Abstract:Food allergy is increasing rapidly in worldwide. In Asia, the incidence of allergic diseases caused by seafood is high, such as fish allergy, shellfish allergy and crustacean allergy, while the standardized cure method is still insufficient. This paper systematically summarized the classification, identification and detection techniques of seafood allergens, the processing treatments to reduce seafood allergenicity, and the means of prevention and control of seafood allergy, such as hypo-allergenic derivatives and anti-allergic nutritional component. It can provide reference for the prevention and control of seafood allergy and other food allergic diseases.
娄海伟,林俊芳,赵仁勇,叶志伟,田双起,王新伟,郭丽琼,赵 玉
Abstract:The aim of this study is to obtain the minimum concentration of glufosinate ammonium that can completely inhibit the growth of Cordyceps militaris and a method for quickly constructing the binary vector of bar gene. The concentration gradient method was used to study the inhibitory effect of glufosinate ammonium on the growth of C. militaris. Double-joint PCR (DJ-PCR) was used to construct the bar gene expression cassette. The T4 DNA ligase method and the homologous recombination method were used to insert the bar gene expression cassette into the T-DNA region of the binary vector pAg1-H3 to construct the binary vector pAg-Bar, and the ligation effects of the above two methods were compared. Agrobacterium tumefaciens-mediated transformation method was used to verify the effectiveness of the vector pAg-Bar and the function of the bar gene in C. militaris. The results showed that the minimum concentration of glufosinate ammonium that could completely inhibit the growth of C. militaris conidia was 400 μg/mL. The bar gene expression cassette could be effectively constructed by the DJ-PCR method. The binary vector pAg-Bar could be successfully constructed by the T4 DNA ligase method and the homologous recombination method. However, the homologous recombination method is simpler and more efficient than the T4 DNA ligase method. The bar gene expression cassette in the binary vector pAg-Bar could be successfully integrated into C. militaris genome by Agrobacterium tumefaciens-mediated transformation method, and the obtained C. militaris transformants were resistant to glufosinate ammonium. The method of constructing vectors established in this study is simple and efficient. It is suitable for constructing vectors with resistance gene, knock-out vectors, and overexpression vectors and so on. These results provide technical support for the identification of C. militaris gene function.
Abstract:It is important to elucidate the interaction mechanisms between tannic acid (TA) and bovine serum albumin(BSA)/human serum albumin(HSA) for developing protein-based carriers of active components and exploring delivery mechanisms. Serum albumin (BSA/HSA) is a commonly used soluble protein-based carrier containing multiple hydrophobic cavities, which was binding sites of active components. The fluorescence quenching effect of BSA/HSA by TA under different conditions was studied by fluorescence emission spectroscopy, the quenching constants and thermodynamic parameters were calculated by mathematical equation to analyze the fluorescence quenching mechanism. Finally, the binding sites were determined by site Marker experiments and molecular docking technique. The results showed that fluorescence quenching of BSA/HSA by TA occur under different pH conditions, the quenching rate is highest at pH 7.4. The binding constants of TA and serum proteins obtained by nonlinear fitting are magnitude of 105-107 L/mol, which indicated that the binding ability is very strong and pH significantly affect the binding constants (P<0.05), the binding constant is highest at pH 7.4. Thermodynamic parameters and molecular docking indicated that the binding of TA to BSA/HSA mainly through hydrogen bonding and hydrophobic interactions, site Marker experiments and molecular docking indicated that in pH 7.4, the binding sites are located in the hydrophobic cavity between domain IIA and domain IIIA, near the Sudlow's site I. The paper confirmed that the binding of TA to BSA/HSA is pH dependent, which provides a theoretical reference for the design and development of protein- TA carriers and provides meaningful guidance for TA applications.
Abstract:It is of great significance to construct bioactive ingredients delivery system based on the interaction between food molecules. In this paper, curcumin is selected as the active ingredient, using lactoferrin, EGCG (epigallocatechin gallate), and polysaccharides (sodium alginate, SA and gum Arabic, GA) as materials. First, alkaline treatment was used to prepare LF-EGCG binary nanoparticles, and then based on thermal induction and electrostatic interaction methods, the ternary composites were constructed, and the interaction between the three was analyzed using fluorescence and infrared spectroscopy. The results showed that a covalent reaction occurred between lactoferrin and EGCG in the ternary composite, and the polysaccharides mainly interacted with each other through hydrogen bonding and hydrophobicity. The effect is combined with the binary complex. On this basis, the curcumin emulsion was constructed by layer-by-layer self-assembly method and its interface structure and stability were analyzed, its rheological properties, bioaccessibility and stability were also measured. The results showed that the double-layer emulsion formed by polysaccharides can effectively prevent the aggregation of droplets, inhibit the degradation of curcumin, improve curcumin's bioaccessibility and storage stability. Gum Arabic itself has strong emulsifying activity and steric hindrance, so in the H(LF-EGCG)-GA ternary composites stabilized emulsion, the loss of curcumin is minimal. The results in this paper provide a useful reference for building a safe, high bioaccessibility and controlled release curcumin delivery vehicle.
