmers markets and supermarkets of Urumqi city, Shihezi city, and Kuitun city of Xinjiang, and 63 E. coli strains were isolated from 198 food samples. Drug resistances to 17 antibiotics in 63 E. coli strains were determined using the Kirby-Bauer (K-B) method, and polymerase chain reaction (PCR) was used to measure nine drug-resistance genes. The results indicated that 63 E. coli strains showed high resistance to tetracycline (44.44%), ampicillin (39.68%), and nalidixic acid (38.10%), and all test isolates showed the highest susceptibility to imipenem (0.00%). Isolates from meat products and vegetables showed the highest drug resistance to tetracycline (57.14% and 52.94%, respectively), isolates from dairy products showed the highest drug resistance to ampicillin (26.67%), and isolates from instant foods were susceptible to 17 antibiotics. The isolates from Urumqi, Shihezi, and Kuitun exhibited the highest resistance to tetracycline (65.00%, 40.00%, and 32.14%, respectively). PCR results showed that among the resistant strains, the detection rate for the sul2 gene was the highest (75.00%), and the detection rate for the aadB gene was lowest (19.23%). The multiple-antibiotic-resistant and triple-antibiotic isolates accounted for 63.49% and 39.68% of the total isolates, respectively. Foodborne E. coli in Xinjiang showed a high level of resistance to common antibiotics.
    42  Detection of AFB1 in Nuts by a Nanoparticle-based Bio-Barcode Assay
    YU Yu-yan WANG Tong-ying ZOU Yan-hui GAO Xuan QIU Ya-li
    2016, 32(8):278-283. DOI: 10.13982/j.mfst.1673-9078.2016.8.042
    [Abstract](959) [HTML](0) [PDF 963.40 K](1275)
    Abstract:
    Gold nanoparticle probes (NP) were prepared using gold (Au) nanoparticles, AFB1 polyclonal antibodies, a complementary gold nanoparticle probe, and barcode DNA, and was characterized after purification using transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectroscopy, and concentration measurement. NPs were coupled with AFB1 monoclonal antibody-modified magnetic microspheres (MMPs) through an antigen-antibody interaction to yield NP-AFB1-MMP sandwich compounds. Fluorescence quantitative-polymerase chain reaction (FQ-PCR) was employed to detect the bio-barcode DNA that was released under high temperature and low salt conditions. A bio-barcode assay for detecting AFB1 was established by investigating the linear correlation between the number of the cycles required for the fluorescence signal in each tube to reach the set threshold value after the reaction, and the number of the corresponding initial template copies, and methodological evaluation was conducted on the detection system. The results indicated that the method established in this experiment is rapid, sensitive, and highly specific. A significant linear relationship was observed between the number of the cycles in each template and the logarithm of the number of initial copies of this template (y = –2.9054x + 54.581, r=0.9991). The detection sensitivity limit was about 10-8 ng/mL, much more sensitive than the limit of an enzyme-linked immunosorbent assay (ELISA). The intra- and inter-assay CV (coefficient of variation) values of FQ-PCR were less than 5%, indicating satisfactory accuracy. The established bio-barcode assay (BCA) was used to conduct a crossover experiment on compounds with similar structures, and the results showed a good specificity. This method can be used to determine trace amounts of AFB1 in peanuts, cashews, and other nuts.
    43  Comparative Study on Milk Fat Globule Membrane Proteomes in Human and Bovine Milk
    YANG Mei PENG Xiu-ming WU Jun-rui SUN Yue WU Ri-na LIU Biao YUE Xi-qing
    2016, 32(8):284-289. DOI: 10.13982/j.mfst.1673-9078.2016.8.043
    [Abstract](1126) [HTML](0) [PDF 1.18 M](2085)
    Abstract:
    Human milk is the sole food source in the initial stage of an infant’s life. Protein is an important nutrient in human milk, and cow’s milk has been widely used in infant formula as a raw material to replace human milk. In this study, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography-matrix-assisted laser desorption/ionization-time of flight (LC-MALDI-TOF) proteomic methods were used to isolate and identify the milk fat globule membrane proteins (MFGPs) from human and bovine milk, and significant differences between the MFGPs in the two types of milk were found. The results showed that 488 and 1545 different protein species were identified in milk fat globule membranes of bovine and human milk, respectively. Among these proteins, there were 173 unique proteins in bovine milk fat globule membranes, 1230 unique proteins in human milk fat globule membranes, and 315 proteins found in both human and bovine milk. According to gene ontology (GO) annotations, 37% of biological processes involving human MFGPs were metabolic processes, 55% of molecular functions were for combination, and 34% of human MFGPs participated in constituting cell organelles. Twenty-four human MFGPs were involved in the immune related pathways, mainly for antigen processing and presentation. By comparing with bovine milk, studying the composition and functions of human MFGPs can improve our understanding of the proteins present in human milk, and provide a reference for adding functional proteins to infant formula products.
