The effect of L-cysteine on the heat-induced aggregation behavior of bighead carp myosin was studied using atomic force microscope (AFM). Changes in the solubility, surface?hydrophobicity and aggregate surface morphology of myosin samples with 5 mmol/L (pH 7.0) L-Cys added were measured after being treated at 25 ℃ for 30 min (control), at 90 ℃ for 30 min (one-step heating) or at 40 ℃ for 60 min and then at 90 ℃ for another 30 min (two-step heating). The results showed that L-Cys significantly increased the solubility of myosin in low ionic strength solutions under all three heating modes (P < 0.05). Under both high and low ionic strength conditions, the surface hydrophobicity increased significantly in the presence of L-Cys after one-step heating (P < 0.05), whereas for two-step heating, it increased significantly only under high ionic strength conditions (P < 0.05). Under both high and low ionic strength conditions, added L-Cys remarkably altered the surface morphology of myosin aggregates, loosening the aggregates and inhibiting aggregation. Conclusively, L-Cys affects the solubility and surface hydrophobicity of fish myosin, thereby affecting the aggregation behavior and altering the aggregate morphology.

In this study, we evaluated the protein emulsions formed during the enzyme-assisted aqueous extraction of soybean oil under different conditions of enzyme dosage (1% and 2%) and hydrolysis time (1, 2 and 3 h). The surface properties and structural characteristics of the emulsion protein/polypeptide were characterized by scanning electron microscopy, emulsion activity index (EAI), emulsion stability index (ESI), surface hydrophobicity (S0), amino acid analysis and Fourier transform infrared spectroscopy. The results showed that as the enzymatic hydrolysis proceeded, the protein in the emulsions changed from a dense and orderly network structure to a loose porous structure, the EAI and ESI gradually decreased; in addition, the proportion of hydrophobic amino acid increased and surface hydrophobicity (S0) decreased due to aggregation of the hydrophobic residues through their mutual interaction, blocking the hydrophobic groups. Fourier transform infrared spectra showed that the proportions of α-helix and β-sheet structure were reduced while the proportion of irregular structure increased with increasing degree of hydrolysis, indicating that the changes in intermolecular force caused by the enzymatic hydrolysis led to conformational changes of protein in the emulsions. The above results can largely emulsion instability during the enzymatic hydrolysis, which will provide theoretical support for understanding the mechanism of emulsion demulsification during the enzyme-assisted aqueous extraction of soybean oil.

Cinnamic acid based rice bran oil organogel, prepared with rice bran oil as solvent and cinnamic acid as gelling agent, was characterized by X-ray diffraction (XRD), fluorescence microscope and rheometer for the analysis of rheological behavior and morphological structure. The results showed that the oil binding capacity and melting point gradually increased with cinnamic acid concentration up to 10%, and then did not significantly increase at higher cinnamic acid concentrations (P > 0.05); the oil binding capacity rapidly increased to 93.62% with temperature up to 85 ℃, and the melting point also reached a high level. The two parameters remain at a high level with increasing cooling temperature from 0 to 5 ℃, and then significantly decreased to 93% at higher cooling temperatures (P < 0.05). Rheological analysis showed that the organogel with 10% of cinnamic acid formed by heating at 85 ℃ and cooling at 5 ℃ was a pseudoplastic fluid and that the relationship between apparent viscosity and shear rate was fitted with the power law equation. Moreover, in the experimental range of frequency sweeping, the storage modulus (G′) was obviously higher than the loss modulus (G′′), indicating that the organogel had a compact structure. Under the microscope, tiny and evenly distributed crystal structures with polymorphism were observed and the main crystal structure types were β and β’.

The effect of pH-shifting (pH 7.0, 2.0, and 11.0) combined with heat treatment (90 and 120 ℃) on the flexibility of soy protein isolate (SPI) and the relationships between flexibility and structure or emulsifying properties were investigated. The results suggest that the flexibility of SPI was increased with heating temperature under different pH-shifting treatment conditions. pH-shifting treatment from 2.0 or 11.0 to 7.0 contributed to the increased flexibility of SPI during heating as compared with that at pH 7.0. The heat treatment increased the flexibility more significantly at pH 11.0. At pH 7.0, the content of free sulfhydryl group was increased with heating temperature, indicating that the increase in the flexibility was related to the cleavage of the disulfide bond of SPI. Under pH-shifting treatment from 11.0, the dissociation of the SPI molecule occurred during the heating process, thereby increasing the flexibility. Under the experimental conditions, the flexibility showed a significantly positive correlation with the emulsifying activity and emulsion stability, with correlation coefficients of 0.945 and 0.936, respectively. UV spectroscopy and endogenous tryptophan fluorescence spectroscopy suggested that the SPI structure became more unfolded as the flexibility increased.

The main objective of this study was to improve the mechanical properties of zein films by glycosylation for producing plant-derived capsule shells. The results showed that zein, which was extracted with 70% ethanol, was the amino donor of glycosylation by amino acid analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimal conditions were determined as follows: ratio between zein and maltose syrup (MS), 11:1; pH, 9; ultrasonic power, 400 W; and time, 15 min. The tensile strength (TS) of the films produced under these conditions was 9.22 MPa, which was increased by about 2-fold compared with that (4.2 MPa) of unmodified zein films, and the degree of glycosylation (DG) was 34.96%. The formation of conjugates was verified by SDS-PAGE with both protein staining and carbohydrate staining. The appearance, shape, color, size, tightness, friability, mass loss during drying and ash content of zein-MS capsule shells met the requirements of the Chinese pharmacopoeia (2015 Edition).

This study investigated the effect of vacuum impregnation on the quality changes of turnip during the pickling process. A texture analyzer and a colorimeter were used to analyze the texture and color of pickled turnip, respectively. The physicochemical properties including sodium chloride, moisture, total acid, amino acid nitrogen and nitrite contents were measured by titration, oven-drying method and spectrophotometry. The volatile components were determined by gas chromatography (GC). The results showed that contents of sodium chloride, moisture, total acid and amino nitrogen gradually rose while the hardness increased at first and then decreased. In addition, the quality characteristics of vacuum impregnated turnip during the pickling process changed faster than turnip subjected to atmospheric impregnation. Vacuum impregnated turnip with a salt content of 20% changed fastest. The quality characteristics of pickled turnip reached steady state on the ninetieth day. The volatile components of pickled turnip produced by vacuum impregnation with 20% salt content and the traditional process were different; 27 and 31 volatile components were detected in the two samples, respectively. In conclusion, vacuum impregnation could improve the pickling speed and shorten the pickling time, but its use in conjunction with microbial fermentation is needed to maintain the flavor of pickled vegetables.

Alkali-soluble protein was extracted from defatted Pleurotus nebrodensis by ultrasonic-microwave assisted extraction. The optimal extraction conditions that provided maximum protein yield of (10.28 ± 0.62)% were determined as follows: extraction temperature 50 ℃, ultrasonic power 500 W, microwave power 24 W, NaOH concentration 0.09 mol/L, solid-to-solvent ratio 1:30 (g/mL), and extraction time 0.8 h. The functional properties and structure of the protein were studied. The results showed that the protein was most soluble at 70 ℃ and pH 8.5. It had the highest water-holding capacity of (325.27 ± 2.40)% at 60 ℃, and highest oil-holding capacity of (189.60 ± 2.58)% at 50 ℃. The foaming capacity, foam stability, emulsifying capacity and emulsion stability increased with the increase in protein concentration. The total amino acid content of the protein was 810.40 mg/g, as determined by ultra performance liquid chromatography (UPLC) analysis. The essential amino acid content was 322.86 mg/g, with histidine being the first limiting amino acid. Circular dichroism analysis showed that in the protein secondary structure, the contents of α-helix, β-sheet, and β-turn and random coil were 53%, 11% and 14%, and 23%, respectively. The protein consisted of four fractions with molecular masses of 48.9, 26.3, 16.4, and 10.9 kDa, respectively. Fourier transform infrared spectroscopic analysis showed obvious absorption peaks of the functional groups of the protein.