Abstract:To research the relationship between structural characterization and immunomodulatory activities of a polysaccharide fraction, a polysaccharide fraction was isolated and purified from Sparassis latifolia polysaccharides and its structure and immunomodulatory activities was investigated. The polysaccharide fraction SlP was isolated and purified from Sparassis latifolia polysaccharides by HZ-830 macroporous resin, DEAE-52, and Sephadex-G100 chromatography. The structure of SlP was investigated using high performance gel permeation chromatography, infrared spectroscopy, ion chromatography, nuclear magnetic resonance, atomic force microscopy, scanning electron microscopy and Congo red. The MTT method was used to measure the proliferation activity of macrophages RAW264.7 neutrophic red staining was used to determine the phagocytosis ability of SlP. Cell supernatants were collected and the production of NO in the supernatant were detect. Cells were collected and total RNA was extracted, then the expression levels of TNF-α, IL-1β, IL-6, IL-3, IL-10 and IFN-β mRNA in macrophages were determined using quantitative RT- PCR. SlP exhibited a triple helical structure with β-D-glucan and its average molecular weight was 1.04 × 104 u. The surface microstructure of SlP exhibited different shapes and sizes of fragments. The molecular morphology revealed that SlP molecules were compact and asymmetric in shape with branching and entangled chains. SlP could promote RAW 264.7 macrophage proliferation at the 1.95-31.25 μg/mL concentration range; in particular, proliferation reached a peak at 7.81 μg/mL SlP. At the 1.95-7.81 μg/mL concentration range, SlP significantly improved the phagocytic capacities of RAW264.7 macrophages, increased the production of NO, and increased tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-3, IL-10, and interferon (IFN)-β mRNA levels. Thus, SlP could be used as good functional food raw materials in food industries.
Abstract:Bacteriocin A32 extracted by acid precipitation was used on Escherichia coli and Staphylococcus aureus. The antibacterial activity and antibacterial mechanism of bacteriocin A32 were investigated by Oxford Cup method, spectrophotometry, scanning electron microscope, electrical conductivity and SDS-PAGE method. The results showed that bacteriocin A32 had antibacterial properties against E. coli and S. aureus, and the minimum inhibitory concentration was 1.25 mg/mL. It had effects on the production curve of the indicator bacteria, cell morphology, cell membrane permeability, cell membrane permeability, cell membrane integrity, cell wall, and protein synthesis. And with the increase of the concentration of bacteriocin A32, the effect gradually increased. The results showed that the antibacterial properties of bacteriocin A32 were due to the damage to the permeability and integrity of the wall membrane of Gram-positive and Gram-negative bacteria, resulting in leakage of the contents, which in turn affected the metabolism and growth of the bacteria. The above research can lay a theoretical foundation for the development and application of bacteriocin A32 as green biological preservative.
Abstract:The B-type wheat starch with a moisture content of 30% was subjected to repeated heat-moisture treatment (RHMT) and continuous heat-moisture treatment(CHMT) at 120 ℃, and their effects on structure, physicochemical properties and digestibility of the starch were compared and analyzed. The results showed that the starch granules appeared to rupture and scallops after RHMT and CHMT. Meanwhile, the double helix structure and the crystalline and amorphous region were broken, and the starch molecules were rearranged and redistributed. As a result, HMT decreased the relative crystallinity and pasting viscosity while increasing starch's gelatinization temperature but reduced the energy required for uncoiling. Thus, the RHMT exhibited more significant advantages than CHMT in modifying starch's structural, physicochemical, and digestibility properties. The results are expected to provide a theoretical basis for further investigating the modification mechanism of heat-moisture modified and the further development and utilization of wheat for B-starch.
Abstract:In order to further elucidate the physiological function of metallothionein from tartary buckwheat Fagopyrum tataricum (FtMT), recombinant FtMT and CPP-FtMT including 11R-FtMT and Tat-FtMT were produced, which were fused with cell-penetrating peptides (CPPs), by a novel secreted expression method using phoA vector in Escherichia coli (E. coli). Three types of proteins were purified by Ni2+ affinity chromatography followed by induction of a low concentration of phosphate and were by identified by SDS-PAGE, Western blot and UV absorption spectrometry. Chemical and functional characteristics of three types of proteins were analyzed including by metal-binding capacity and hydroxyl radical scavenging ability. The results showed three types of proteins have almost the same motif of UV absorption spectrometry and exhibited intact metal binding ability and hydroxyl radical scavenging ability. Cell penetrating ability of CPP-FtMT proteins was investigated using FITC labeled peptide internalization into Ins-1 beta cells and H9c2 cardiomyocytes under fluorescent microscopy. Moreover, Ins-1 beta cells and H9c2 cardiomyocytes were treated with CPP-FtMT to reveal protective effects against glucolipotoxicity-induced and hyperglycemia-induced apoptosis with or without hypoxia, respectively. The results demonstrated CPP-FtMT proteins strongly protected Ins-1 beta cells against oxidative stress and apoptosis induced by glucolipotoxicity with or without hypoxia, and also protected H9c2 cardiomyocytes against hyperglycemia-induced apoptosis with or without hypoxia. These present studies provide a scientific basis for the development and application of FtMT.