    44  Synthesis and Identification of Artificial Antigen for the Rapid Immunological Detection of Fluoxetine
    LIU Bo YUAN Li-peng NIE Yan-hua YIN Kai-dan XIONG Bo
    2016, 32(8):290-294. DOI: 10.13982/j.mfst.1673-9078.2016.8.044
    [Abstract](832) [HTML](0) [PDF 892.95 K](945)
    Abstract:
    Currently, fluoxetine residues in drugs and slimming health foods pose a health problem. Therefore, the synthesis of artificial antigens for fluoxetine was explored, and the structures and specificities of the synthesized hapten and artificial antigen were identified. Fluoxetine reacted with methyl acrylate and underwent hydrolysis to produce the hapten (H-FXT). Subsequently, the active ester method was used to conjugate H-FXT with bovine serum albumin (BSA) and ovalbumin (OVA) separately, to obtain the fluoxetine immunogen (H-FXT–BSA) and coated fluoxetine antigen (H-FXT-OVA), respectively. The H-FXT-BSA immunogen was used to immunize Balb/c mice and the generated anti-serum was analyzed by indirect enzyme-linked immunosorbent assay (ELISA). The artificial antigens, H-FXT-BSA and H-FXT-OVA, were analyzed by ultraviolet (UV) spectroscopy, and calculations showed that the coupling ratios were 14.5:1 and 11.3:1, respectively. The antiserum titers after the immunization of Balb/c mice were all above 30 000, and the half maximal inhibitory concentration was approximately 100 ng / mL. The artificial fluoxetine antigens were successfully synthesized for the first time and anti-fluoxetine antibodies were obtained. This study can provide a key technical basis for further studies involving the establishment of a method for the rapid immunological detection of fluoxetine, including the development of an ELISA kit and other related products.
    45  Techniques for Identifying Common Meat Adulterations Based on DNA Barcoding
    TIAN Chen-xi ZHOU Wei WANG Shuang WANG Zan ZHANG Cui-Xia LI Yong-yan ZHANG Yan ZHANG Zhi-sheng
    2016, 32(8):295-301. DOI: 10.13982/j.mfst.1673-9078.2016.8.045
    [Abstract](972) [HTML](0) [PDF 724.67 K](1393)
    Abstract:
    According to the cases of common meat adulteration seen in the market, four kinds of adulteration models were built: mixed beef-pork, mutton-pork, beef-duck, and mutton-duck by extracting genomic DNAs from fresh beef, mutton, pork, and duck and premixing them at certain ratios. Through polymerase chain reaction (PCR) and sequence comparison using the universal primers COI-1 and COI-2, a COI gene–based method was established to detect adulteration in foods of animal origin. According to the pure meat DNA extraction rate T obtained from the experiment, the conversion of the adulteration ratio from the DNA level into the meat weight level was achieved. At the meat weight level, COI-2 primers provided a relatively accurate detection, and the detection limits of beef-pork, mutton-pork, beef-duck, and mutton-duck adulteration models were 5%, 8%, 1%, and 4%, respectively. The method was tested on 28 batches of collected meat product samples, and the ingredients of 89% of the identified samples were consistent with those described on the product labels. As a simple, rapid, and effective molecular identification approach, DNA barcoding can be directly applied to determine the animal species present in foods of animal origin and to detect adulteration.
    46  Multivariate Statistical Analysis of the Stability of Ten Commercially Available Whipped Creams
    WANG Liang-jun ZHAO Qiang-zhong
    2016, 32(8):302-308. DOI: 10.13982/j.mfst.1673-9078.2016.8.046
    [Abstract](793) [HTML](0) [PDF 949.33 K](1198)
    Abstract:
    To study how to use rheological properties to quickly and accurately determine the stability of whipped cream, eight rheological parameters that were significantly correlated to stability (P < 0.05) were selected by the correlation analysis in this paper, to conduct factor analysis (FA) and cluster analysis (CA) on ten commercially available whipped creams with significant differences in stability. The FA results showed that there were three main factors in stability: "main stability factor", "thixotropic loop factor", and "strain equilibrium factors". The loading analysis suggested that time scanning G', the area of thixotropic loop S, and the strain equilibrium r were the key rheological indicators affecting whipped cream stability. In addition, the total factor score (TFS) expression was TFS = f1 × 0.38476 + f2 × 0.25671 + f3 × 0.22858. The TFS ranking reflected differences in the stability of whipped cream. The CA results showed that the ten whipped creams examined could be classified into three clusters. The first kind included seven samples: samples 5, 6, 1, 8, 9, 10, and 2. Samples 3 and 4 were classified into the second cluster and sample 7 was classified into another cluster.
