This study aimed to examine the effects of different processing methods and processed products on the collagen content of velvet antler (Cornu Cervi Pantotrichum). The contents of four amino acids constituting collagen, i.e., hydroxyproline, proline, glycine and alanine, in different samples of velvet antler, were determined using an automatic amino acid analyzer and then converted into collagen content. The results showed that collagen contents in wax slices, powder slices, gauze slices and bone slices of freeze-dried velvet antler and whole freeze-dried antlers were 37.43%, 30.01%, 32.16%, 40.81% and 36.47%, respectively. Collagen contents were 31.40%, 31.59%, 35.69%, 44.07% and 39.44% in their boiled counterparts; 43.89%, 39.04%, 45.94%, 46.23% and 42.24% in their exsanguinated counterparts; and 37.84%, 32.24%, 35.11%, 43.62% and 37.64% in their unexsanguinated counterparts, respectively. Collagen contents in three powdered samples of unexsanguinated, boiled velvet antler were 25.51%, 24.93% and 26.12%, and increased to 26.93%, 28.89% and 29.08% when soaked with 40%, 50% and 60% ethanol, respectively. Collagen contents in boiled antler velvet were significantly higher than in freeze-dried antler velvet (except for wax slices). Collagen contents in antler velvet increased after exsanguination. High collagen content was found in wax slices, and collagen contents in powder slices, gauze slices and bone slices increased in this order. The collagen content of antler velvet slices soaked with ethanol was significantly higher than that of antler velvet powder without soaking treatment, and increased with ethanol concentration.

Crude polysaccharide (CP) was obtained by hot water extraction from the stalk residue of Pleurotus eryngii. The molecular mass distribution of CP was assayed by the combined use of gel permeation chromatography (GPC), differential refraction detector (RID), and multi-angle light scattering (MALLS). The monosaccharide composition was assayed by gas chromatography (GC). The glycosyl linkages were analyzed by gas chromatography-mass spectrometry. The antioxidant activity was measured by the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation assay. The antitumor activity was assayed by both in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and in vivo methods. Results showed that glucose was the predominant monosaccharide (84.4%) of CP; the molecular mass of CP was widely distributed and mainly composed of 4 peaks (i.e. 3.816 × 107, 2.010 × 106, 4.572 × 105 and 1.849 × 105 Da). The glycosyl linkages mainly consisted of 1,3-linked (42.7%) and 1,6-linked (35.3%) glucose residues. At a concentration of 5 mg/mL, the crude polysaccharides exerted 70.9% scavenging rate against ABTS radical cation. In addition, the in vivo test showed that CP could significantly inhibit 39.84% of the growth of transplantable U14 cervical cancer in mice at a dose of 200 mg/(kg·d) after 12 days of intragastric administration.

Oleogels were prepared by the formation of composite gels from natural phospholipids in virgin soybean oil with added β-sitosterol. The effects of the amount of β-sitosterol on the hardness, thermodynamic properties, solid fat content (SFC), X-ray diffraction (XRD) pattern and microstructure of oleogels were investigated. The results showed that gel behavior could occur at 20 ℃ when the amount of β-sitosterol was no less than 12%. Both the hardness and SFC of oleogels increased with the addition of β-sitosterol, and the hardness changed significantly at different storage temperatures. The amount of β-sitosterol added had a great influence on the thermodynamic characteristics, and the molten crystals all showed single peaks. The oleogels mainly formed β crystals, which were long needle-like and evenly distributed. With β-sitosterol addition, the density of oleogel crystals increased, the size became smaller, and the three-dimensional network structure formed was more compact, along with a gradual increase in oil retention ability, indicating that β-sitosterol can combine with natural phospholipids in virgin soybean oil forming oleogels, which contained no trans fatty acids (TFAS), were rich in natural nutrients, and had desirable gel hardness and good structural stability.

The type I L-asparaginase (BlAase 1) gene from Bacillus licheniformis was cloned and expressed in Escherichia coli. The recombined L-asparaginase had an activity of (63.64 ± 3.18) IU/mL, and its specific activity was 945.79 IU/mg. BlAase I exhibited maximum catalytic activity at pH 10.0 and 45 ℃. The relative enzymatic activity was above 90% at 45 ℃ for 12 h. In addition to L-asparagine, BlAase I showed catalytic ability to D-asparagine, which represented 23.38% of L-asparaginase activity. The Km value of BlAase I was 12.19 mmol/L, and the Vmax value was 2.69 IU/mL. Moreover, BlAase I had the ability to mitigate acrylamide formation in French fries. Compared with the untreated group, the acrylamide content in samples treated with BlAase I was effectively decreased by 58.39%. These results indicate that the novel type I L-asparaginase BlAase I has the potential for application in the food processing industry.

The effects of surfactants, Span and Tween, on pullulan production by bioconversion using whole cells of Aureobasidium pullulans were investigated. The pullulan biosynthesis capability of these cells was increased by 46.5% and 32.9%, respectively, when Span 80 (20 g/L) and Tween 80 (5 g/L) were added individually into the bioconversion broth. The combination of the two surfactants further improved the yield and efficiency of pullulan production. Based on the determined physiological and biochemical parameters, Span 80 and Tween 80 were found to improve the permeability of the cell membrane, increase the activities of the key enzymes involved in pullulan biosynthesis, elevate the levels of intracellular uridine diphosphate glucose and energy substance ATP, and accelerate the rate of ATP regeneration, promoting the metabolism of substance and energy and ultimately resulting in improvement in the yield and efficiency of pullulan production. The results presented in this study partly elucidate the physiological mechanism underlying the increase in efficiency of pullulan production by surfactants and also provide a technical basis for efficient production of other analogous microbial polysaccharides.

This study determined the effects of ferulic acid on the growth, gene expression and tyramine accumulation of Enterococcus faecalis XL-M66 and E. faecium XL-M76. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to analyze the expression of tyramine synthesis-related genes in the tyrosine decarboxylation pathway in E. faecalis XL-M66 and E. faecium XL-M76. Additionally, the accumulation of tyramine during 48 h culture was monitored by high performance liquid chromatography (HPLC). Results showed that ferulic acid had little effect on the transcription of the tyrosine decarboxylase (tyrDC) and tyrosine/tyramine permease (tyrP) genes (P > 0.05) in the absence of the substrate tyrosine, but promoted the transcription of the tyrosyl-tRNA synthetase (tyrS) gene (P < 0.05). On the contrary, in the presence of tyrosine, ferulic acid had little effect on the expression of the tyrS gene (P > 0.05), but it could significantly (P < 0.05) inhibit the expression of the tyrDC and tyrP genes. Moreover, ferulic acid significantly (P < 0.05) inhibited the growth of E. faecalis XL-M66 and E. faecium XL-M76 and reduced tyramine production by 27.0% and 19.9%, respectively.