Abstract:Objective: To investigate the hypoglycemia effect of α-linolenic acid (ALA) on type Ⅱ diabetic mice. Methods: A high-fat diet combined with intraperitoneal injection of streptozotocin was used to establish a type Ⅱ diabetic mice model. The mice were randomly divided into a normal control group, a diabetic model group, and a low-, medium-, and high-dose ALA group. After 42 consecutive days of ALA intervention, the organ index, glucose and lipid metabolism related indexes and endotoxin levels in blood were determined, and the relative mRNA expression genes related to glucose transport, gluconeogenesis, inflammation and lipid metabolism in liver tissue were also detected. Results: Low-, medium- and high- doses [0.25, 0.50, 1.00 g/(kg·d)] of ALA can improve the organ index, blood glucose level, glucose tolerance and insulin resistance index of diabetic mice to varying degrees, with better effects in the medium- or high- doses of ALA group. The medium- and high- doses of ALA significantly reduced serum total cholesterol, triglycerides and endotoxin levels of diabetic mice; the high- dose of ALA significantly reduced the relative mRNA expression levels of liver monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α) and glucose-6-phosphatase (G6pc), and significantly increased the relative mRNA expression level of hepatic peroxisome proliferators-activated receptor α(Pparα); the medium-dose of ALA had a certain regulating effect on the relative mRNA expression levels of MCP-1, TNF-α, G6pc and Pparα. Conclusion: Both medium- and high- doses of ALA could effectively improve metabolic endotoxemia, liver tissue inflammation, and glucose and lipid metabolism in type Ⅱ diabetic mice.
Abstract:Probiotics can improve functional dyspepsia (FD), but probiotics are strain-specific, and the role of probiotics and their mechanism by which probiotics improve FD symptoms are not well studied. In this study, the effect of Lactobacillus paracasei LC-37 Lactobacillus beverage on improving functional dyspepsia and regulating intestinal flora was studied. Methods: a total of 30 subjects with functional dyspepsia were recruited for a 21-day clinical trial, including a 7-day emptying period, a 14-day ingesting period. During the ingesting period, subjects will drink 200 g LC-37 Lactobacillus beverage(the total number of viable Lactobacillus paracasei LC-37 is 5×108 CFU/g, 100 g/bottle) per day. On the 7-day emptying period and the 28-day ingesting period, fecal samples were collected, and clinical symptom scores were evaluated by doctor. Intestinal flora of fecal samples was analyzed by 16S rDNA high-throughput sequencing. Results: there were 29 effective subjects. After ingesting the LC-37 Lactobacillus beverage for 14 days, the clinical symptoms in FD population was significantly improved (P<0.05), and the composition of the intestinal flora was changed, the abundance of beneficial Bifidobacterium, Prevotella_9 and Alistipes genus increased, and Lactobacillus increased significantly, and the abundance of harmful Dorea genus decreased. Conclusion: ingesting LC-37 fermented milk for 14 days, functional dyspepsia could be improved significantly, and intestinal flora was regulated.
Abstract:Objective: The protective effects of swimming bladder peptides (SWP) from cod on premature senescence human embryonic lung diploid fibroblast (2BS) cells were studied. Methods: 2BS cells were used to establish the model of precocious senescence induced by H2O2. Different concentrations of SWP were added to the precocious senescence cells and resveratrol was used as positive control. The proliferation rate, the cellular apoptosis, the content of β-galactosidase, the level of ROS and the content of peroxidase were measured. Results: Compared with model control group, the survival rates of cells treated with SWP and resveratrol was improved, the ROS level and cellular apoptosis were decreased. Besides, the activities of SOD and CAT were increased and the content of MDA was decreased. The protective effect of swimming bladder peptides was positively correlated with the dose administrated. Conclusion: SWP possessed the ability of relieving premature senescence of 2BS cells induced by H2O2 and partly reducing oxidative damage.
Abstract:Objective: This study was aimed to investigate the protective effects of polyphenols from Phyllanthus emblica L. (PPE) against ethanol-induced oxidative damage in rats liver cell, and further reveal the molecular mechanisms by examining the Nrf2/HO-1 pathway. Methods: BRL-3A mice were used to evaluate the hepatoprotective effect of PPE on liver injury induced by ethanol exposure. The biochemical parameters (MDA, SOD, ALT, AST and GSH) were measured using commercial kits. HO-1 mRNA level was determined by Q-PCR. Protein levels were measured by western blot. Results: A decreased amount of MDA, ALT and AST release were observed, whereas PPE pretreatment significantly increased the leakage of SOD and GSH in BRL-3A cells. Furthermore, PPE pretreatment apparently up-regulated HO-1 expression, and prevented the overexpression of Nrf2 expressions. Conclusion: These results demonstrate that PPE-mediated up-regulation of HO-1 via Nrf-2 signaling pathway may provide a pivotal mechanism for its hepatoprotective activity. The phenolic compounds including gallic acid, corilagin and ellagic acid present in PPE might be playing a major role against alcohol-induced oxidative damage in rat cells.
Abstract:In present study, the processing characteristics, sensory properties and ultrastructure were explored after the black barleys were treated with different ultra-high pressure (UHP) conditions, which were 100, 300 MPa and 600 MPa for 5 min and 15 min, respectively. The results showed that UHP treatment could reduce the enthalpy of starch gelatinization, thus significantly shortened the cooking time (P < 0.05). The hardness and chewiness obvilusly decreased, with a maximum decrease of 22.3% and 38.2%, respectively(P< 0.05). The sensory evaluation scoresof smell, luster, hardness, taste and of cold barley texture increased with the increase of treatment pressures. Compared with the untreated group, when the pressure was increased to 300 MPa and 600 MPa, the score of black barley hardness increased by 45 and 53 points, and the score of texture of cold barley increased by 16 and 22 points, respectively. Ultrastructure observation results showed that the UHP could destroy the arrangement structure and crystal structure of starch of black barley. The present study showed that the processing characteristics and food qualityof black barley could be effectively improved by UHP treatment.