    47  Effect of Vacuum Freeze-drying on the Aroma Characteristics of Instant Tea Powder
    LI Hong NI Hui JIANG Ze-dong YANG Yuan-fan LI Li-jun DU Xi-ping XIAO An-feng CHEN Feng HUANG Gao-ling
    2016, 32(8):309-316. DOI: 10.13982/j.mfst.1673-9078.2016.8.047
    [Abstract](955) [HTML](0) [PDF 1003.17 K](1107)
    Abstract:
    In order to investigate the effect of vacuum freeze-drying on the aroma characteristics and volatile matter of instant tea powder, headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (GC-MS) was used to analyze the volatile components in concentrated Oolong tea extract and its tea powder prepared by vacuum freeze-drying. GC-MS analysis showed that 74 volatile components were identified, with the main volatile compounds in concentrated Oolong tea extract being indole, 2-ethyl-furan, and para-cymene, and the main volatile compounds in the vacuum freeze-dried Oolong tea powder being indole, hexanal, and linalool. Cluster analysis showed that nine volatile compounds, including 2-ethyl-furan, disappeared, while 23 new volatile compounds, including hexanal, were generated after vacuum freeze-drying. Additionally, the concentrations of 2-heptanone and (E)-β-ocimene decreased during vacuum freeze-drying, while the concentrations of (E)-nerolidol and six other compounds increased simultaneously. The result of odor-activity values showed that (E)-2-nonenal and (E,E)-2,4-decadienal were the main odor-active contributors of the concentrated tea extract. As for the freeze-dried tea powder, the main odor-active compounds were 1-octen-3-ol, linalool, and n-hexanal. These results indicated the significant effects of vacuum freeze-drying on the volatile components and aroma characteristics of concentrated Oolong tea extract and provided a theoretical reference for the production of instant tea powder.
    48  Quantification of the Umami Taste of Edible Fungi Using Electronic Tongue
    BING Fang-ling FENG Tao YANG Yan ZHUANG Hai-ning LI Xiao-bei XIE Ke-lin GAO Lin-lin
    2016, 32(8):317-321. DOI: 10.13982/j.mfst.1673-9078.2016.8.048
    [Abstract](797) [HTML](0) [PDF 593.15 K](1262)
    Abstract:
    An electronic tongue of the company Alpha M.O.S was used to rapidly quantify the umami taste of five species of edible fungi with the aim to differentiate the fungi on the basis of the quantitative data. In addition, umami taste data were obtained through classical sensory evaluation, and the consistency between both methods was compared. The results showed that the electronic tongue could successfully distinguish the five fungal species; the discrimination index was 99. In addition, the signals of the electronic tongue and sensory evaluation were used to generate partial least squares models to estimate the umami intensity of the different fungi. A well-fitting model was obtained (the correlation coefficient was 0.94). To a large extent, the electronic tongue could predict the sensory evaluation. The result of this study indicates that the electronic tongue, as a modern detection technology, has promising potentials for qualitative as well as quantitative analyses of the umami taste of edible fungi.
    49  Determination of Various Mycotoxins in Fermented Tea by Ultra-high Performance Liquid Chromatography-tandem Mass Spectrometry
    LIU Yan TAN Gui-liang LIU Zi-xiong LI Xiang-li CHEN Jian
    2016, 32(8):322-327. DOI: 10.13982/j.mfst.1673-9078.2016.8.049
    [Abstract](1843) [HTML](0) [PDF 630.70 K](1854)
    Abstract:
    A method for the determination of five mycotoxins in fermented Pu'er tea, and Hunan dark tea and black tea samples was established. Ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to identify aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), aflatoxin G2 (AFG2), and ochratoxin A (OTA) under the multiple reaction monitoring (MRM) mode. Tea samples were extracted with an acetonitrile/water solution (84 / 16), and purified using a MycoSpin 400 multifunctional clean-up column. Samples were separated on an Agilent Zorbax Rrhd SB-C18 column (2.1 mm ? 100 mm, 1.8 μm), and qualitative and quantitative analyses were performed using MRM mode. Quantitation was conducted using the external standard method. The results indicated that, under the optimal conditions, five mycotoxins showed a good linear relationship within their own linear response range, with correlation coefficients (r) more than 0.9983, and limits of quantification (LOQ) ranging from 0.1 to 0.5 μg / kg. The recovery of the five mycotoxins at low, medium, and high spiking levels ranged from 63.5% to 125.0%, and the relative standard deviation (RSD, n=3) values were between 3.9% and 17.2%. This method has a simple pretreatment, can provide rapid detection, good purification, and accurate and reliable results, and is suitable for the rapid detection of multi-component mycotoxin contaminants in fermented tea.

    Editor in chief:李琳

    Inauguration:现代食品科技

    International standard number:ISSN 1673-9078

    Unified domestic issue:CN 44-1620/TS

    Domestic postal code:46-349

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