In this study, in order to further understand the structural properties of microbial milk clotting enzyme (MCE), we firstly designed the whole gene sequence of MCE (I3EB99) from Bacillus methanolicus according to the amino acid sequences obtained from the GenBank and the codon preference of Escherichia coli, and then constructed a prokaryotic expression vector. The fusion protein was expressed in E. coli BL21 (DE3), and it was subjected to His-tag specific affinity purification. The three-dimensional spatial structure of the purified MCE was studied by bioinformatics methods. Results showed that the recombinant MCE was expressed at a level 0.7 mg/mL with milk clotting activity (MCA) of (15 870 ± 1.17) SU/g, proteolytic activity (PA) of (263.81 ± 0.94) U/g and MCA/PA ratio of 60.16, which met the requirements for cheese processing. Studies on its structural properties showed that the MCE exhibited hydrophobicity and it contained a transmembrane structure and a signal peptide; the α-helix secondary structure was less abundant than β-sheet in the MCE, which was unstable and easily degraded during the separation and purification process. The MCE was homologous to an unknown protease from B. methanolicus, and its three-dimensional structure had the highest similarity to the template protein 2ra1.1.A in the PDB protein database. By studying the structural characteristics of MCE from B. methanolicus, we have established the theoretical basis for an in-depth understanding of the mechanism and function of the MCE.

In this study, an electronic tongue was used to evaluate the taste profiles of pasteurized milk samples stored at five different temperatures for different periods. Sensory evaluation was also carried out on these samples, and bacterial?diversity?was analyzed by high-throughput sequencing. Furthermore, statistical software was used to perform principal component analysis and correlation analysis on the taste values and the bacterial species, aiming to uncover the influence of storage temperature on the sensory quality and microbial diversity of pasteurized milk and the relationship between the main residual microorganisms in pasteurized milk and its sensory quality during storage and transportation. The results showed that pasteurized milk could maintain good milky aroma within 3 d of storage at 0, 4 or 10 ℃, while its sweetness significantly dropped when stored at 15 or 25 ℃. The bacterial count increased with the increase of storage temperature and storage time, leading to the fermentation and spoilage of pasteurized milk, and the bacterial diversity and community structure were significantly correlated with the sensory quality of pasteurized milk. This study also found that Aeromonas, Cronobacter, Serratia and Costridium had the least influence on the fresh taste, and showed negative correlations with the bitterness, saltiness and sweetness of pasteurized milk. In addition, all other species showed significantly positive correlations with the bitter taste. Therefore, these bacteria may be the key factors leading to the deterioration and spoilage of milk products. This study provides a theoretical basis for better understanding the interaction between bacterial species composition and quality changes, as well as for the rapid and accurate determination of quality changes in dairy products.

This study investigated the effects of two quorum sensing inhibitors, D-ribose and cinnamaldehyde, on the microbial community structure in Sichuan pickle by high throughput sequencing and it further analyzed their effects on the physiological behavior on specific spoilage bacteria isolated from Sichuan pickle. The results revealed that D-ribose significantly increased the relative abundance of Lactobacillus from 19.38% (the second highest) to 80.10% (the highest). In addition, Staphylococcus equorum (OTU4), Lactobacillus ginsenosidimutans (OTU6), Propionibacterium acnes subsp. acnes (OTU8) and Lactococcus lactis subsp. lactis (OTU9) were not detected in D-ribose-treated samples. In contrast, cinnamaldehyde had no significant effect on the microbial community structure. Growth curves showed that D-ribose had no influence on the growth of specific spoilage bacteria but cinnamaldehyde inhibited their growth. Moreover, they both significantly decreased the biofilm formation of spoilage bacteria. Compare with their control counterparts, after being treated with D-ribose and cinnamaldehyde, the biofilm formation of Pantoea calida was reduced to 11% and 10%, respectively; the biofilm formation of Pantoea ananatis was reduced to 21% and 17%, respectively; the biofilm formation of Pantoea anthophila was reduced to 11% and 9%, respectively; the biofilm formation of Staphylococcus saprophyticus was decreased to 11% and 15%, respectively. This study provides useful information for further exploration of the regulatory mechanism of the microbial diversity in Sichuan pickle, and also provides new ideas for developing new preservation technologies for fermented foods.

A total of 40 strains of Bacillus were isolated from 10 naturally fermented soybean pastes from 8 regions in northeastern China, including Qiqihar, Daqing and Shenyang. Strains QQHE-2 and DQ1-3, with good inhibitory effects (83.42% and 46.83%, respectively) on Penicillium, were obtained by plate confrontation method and agar column method. The two strains were identified as Bacillus subtilis by 16S rRNA gene analysis. It was found by scanning electron microscopy (SEM) that the fermentation supernatant of QQHE-2 changed the morphology of Penicillium hyphae, making the spores become dry and winkled and reducing the number of spores. Upon pH and temperature adjustment and treatment of the fermentation supernatant with protease, it was found that the acid and heat resistance of the antimicrobial substance were poor, and the inhibition rate against Penicillium was significantly reduced by protease treatment. It can be confirmed that the antimicrobial activity was attributed to the presence of a protein or peptide. The molecular mass of the antimicrobial substance produced by QQHE-2 strain was about 35 kDa as revealed by sodium dodecyl sulfate-polyacrymyl gel electrophoresis (SDS-PAGE).

Psychrotolerant probiotic lactic acid bacteria were isolated from the guts of 7 cold-water fish species in Xinjiang and were analyzed for genetic structure differences according to the sequences of their 16S rRNA gene by rep-PCR fingerprint typing technology. The results showed that 15 strains of Carnobacterium were obtained, including 4 strains of C. maltaromaticum, 10 strains of C. divergens and 1 unidentified strain of Carnobacterium spp.. By the Oxford cup method, it was found that the metabolites of 8 of these strains had different inhibitory effects on three pathogens, and the strongest antibacterial effect was observed against Listeria monocytogenes. The fermentation supernatants of the 8 strains were subjected to exclusion of organic acids and hydrogen peroxide or protease treatment. After protease treatment, all the supernatants except BS-JYC-3 completely lost their antibacterial activity, indicating that the bacteriostatic substance in the fermentation supernatants may be a bacteriocin. Drug susceptibility tests showed that all of the 8 strains were very sensitive to ampicillin, minocycline and chloramphenicol, and moderately sensitive to gentamicin, tetracycline, rifampicin and teicoplanin.

The effects of repeated heat stress at 50, 60 or 70 ℃ and different growth temperatures (10, 28, 36 and 45 ℃) on the resistance of Escherichia coli O157:H7 ATCC 43889 to high temperature of 80 ℃ were studied. The change in D value (time necessary to kill 90% of microorganisms) was determined during repeated heat stress, and the changes in colonial and cellular morphology were observed. The survival rate of this strain, grown to the stationary phase at different temperatures, was measured at 80 ℃. The thermal death curves were fitted to the Weibull model. The experimental results showed that the heat resistance of E. coli ATCC 43889 was increased by heat stress at each temperature tested. The D values of the passaged cells subjected to heat stress at 50, 60 or 70 ℃ 10 times were 1.88, 2.38 and 8.18 times higher than those undergoing one cycle of heat stress, respectively, D value was increased with increasing number of heat stress cycles. This demonstrates that heat stress at a higher temperature resulted in a larger D value and stronger heat resistance. After heat stress at 60 or 70 ℃, significant variations in colonial and cellular morphology were found relative to the control group. The thermal death curve at 80 ℃ also showed that the higher the stress temperature, the stronger the heat resistance (P < 0.05). The heat resistance was increased with the increase in growth temperature from 10 to 45 ℃ (P < 0.05). The Weibull model could well fit the heat resistance data after heat stress at 50, 60 or 70 ℃ for 10 times and growth at 10, 28, 36 or 45 ℃. The heat resistance increased with increasing either stress temperature or growth temperature. In conclusion, certain heat treatments and incubation temperatures can cause enhanced heat resistance and morphological changes in E. coli ATCC 43889.