Abstract:In this study, we utilize the high-throughput sequencing to profile while analyzing the bacterial communities and the quality of pickles with chitosan oligosaccharides. The results have indicated that chitosan oligosaccharides can effectively reduce the nitrite content, increased the total acid and amino acid nitrogen content in pickles. When the chitosan percentage in pickles was 1%, the nitrite content of the test group was (1.08±0.39) mg/kg (50%), the total acid was (7.42±0.25) g/kg(187%) and the amino acid nitrogen was (56.67±7.5) g/kg (132%). The microbial community structure was obviously affected by chitosan oligosaccharides. Further analysis indicated that Firmicutes and Proteobacteria were the dominant phyla in the samples during the fermentation. Among them, a total of 17 species of microorganisms were observed as the genus during the natural fermentation group. However, only 9 species of microorganisms were observed in chitosan pickles. At the middle stage of fermentation (3 d), the addition of chitooligosaccharide caused the dominant bacteria Exiguobacterium to be replaced by Lactococcus in the natural fermentation process. After 5 days of fermentation, Pantoea and Leuconostoc dominate the fermentation process in the naturally fermented samples, while the dominant genus in chitosan pickles is Lactococcus and continues to the end of the fermentation process. In summary, the results showed that chitosan oligosaccharide (COS) is expected to improve the growth of beneficial bacteria and the quality of pickles during the fermentation process.
Abstract:The effects of low temperature plasma voltage and treatment time on the texture and physicochemical properties of fresh-cut kiwi slices were studied to provide theoretical basis for the application of low temperature plasma technology in the non-thermal sterilization and preservation of fresh-cut kiwi slices. Using fresh-cut 'Hayward' kiwi slices as raw materials, they were treated with different times (70, 90, 110, 130, 150 s) and different voltages (5, 15, 25, 35, 45 kV) by low temperature plasma treatment. The hardness, brittleness, SSC, TA, soluble sugar, total phenol, chlorophyll, VC, POD activity, APX activity, L* value, a* value and b* value were determined, and analyzed the effect of different voltages and different times on the texture and physicochemical properties of fresh-cut kiwi slices. The results showed that low temperature plasma treatment had no significant effect on SSC, TA and color in fresh-cut kiwi slices (P > 0.05); the hardness, brittleness, soluble sugar content, total phenol, chlorophyll, VC, POD and APX activities of the samples in the treatment group all changed significantly (P < 0.05); POD and APX activities in the treatment group samples were significantly lower than the control group (P < 0.05); plasma treatment can delay the color change of fresh-cut kiwi slices. Results: Low temperature plasma treatment can better maintain the original color, taste and nutritional quality of fresh-cut kiwi slices, extend shelf-life, and can be used for non-thermal sterilization and preservation of fresh-cut kiwi slices.
Abstract:104 Lactic acid bacteria (LAB), with different colony morphology, were selected from traditional fermented food produced in different regions. Through the hydrogen peroxide resistance tests, 20 LAB with antioxidant capacity were screened and the ability to produce superoxide dismutase (SOD) were determined. The results indicated that C8 showed the highest SOD activity among 20 LAB, reaching 349.62 U/mg. Then gram staining, catalase experiments, and 16S rRNA gene sequence analysis were conducted to the identification of C8. Phylogenetic trees were constructed and C8 was determined as Lactococcus lactic according to the homology analysis. In order to improve the ability of Lactococcus lactic to produce SOD, the effects of fermentation temperature, initial inoculation amount, initial pH value and liquid volume on the activity of SOD were explored through single factor experiments, and the fermentation conditions were further optimized through orthogonal experiments. Finally, the optimal fermentation conditions were determined: fermentation temperature 37 ℃, initial inoculation volume 3%, initial pH 7.5, liquid volume 75 mL. The activity of SOD reached to 93.95 U/mL under the optimized fermentation conditions, which was 2.2 times than before, providing a foundation for the application of Lactococcus lactis in fermentation industry.
Abstract:The effects and correlation of different concentrations of ascorbic acid (AA) on enzymatic browning and quality characteristics of fresh lotus rhizome juice were studied. The changes of 5 enzymatic browning parameters, such as the browning degree, total phenol content, soluble quinone content, polyphenol oxidase (PPO) and peroxidase (POD) activity of lotus rhizome juice treated with 0(control group), 2, 4, 6, 8 mmol/L AA, and 6 quality indexes, such as whiteness, soluble solids, viscosity, pH value, protein and VC were measured, and the correlation between them was analyzed. The results showed that compared with the control group, with the increase of AA concentration, the total phenol content of lotus rhizome juice increased; the browning degree, soluble quinone content, PPO, POD enzyme activity decreased; the whiteness, viscosity, titratable acidity, VC content increased, the pH value, protein content decreased, and the soluble solid content basically remained stable. The correlation analysis showed that the parameters of enzymatic browning, such as total phenol content, soluble quinone content, PPO enzyme activity and pod enzyme activity, were closely related to the changes of quality indexes such as pH and whiteness. Generally speaking, the enzymatic browning degree and quality characteristics of lotus rhizome juice treated with AA were better than those of the control group, and within the scope of the study, the effect was better with the increase of AA concentration, and there was a close relationship between enzymatic browning and quality.
