The effects of tea polyphenols (TPs) on the quality of rapeseed oil during the deep frying of potato slices were investigated by measuring changes in physicochemical indexes, fatty acid composition and volatile compounds, and the content of total phenols and the thermodynamic properties of the oil were further determined to elucidate the underlying mechanism. The results showed that compared with control, TPs significantly inhibited the decrease in physicochemical quality of the frying oil. Besides, the addition of TPs could inhibit the degradation of unsaturated fatty acids and the generation of trans fatty acids in the frying oil and suppressed the production of volatile aldehydes. The addition of TPs could increase the content of phenols and oxidative stability of the oil, thus protecting its quality in the deep-frying process. All these findings suggested that TPs could be potential to be used for protecting the quality of frying oil in the food and chemical industries.

This investigation aimed to study the synergistic effect of a mixed meat tenderizer of calcium chloride, fig protease and kiwifruit protease on the structure of myofibrillar protein in rabbit hind leg meat. We measured and compared the myofibrillar fragmentation index (MFI), myofibrillar protein solubility, soluble protein content (SPC) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles of myofibrillar protein in meat samples treated with each meat tenderizer alone and their combination. The results showed that the mixed tenderizer could degrade myofibrillar protein more effectively than the single tenderizers (P < 0.05). The surface hydrophobicity of myofibrillar protein in the calcium chloride group was significantly higher than that in other single treatments (P < 0.05). The solubility of myofibrillar protein and SPC in the single enzyme treatments were significantly higher than those in the calcium chloride group (P < 0.05). The SDS-PAGE showed that the myosin light chain and C-protein were mainly degraded by fig protease while the myosin heavy chain was mainly degraded by kiwifruit protease. The above results indicate that combined treatment with the meat tenderizers could synergistically enhance the degradation of myofibrillar protein, possibly due to the fact that calcium chloride could make myofibrillar protein unstable, resulting in its unfolding and exposure of more enzyme binding sites, and that the two proteases showed different specific substrate binding patterns prompting protein degradation and solubilization.

Self-assembled nanofibrils from the triterpenoid glycyrrhizic acid (GA) were used as structural building blocks to prepare tea tree oil emulsion gels. The effects of the concentration of GA nanofibrils and tea tree oil (TTO), and oil phase composition on the appearance, microstructure and rheological properties of the emulsion gels were investigated. The results showed that the synergistic combination of gelation and emulsifying behaviors offered GA nanofibrils the potential as natural structuring agents for TTO emulsion gel systems with honeycomb-like microstructure and small droplet size (2.5 μm). The emulsion gels exhibited many interesting rheological behaviors such as high gel strength. The gel system with higher concentrations of GA nanofibrils (4%) and essential oil (40%) showed enhanced viscoelastic properties and stability. In addition, the change in oil phase composition (addition of sunflower oil or medium chain fatty acid triglycerides) could significantly affect the particle size, appearance and structural characteristics of the emulsion gels.

The effects of alkaline pH-shifting (pH 11) combined with heat treatment (50 and 60 ℃) on the structural and functional properties of rice bran protein were investigated. The results indicated that the secondary structures of rice bran protein were transformed from an ordered state to a disordered one by alkaline pH-shifting treatment. Alkaline pH-shifting combined with heat treatment led to complex changes in the protein’s secondary structures from folding to unfolding to refolding, which was accompanied by oxidation of sulfhydryl groups. Alkaline pH-shifting treatment resulted in unfolding of rice bran protein. As the treatment time increased, the protein re-aggregated, which was aggravated by heat treatment. Alkaline pH-shifting treatment resulted in a significant decrease in the water-holding capacity, foaming capacity, foam stability, emulsifying activity, and emulsion stability of rice bran protein, but a significant improvement in the oil-holding capacity. As the treatment time increased, the water-holding capacity, foaming stability, emulsifying activity, and emulsion stability gradually increased, with the emulsifying activity showing the most significant increase. Alkaline pH-shifting combined with heat treatment could significantly improve the water-holding capacity, foaming capacity, foam stability and emulsion stability of rice bran protein while reducing its oil-holding capacity and emulsifying capacity.