A β-mannanase gene, nsMan5B, was cloned from the thermophilic fungus Neosartorya sp. HBFH9 and successfully expressed in Pichia pastoris. Sequence analysis indicated that the complete DNA sequence of nsMan5B was 1 491 bp in length (containing 2 Introns). The cDNA sequence of nsMan5B was 1 371 bp in length, which could encode a protein of 456 amino acids with a molecular mass of 49 kDa. Structural analysis indicated the presence of a putative signal peptide, a carbohydrate-binding module of family 1 (CBM 1), a linker region and a catalytic domain of GH5 in NsMan5B. The recombinant NsMan5B was optimally active at pH 4.0 and 60 ℃, and had good stability over the wide range of pH 2.0–10.0 and at 50 ℃ or below. The effects of metal ions and chemical reagents on its enzymatic activity were different. The enzymatic activity was increased by 271%, 123% and 100% in the presence of K+, Mg2+ and Cu2+, respectively. With increasing carbon chain length and concentration of alcohol, the inhibitory effect on NsMan5B activity was markedly enhanced. Its enzymatic activity was reduced by 86% by n-butanol (2.5%, V/V). It was observed that NsMan5B was effective in the clarification of orange juice as well as persimmon, apple, peach and grape juices, whose clarity was increased by 31.8%, 7%, 4% and 4%, respectively. Consequently, it was concluded that the NsMan5B could be successfully used in the fruit juice industry.

This study aimed to obtain a lactic acid bacterial strain producing β-galactosidase with high transglycosylation activity in order to provide a novel source of β-galactosidase for efficient synthesis of galacto-oligosaccharides (GOS). Lactic acid bacterial strains were isolated from traditional cheese samples collected from pastoral households in Yili, Xinjiang autonomous region. Primary screening on MRS plates with added 5-bromo-4-chloro-3-indolyl-β-D-galactoside (X-Gal) using lactose as the sole carbon source was performed based on calcium dissolution zone size, and secondary screening was carried out by thin layer chromatography (TLC) analysis of the lactose hydrolysates obtained with β-galactosidases produced by the selected strains. The isolate with the highest transglycosylation activity was identified by physiological and biochemical characteristics, together with sequence analysis of the 16S rRNA gene. The optimal temperature, pH and lactose concentration for the synthesis of GOS using lactose as substrate were investigated, and GOS produced under optimal reaction conditions were quantified by TLC and high performance liquid chromatography (HPLC). Six lactic acid bacterial strains producing β-galactosidases with transglycosylation activity were isolated, among which β-galactosidase produced by Lactobacillus plantarum YLBGNL-S7 showed the highest transglycosylation activity. An initial lactose mass concentration of 300 mg/mL, a reaction temperature of 50 ℃, an initial pH of 6.0 and a reaction time of 4 h were determined as the optimum conditions for GOS synthesis with β-galactosidase produced by YLBGNL-S7, which resulted in a GOS yield of 43.40%. The GOS mixture contained 18.29% diaccharides and 12.95% trisaccharides. These results demonstrated that L. plantarum YLBGNL-S7 is a novel promising source of β-galactosidase with good potential for prebiotic GOS synthesis.

In this experiment, high-throughput sequencing was used to study the bacterial community structures in traditional naturally fermented soybean mash, soybean paste and the surrounding soil environment. Samples were collected from two different regions of Liaoning province, China, namely Siping, and Liaozhong district, Shenyang. The dynamic changes in the bacterial community in naturally fermented soybean paste were examined along with the effects of soil environment on the bacterial flora structure. The results showed that the main bacterial genera in both fermented soybean mash and soybean paste were Tetragenococcu, Lactobaillus, Bacillus, Leuconostoc, Enterococcus, Pseudomonas, Acinetobacter, and Weissella, and they changed dynamically during the fermentation process. Meanwhile, the soil environment influenced the bacterial community structure in fermented soybean paste, and the main diffusing bacteria were the genus Kocuria in the phylum Actinobacteria. However, as the fermentation progressed, the bacterial community structure tended to be relatively stable, and the chance for contact between the soil environment and fermented soybean paste was reduced, so that the effect was gradually weakened and maintained at a certain level.

In this study, we adopted Illumina MiSeq high-throughput sequencing technology to sequence the V3-V4 region of the 16S rRNA gene of bacteria in Qula samples from the southern area of Gansu province, and analyzed the diversity and community structure of bacteria in Qula through α diversity, species composition and β diversity analysis. The results showed that Qula samples from different pastoral households differed in terms of bacterial community composition. Firmicutes and Proteobacteria were the dominant phyla. Lactobacillus, Acetobacter and Lactococcus were the dominant genera. The functional genes of bacteria in the samples showed that the bacterial communities from different sources were different. The results can provide a theoretical basis for the utilization and food safety of Qula.

In this study, cellulose acetate-polypropylene composite membrane was prepared, and microbial transglutaminase (MTG) was immobilized onto the membrane, yielding an MTG-immobilized membrane, whose enzymatic activity was determined to be 17.6 U/g. Then the enzyme-loaded membrane was fixed on a stainless steel mesh frame and suspended in a beaker in order to use it to treat protein in rice bran wastewater. The effects of material temperature, material pH, rotor speed and enzyme-loaded membrane area on protein polymerization rate were investigated by one-factor-at-a-time method. Furthermore, using response surface optimization, the optimum polymerization conditions were obtained as follows: material temperature 43 ℃, pH 6.6, rotor speed 124 r/min, ratio between enzyme-loaded membrane area and substrate amount 80:1 (cm2/g), and reaction time 1.8 h. Under these conditions, protein polymerization rate was 70%. The enzyme-immobilized membrane remained above 74.3% of the original activity after its fifth repeated use. This study provides a theoretical basis for the continuous polymerization of proteins in rice bran wastewater and the retention of nutrients.

Four strains of Bifidobacterium animalis subsp. lactis isolated from infants were evaluated for tolerance to acids, bile salts and simulated digestive tract environment, adhesiveness to Caco-2 cells and inhibitory effects on pathogen adhesion. In addition, the ability to synthesize exopolysaccharides was determined and the relationship between tolerance and adhesion was discussed. Strain H15-2, with good environmental tolerance and adhesiveness, was further evaluated for its immunomodulatory activity by considering splenocyte proliferation, energy metabolism level in macrophages and macrophage phagocytosis of neutral red. The results showed that B. animalis H15-2 had strong tolerance to simulated gastrointestinal environment, high adhesion ability to Caco-2 cells, and good regulatory effects on the activities of immune cells. This study indicates that B. animalis H15-2 has great potential for application development.