Abstract:Enzymes can catalyze the oxidative cross-linking of proteins, and there is molecular interaction between polysaccharides or polyphenols with proteins. In order to enhance the application range of casein(CA) edible film, the effects of transglutaminase (TG enzyme), epigallocatechin gallate (EGCG) and chitosan (CS) on film structure and properties were studied. The particle size and zeta-potential of the film solution were measured, and the mechanical properties, color and water vapor permeability of the composite film were characterized. The results showed that TG enzyme, EGCG and CS all had significant effects on the film structure, and the CAEC group with EGCG and CS added had the best performance among the groups of samples. After adding TG enzyme, the mechanical property of the film was improved, but the water barrier property decreased. After the addition of EGCG, the color of the film darkened, and the tensile strength was improved, but the toughness of film was greatly reduced. After the addition of CS, the tensile strength of the film increased, and its toughness also decreased. After adding both EGCG and CS, the film not only had good tensile strength but also exhibited certain water vapor barrier ability. It exhibited stronger free radical scavenging ability compared with other composite films, and its toughness decreased compared with the original casein film. This study introduced TG enzyme, EGCG and CS to the CA film, which gave it good mechanical properties, free radical scavenging ability and water barrier ability. Overall, this study has some guiding significance for the development of new protein-based edible film.
Abstract:In this work, sea bass was used as a raw material to study the effect of ultrasonic-assisted freezing and low-temperature quick-freezing at the same temperature (-20 ℃ and -40 ℃) on the ice crystal morphology of sea bass fillet and the physicochemical properties and structure of fish myofibrillar protein during freezing at -18 ℃. The results indicated that the -40 ℃ ultrasound-assisted frozen samples had a fast freezing rate, small and uniform distribution of ice crystals, and the highest solubility and content of total sulfhydryl groups compared to the other three groups, and could effectively reduce the degree of myofibrillar protein oxidation. At the same time, it could also improve the thermal stability of fish protein and better maintain the structure of sea bass protein.
Abstract:In order to extend the shelf-life of roast duck, the preservation effect of oregano essential oil or tea tree essential oil combined with MAP was investigated in comparison with the MAP (30%CO2/70%N2) as control. The meat color (L*, a*, b*), thiobarbituric acid reactive substance(TBARS), microbiological qualities and sensory attributes were measured, and microbial community was analyzed during chilled storage. The results showed that all treatments maintained the color stability, the sensory characteristics, and delayed the increase of TBARS (0.11~0.60 MDA mg/kg). However, both essential oil groups presented greater ability to retard the onset of bacteria spoilage, extending the shelf-life by 4 and 7 days, respectively. There was different microbial community succession in all treatments during storage. Notably, Vibrio spp., Photobacterium spp., and Brochothrix spp. were the dominant bacteria in all samples during chilled storage, indicated the inhibition of these dominant bacteria growth by essential oil may be the possible reason for the extension of the shelf-life.
Abstract:Flavor is an important factor affecting meat quality and consumption. It is mainly converted from some flavor precursors through complex chemical reactions. There is a significant correlation between mutton flavor and oleic acid (C18:1) content, and stearic acid (C18:0) content is positively correlated with the unpleasant flavor of mutton. In this paper, the visible/near infrared hyperspectral (400-1 000 nm) was used to quickly detect the content of characteristic fatty acids in flavor precursors in Tan Mutton. First select the spectral image after the mask as the region of interest, adopt six methods for spectral preprocessing, and compare and analyze to select the best preprocessing method. Combining successive projection algorithm (SPA), uninformative variable elimination(UVE) and variable combination cluster analysis (VCPA) extracts characteristic wavelengths and establishes a regression prediction model. Finally, the fatty acid content is quantitatively inverted on the sample image through the established optimal prediction model. The results show that oleic acid has the best modeling effect with MSC-UVE-MLR, and its RC=0.9099, RP=0.8759, and stearic acid has the best modeling effect with SNV-SPA-MLR, whose RC=0.8691, RP=0.8446. The use of spectral reflectance values combined with optimal model parameters achieves a good visual representation of the fatty acid content on the hyperspectral image of lamb samples, enabling quick and non-destructive testing of lamb quality in a more intuitive and clear way.
孟令缘,牛沁雅,廉鲁昕,黄巾凌,崔生辉,闫韶飞,李凤琴,杨保伟
Abstract:Salmonella and Staphylococcus aureus are prevalent in food and environment, and pose certain threats to food safety. During foodborne pathogens identification, appropriate identification method choosing can shorten time, save manpower and material resource, increase the trace ability. In this study, 210 Salmonella and 18 Staphylococcus aureus strains acquired in our previous study were further identified using 16S rDNA sequencing, MALDI-TOF-MS and VITEK automatic microbiological identification system. Identification level and efficiency of each method and the correlation among the identification results were statistically analyzed using R software(v3.6.1). The results indicated 210(100.0%) Salmonella strains could be identified into genus level via the 3 methods, 18 (100.0%) Staphylococcus aureus strains could be identified into species level by any of MALDI-TOF-MS and VITEK. When 16S rDNA sequencing method was used, 18 (100.0%) Staphylococcus aureus could be identified to genus level, and 15 (83.3%) strains could be identified into species level. In addition to 16S rDNA sequencing method, the other 2 methods had the same identification ability for Staphylococcus aureus and Salmonella, however, time usage of MALDI-TOF-MS was the shortest.