The goal of this research was to explore the antioxidant effect of α-tocopherol on lipid-protein systems from crab muscles. Changes in the sulfhydryl content, surface hydrophobicity, secondary structure and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profile of myofibrillar protein from the model systems were examined during storage at room temperature. The results showed that after oxidation for 12 and 24 h, fatty acid composition of crab lipids changed; a significant decrease was observed in the content of unsaturated fatty acids. The sulfhydryl content of crab muscles mixed with 24 h oxidized crab lipids decreased and the surface hydrophobicity significantly decreased; as the degree of oxidation increased, the contents of α-helix and β-sheet decreased, while β-turn content increased. Compared with the control group, the addition of α-tocopherol displayed a lower sulfhydryl content and a significantly slower rate of increase in the surface hydrophobicity, as well as an increase in α-helix and β-sheet and a decrease in β-turn. SDS-PAGE showed the inhibitory activity of the antioxidant against the degradation of myofibrillar protein. Optical density analysis using Gel Image System software showed that a significant difference existed between only a few bands, indicating that SDS-PAGE was a less sensitive tool than sulfhydryl content and surface hydrophobicity for evaluating the protein oxidation. The results in this study indicated that oxidized crab lipids could accelerate protein denaturation and the effect was dependent on the degree of oxidization; α-tocopherol had significant inhibitory activity against the consequent protein oxidation.

This study investigated the influences of curdlan (0.3%) and water addition (20%, 23%, 26% or 29%) on the quality characteristics of frankfurters. Cooking loss, emulsion stability, color, texture profiles, rhelogical properties, microscopic structure and sensory evaluation were measured. The mobility of water molecules in sausages was measured by low field nuclear magnetic resonance (LF-NMR). The results showed that for the control group without curdlan added, cooking loss and L* value significantly increased (P < 0.05), and emulsion stability, hardness, and overall acceptability decreased significantly (P < 0.05) with increasing water addition. However, for each addition level of water, frankfurters containing curdlan showed significantly lower cooking loss and significantly improved emulsion stability, hardness, springiness and overall acceptability than those without curdlan (P < 0.05). LF-NMR analysis showed that curdlan could decrease remarkably the relaxation time of water protons and increased the water binding capacity of frankfurters with higher amounts of water added. In addition, rheological analysis revealed that for each addition level of water, the addition of curdlan significantly increased the storage modulus (G’) and loss modulus (G”) were and decreased the phase angle tangent (tanδ) of meat batter at the end of heating, indicating that curdlan could improve the viscoelasticity of meat gels. At the same time, scanning electron microscope showed that higher levels of water addition loosened the structure of protein gels, while the addition of curdlan could improve the network structure of protein gels remarkably. The above results showed that although excessive addition of water would lead to deterioration in the quality of frankfurters, the addition of curdlan could reverse this deterioration. These findings can provide a theoretical basis for the application of curdlan in emulsified meat products.

The effects of NaCl concentration on the microstructure and physical properties of cured pork including color and water activity (aw), percentage volume change, longitudinal shrinkage rate (LSR) and transverse shrinkage rate (TSR) during hot air dehydration were studied and the correlation of these properties was analyzed. The results indicated that NaCl concentration mainly influenced a* and L* values of cured pork and reduced the color change, but the effects were limited. During the dehydration process, aw decreased faster with increasing NaCl concentration from 1% to 8%, while the effect was attenuated when NaCl concentration was greater than 8%. The volume change rate of samples with 1% NaCl was significantly higher than that of other samples (P < 0.05). The TSR of samples with 4% NaCl was significantly lower than that of other samples (P < 0.05). However, the LSR was not significantly affected by NaCl concentration (P > 0.05). The moisture content, aw, percentage volume change, LSR and TSR were not correlated with NaCl concentration. The changes in myofiber and myofiber membrane in cured pork were more pronounced with increasing NaCl concentration.

Ochratoxin A (OTA) is an important mycotoxin that contaminates a variety of agricultural products, thus posing a serious threat on the health of humans and animals. To find a new method for the biological detoxification of OTA in vitro, in this study, we attempted to isolate and screen intestinal bacteria from mice for OTA detoxification. Firstly, BALB/c mice were fed on a diet containing 210 μg of OTA per kg of body mass, and their faeces were collected for successive isolation of 12 strains capable of growing well at high OTA concentration using solid Luria-Bertani (LB) medium with a certain concentration of OTA. All these strains were cultivated in liquid LB broth for 20 h and their OTA-detoxifying abilities were then tested by high performance liquid chromatography (HPLC). The results showed that one strain, named YH7, exhibited strong ability to remove OTA with a maximum efficiency of 84.6%. Then YH7 was identified as Escherichia coli by its morphological features and 16s rDNA sequencing. This strain grew best at pH 7.5 and 37 ℃ with shaking at 200 r/min.

Two α-L-rhamnosidase genes, PhRha78E and PhRha78G, were amplified from the genome of Pedobacter heparinus by polymerase chain reaction (PCR), and ligated into the expression vector pET-28a. The recombinant plasmids were transformed into Escherichia coli BL21(DE3) for heterologous expression, respectively. PhRha78E and PhRha78G were expressed in the precipitate as the form of insoluble inclusion bodies. The production of target inclusion bodies were 0.42 g/g and 0.39 g/g bacteria, respectively. Enzymatic activity assay showed that both insoluble inclusion bodies could catalyze the hydrolysis of p-nitrophenol-α-L-rhamnopyranoside (PNPR). These results revealed that PhRha78E and PhRha78G were successfully expressed heterologously as catalytically active inclusion bodies (CatIBs) in E. coli. The optimum pH valuess of PhRha78E and PhRha78G CatIBs were 6.5 and 7.0, respectively. PhRha78E maintained 62% activity at acidic pH 4.8, while PhRha78G retained 72% activity at alkaline pH 8.6. The optimum temperatures of PhRha78E and PhRha78G CatIBs differed remarkably, which were 60 and 40 ℃, respectively. PhRha78E retained 69% activity at high temperature (70 ℃), but PhRha78G displayed 43% activity at low temperature (20 ℃). The enzyme kinetic parameters kcat of both α-L-rhamnosidases were 0.18 and 0.12 s-1, respectively, and Km values were 0.55 and 0.40 mmol/L, respectively. In this study, the two enzymes had different properties and could be used in different biotransformation fields to enrich α-L-rhamnosidase resource.

Bifidocin A, a novel bacteriocin with antimicrobial activity against a wide range of foodborne bacteria produced by Bifidobacterium animalis BB04, has a potential application as biopreservative in the food industry. The objective of this study was to investigate the antibacterial mechanism of action of bifidocin A against Gram-negative strain based on the level of protein expression. The difference in the expression level of total cell proteins in Escherichia coli CGMCC1.90 before and after treatment with bifidocin A was analyzed by using two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Functional classification and enrichment analysis of differentially expressed proteins were carried out based on gene ontology annotation analysis. Results showed that a total of 12 differentially expressed protein spots were found after treatment with bifidocin A, two of which were upregulated and ten of which were downregulated. Ten differentially expressed proteins were identified by MALDI-TOF, which were mainly involved in cell membrane composition, energy metabolism and stress response. These results suggested that bifidocin A might inhibit the growth of E. coli by altering the cell membrane structure, blocking the tricarboxylic acid cycle, reducing the availability of energy and adenosine triphosphate (ATP) and decreasing the resistance of the cells to external stress conditions.