Nine yeast strains capable of producing exopolysaccharides as determined by the phenol/sulfuric acid method were isolated and purified from dairy fan, a traditional fermented milk product in Yunan, China by the streak plate method. These strains were identified through morphological, physiological characteristics and molecular biology techniques, including 3 strains of Rhodotorula mucilaginosa, 1 strain of Candida albicans, 4 strains of Candida zeylanoides and 1 strain of Papiliotrema aurea. A high-yield exopolysaccharide (EPS)-producing strain, namely P. aureus DF-12, was obtained, which could synthesize EPS by using various carbon sources such as glucose, sucrose and molasses, and the highest yield of EPS of 3 510 mg/L was obtained after 168 h fermentation at 28 ℃ using sucrose as carbon source. In vitro antioxidant tests indicated that the EPS from DF-12 had strong scavenging ability against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion radicals. The experimental results provide a basis for the development and application of EPS in the food and pharmaceutical industries.

In order to prepare flavor peptides, we hydrolyzed goose meat separately with neutral protease, alkaline protease, flavorzyme, and papain. We also comparatively analyzed the degree of hydrolysis and oligopeptide content of the four enzymatic hydrolysates. Moreover, we detected the free amino acid compositions by using an automatic amino acid analyzer, and investigated the taste characteristics including umami with an electronic tongue and sensory evaluation as well. The results showed that under the following conditions: solid-to-liquid ratio (g/mL) 1:3, temperature 45 ℃, pH 7, enzyme-to-substrate ratio, 1 200 U/g protein, and incubation time 6.5 h, the highest degree of hydrolysis and oligopeptide content were obtained with papain, followed by neutral protease. The degree of hydrolysis and oligopeptide content of the neutral protease hydrolysate were 29.69% and 0.18%, respectively. In addition, the neutral protease hydrolysate had the best taste and contained a wide variety of amino acids, the most abundant ones being glutamic acid and alanine. This hydrolysate had a strong umami taste, accompanied by sourness. Therefore, we identified neutral protease as the optimum protease to prepare flavor peptides derived from goose meat.

The high cell density culture of Lactobacillus buchneri IMAU80233 with potential probiotic characteristics was optimized for industrial production in this study. MRS medium was improved and rapid selection and optimization of suitable medium components for the growth and proliferation of this strain were carried out using Bioscreen C system. The optimal medium composition was determined as follows: fructose 80 g/L, soybean peptone 23.90 g/L, yeast powder 11.90 g/L, citric acid 1.59 g/L, sodium citrate 20.06 g/L, MnSO4·5H2O 0.09 g/L, MgSO4·7H2O 0.60 g/L, arginine 0.50 g/L, and Tween-80 1.00 g/L. Five-liter fermenters (× 3) were used to carry out small-scale experiments. The initial pH value was 6.5, and IMAU80233 was cultured at 37 ℃ for 20 h during which the pH was held constant at 5.9. Nitrogen gas was introduced during the initial fermentation stage. Under the optimized conditions, the viable cell count of the fermentation broth was 3.81 × 109 CFU/mL.

This study aimed to investigate the quorum sensing (QS) activity and biofilm formation of Aeromonas spp. isolated from refrigerated grass carp as the dominant spoilage organism. The QS activity was detected using the reporter strain Chromobacterium violaceum CV026, and the biofilm formation was quantified by staining method. Then the effect of temperature and QS signaling molecules on the biofilm formation was explored. The results showed that the isolated Aeromonas spp. contained a plurality of species, and 90% of the 20 isolates could secret acyl-homoserine lactones (AHLs). Two strains of A. salmonia W41 and A. salmonia W69 with strong biofilm formation ability were chosen for further analysis. The results indicated that the biofilm formation ability of the two strains was significantly higher at 30 ℃ and 8 ℃ than at 37 ℃. Both strains mainly produced N-butanoyl-L-homoserine lactone (C4-HSL) and N-hexanoyl-L-homoserine lactone (C6-HSL) signaling molecules. The biofilm formation of W41 was significantly promoted by 50 μmol/L C6-HSL. Low concentrations of C4-HSL and C6-HSL promoted the biofilm formation of W69, but high concentrations of C4-HSL and C6-HSL had an inhibitory effect. The present study exhibited that most Aeromonas spp. showed QS phenomenon, and the biofilm formation of Aeromonas spp. was affected not only by individual differences and temperature, but also by the concentration and type of QS signaling molecules.

Objective: The study aimed to define the acid-alkali property of Trichothecium roseum when inoculated to apple fruit and to determinate the effect of inoculation with its spore suspensions at three different pH values (3, 5 and 7) on lesion diameter and extracellular enzymes activities in apple fruit. Method: ‘Fuji’ apple fruit was artificially wounded and inoculated with T. roseum, and the pH change in lesion tissue was detected during incubation. Meanwhile, the lesion diameter and the activities of pectinase and cellulase in the inoculated fruit were determined. Results: The pH of lesion tissue increased by 36.7% from 3.54 on day 0 to 4.84 on day 12 after inoculation. The fruit inoculated with the spore suspension at pH 7 showed the largest lesion diameter, which was respectively 35.2% and 68.0% higher than that of the spore suspensions at pH 5 and pH 3 on day 9 after inoculation. The fruit inoculated with the spore suspension at pH 7 also had the highest activities of pectinase and cellulose in lesion tissue. The activities of pectin methylesterase, pectin methyl polygalacturonase and polygalacturonase were 2.95, 1.61 and 1.68 folds higher than those in the fruit inoculated with the spore suspension at pH 3, and were 2, 1.25 and 1.39 folds higher than those in the fruit inoculated with the spore suspension at pH 5, respectively. Moreover, the activities of cellulase and β-glucosidase in the fruit inoculated with the spore suspension at pH 7 were 1.97 and 1.64 folds higher than those in the fruit inoculated with the spore suspension at pH 3, and 1.33 and 1.3 folds higher than those in the fruit inoculated with the spore suspension at pH 5, respectively. Conclusion: T. roseum can produce alkaline substances. A neutral or alkaline environment increases the activities of extracellular enzymes in lesions, and enhances the pathogenicity of the pathogen.

The objective of this work was to research the enzymatic characteristics of three lactases derived from different sources, and their application in the production of lactose-free raw milk. The composition and molecular mass of the lactases were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Lactase activity was detected using o-nitrophenol β-D-galactoside (ONPG). An electronic nose was used for detecting changes in the odor of raw milk during storage. The results showed that the isoelectric points of lactase A was 4.0 and 5.0, the isoelectric point of lactase B was 5.0, and the isoelectric point of lactase C was 3.0. Lactase A had the highest enzymatic activity at 40 ℃ and pH 6.5, B had the highest enzyme activity at 35 ℃ and pH 6.5, and C had the highest activity at 45 ℃ and pH 5.0. The results of electronic nose showed that there was no significant difference in the odor of raw milk stored at 4–10 ℃ for 12 h. In addition, after hydrolysis with 6 000 U/g of lactase A for 5–6 h or lactase B for 8–9 h at 4–6 ℃, the lactose content in raw milk was reduced to less than 0.5%. Therefore, lactases A and B were neutral lactases while lactase C was an acid lactase, and the use of neutral lactase A was more suitable to produce lactose-free raw milk.