Abstract:In order to analyze the fungal communities structures and diversity in Shanxi aged vinegar Daqu, the total DNAs of the mature Daqu sample were extracted. And the Illumina MiSeq high-throughput sequencing technology combined with the fungal ITS sequence was used to analyze the fungal community structure and diversity of the Daqu. The results showed that, the fungus in Daqu were rich, including Ascomycota, Basidiomycota, and Zygomycota at phyla level. Ascomycota was dominant phylum, and its abundance was 94.74%. The proportion of Basidiomycota and Zygomycota were 2.70% and 2.51%, respectively. A total of 26 fungi were detected at a genus level in the mature Daqu from Shanxi aged vinegar. The main fungi were Candida (35.24%), Wickerhamomyces (11.11%), Aspergillus (27.57%), Alternaria (9.34%), Saccharomyces (2.11%), Cryptococcus (1.13%), Lichtheimia (1.14%) and Rhizopus (1.04%). These results not only systematically reflected the diversity of fungal communities of Shanxi aged vinegar Daqu, but also were valuable for revealing the fermentation mechanism of Shanxi aged vinegar.
Abstract:A total of 81 main aroma compounds were identified by liquid-liquid extraction (LLE) and headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS) in Moutai Baijiu. Among them, 69 aroma compounds were detected from the extracts extracted by LLE, mainly containing esters, alcohols and acids; a total of 57 kinds of aroma compounds were detected from the extracts extracted by HS-SPME, mainly containing esters, alcohols and aldehydes. Based on the dilution factor (FD) value and odor activity value (OAV) of aroma compounds, a total of 45 aroma compounds were identified as the key aroma compounds in Moutai Baijiu. The perceptual interactions among three key ester aroma compounds were further studied. The results of S-curve method and OAV method showed that ethyl hexanoate mixed with ethyl acetate or ethyl lactate had synergistic effect, and the addition effect occurred after the mixture of ethyl acetate and ethyl lactate. The results of Vector model showed that the mixture of these three aroma compounds may show a similar interaction effect in most cases.
Abstract:According to GB 4789.35-2016 National Food Safety Standard, Food microbiology examination: Lactic acid bacteria, the dilution and add sample can be conducted with two different kinds of tools, the pipette or the micropipettor. However, using these two different tools whether significantly affects the uncertainty of counting result, when counting Bifidobacterium of health food samples. The uncertainty of Bifidobacterium count of health food samples is measured in accordance with Evaluation and Expression of uncertainty in Measurement, publish by People's Republic of China State Administration of Quality Supervision, Inspection and Quarantine, JJF 1059.1-2012. The uncertainty is evaluated from the perspectives of the sample preparation, sample dilution, sample addition and the repetitive test, and using the pipette or the micropipettor in testing. For the sample diluted and added by the pipette, the uncertainty level U is 0.28 under 95% confidence level. The counted number for the Bifidobacterium is (2.2-8.1)×109 CFU/g which is equal to 9.35-9.91 after the natural logarithm. The confidence interval for the sample diluted by pipette is (2.2-8.1)×109 CFU/g. As for the sample diluted and added by the micropipettor, the uncertainty level U is 0.36 under 95% confidence level. The counted number for the Bifidobacterium is (2.7-14)×109 CFU/g which is equal to 9.43-10.15 after the natural logarithm. The confidence interval for the sample diluted by micropipettor is (2.7-14)×109 CFU/g. The uncertainty of count of Bifidobacterium in health food sample is about 90% caused by sample dilution, because the count of Bifidobacterium is huge, and dilution factor is big. The uncertainty by using pipette is a little bit smaller than using micropipettor, but a little bit bigger in the uncertainty A. The confidence interval using pipette is a little bit smaller than using micropipettor. Specially, the result of Bifidobacterium counting is significant differences in the same sample, using pipette and micropipettor.
Abstract:In order to understand the formation mechanism of metabolites and the influencing factors of each link in the fermentation process of job's tears mash, the changes of metabolites in the fermentation process of job's tears mash were studied. The results showed that 49 small molecular metabolites were detected during the fermentation of job's tears mash, and their contents were significantly different (P<0.05). There was little difference in the content of 17 free amino acids detected at the beginning of fermentation, only the content of threonine was slightly higher. After 24 hours of fermentation, the free amino acids began to increase significantly, and glucose and galactose also increased significantly. The changes of non-free fatty acids other than oleic acid and linoleic acid are not obvious. The content of unsaturated fatty acids such as oleic acid, linoleic acid, and 11-octadecenoic acid in free fatty acids is significantly reduced. The saturated fatty acids tend to increase, decrease, and increase. Microbial metabolism is the main cause of basic metabolic changes in the process of barley mash fermentation.