In order to obtain the gene encoding rutin-hydrolyzing enzyme in Fagopyrum tartaricum (FtRHE), the enzyme was obtained from the seeds of the tartary buckwheat cultivar ‘Yunqian 1’ and its peptide mass sequence was determined by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) and then transcriptomic analysis and gene amplification were carried out. Results showed that molecular mass of RHE was about 62 kDa, and RHE was a β-glycosidase as evident from its peptide mass fingerprint. FSISWSR was a characteristic peptide fragment of RHE with mass-to-charge ratio of 914.428 6. Based on the DNA sequences obtained from the transcriptome of tartary buckwheat seeds, FtRHE gene was obtained by reverse transcription PCR amplification using specific primers. The open reading frame of FtRHE consisted of 1 539 bases, encoding 512 amino acids with amino acid residues 1–29 making upa signal peptide. Multiple sequence alignment showed that RHE shared a 54%–62% similarity with other β-glycosidases from various plants, indicating a low level of gene conservation. Bacmid-FtRHE was constructed by DNA recombination, and then transfected into insect cell Sf9. FtRHE was successfully expressed with higher rutin hydrolysis activity, indicating that the obtained FtRHE was the gene encoding rutin-hydrolyzing enzyme in tartary buckwheat seeds. This study may provide a theoretical basis for the breeding of buckwheat cultivars with high rutin content and without bitter or astringent taste and for the biotransformation of rutin into quercetin.

In this paper, the enzymatic properties of two aspartic proteases, cathepsin D (Cat D) and cathepsin E (Cat E), in sea cucumber were studied, and their involvement in the autolysis of sea cucumber was also investigated. Crude enzyme was extracted from the body wall of sea cucumbers with Tris-HCl buffer (pH 7.0). The specific substrate fluorescence method was used to determine the enzymatic properties of Cat D and Cat E. Results showed that Cat D and Cat E exhibited maximum activities at pH 5.0 and 60 ℃, and pH 4.0 and 40 ℃, respectively. Their activities kept stable at 20–40 ℃. Zn2+, Cu2+, Fe3+, and Mn2+ inhibited Cat D activity by 86%, 76.3%, 29.2%, 56.5% and 48.5%, respectively. Fe3+, Fe2+ and Cu2+ inhibited Cat E by 99.1%, 82.2% and 28.6%, respectively. Pepstatin A, Z-LLL, PMSF, and 1,10-phenanthroline inhibited the two proteases by 98%–99%, 65%–78%, 30%–35%, and 19%–23%, respectively. L-Cys, DDT and EDTA increased their activities by 30.4%–31.1%, 7.58%–9.64%, and 6.6%–7.9%, respectively. These results suggested that Cat D and Cat E were sensitive to metal ions and they were metal ion-dependent aspartic proteases, with cysteine and serine around the active center involved in modulating the enzymatic activities. Moreover, they might be involved in protein degradation during the autolysis of sea cucumber.

The objective of the present study was to develop mutant strains of Candida versatilis for the production of soy sauce. A mutant library of spt15 encoding the TATA-binding protein of C. versatilis was constructed by error-prone PCR and it was recombined into the expression vector YEplac195 and then introduced into uracil auxotrophic strains W303 and WM2 for screening purpose. The results showed that the four best mutant strains A1, A2, A3, and A4 were obtained through screening in solid medium with different salt concentrations. Compared with the control group, their salt tolerance was improved and soy sauces fermented by these mutant strains contained higher contents of amino nitrogen. The sequence of the recombinant plasmid showed base insertion, deletion and substitution as indicated by the sequencing of PCR products.

In this research, we analyzed the diversity of Lactobacillus isolated from banana plants (Musa nana Lour.), aiming to find new plant-derived strains of Lactobacillus for the silage and food fermentation industries in the future. The classical method was used for bacterial isolation and bacterial identification was performed by molecular biology techniques. In addition, the physiological and biochemical characteristics, growth rate and acid production rate of the isolates were evaluated and typical strains were selected for sequencing, 16S rDNA sequence analysis and phylogenetic analysis. The bacteriostatic effects of the selected strains were investigated on the common foodborne pathogens Escherichia coli, Salmonella, Bacillus subtilis and Listeria monocytogenes. The results showed that 44 suspected strains were isolated from?six parts of banana plants. Five typical strains were identified, namely 3 Lactobacillus plantarum (WFr6-4, WSt6-4 and WL7-3), 1 Lactobacillus pentosus (WFl5-3) and 1 Enterococcus casseliflavus (WR7-1). All the five strains showed significant antibacterial activity, with WL7-3 demonstrating the highest bacteriostatic effect. Thus, Lactobacillus was the?dominant?bacterium on banana plants, which had a strong bacteriostatic effect on all pathogens tested.

The effects of 8 amino acids supplemented at 50%, 100%, and 200% of the original amounts (Met, Phe, Trp, Arg, His, Ile, Leu, and Lys) on the fermentation performance of yeast during high gravity brewing (24 °P) were studied. The results showed that amino acid supplementations significantly increased wort fermentability and ethanol yield, promoted yeast cell growth, and improved yeast cell viability and beer color value. High gravity wort supplemented with 100% of amino acids exhibited better fermentation performance in terms of wort fermentability, ethanol yield, maximum number of suspended cells and cell viability, which increased by 6%, 17%, 11% and 10%, respectively, compared with those of the control. Furthermore, the color of diluted beer supplemented with 100% of amino acids was still bright, and exhibited the minimum color difference ΔE value, which was most similar to Qingdao draft beer.

Lactic acid bacteria (LAB) with inhibitory activity against quorum sensing of Aeromonas hydrophila were screened from traditional fermented vegetables using the filter paper method. The biofilm inhibitory activity of the LAB isolates was measured by a 96-well microtiter plate reader, and their effect on the biofilm formation of A. hydrophila was observed by light microscopy and scanning electron microscopy (SEM). The proteolytic activity, siderophore production, swarming and swimming were used as indicators to evaluate the effects of these quorum sensing inhibitors (QSI) on the virulence of A. hydrophila. In this study, a strain designated SCT-2, with inhibitory activity toward quorum sensing of A. hydrophila, was isolated from pickled cabbage from Jinzhou, Liaoning province. Crude metabolite extract from strain SCT-2 at 8 mg/mL inhibited the biofilm formation of A. hydrophila by 45.16%. Light microscopy revealed that the crude extract pronouncedly inhibited the biofilm formation of A. hydrophila. The SEM images also revealed that the crude extract not only decreased the production of biofilm of A. hydrophila, but also destroyed the biofilm. The secretion amount of proteolytic and siderophore in A. hydrophila treated with 8 mg/mL of the crude extract was decreased by 27.18% and 22.11%, respectively. In addition, the crude extraction degraded 32.27% of the N-acylhomoserine lactones (AHLs) of A. hydrophila. It also inhibited obviously the swarming and swimming of A. hydrophila. Strain SCT-2 was identified as Lactobacillus plantarum by physiological and biochemical tests and 16S rRNA sequence analysis. This study may pave the foundation for the development LAB-based biological agent for inhibiting quorum sensing of A. hydrophila.