During the natural fermentation process of Zhejiang rosy vinegar, alcoholic and acetic acid fermentation of saccharified cooked rice starch with microorganisms in the air took place after water addition. This study revealed the composition and diversity of the bacterial community and changes in organic acid contents during the fermentation process of rosy vinegar. The V4 region of the bacterial 16S rRNA gene from rosy vinegar was subjected to Illumina MiSeq high-throughput sequencing and organic acid contents of rosy vinegar were determined by high performance liquid chromatography (HPLC). Furthermore, the correlation between organic acid contents and relative bacterial abundance was investigated by using bidirectional orthogonal partial least squares (O2PLS) analysis. The results showed that Acetobacter and Lactobacillus dominated the bacterial community after water addition and the total relative abundance was higher than 80%. Organic acid contents gradually increased as the fermentation proceeded, with the most abundant being acetic acid and lactic acid. Using hierarchical cluster analysis (HCA) and principal component analysis (PCA), vinegar samples at the early, middle and late stages of fermentation were clearly distinguished based on organic acid contents, and organic acid composition was significantly different among vinegar samples. Through the correlation analysis a total of 23 bacterial genera with VIP(pred) greater than 1 were obtained, including Acetobacter, Lactobacillus, and Methylobacterium. In addition, a heatmap for the correlation between bacteria with VIP(pred) > 1 and organic acids was established, and the bacteria with correlation coefficients |ρ| > 0.6, indicating high correlation, were obtained. This study provides supporting data for finding functional microorganisms involved in the fermentation process of rosy vinegar and improving the quality of rose vinegar.

In this study, bifidobacterial strains isolated from the breast milk of Uygur women in Kashi, Xinjiang were identified at the species level and then their genetic variations were analyzed by using a combination of repetitive polymerase chain reaction (rep-PCR) fingerprinting and sequence analysis of the 16S rRNA gene. Meanwhile, routine physiological and biochemical parameters and phenotypic characteristics of sugar metabolism were examined, and the antibacterial activity of these isolates against 6 common pathogens and 3 conditional pathogens from breast milk was investigated along with their gastrointestinal tolerance. Our results showed that a total of 15 bifidobacterial strains including Bifidobacterium pseudocatenulatum (8 strains), B. breve (2 strains), B. longum subsp. longum (2 strains) and B. longum subsp. infantis (3 strains) were isolated from 15 breast milk samples. Among these strains, four B. pseudocatenulatum stains, namely MY92, MY75-1, MY72 and MY81, had a more potent and?broader-spectrum antibacterial activity, and strain MY92 showed the highest survival rate (20.37% and 0.302%) after challenge with simulated gastric and intestinal juices. Based on the above data, B. pseudocatenulatum MY92 is promising for application as a potent probiotic strain and shows great potential for the development of adjuvant preparations for preventing diarrhea in infants and young children.

Antimicrobial hydrolysate was obtained from crucian carp scales by citric acid extraction and enzymatic hydrolysis after pretreatment. Then after dialysis, the hydrolysate was separated and purified successively by Sephadex G-15, Sephadex G-50 gel filtration and cellulose DEAE-52 anion exchange chromatography, yielding peptides with strong antimicrobial activity. The molecular mass, antimicrobial activity and minimal inhibitory concentration (MIC) against various bacteria and fungi of the purified antimicrobial peptide were determined. The results showed that AcIII, a purified protein with antibacterial activity, was obtained. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed a single band, indicating that AcIII was electrophoretically pure. Its molecular mass was about 20.1 kDa. AcIII showed that crucian carp scale antimicrobial peptide had strong and broad-spectrum antimicrobial activity. The MIC against Staphylococcus aureus, Bacillus subtilis, Staphylococcus albus, Vibrio parahaemolyticus, Pseudomonas fluorescens and Shewanella putrefaciens were 16 μg/mL while the MIC against Escherichia coli and Salmonella choleraesuis were 32 μg/mL.

Lactic acid bacterial isolates derived from three traditional fermented foods in Northeast China, known as NianMianZi, spicy cabbage and chilli sauce were screened for cholesterol-lowering property, and the cholesterol-lowering mechanism was interpreted from the aspects of cell membrane adsorption, bile salt hydrolase gene expression and enzymatic activity, bile acid co-precipitation of cholesterol, cholesterol-inhibiting micelles. Strains C1, C2, H6, H9, L22 and L30 were found to have high cholesterol scavenging ability and their clearance rates were all above 85%. All the strains could effectively exert their cholesterol-lowering effects through bile salt hydrolase as well as membrane adsorption, coprecipitation, and inhibition of cholesterol micelles.

Using chitin as the sole carbon source, a chitinase-producing strain of Actinomycetes X1 was isolated from naturally fermented Jinga shrimp (Metapenaeus affinis) paste. It was identified as Streptomyces diastaticus by morphology, molecular biology and physiological and biochemical experiments and was named CS 1801. The chitinase enzyme activity produced by this strain was 117.4 U/L after culture at 30 ℃ for 7 days. By ultra-high performance liquid chromatography-mass spectrometry (UPLC-Q-TOF-MS), chitobiose, chitotriose, chitotetraose, chitopentaose and chitohexaose were identified from the fermentation broth of strain CS 1801.

This work was undertaken in order to study the effect of biotin addition on L-valine production by Corynebacterium glutamate XV0505 (Leu－+Ile－+2-TAr+α-ABr+SGr). The amount of biomass, sugar consumption, acid production and the production of L-alanine as a by-product were investigated at different concentrations of biotin. As a result, the optimum amount of biotin addition was determined to be 50 μg/L. Fermentation coupled with membrane dialysis effectively relieved feedback inhibition while reducing the production of the by-product and improving the conversion rate and yield of L-valine. The L-valine production by the new process was 106.1 g/L, which was increased by 47.4% compared with single batch fermentation, and the conversion rate of sugar and acid was increased to 34.5%.

In this study, two-dimensional gas chromatography-time-of-flight-mass spectrometry combined with odor activity value (OAV) analysis and gas chromatography-olfactometry-mass spectrometry (GC-O-MS) were used to analyze the volatile components and the key aroma components of green teas with fresh scent flavor from several different tea varieties made by the same process. Results showed that a total of 270 aroma compounds were found to be common to 7 green teas, mainly including aldehydes, ethers, alcohols, alkanes, aromatic hydrocarbons, and esters. Twenty and twenty-eight key aroma components were determined using OAV and GC-O-MS, respectively. Seven aroma component were common to both methods, including linalool, furfural, (E)-β-ionone, (Z)-hexanoic acid-3-hexene ester, ethylbenzene, naphthalene, and 2-n-pentylfuran. Therefore, these aroma components made important contributions to the aroma quality of fresh-scent green tea.