林 昕,王 丽,陈兴莲,邵金良,兰珊珊,魏茂琼,沙林杰,刘宏程
Abstract:This paper was to discriminate raw Pu-erh tea model from different storage times by the feature of polyphenols. The representative contents of 18 samples obtained from different storage times were analyzed by high performance liquid chromatography. Principal Component Analysis, Cluster Analysis and Partial Least Squares Discrimination Analysis model were applied to identify as the significant components which was visibly altered in the different storage of raw Pu-erh tea. The results showed that the catechin showed a gradually decreasing trend, the theaflavins showed a gradually increasing trend. Some components of flavonoid and flavonoid glycosides showed a downward trend while others showed an upward trend. The results of stoichiometric analysis showed that the raw Pu-erh tea samples from the same storage times could be aggregated, but the results of separation between the raw Pu-erh tea samples with different storage times were not good. It showed that obvious separation trend of the raw Pu-erh tea samples in the different storage of times by partial least squares discrimination analysis model. According to the Variable Importance Plot (VIP>1) in partial least square analysis model, combined with the content difference analysis, the result showed that gallic acid, kaempferol, theaflavin-3-gallic, epigallocatechin, epicatechin, gallocatechin and gallocatechin gallate had obviously change during the storage of the raw Pu-erh tea. To sum up, the result showed 7 components were used as signature by discrimination model.
Abstract:In order to understand the content and distribution of antibiotic resistance genes (ARGs) and intI1 in aquatic products, a quantitative real-time PCR method was established. Quantitative real-time PCR method was set up using recombinant plasmid containing the target genes as templates. And antibiotic resistance genes including tetA, sul2, blaPSE, cmlA, qnrS, aac(6')-Ib and intI1 were quantify by established qPCR methods. Results indicated that all the detected genes could be detected in the commercial Macrobrachium, Carassius auratus, Pelteobagrus fulvidraco and Larimichthys crocea. The detection limit of blaPSE was 6.6×104 copies/μL, and the detection limits of other ARGs were between 11.5 and 202 copies/μL. Among the four kinds of aquatic products, the relative abundances of blaPSE were the highest, ranging from 1.17×10-4 to 5.96×10-3, followed by the relative abundances of aac(6')-Ib ranging from 2.38×10-8 to 6.71×10-7. The obtained detection system can quantify 6 ARGs and intI1 gene in aquatic products simultaneously with the total bacterial DNA from the samples. The result could reveal the contaminated ARGs type and quantity of the commercial aquatic products, which is significant for controlling the ARGs pollution in aquatic products and ensuring the safety of aquatic food.
Abstract:At present, systematic analysis of the main pollution sources of blaTEM resistance genes in dairy products in Beijing had not been reported. In order to understand the main pollution sources of drug-resistant microorganisms and drug-resistant genes in dairy products. It had been taken as the research object that drug-resistant microorganisms in dairy products and corresponding farm environmental samples, Adenosine triphosphate(ATP) fluorescence detection and Polymerase Chain Reaction(PCR) methods were used to analyzed the distribution of milking contamination and build a molecular development tree to traced the potential pollution sources of blaTEM drug resistance genes. The results showed that the contamination risk was relatively high of some pipeline interfaces with more contact with the outside world in the milking process, and there were great differences in microbial drug resistance among different pastures, in which the detection rate of ampicillin resistant strains at 61.5%. The detection rate was as high as 95.3% of β-lactam antibiotic blaTEM resistance gene in environment and milk samples, and milking was the blaTEM genes potential link of pollution, and drinking water might be the main source of pollution. In summary, the pasture is a potential contamination link of drug-resistant microorganisms and blaTEM resistance genes in dairy products. There is a risk that blaTEM resistance genes will migrate along the production chain.
Abstract:This study has developed a sensitive and inhibitory surface plasmon resonance(SPR) immunosensor based on the Biotin-avidin system (BAS) for the detection of streptomycin (STR) residue in milk. Methods: STR hapten (STR-OVA) is prepared by direct cross-linking method, and coupled with biotin (BHNS) by activated ester method to obtain antigen (BNHS-STR-OVA), the antigen is combined with streptavidin (SA) on the SA chip. Based on the principle of immune suppression, the antibody for STR at a stable concentration was simultaneously bound by the STR and the antigen BNHS-STR-OVA. According to the SPR response value obtained under different STR concentretions, the inhibition ratio was calculated and the accurete, sensitivity and celerity analysis of STR in milk could be realized according to the inhibiting ratio curve. HPLC-MS was used to test the accuracy of the method. Results: the antigen was fixed at 6 μg; the mass concentration of antibody was established at 60 mg/mL; the detection limit (IC15) and the sensitivity (IC50) for STR using the proposed SPR immunosensor achieved to 0.37 μg/L and 1.65 μg/L; the detection process could be finished within 10 min, and one chip could be reused more than 90 times. Conclusion: BAS-SPR enhanced and suppressed SPR immunosensor has offered a simple, fast, low-cost detection strategy with high sensitivity for STR, which can meet the requirements of efficient detection of STR in milk samples.
Abstract:Lactic acid bacteria (LAB) bacteriocins are ribosomally synthesized peptides with antibacterial activity. Class II bacteriocins have a broad antibacterial spectrum and high antibacterial activity. However, large-scale production has not yet been achieved due to the low yield under natural conditions and few studies on the mechanisms of their biosynthesis and regulation. In order to deeply understand the biosynthesis and regulation mechanisms of class II bacteriocins, this paper reviewed biosynthesis gene structure, polypeptide structure, bactericidal mechanism, immune and regulatory mechanisms of class II bacteriocins. Besides, their application in food preservation was also summarized.