In this study, the probiotic characteristics of Lactobacillus plantarum SWUN5815, a bacteriocin-producing strain isolated from yak, were evaluated by measuring its antibacterial activity, acid and salt tolerance, adhesion ability and effect on body mass gain and intestinal mucosal immunity in mice. The results showed that the strain had potent broad-spectrum antimicrobial activity against the foodborne pathogenic microorganisms of yak. The survival rates of this strain were 58.2% at pH 2, 86.9% at pH 3, 66.8% at bile salt concentration of 0.3%, and it had strong acid and salt resistance. Its adhesion rate to Caco-2 cells was 42%; it was sensitive to common antibiotics without drug resistance. L. plantarum SWUN5815 could significantly increase body mass gain in mice (P < 0.01), and also significantly enhance the expression level of intestinal SIgA in mice (P < 0.01). In summary, L. plantarum SWUN5815 can well adapt to the gastrointestinal environment, effectively improve body mass gain and immune function in mice, thus serving as a candidate probiotic strain.

In order to investigate the effect of different environmental conditions on the growth rate of Salmonella enteritis, the bacterium was cultured in a liquid medium in this study, and the Baranyi model and cardinal parameter model (CPM were established and evaluated as primary and secondary model, respectively. Temperature (30–42 ℃), pH (6.6–8.0) and water activity (aw, 0.976–0.997) were taken as independent variables to develop the cardinal parameter models and based on the Gamma concept, the independent effects of three environmental conditions were studied. The coefficient of determination was used to evaluate the goodness of fit of the primary model and the secondary models were validated by mathematical test values. The results the experimental data were well fitted with the Baranyi model (R2 > 0.900). The estimated values of Tmax, Topt, pHmax, pHmin, pHopt, aw(min) and aw(opt) were 44.51 ℃, 34.24 ℃, 8.14, 6.09, 7.55, 0.957 and 0.997, respectively. In the external validation with random data in the experimental range investigated, acceptable mean squared error (MSE, 2.311 × 10-5), bias factor (0.963) and accuracy factor (1.267) were obtained. These results indicated that the CPM we developed could accurately predict the growth rate of S. enteritis, which could provide a valuable theoretical basis for reducing the food safety risk caused by S. enteritis.

During the investigation of the prevalence of multidrug-resistant bacteria from food-producing animals, an mcr-1-carring multidrug-resistant strain of Proteus mirabilis was isolated and designated as F160211. Its drug-resistant profile and genotype were further investigated. The isolate was identified by 16S rRNA gene amplification and its drug-resistant profile was defined using a disk-based test and minimum inhibitory concentration (MIC) test. The drug-resistance genes were amplified by polymerase chain reaction (PCR). At last, the replication type of mcr-1-carring plasmid was analyzed. The results showed that the isolate F160211 was identified as P. mirabilis, and it was resistant to penicillin, first- and second-generation cephalosporins, macrolides, aminoglycosides, amphenicols, tetracyclines, sulfanilamides and rifamycins, and was intermediate to furans, polypeptide and quinolones, and was susceptible to third- and fourth-generation cephalosporins, monobactams, carbapenems, glycylcyclines and polymyxins. The drug-resistance genes that F160211 carried included blaCTX-M-1, blaCTX-M-9, blaTEM, blaOXA-1, mph(A), qnrS and mcr-1. The replicon PCR showed that mcr-1 was located in a IncI2 type plasmid, which was similar to pHNSHP45. These results showed that the mcr-1-harboring host bacteria have been extended from Escherichia coli and Salmonella to P. mirabilis and that the grim problem of multidrug-resistant bacteria from food-producing animals will pose a great threat to food safety and public health.

The purpose of this study was to investigate the effect of 732 cation-exchange resins on the activity of glutamate decarboxylase (GAD, EC4.1.1.15) in Enterococcus faecium and to establish a novel 732 cation-exchange resin-E. faecium cell suspension complex system for the biotransformation of L-glutamic acid (L-Glu) to γ-aminobutyric acid (GABA). The results indicated that 732 cation-exchange resins fully equilibrated in 0.2 mol/L sodium acetate buffer (pH 4.2) containing 0.2 mol/L L-Glu could significantly enhance the GAD biotransformation activity of E. faecium cells, increasing the yield of GABA by 32.30% as compared to the control group. A solid mixture of L-Glu and MSG (monosodium glutamate) (2:1) also could significantly improve GABA production by effectively regulating the pH value and maintaining the substrate concentration in the reaction solution. When the addition amount of the solid mixture was 30 g/L, the yield of GABA was improved by 52.40% as compared to that obtained without the addition of the mixture. Moreover, 732 cation-exchange resins and L-Glu/MSG (2:1) solid mixture could synergistically enhance the biotransformation activity of GAD in the cells. The optimal system was composed of 10 g of 732 cation-exchange resins, 10 mL of 0.2 mol/L sodium acetate solution containing 0.3 mol/L MSG (pH 4.2), 10 mL of 100 mg/mL E. faecium cell suspension and 30 g/L of L-Glu/MSG (2:1) solid mixture. When the system was incubated at 40 ℃ in water bath oscillator at 80 r/min, the yield of GABA was (4.57 ± 0.11) mmol, which was improved by 99.56% as compare to that ((2.29 ± 0.08) mmol) of the control group.

Zhayu, a traditional Chinese fermented fish product with low salt content, high nutritional value, unique flavor and long-term storability, is made from medium-sized (2–4 kg) grass carp (Ctenopharyngodon idella). In order to reveal the evolution of bacterial flora during the fermentation process of Zhayu, changes in the bacterial community structure at 10 different time points from day 0 to day 180 of fermentation were analyzed by Illmina HiSeq high-throughput sequencing technique. Moreover, changes in texture characteristics, amino acid composition and fatty acid composition were also monitored. The results showed that during the whole fermentation process, 130 genera in 90 families in 60 orders in 30 classes in 10 phyla were found. In the early stage of fermentation (day 0 to day 10), the bacterial community diversity was rich, and there were more than 40 families with a relative abundance greater than 0.1%. The dominant families were Staphylococcaceae (48%), Enterococcaceae (9.46%), Cenarchaeaceae (5.57%), and Rhodobacteraceae (2.12%). From day 10 to day 50 of fermentation, the relative abundance of Bacillusaceae increased from 0.017% to 1.35%, Lactobacillaceae from 0.018% to 0.88%, Leuconostocaceae from 0.0% to 0.61%, Streptococcaceae from 0.002% to 0.32%, and Moraxellaceae from 0.006% to 0.31%; while Flavobacteriaceae, Oceanospirillaceae, Pseudoalteromonadaceae and Alteromonadaceae decreased rapidly, and Cenarchaeaceae decreased to zero. The dominant bacteria during this period were Staphylococcus, enterococci and lactic acid bacteria. In addition, Enterobacteriaceae tended to rapidly growth after 50 days of fermentation, which had a negative impact on the product quality. At the same time, it was found that the texture quality and the contents of amino acids and saturated fatty acids decreased with fermentation time, showing a significantly negative correlation at 0.01 level (bilateral). Therefore, the proper control of fermentation time is very important to ensure the product quality and safety of Zhayu.