This research was designed to identify the major chemical constituents of the ethyl acetate fraction of lotus leaf extract by using ultra-high performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UPLC-QTOF-MS/MS). The compounds were identified based on the accurate molecular mass, parent ions, MS/MS fragment ions, and MS/MS fragmentation pattern of each peak, along with the information about the compounds previously identified in lotus leaves as well as available literature data. Totally, 40 compounds were identified, including 27 flavonoids, 6 phenolic acids, 4 organic acids, 2 fatty acids and 1 amino acid. Flavonoids were the major chemical constituents with quercetin glycosides, kaempferol glycosides, isorhamnetin glycosides and flavan-3-ols being the predominant ones, followed by phenolic acids. This research can provide a theoretical foundation for the application of lotus leaves in the food processing industry and for health-promoting food development.

An analytical method was developed for the simultaneous determination of tomatine and tomatidine in tomatoes by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Samples were homogenized, separated on a Proshell 120 EC-C18 column, and purified by solid phase extraction (SPE) with C18 as sorbent and tomatine and tomatidine were then analyzed by triple quadrupole tandem mass spectrometry under the multiple reaction monitoring (MRM) mode. The mobile phase consisted of 5 mmol/L ammonium acetate (containing 0.05% formic acid) and acetonitrile. The results showed that good linearity was observed for tomatine and tomatidine with correlation coefficients above 0.999 1 and 0.999 4 in the range of 50–1 000 and 5–100 ng/mL, respectively. The average recoveries at three spiked levels ranged from 85.6% to 105%, with relative standard deviations (RSDs) varying from 1.0% to 6.8%. The developed method was simple and rapid with high sensitivity and repeatability, which was suitable for rapid and simultaneous determination of tomatine and tomatidine in tomatoes. Tomatine was significantly more abundant than tomatidine in tomato samples as determined by this method.

This study aimed to explore the effect of variable-temperature variable-pressure puffing on the umami and aroma components of Pleurotus geesteranus. High performance liquid chromatography, an amino acid analyzer, an electronic tongue, headspace solid phase microextraction and gas chromatography-mass spectrometry (GC-MS) were used to determine the aroma and taste compounds. The results showed that the umami amino acid contents of fresh, pre-dried and puffed samples were 2.941, 8.820 and 3.759 mg/g, respectively; the flavor nucleotide contents were 0.220, 0.850 and 1.278 mg/g, respectively. The equivalent umami concentration (EUC) values were 1.839%, 27.211%, and 9.687%, respectively. A total of 29 volatile flavor components were identified from fresh, pre-dried and puffing samples, including alcohols, aldehydes, ketones, alkanes and furans. The three samples contained 18, 16 and 13 volatile flavor components, respectively. After variable-temperature variable-pressure puffing, the contents of umami components increased; the relative contents of aldehyde, olefin and furan compounds increased, while the relative contents of alcohols and ketone decreased. In summary, variable-temperature variable-pressure puffing can enhance the umami taste of P. geesteranus, and the contents of hexanal and benzaldehyde increase after puffing, which have a green grass and almond-like aroma, contributing to the unique aroma of puffed P. geesteranus. Variable-temperature variable-pressure puffing is a suitable processing method for P. geesteranus.

The volatile components of kiwifruit wines made from three different cultivars, namely Actinidia deliciosa ‘Hayward’, ‘Xuxiang’ and A. chinensis ‘Hort16A’, were investigated by the combined use of solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and electronic nose (E-nose). The results showed that a total of 63 volatiles were identified in the three wines, with the most abundant being alcohols, esters, acids and terpenoids. Out of the 63 compounds, 52, 45 and 46 were found in ‘Xuxiang’, ‘Hayward’ and ‘Hort16A’ wines, respectively, with total concentrations of 81.56, 43.92 and 15.07 mg/L, respectively. Methyl butyrate, isoamyl acetate, ethyl hexanoate, eugenol, octanoic acid, eucalyptol and 2-methoxy-4-vinylphenol were the characteristic aroma compounds common to the three wines. Meanwhile, the results of E-nose and GC-MS were consistent with each other, showing that there were significant differences?in?the?aroma?profiles?of the kiwifruit wines,?especially between ‘Xuxiang’ and ‘Hayward’ wines. The kiwifruit wines could?be completely discriminated using principal?component analysis (PCA).

Crushed garlic cloves with four different colors of white, blue, green and yellow were prepared from garlic cloves overcoming dormancy and they were comparatively analyzed for flavor and volatile components by electronic nose and gas chromatography-mass spectrometry (GC-MS). The radar map and principal component analysis (PCA) of the electronic nose sensor responses showed significant flavor differences among the samples. A total of 83 volatile substances were detected from these samples. The main volatile substances were thioether compounds and aldehyde compounds, which were also identified as the main flavor substances of crushed garlic. PCA could distinguish the four garlic samples and the volatile compounds causing the flavor differences were identified, which provides a theoretical basis for studying the flavor differences among crushed garlic cloves with different colors.

An analytical method for the determination of phospholipids contents in bell pepper by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established. Samples were extracted with isopropanol-methanol-water and the extract was purified by liquid-liquid extraction, and then separated on a hydrophilic interaction liquid chromatography (HILIC) (2.1 mm × 100 mm, 1.7 μm) system before being analyzed by electrospray ionization tandem quadrupole mass spectrometry. Relative quantification was carried out with phosphatidylcholine (PC), lysophosphatidylamide ethanolamine (LPE), lysophosphatidylcholine (LPC), phosphatidylglycerol (PG), phosphatidyl amide glycerol (PA), and lysophosphatidyl amide serine (LPS) as reference materials, separately. The extraction solvent and the purification method were selected in the experiment. The pretreatment method that could extract the largest number and amount of phospholipids was used, and its applicability was tested. The results showed that good linearity was observed for the six phospholipids in the range of 10–1 000 ng/mL. The limits of detection (LODs) were 2–300 ng/mL, and the limits of quantitation (LOQs) were 10–1 000 ng/mL. At spiked levels of 125, 250, and 375 ng/mL, the recovery was 68.06%–84.17%, with relative standard deviations (RSDs) of 3.40%–9.60%. The method provides a reliable platform for the determination of phospholipids in bell pepper, and more broadly for research on cold injury based on membrane lipid metabolism.

In order to provide an experimental basis for the development of black chokeberry wine with good consumer acceptance, the aroma components of black chokeberry wine were analyzed head space-solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and sensory evaluation was conducted in comparison to the reference Cabernet Sauvignon wine. The results showed that the aroma content of black chokeberry wine was 2.73 times higher than that of Cabernet Sauvignon wine, and 41 and 40 aroma compounds were detected from black chokeberry and Cabernet Sauvignon wines, respectively. A total of 18 aroma compounds were common to both. In the two wines, alcohols were the most dominant compounds, accounting for 62.11% and 73.87% of the total aroma compounds, respectively. According to odor activity values (OAVs), esters contributed mostly to the aroma of wine, with contribution rates of 36.57% and 22.04% for black chokeberry and Cabernet Sauvignon wines, respectively. The main aroma components of black chokeberry wine were β-damascenone, ethyl octanoate, ethyl n-hexanoate and isoamyl acetate, while in Cabernet Sauvignon wine, α-ionone, ethyl octanoate, ethyl caproate and phenylacetaldehyde were dominant. The aroma components found in both black chokeberry and Cabernet Sauvignon wines accounted for 34.20% and 21.81% of the total aroma compounds, respectively, indicating a certain similarity, while the contribution ratio of β-damascenone and α-ionone to the odor activity values of black chokeberry and Cabernet Sauvignon wines were 63.22% and 76.36%, respectively. Both wines had their own characteristics. The sensory evaluation score of black chokeberry wine was 2 points higher than that of Cabernet Sauvignon wine. The above results indicated that the black chokeberry can be used for winemaking as a black berry.