Abstract:Aflatoxin is a secondary metabolite produced by Aspergillus flavus and Aspergillus parasite, which widely exist in various spoiled foods. It is stable, high toxic, and easy to cause cancer, which can cause disease in livestock and humans, seriously endangering the health of animals and consumers. Under improper storage conditions, foods are susceptible to mold infection to produce aflatoxin. Therefore, accurate and rapid aflatoxin detection methods are essential to ensure food safety and consumer safety. The immunoassay has the advantages of strong specificity, high sensitivity, safety and reliability, and has become one of the most competitive detection technologies. This article summarized the research progress of rapid detection technology for aflatoxin based on immunoassay in recent years, mainly including colorimetry, fluorometry, immunochromatography, electrochemical method, quartz crystal microbalance and microcantilever. The basic principle, performance, domestic and foreign research situation, drawbacks of these method were reviewed. It maybe provides a strategy and basis for the development of new ideas.
Abstract:The high water content and high endogenous enzyme activity of aquatic products make it prone to spoilage and deterioration by microorganisms. Therefore, appropriate pretreatment method is of great significance for maintaining the quality of aquatic products during processing and storage. As an emerging non-thermal food processing technology in recent years, non-thermal plasma (NTP) technology has the advantages of non-destructive, high efficiency and short treatment periods. Besides, compared to traditional food processing technology, NTP can enhance the safety and quality of aquatic products through reducing the allergenicity and the use of nitrite, endowing NTP great potentials in the green processing of aquatic products. However, the free radicals generated by the overtreatment of NTP may induce the oxidative reaction of proteins and lipids, which may have a negative effect on the quality of aquatic products. Therefore, it is necessary to control the operating conditions of NTP during processing. In this review, the working principle of NTP technology are summarized, and the application of NTP in the sterilization and the quality improvement of aquatic products are also emphasized. Finally, the influence of NTP on aquatic product components (lipids and proteins) and their possible mechanisms are proposed, which may provide valuable references for the reasonable and effective application of NTP in the field of aquatic products.
Abstract:In recent years, with the upsurge of research interest of “plant-based meat”, more and more attention has been paid to plant-based protein, which is nutritious, economical and environmentally friendly. Wet fractionation is a common technology to obtain plant-based protein with high protein content. Unfortunately, wet fractionation involves consumption of large amounts of water and energy. Meanwhile, much of native functionality of protein is lost during processing. Dry fractionation of plant-based protein has simple steps and mild conditions, and the protein product has complete composition and low denaturation degree. In this paper, dry fractionation processes and influencing factors, the functional properties of protein isolates and application in food industry, as well as the existing challenges and future development trend of dry fractionation technology were reviewed.
Abstract:The processing of animal aquatic products are not only to solve the problems of freshness preservation and flavor improvement, but also to solve major food safety issues caused by allergic reactions of aquatic products. This paper reviewed the various allergens and their characteristics in animal aquatic products and introduces the research progress of food processing technology including the enzymatic hydrolysis processing, ultra-high pressure processing, irradiation processing, Maillard reaction, microbial fermentation in reducing allergens of aquatic products, and compare individual limitations. The application of combined technology is discussed reduce allergen with an aim to produce and process low-sensitivity or desensitization products.
Abstract:Gelatin is the denaturation product of collagen, which has good value in food, medicine and other industries. Most of the gelatin in the market is mammalian gelatin, but when it needs to be applicated, it will be hindered by problems like animal-derived virus and religious culture. Fish gelatin is not restricted by the above factors and it has similar functional characteristics to mammalian gelatin, so it is good to development and has a good application value. However, the gelatinization and rheology of fish gelatin are weaker than that of mammalian gelatin. In this paper, the differences between fish gelatin and mammalian gelatin were discussed, and the research progress of fish gelatin modification methods was emphatically discussed, so as to provide reference and basis for the improvement of fish gelatin properties.
Abstract:Fruits and vegetables as important diet, are rich in various nutrients, and they are also the ideal substrate for microbial fermentation. With the rise of “enzymes” product, fermented fruits and vegetables juice have attracted widespread attention. Previous studies by scholars found that some nutrients could not be synthesized by a single strain, and they had to be obtained by the co-fermentation with multiple strains. Compared with single strain fermentation, mixed strain fermentation had more complex metabolic mechanism and more abundant fermentation products. In this paper, the research progress of mixed strain fermentation juice was summarized, and the characteristics of fermentation strains and the influence mechanism of mixed strain fermentation on flavor, function and storage quality of fruits and vegetables juice were emphatically expounded. This review could provide some reference on the product development and quality improvement of mixed fermentation juice.
Abstract:This paper presents an overview of the research initiatives in recent years to address the issue of viscous liquid food adhering to packaging materials, which includes materials and coatings based on superhydrophobic surfaces, SLIPS and other research methods for reducing adhesion. The functional substances, preparation methods and anti-adhesion effects of different kinds of food packaging materials are discussed here. Also, some deficiencies in preparation and application and the development direction in the future are summarized in this paper.
Abstract:The construction of food safety standard system is an important means to improve food quality and support food safety supervision, and plays an important role in promoting the regulation of food production and operation behavior. In this paper, the literature analysis method, deductive analysis method and other methods from the current situation of China's food safety standard construction, the analysis of relevant experts and scholars on the existing system, to further summarize and analyze the problems existing in China's food safety standard system. In order to promote the healthy development of the food industry through standardization construction research and provide strong standard technical support for food safety production, circulation and other aspects, from the technology research, management mode and mechanism construction to propose the next step of the system construction direction.