In the present study, we analyzed the genetic diversity of Bacillus cereus isolated from the production line of goat milk-based infant formula, and we compared their gene sequences with published sequences of isolates from milk products, aiming to detect the specific sequence types of the isolates in this study, which will provide useful information for further research on pathogenesis, prevalence, traceability, prevention and control. A total of 350 B. cereus isolates were obtained in this study, which had been subtyped to 12 clusters (42 isolates) by random amplification of polymorphic DNA (RAPD). The multiple locus sequence typing (MLST) profiles for 42 isolates were conducted based on the house-keeping genes glpF, gmk, ilvD, pta, pur, pycA, and tpi. The clonal complexes for these isolates were analyzed by the online Burst (n-4). The results showed that 42 isolates were detected and classified into 7 sequence types: ST-770 (4.8%, 2/42), ST-1000 (71.4%, 30/42), ST-1084 (9.5%, 4/42), ST-1348 (2.4%, 1/42), ST-1349 (2.4%, 1/42), ST-1350 (2.4%, 1/42) and ST-1351 (7.1%, 3/42). Clonal complexes 205, 142, 23, and two groups (ST-770 and ST-1351) were detected as well as two singletons (3L33 with ST-1349 and 3L47 with ST-1350). Four novel STs (ST-1348, ST-1349, ST-1350, and ST-1351) and four novel alleles (glp-253, glp-254, ilv-277 and pyc-199) were found.

The objective of this study was to isolate a microorganism capable of producing β-glucosidase to transform ginsenoside Rg3. A modified esculin agar medium was used to the strain from kefir fermented ginseng slurry and this strain produced black hydrolysis spots on the medium and was identified as Kluyveromyces marxianus by observing its colony morphology and sequence analysis of the 26S rDNA D1/D2 region. The fermentation conditions of ginseng for the transformation of ginsenoside Rg3 by Kluyveromyces marxianus were optimized using one-factor-at-a-time method and response surface methodology with a three-factor, three-level Box-Behnken design. A regression model was established with ginseng-to-water ratio (m/m), inoculum concentration and fermentation time as independent variables. The results indicated that the optimized fermentation parameters were as follows: ginseng-to-water 1:2.65, inoculum concentration 2.94%, and fermentation time 3 days. Under these conditions, the content of Rg3 was 3.31 mg/g and its transformation rate was 248%. In conclusion, the results of this study can provide theoretical data for industrial production of fermented ginseng.

Burkholderia contaminans B-1, isolated from the surface of apricots, is an antagonistic bacterium against Botrytis cinerea and other important postharvest pathogenic fungi in fruits and vegetables. In order to investigate the mechanism of action of B-1, we extracted a protein with antimicrobial activity after lysis of the cells. The protein was purified by bioassay-guided fractionation using fractional ammonium sulfate precipitation, DEAE-cellulose DE-52 ion-exchange and Sephadex G-100 gel filtration column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis suggested that the purified protein was homogeneous and its apparent molecular mass was 17.6 kDa. The protein was stable to heating and pH variations and was insensitive to organic reagents, protease and UV irradiation. Its inhibitory activity was increased by 12.5% in the presence 50 mg/mL Tween-80 as compare to that of the control (CK). The protein was sensitive to SDS and dithiothreitol (DTT).

A high-yield nattokinase-producing strain, designated as GULR06, was isolated from smoked cured meat produced by local farmers in Zhijin, Guizhou by measuring fibrinolytic activity of the enzyme produced by this strain. The strain GULR06 was identified as Bacillus subtilis based on morphology, physiological and biochemical characteristics, 16S rDNA sequence analysis and phylogenetic analysis. Natto was prepared by solid state fermentation with soybean as the major ingredient, and the changes of biogenic amines during the fermentation process were detected by high performance liquid chromatography (HPLC). The changes of nattokinase activity and biomass were also investigated. The results showed that cadaverine, putrescine, 2-phenethylamine, tryptamine, spermine, tyramine, spermidine and histamine were well separated by HPLC. The method showed good linearity with R2 greater than 0.994 0, and relative standard derivation (RSD) lower than 4%. The total content of biogenic amine during natto fermentation was in the range of 26.47–72.97 mg/kg, which was safe for human body. After fermentation for 54 h, the activity of nattokinase, (5 439.5 ± 149) IU/g, was the highest, the number of viable cells was 13 (lg(CFU/g)), and the total amount of biogenic amines was (56.18 ± 4.94) mg/kg.

This study was conducted to optimize the fermentation conditions of wheat bran for improved yield of polysaccharides using response surface methodology and to investigate the anti-inflammatory effects of the polysaccharides extracted from fermented wheat bran in Wistar rats injected with diquat. Solid-sate fermentation of wheat bran was carried out with a mixed stater culture of Saccharomyces cerevisiae and Bacillus subtilis. The fermentation conditions (temperature, time, inoculum size and solid-to-water ratio) were optimized using response surface methodology. The anti-inflammatory effects were evaluated by measuring the levels of TNF-α, IL-6, IL-2 and IL-1β in the plasma and liver of rats challenged with diquat. The results showed that a temperature of 35.4 ℃, a fermentation time of 52.7 h, an inoculum size of 10.4% and a solid-to-water ratio of 1:1.16 (g/mL) were found to be the optimal conditions to obtain a higher yield of polysaccharides of 130.21 mg/g. Diquat significantly increased the levels of TNF-α, IL-6, IL-2 and IL-1β in the plasma and liver of rats (P < 0.05), and oral administration of the polysaccharides extracted from fermented wheat bran significantly decreased these cytokine levels in rats under oxidative stress by diquat (P < 0.05) and returned them to normal with its increasing concentration. In summary, the polysaccharides from fermented wheat bran can exert anti-inflammatory effects.

The aims of this study were to explore the diversity of lactic acid bacteria (LAB) in traditional fermented milk in western China and to analyze the nitrite degradation capability of the dominant strains in order to provide useful data for their industrial application. The LAB isolates, isolated from different fermented milk products from different pastoral areas, were identified by 16S rDNA sequence analysis, and their nitrite degradation capabilities were comparatively determined by colorimetry. The results obtained showed that: 1) A total of 275 LAB strains were isolated from 104 fermented milk samples, belonging to 23 species in 6 genera. Lactobacillus helveticus was detected from the samples from Qinghai, Gansu, Xinjiang, Inner Mongolia and Tibet. Meanwhile, L. helveticus and L. plantarum were isolated from fermented yak milk, koumiss, shubat and milk dreg. 2) The nitrite degradation rates?of 275 LAB isolates were between 4.8% and 99.9%, 50% of which had good nitrite degradation capability with an average of over 91.3%. 3) The nitrite degradation capability of these LAB isolates varied depending on the sources and species. The effect of LAB from Tibetan was significantly higher than that of LAB from Qinghai, Gansu and Xinjiang (P < 0.05), and the effect of LAB from milk dreg was significantly higher than that of LAB from fermented yak milk and koumiss (P < 0.05). L. plantarum, L. paracasei and L. breris could stably and efficiently degrade nitrite, and L. plantarum had the strongest nitrite degradation ability among the 8 dominant strains. However, a significant difference in the nitrite degradation ability was found among some dominant strains (P < 0.05).

Streptomyces sp. FBKL4.005 was a heat-resistant strain isolated from Moutai-flavor Daqu, which could grow and metabolize at 37–55 ℃. In order to get insights into the metabolic mechanism and functional role of the strain in liquor-making for the exploitation and application of extremophiles in Daqu, whole genome sequencing of strain FBKL4.005 was performed on the Illumina HiSeq 2000 sequencing platform. A total of 67 771 429 reads and 2.47 G data were obtained. By de novo sequence splicing, 69 contigs were also acquired. The complete genomic size of stain was 9 454 406 bp with a GC content of 73.03%. After filtration treatment, 7.33 Mb effective data and 7 946 annotated genes were acquired. We conducted a comparative analysis among the GO, COG, KEGG, NR and TCDB database for genomic prediction and functional annotation. The acquirement of gene annotation information can provide an important foundation for further research on the metabolic pathways and mechanism of heat resistant Streptomyces sp. in Moutai-flavor Daqu.