The nutritional and aroma components of passion fruit juices from five cultivars were comparatively analyzed by high performance liquid chromatography (HPLC) and solid phase micro extraction combined with gas chromatography-mass spectrometry (SPME-GC-MS) and the data obtained were analyzed by principal component analysis (PCA) employing SPSS 19.0 software. The results showed that the nutritional components of passion fruit juice significantly differed among varieties (P < 0.05). The Guava-Flavored Golden Fruit (GFGF) cultivar had the highest contents of total sugar (16.00%), soluble solid (18.43%) and total amino acid (TAA) (928.80 mg/100 g). GTGF, purple-fruited seedling strain and Mantainxing had lower contents of total acid (1.82%, 1.79%, and 1.80%) than the two other cultivars. A total of 68 aroma components were identified, of which 24 were common to all the cultivars. The number (58) of aroma components identified in the Zixiang cultivar was the biggest, followed by purple-fruited seedling strain (56), Tainong (55), GFGF (47) and Mantainxing (39). The average percentages of esters, alcohols, ketones, terpenes, alkanes, ethers and heterocycles relative to the total aroma components were 83.1%, 3.6%, 4.8%, 3.7%, 2.3%, 1.7%, and 0.8%, respectively. The dominant aroma compounds were thyl butyrate (295.48–2 025.83 μg/100 g), ethyl hexanoate (573.75–2 345.34 μg/100 g), hexyl butanoate (166.08–962.66 μg/100 g), hexyl 1-methylbutanoate (33.61–818.09 μg/100 g), hexyl hexanoate (332.19–1 216.03 μg/100 g) and 3-pentyl hexanoate (635.25–900.74 μg/100 g). The results of PCA showed that ethyl butyrate, ethyl hexanoate, hexyl butanoate and β-ionone may be identified as the key aroma components of passion fruit. GFGF contained the highest levels of ethyl butyrate (2 025.83 μg/100 g), ethyl hexanoate (2 345.34 μg/100 g), esters with less than 10 carbon atoms (5 985.49 μg/100 g), total esters (8 925.01 μg/100 g) and total aroma components (10 740.52 μg/100 g) as compared with the other four cultivars (P < 0.05). GFGF had the best overall quality among the cultivars tested. Thus, it is suitable for breeding of new passion fruit cultivars for fresh consumption.

An electronic nose and gas chromatography-mass spectrometry (GC-MS) were used to analyze the volatile flavor components of kvass made in our laboratory and four commercial brands of kvass, Ochakovskiy, Pabaebckhh, Qiulin and Wahaha. The obtained data were analyzed by principal component analysis (PCA). The results showed that the electronic nose could clearly distinguish among the flavors of the five kvasses. The flavor of laboratory made kvass was close to that of Pabaebckhh and Ochakovskiy kvass, but was greatly different from that of Qiulin and Wahaha kvass. This difference may be caused by the use of different fermentation starters. GC-MS analysis demonstrated that the flavor difference could be caused by differences in the contents of volatile flavor compounds such as ethanol, sorbic acid, phenylacetaldehyde, phenylethyl acetate and benzaldehyde.

In the present study, an ultra-high performance liquid chromatography (UPLC) method and a high performance liquid chromatography (HPLC) method were developed for the determination of tetramethylpyrazine in Zhenjiang balsamic vinegar and related products. Tetramethylpyrazine was extracted from samples with acidic ethanol aqueous solution. The mobile phase was a mixture of 25% methanol and 75% acidic aqueous solution (containing 1% acetic acid and 0.05% trifluoroacetic acid, pH 2.4). A C18 column with small packing particle size (2.1 mm × 100 mm, 1.5 μm) was used in UPLC while an SB-C18 column (4.6 mm × 250 mm, 5 μm) was used in HPLC. The flow rates of the columns were 0.3 and 0.8 mL/min, respectively, and the detection wavelength was set at 297 nm. The calibration curves obtained were linear over the range of 0.50–50.00 μg/mL. The mean absolute recoveries were at least 87.9% with relative standard deviations less than 3%. The retention time of tetramethylpyrazine was 1.6 min in the UPLC method compared to 9.7 min in HPLC. Moreover, the limits of detection (LODs) of the two methods were 0.000 3 and 0.008 g/kg, respectively, and the limits of quantitation (LOQs) were 0.001 and 0.025 g/kg, respectively.

This study was done in order to investigate the yellow pigment composition of Cordyceps militaris and to determine the optimal processing conditions for the extraction of?yellow pigment from C. militaris. We applied high performance liquid chromatography (HPLC), high-resolution mass spectrometry (HRMS) and Fourier transform infrared (FTIR) spectroscopy to the separation, purification and structural identification of yellow pigment. A new yellow pigment was found and named cordycepene, which had similar UV-visible and infrared absorption characteristics to carotenoids. By using the response surface methodology, the optimal extraction conditions were obtained as follows: 57.68% ethanol as the extraction solvent and extraction for 52.44 min at 44.40 ℃. Under these optimized conditions, the highest yield of cordycepene of (2 780.97 ± 170.38) μg/g was obtained.

In this study, the effect of NaOH concentration, liquid-to-solid ratio, extraction time and number of extraction cycles on the recovery of phenolic acid from wheat grains using ethyl acetate as the extraction solvent were investigated. The extraction conditions were optimized by response surface methodology. High performance liquid chromatography-mass spectrometry (HPLC-MS) was used to quantify phenolic acid in wheat grains from different varieties grown in different areas of China. The results showed that all the conditions had significant effects on extraction efficiency. Using response surface methodology, the optimum conditions were obtained as follows: NaOH concentration 1.56 mol/L, liquid-to-solid ratio 15.53:1 (mL/g), extraction time 17.33 min, and two extract cycles. Under these conditions, the yield of phenolic acids was 1 055.99 mg/kg. In total, 9 phenolic acids were detected in wheat grains, including gallic acid, protocatechuic acid, 4-hydroxybenzoic acid, vanillic acid, caffeic acid, eugenoic acid, p-coumaric acid, sinapic acid and ferulic acid. Ferulic acid was the main phenolic acid, accounting for 73.07%–89.10% of the total phenolic acids. The Ningmai 14 cultivar contained the highest total phenolic acid content (1 001.12 mg/kg) of the various cultivars grown in Yangtze–Huaihe River region, showing significant differences from Baomai 6 and Huaimai 33. The total phenolic acid content of Xinmai 26 was the highest (1 016.03 mg/kg) in the Yellow-Huaihe River region, which was significantly different from that of Aikang 58 and Bainong 207, grown in this area. It can be concluded that phenolic acid content varies greatly among different wheat varieties.