Four strains of yeast, designated as S1, S2, S3 and S4, were isolated and purified from vineyard soils from Shanghai’s Fengxian, Chongming and Songjiang districts; Wuhan, Hubei province; Shaoxing, Zhejiang province; Heze, Shandong province; Tieling, Liaoning province. Phylogenetic tree analysis was carried out based on the 26S rDNA D1/D2 domain sequence. The results showed that S1, S2 and S3 were identified as Saccharomyces cerevisiae and S4 as Wickerhamomyces anomalus. The volatile aroma compounds of wines (W1, W2, W3 and W4) fermented by the four strains were determined by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS), and commercial yeast served as control. It was found that the volatile aroma compounds of wines fermented by theses isolates were different. Seven aroma compounds including ethyl myristate, 2-methyl-1-butanol, nonyl aldehyde, capraldehyde, acetophenone and 1-octadecene were exclusively detected in wine S1 rather than in control wine, and 10 aroma compounds in wine S2, such as ethyl myristate, ethyl palmitate, glycerol, n-hexanol, 2-methyl-2-hexanol and d-limonene. Phenylethanol and phenylethanol were significantly more abundant in W4 than in the control. Overall, W1 and W2 had stronger floral and fruity aroma. W3 contained higher content of ethanol. The acetic acid content of W4 was the highest.

In order to fully understand the change of flavor compounds during the fermentation of mechanically produced Shaoxing rice wine, samples were taken throughout the fermentation process for measurement of organic acids, polyphenols, amino acids and volatile components by high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). Principal component analysis (PCA) was used to discriminate among the samples from different stage of fermentation based on their characteristic flavor profilesss. The results showed that concentrations of organic acids, amino acids and higher alcohols increased rapidly in the first 48 hours, volatile phenols in the first 72 hours and esters in the first 120 hours, which indicated that the flavor components were mainly produced in the early fermentation stage. Bitter amino acids dominated the amino acid composition in all samples. The phenol composition was dominated by catechin in the early fermentation stage but epicatechin in late fermentation stage. PCA results demonstrated that the cumulative contribution rate of the first PCs to the total variance was 60.52% and that PC1 could clearly distinguish between the samples from the early and late stages. In addition, nonvolatile components could well explain the samples from different stage of fermentation.

In order to investigate the effect of freezing methods on the volatile flavor of grass carp meat, three different freezing methods, namely quick freezing, ethanol immersion freezing and refrigerator freezing, were used to pretreat the fresh dorsal meat and red meat of grass carp. A new type of material (MonoTrap) was applied as a solid phase extraction (SPE) stationary phase to extract the volatile compounds of fish meat. The volatile flavor components were analyzed and identified by electronic nose and gas chromatography-mass spectrometry (GC-MS). The odors of fresh and frozen grass carp meat could be clearly discriminated by electronic nose. Principal component analysis (PCA) showed that the differences in odor components between ordinary refrigerator freezing and fresh meat was maximum. By GC-MS analysis, 45, 33, 28 and 22 volatile compounds were identified in fresh, quick-frozen, ethanol immersion frozen and refrigerator frozen dorsal meat, respectively, and 49, 38, 33 and 25 volatile compounds were detected in fresh, quick-frozen, ethanol immersion frozen and refrigerator frozen red meat, respectively. The main volatile compounds were aldehydes and alcohols. Also, this study demonstrated that pentanal, hexanal, heptanal, octanal, 2-octenal, nonanal, 2-nonenal, decanal, 2-decenal, undecanal, 2,4-decadienal, hexanol, 2-octen-1-ol, 1-octen-3-ol, and xylene made an important contribution to the overall flavor of grass carp meat. In terms of the type and amount of volatile components, fresh fish meat was similar to the quick-frozen sample but dissimilar to the refrigerator frozen sample. Conclusively, quick freezing was more beneficial to maintaining the quality of grass carp meat, and the flavor of frozen fish meat was similar to that of fresh fish.

This study aimed to analyze the non-volatile taste compounds in soldier crab. Free amino acids, 5’-nucleotides, organic acids and inorganic ions were analyzed by an automatic amino acid analyzer and high performance liquid chromatography (HPLC) and inductively coupled plasma optical emission spectrometry (ICP-OES). The taste active compounds and their contribution were evaluated by taste activity value (TAV). Also, the synergistic effect between free amino acids and nucleotides was evaluated by equivalent umami concentration (EUC) (calculated as monosodium glutamate equivalent) method. The results indicated that arginine, histidine, glycine, glycine, alanine, glutamic, IMP, GMP and Na+ were the major contributors to the taste of crab meat. The EUC was 6.4 g/100 g, suggesting that the umami taste of soldier crab meat was very intense.

The volatile flavor components of cooked pig ear reheated by different methods (pasteurization, steaming, microwave and high temperature) were investigated by purge and trap-thermal desorption combined with gas chromatography-mass spectrometry. Thiobarbituric acid reactive substance (TBARS) value was used as an indicator to evaluate the degree of lipid oxidation. The results showed that a total of 58 flavor substances were identified in all reheated samples, the predominant ones being aldehydes and hydrocarbons. Hexanal, octanal, nonanal, decanal, (E)-2-decenal, (E,E)-2,4-decadienal, 1-octen-3-ol, phenol and eugenol contributed greater to the flavor of reheated pig ear based on their odor activity value (OAV). Principal component analysis (PCA) revealed that steam heating did not significantly change the flavor of cooked pig ear. The warmed-over flavor (WOF) profile of reheated cooked pig ear was dominated by linseed oil-like flavor with slighter metallic and rancid flavor. Pasteurization reheating significantly increased the contents of the key flavor factors responsible for WOF and TBARS value, while microwave heating avoided WOF formation better than other methods.

In the current study, the texture profile, nutrients, and flavor components of Gomphidius rutilus without worms (GW), G. rutilus infected by a small amount of worms (GS; infected area less than 50%), and G. rutilus infected by a large amount of worms (GL; infected area more than 50%) were explored. Texture analyzer, high performance liquid chromatography (HPLC) and electronic tongue sensory evaluation were used to evaluate the effects of varying degrees of worm infection on the texture profile, nutritional and flavor components of G. rutilus. The results indicated that the hardness ((1.65 ± 0.24) N) and chewiness ((3.50 ± 0.85) mJ) of GW were the highest among the three samples. GL had the highest moisture content ((819.92 ± 4.03) g/kg), whereas GW had the lowest value ((810.80 ± 3.48) g/kg). GS had the lowest fat and highest protein content, which were (2.58 ± 0.16) and (0.64 ± 0.05) g/kg, respectively. Monosodium glutamate-like (MSG-like) content was expressed as the sum of aspartic acid and glutamic acid. MSG-like content was higher in GL and GS than in GW. GL contained the highest amount of MSG-like components ((33.37 ± 0.08) mg/100 g), which was 1.72 and 1.51 times higher than that of GW and GS, respectively. The ?avor 5’-nucleotide content ((22.54 ± 1.43) mg/100 g) in GL was the highest, whereas that ((8.75 ± 0.20) mg/100 g) in GS was the lowest. The equivalent umami concentration (EUC) (calculated as MSG equinvlent) ranged from 3.34 mg/g in GS to 9.10 mg/g in GL. In conclusion, the effects of varying worm-infection degrees on the texture, nutritional and flavor components of G. rutilus should not be analyzed from a single point of view but from the three angles: firstly, the taste of GL is the most desirable from the point of flavor composition; secondly, the nutritional value of GS is the highest from a nutritional standpoint; and finally, the quality of GW is the best from the perspective of texture analysis.

To conveniently and nondestructively detect the soluble solids content (SSC) of kiwifruits, near infrared (NIR) spectra of ‘Huayou’, ‘Xuxiang’, and ‘Xixuan’ kiwifruits were obtained by using a portable system for SSC detection in kiwifruit based on a mini-spectrometer. The effective wavelengths were selected by different methods, and the effects of the selected characteristic wavelengths and the full spectra on the prediction precision of the models established by partial least square regression (PLSR) were compared. Slope/bias (S/B) algorithm was used to correct the model for ‘Huayou’ kiwifruits to predict the SSCs of ‘Xuxiang’ and ‘Xixuan’ kiwifruits. The results showed that the SPA algorithm could effectively extract the effective wavelengths. The root mean square error of predictions (RMSEPs) were 0.583, 0.678 and 0.646 °Brix for ‘Huayou’, ‘Xuxiang’, and ‘Xixuan’ kiwifruits, respectively. A total of 10 ‘Xuxiang’ and 50 ‘Xixuan’ samples were sufficient to improve the prediction performance of the corrected model with RMSEP of 0.966 and 0.875 °Brix, respectively. This study can offer useful information for developing a more accurate and portable miniature integrated detector for kiwifruit SSC.

The present research aimed to analyze and compare the chemical composition of volatile oils from five batches of galangal (the rhizome of Alpinia officinarum Hance) with different ages grown in Xuwen, Zhanjiang, Guandong province. The volatile oils were obtained by steam distillation and analyzed by gas chromatography-mass spectrometry (GC-MS), and their compounds were identified according to their retention indices and quantified by peak area normalization. The results showed that the chemical constituents of all volatile oils were found to be broadly similar. The content of the indicator constituent, 1,8-cineole, was almost consistent among these samples. The contents of terpenoids and oxide compounds?continuously increased in 1 to 4 year-old galangal but declined in 5-year-old galangal. The contents of alcohols were increased in 1 to 3 year-old galangal but decreased gradually in 4 to 5 year-old galangal. The contents of ketones, esters and aldehydes kept on rising year by year. The chemical composition of volatile oils from Xuwen grown galangal was stable and the one from 4-year-old galangal had the best quality. Earlier or later harvesting of galangal deteriorated the quality of volatile oil. Furthermore, the fingerprint was established by choosing 25 main characteristic constituents. The fingerprint was validated on three batches of commercial galangal samples and showed good performances in terms of stability, similarity and repeatability. The above results will provide the foundation for optimal harvest time and quality control of galangal.

The aroma quality of tea is closely related to the harvesting seasons. It is important to identify the difference in volatile compounds of green teas from different harvesting seasons. In our present study, headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to qualitatively and quantitatively analyze the volatiles compounds of green tea samples harvested in spring, summer and autumn. Subsequently, discriminant and cluster analyses of the volatile compounds in these green teas were carried out by using multivariate statistical analysis. The results showed that a total of 32 volatile components were identified, including alcohols, aldehydes, ketones, esters, alkanes, heterocyclic compounds and other substances. A model of partial least squares-discriminate analysis (PLS-DA) based on the relative contents of the identified compounds could effectively differentiate among the green tea samples from spring, summer and autumn seasons (fitting parameters R2Y = 0.903, Q2 = 0.570). A total of 12 key components, including cis-jasmone, benzyl alcohol, (E)-2-octenal, β-cyclocitral, 1-hexanol, 5,6-epoxy-β-ionone, (E,E)-2,4-heptadienal, nonanal, hotrienol, 2,2,6-trimethyl-cyclohexanone, 3-methyl-furan and 1-heptanol were identified. Furthermore, the results of cluster analysis based on the contents of the key components showed that cis-jasmone, aliphatic alcohol and benzyl alcohol in spring green tea, which generally have the characteristic aroma of grass as well as fruits and flowers, were remarkably higher than those in summer and autumn teas. The contents of aldehydes and ketones with sweet and fatty aromas were higher in green tea harvested in summer than those harvested in spring and autumn, among which (E,E)-2,4-heptadienal was the most abundant. Autumn tea contained the fewest number of key volatiles, and only hotrienol with grass, floral and woody scents was higher in most autumn green tea samples than in spring and summer green teas.

The change of flavor compounds in coix seed beverage during constant-temperature storage was investigated using solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and an electronic nose system. The key flavor compounds were identified by their relative odor activity value (ROAV). Principal component analysis (PCA) and cluster analysis (CA) were applied to discriminate between samples stored for different periods. The results showed that after storage at 37 ℃ for 35 d, a total of 39 major volatile compounds were detected in coix seed beverage. The relative contents of aldehydes, alcohols, ketones, hydrocarbons and esters were increased with storage time. 1-Octen-3-ol, nonanal, 3-methylbutanal, hexanal, octanal, 2-methylbutanal, 1-pentanol, octanol and 1-hexanol, with ROAV no less than 1, were the key odor compounds of coix seed beverage during storage. The volatile compounds of aldehydes, ketones, acids and alcohols, produced from the oxidation of coix seed oil, were the main flavor components of coix seed beverage. PCA and CA could clearly distinguish between coix seed beverages with different storage times, and the PCA plot showed no overlapping between the early and mid-late stages of storage and differences in volatile compounds. By CA analysis, the samples with different storage times were discriminated effectively and classified into six clusters. Based on PCA analysis, ROAV and the changes in the relative contents of volatile compounds, nonylaldehyde, hexanal, octanal, 1-octen-3-ol were the characteristic volatile compounds causing quality deterioration of coix seed beverage during storage.

This study aimed to select a high-quality edible fungus to be cooked into soup stock with chicken, which is rich in taste compounds and highly nutritious and tastes delicious. Ten common commercial edible fungi: shiitake mushroom (Lentinula edodes), Flammulina velutipes (Fr.) Sing., Pleurotus eryngii (DC. ex Fr.) Quel., Agrocybe aegerita, Tricholomataceae, Pleurotus geesteranus, white beech mushroom (Hypsizygus marmoreus (Peck) H. E. Bigelow), brown beech mushroom (Hypsizygus marmoreus (Peck) H. E. Bigelow), Armillaria mellea and flower mushroom (Lentinula edodes) were separately cooked with three-yellow chicken to obtain soup stocks. The contents of free amino acids, nucleotides and soluble solids in the broths were determined, and equivalent umami concentration (EUC) was calculated. Also, sensory evaluation was carried out. The broth with flower mushroom scored highest in terms of the weighted average of all above parameters, being rich in nutrients and tasty.

Commercial soybean power was hydrolyzed under alkaline conditions and then treated at low pressure levels. Our aim was to investigate the effect of alkaline hydrolysis under optimized conditions followed by low pressure processing on the conversion of soybean isoflavones to aglycones. Soybean isoflavones and aglycones were detected by high performance liquid chromatography (HPLC). The two processes were optimized using one-factor-at-a-time method and response surface methodology. In the alkaline hydrolysis process, hydrolysis time, temperature and pH were taken as independent variables, and the percentage increase in glucoside isoflavones as response variable. Subsequently, low pressure processing time, solid-to-solvent ratio and pressure were optimized for higher conversion rate of aglycones. The results showed that pH 11.5, a temperature of 63 ℃ and a hydrolysis time of 49 min were found to be the optimal conditions to obtain a higher increase in glucoside isoflavones of 286.40%. The conversion rate of aglycones was 16.65% when the hydolysate was processed for 10 min at 0.25 MPa with a solid-to-solvent ratio of 1:120 (g/mL).