Mixed gels were prepared from silver carp surimi with the addition of 0.3% transglutaminase (TG) and precocious crab meat. The effects of crab meat proportion, gelation time and gelation temperature on gel strength and water-holding capacity (WHC) were investigated in this study. By employing a combination of one-factor-at-a-time method and response surface methodology based on a three-variable, three-level Box-Behnken design, the optimal processing conditions were obtained as follows: crab meat ratio 10%, gelation time 3.0 h, and gelation temperature 35 ℃. The results of verification experiments demonstrated that compared with traditional fish sausage, the mixed gel strength significantly increased (P < 0.05), along with a slight reduction in WHC (P > 0.05). In the presence of TG, the band intensity of myosin heavy chain (MHC) decreased and the surface of mixed gels became more uniform and compact, as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscopy (SEM), respectively.

Objective: In this study, the serotype, antimicrobial susceptibility to nalidixic acid and ciprofloxacin, genes associated with quinolone and fluoroquinolone resistance of the foodborne pathogen Salmonella isolated in nine provinces and municipalities of China, including Shaanxi, Xinjiang and Guangdong, were identified and analyzed, aiming to better understand the development and transmission of antimicrobial resistance, and more broadly, to ensure food safety. Methods: Salmonella serovars were determined by the slide agglutination method, the antimicrobial susceptibility was tested by the agar dilution method, and nine genes associated with resistance to quinolone and fluoroquinolines were determined using PCR. Results: A total of 83 serotypes were identified from 814 Salmonella isolates. The most prevalent serotype was S. typhimurium (24.08%), followed by S. enteritidis (19.41%), S. indiana (13.27%) and S. derby (5.16%). Out of the 814 isolates, 553 (67.94%) and 219 (26.90%) resisted to nalidixic acid and ciprofloxacin, respectively. The average prevalence of oqxB positive isolates (31.82%) was significantly (P < 0.05) higher than that of qnrA (24.94%), oqxA (24.57%), qnrB (24.45%)，qnrS (10.32%) and qepA (3.07%) positive isolates, and it showed no significant difference from that of aac(6’)-Ib positive isolates (27.52%). A difference could be found among five common serotypes, different sampling sites, different sample types and different geographical areas in the prevalence of the seven antibiotic resistance-associated genes. A total of 221 mutations were detected in gyrA, with the most prevalent one being Ser83Phe/Asp87Gly (21.27%), followed by Ser83Phe (16.29%), Asp87Gly (13.57%), Ser83Tyr (12.22%), Asp87Tyr (11.31%), Asp87Asn (10.41%), Ser83Phe/Asp87Asn (9.95%), Ser83Tyr/Asp87Gly (2.71%), Asp87Val (0.90%), Gly75Phe (0.45%), Asp87Asn/Ile89Val (0.45%), and Asp87Asn/Val90Gly (0.45%). A total of 217 mutations were detected in parC, the most prevalent one being Ser80Arg (64.49%)，followed by Thr57Ser (35.05%) and Ser80Arg/Gly72Phe (0.47%). Conclusion: The serovars of Salmonella isolates from the nine provincial regions were diverse, and the resistance to nalidixic acid and ciprofloxacin was highly prevalent. oqxA, oqxB, qepA, qnrA, qnrB, qnrS and aac(6’)-Ib were prevalent in Salmonella, and multiple mutations could be detected in both gyrA and parC. The existence of these antibiotic associated genes and mutations in the quinolone resistance-determining region (QRDR) may play important roles in nalidixic acid and ciprofloxacin resistance.

In this experiment, gold magnetic nanoparticles (Fe3O4@Au) were formed by the self-assembly of Fe3O4 nanoparticles, prepared using the hydrothermal method, after surface amination. The performance of Fe3O4@Au was characterized. A simple method for visual detection of glucose was established on the basis of its peroxidase mimicking activity combined with the fact that glucose oxidase (GOx) catalyzes glucose oxidation to produce H2O2, which reacts to form a color with 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as a peroxidase substrate. The glucose detection system was optimized and the selectivity and recovery of the method were determined. The results showed that Fe3O4 functionalized with amino groups could be effectively loaded with gold nanoparticles, and the saturation magnetization of Fe3O4@Au was 43 emu/g. The optimum detection conditions were as follows: amount of Fe3O4@Au suspension 0.15 g/mL, temperature 70 ℃, and time 50 min. Under the optimized conditions, a good linear relationship was observed for glucose concentration within the range of 1–20 mmol/L with a correlation coefficient (R2) of 0.992 5. The limit of detection (LOD) was 2.45 μmol/L, and the recoveries for spiked samples were 96%–104%. The proposed method had good selectivity and stability. This study will broaden the application of nanoparticle enzyme mimics in food detection and provide a new idea for improving glucose detection in foods.

Four methods were compared for their removal efficiencies for aflatoxin B1 (AFB1) from peanut oil as well as their effects on the acid value (AV), peroxide value (POV), vitamin E (VE) content and phytosterol content of peanut oil. The mechanism of AFB1 removal by alkali treatment was explored, and the safety, free alkali residue and flavor of peanut oil after being treated with alkali were further evaluated. The content of AFB1 in crude peanut oil was 21.50 μg/kg, and decreased to 2.00 μg/kg (removal efficiency of 90.7%) after 30 min alkali treatment at pH 13.44 with a liquid-to-solid ratio of 10% (m/m). After one adsorption cycle with 2.0% (m/m) bentonnite for 30 min, the removal efficiency of AFB1 was 99.4% and the residual AFB1 level was 0.13 μg/kg. After two adsorption cycles with bentonite at 1.0% first and then at 0.5% for 30 min each cycle, the removal efficiency of AFB1 was 99.5% and the residual AFB1 level was 0.10 μg/kg. Alkali refining and deacidification at 50 ℃ with 0.8% excess alkali for 30 min decreased the AFB1 content in peanut oil to 0.10 μg/kg, with a removal efficiency of 99.5%. The retention rate of vitamin E in peanut oil treated with alkali was the highest among the four methods. Sensory evaluation indicated that alkali treatment also resulted in the lowest flavor loss of peanut oil.

Based on the aggregation-induced emission (AIE) characteristics of 9,10-distyryl sulfonium quaternary ammonium salt (DSAI), a method for the detection Ag+ was developed by a combination of aptamer recognition and fluorescence resonance energy transfer. When Ag+ was added, the target and the aptamer specifically bound to each other, forming a U-shaped structure which could cause conformational changes in the aptamer. At the same time, the adsorbed aptamer was desorbed from the black phosphorus nanosheets (BPNS) and then combined with DSAI by electrostatic adsorption and hydrophobic interaction, enhancing the fluorescence intensity of the solution system. In order to develop the Ag+ detection method, a fluorescent aptamer sensor based on AIE was constructed, which showed a good linear relationship within the concentration range of 0.01–100 ng/mL, and the limit of detection (LOD) was 0.002 ng/mL. Thanks to its advantages such as simplicity, easy operation, low cost, good sensitivity and high selectivity, this aptasensor can also apply to other targets.