Polyphenol oxidase from Huangguan pear was applied to catalyze the synthesis of theaflavin-3,3’-O-gallate (TFDG) from epigallocatechin gallate (EGCG) and epicatechin gallate (ECG). By using one-factor-at-a-time method, the levels of EGCG/ECG molar ratio, pH and reaction temperature were selected in the range of 3:1, 4.0 and 35 ℃, respectively. These reaction conditions were optimized by response surface methodology using a three-variable, three-level Box-Behnken design. The optimal synthesis conditions for TFDG were determined as follows: EGCG/ECG molar ratio 3.1:1, pH 4.1, and 37 ℃. TFDG was obtained from the reaction mixture by AB-8 column chromatography and high-speed counter current chromatography with a yield of 85.14% and a purity of 97%.

In this experiment, antimicrobial composite films were prepared from soy protein isolate (SPI) surface-modified nano-TiO2. The formulation was optimized using one-factor-at-a-time and orthogonal array design methods. Tensile strength (TS), breaking at break (EAB), water vapor permeability (WVP), light permeability, oxygen permeability and carbon dioxide permeability were used as response variables. Results showed that the optimum combination was determined as 4.5 g/100 mL of SPI, 2.0 g/100 mL of modified nano-TiO2 and 1.5 g/100 mL of glycerol. The contact angle of the formed film was 115.3°. Fourier transform infrared spectroscopy (FTIR) revealed that the spectral patterns of modified nano-TiO2/SPI composite films, nano-TiO2/SPI composite films and ordinary SPI films were similar in the range of 4 000-600 cm-1. The results of scanning electron microscope (SEM) and atomic force microscope (AFM) consistently showed that compared with nano-TiO2/SPI composite films and ordinary SPI films, the surfaces of modified nano-TiO2/SPI composite films were more compact and flatter and the surface performance was better; furthermore, the structural property was also improved. After being exposed to UV light at 365 nm for 6 h, the strongest bacteriostatic activity of the films containing 2 g/100 mL of modified nano-TiO2 against Escherichia coli and Listeria monocytogenes were observed with 91.14% and 92.81% inhibition, respectively. Owing to its good mechanical properties and antibacterial activity, nano-TiO2/SPI antimicrobial film has huge potential for application in food packaging.

A novel sensor based on CuHCF/Nafion/g-C3N4 nano-sheet nanocomposite has been developed for rapid and selective sensing of hydrazine hydrate. The nanocomposite was prepared by ultrasonic dispersion of the mixture of copper hexacyanoferrate (CuHCF), prepared from the reaction between potassium ferricyanide and copper nitrate, and C3N4 nano-sheet, obtained by high temperature pyrolysis of melamine followed by ultrasonic treatment of the g-C3N4 suspension, in aqueous ethanol containing Nafion. The morphology and structure of the materials were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD) and Brunauer-Emmett-Teller (BET) specific surface area analyzer. The as-prepared CuHCF/Nafion/g-C3N4 nanocomposite modified glassy carbon electrode showed excellent electrochemical performance towards the oxidation of hydrazine by means of cyclic voltammetry and chronoamperometry. Under optimized experimental conditions, the anodic current was linearly proportional to the hydrazine hydrate concentration in the range of 10 to 1 100 μmol/L. The detection limit of the method was as low as 1 μmol/L. Furthermore, results also showed that the sensor had good selectivity, stability and reproducibility.

A PCR with degenerate primers method was established for the detection of genetically modified crops with cry1A gene according to its conservative region sequence. The cry1A genes, cry1Ab, cry1Ac, cry1Ab/Ac, cry1A.105, and mcry1Ac, the most frequently used genes in insect-resistant transgenic crops, are commonly used as targets for screening genetically modified ingredients. In the present work, using Vector NTI Advance 11.5 software, we aligned the primers used for more than 20 conventional or real-time PCR methods for detecting the cry1A genes with the whole sequences of 11 collected cry1A genes. The results revealed that all of the primer pairs could not be completely matched with the cry1A gene sequences. There were more than three mismatched bases for each primer, and the mismatching occurred frequently at the 3’-end of the primer, which indicates that the reported cry1A gene detection methods are only suitable for some specific target genes. Based on the nucleotide sequence analysis of 11 cry1A genes from transgenic crops such as MON810, Bt11 and Bt176, a pair of degenerate primers were screened out to develop a PCR assay using the conserved nucleotide sequence at the 5’-end as template. The PCR assay developed showed high specificity and sensitivity with a relative limit of detection (LOD) of 0.1% and could offer an efficient method for screening cry1A genes in genetically modified crops.

A rapid, accurate, highly sensitive dual-wavelength Rayleigh light scattering method for quantifying Cu(II) was established. The Rayleigh light scattering spectral characteristics, the appropriate reaction conditions and the influence of coexisting substances were studied. At the maximum Rayleigh scattering wavelength of 528 nm and the second major Rayleigh scattering wavelength of 361 nm, the mass concentration of Cu(II) in the range of 0.003 to 0.21 mg/L was directly proportional to the Rayleigh light scattering quenching degree（ΔIRLS）of the system. The limits of detection (LOD) were 9.81 ng/mL (RLS, 361 nm), 8.62 ng/mL (RLS, 528 nm) and 4.61 ng/mL (DWO-RLS, 361 nm + 528 nm), and the limits of quantitation (LOQ) were 0.16 mg/100 g (361 nm), 0.14 mg/100 g (528 nm) and 0.077 mg/100 g (361 nm + 528 nm), respectively. The method can be used for the rapid determination of copper in various foods.

A method for the simultaneous separation and determination of nine species of arsenic, selenium and chrome in water was established by microwave-assisted extraction combined with high performance liquid chromatography-inductively coupled plasma tandem mass spectrometry (HPLC-ICP-MS/MS). Samples were extracted with 0.5 mmol/L EDTA buffer (pH 7.5) at 100 ℃ for 2 min and then the extract was separated by Hamilton PRP-X100 anion exchange chromatography. The mobile phase was adjusted to pH 7.5 with aqueous ammonia for gradient elution by using 4 mmol/L NH4HCO3 as mobile phase A and 0.3 mol/L NH4HCO3 as mobile phase B. The nine element species including arsenic betaine, arsenite, dimethyl arsenate, monomethyl arsenate, arsenate, selenite, selenium, trivalent chromium and hexavalent chromium were successfully separated by the developed method. The ICP-MS instrument with two independent mass screening filters could effectively eliminate mass spectral interference. In the case where organic matters such as methanol were not used, a new target ion was generated by reacting oxygen with the target ion, thereby reducing the background equivalent concentration and improving the sensitivity. The detection limits (LODs) of the nine analytes were 0.023, 0.056, 0.032, 0.064, 0.061, 0.091, 0.089, 0.21 and 0.18 μg/L, respectively, which are well below the standard limit. This method displayed good linearity, precision (0.23%–11.9%) and recovery rate (72%–119%), all of which meet the analytical requirements. The establishment of this method can provide a useful tool for the speciation analysis of arsenic, selenium and chrome in food.