The interaction mechanism of ovalbumin (OVA) with resveratrol (RES) was examined by analyzing the type of fluorescence quenching, binding site number, thermodynamic parameters and the content of secondary structures using fluorescence and circular dichroism (CD) spectroscopy. Furthermore, the effect of RES on the potential allergenicity of OVA was evaluated by enzyme-linked immunosorbent assay (ELISA) in vitro. Results showed that RES could quench the fluorescence of OVA dynamically. OVA-RES interaction was a spontaneous process (ΔH < 0, ΔS < 0, ΔG < 0) driven by hydrogen bond and van der Waals force. The microenvironment around amino acid residues in OVA and its conformation were changed by RES, thereby increasing the potential allergenicity of OVA.

The antibacterial peptide brevilaterin was microencapsulated with pectin to achieve slow-release antibacterial properties in foods without inhibition by yeast. The optimal experimental conditions that provided maximum microencapsulation efficiency of 98.27% were determined as follows: pectin concentration 0.8 mg/mL, brevilaterin concentration 0.4 mg/mL, pH 5.5, homogenization speed 3 000 r/min, temperature 50 ℃, and homogenization time 30 min. Observation by scanning electron microscopy (SEM) demonstrated that the microcapsule was spherical in shape. Laser particle size analysis showed that the size distribution was in the range of 0.6–8 μm with an average particle size of 1.8 μm. Infrared spectroscopy suggested no characteristic peaks of brevilaterin, indicating that brevilaterin is successfully microencapsulated. As determined by agar diffusion method, the diameter of the inhibition zone of microencapsulated brevilaterin against Staphylococcus aureus was 10.5 and 13.1 mm greater at 48 and 60 h of culture than at 12 h, respectively, suggesting slow release of brevilaterin from the microcapsule. Microencapsulated brevilaterin at 3 000 AU/g had a better preservative effect on bread than 1 g/kg calcium propionate, indicating that the former shows good application potential in the preservation of bread. In conclusion, microencapsulation broadens the application range of brevilaterin in the food industry.

The aim of this research was to study the effect of calcium lactate on the emulsifying properties of high methoxy citrus pectin (HMP). Differences in the morphology and size of HMP micelles in aqueous solution were compared in the presence and absence of calcium lactate. Addition of calcium lactate distinctly affected the morphology and size of HMP micelles in aqueous solution, increasing the size of HMP micelles and inducing cross-linking of HMP micelles and HMP molecules to form a reticular structure. Calcium lactate significantly improved the emulsion stability index of HMP and inhibited creaming. After storage for 28 days at room temperature, no creaming occurred in the presence of 12.50 mmol/L calcium lactate. Calcium lactate affected the droplet size distribution and morphology. The d(0.9) value of the emulsion droplets was decreased slightly and the droplet morphology of irregular spheres appeared in the presence of calcium lactate. The morphology of the dyed emulsion droplets showed that there were substances adhered on the surface in the presence of calcium lactate. The emulsion prepared from HMP with added calcium lactate was similar to the Pickering emulsion.

The effects of glutamine transaminase (TG) on the mixing properties, stretching properties, rheological properties, microstructure and protein profile of whole wheat dough were investigated using Mixolab, texture analyzer, dynamic rheometer, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and electrophoresis apparatus. The results showed that with increasing the amount of added TG, the water absorption rate of whole wheat dough decreased and the dough development time and dough stability time increased first and then decreased, the peak viscosity increased, the setback decreased, and the tensile strength increased first and then decreased. With increasing TG concentration and reaction time, the elastic modulus (G’) and viscosity modulus (G”) increased, and the tangent of loss angle (tanδ) decreased. However, when the TG concentration was higher than 2.4 U/g and the reaction time was longer than 120 min, excessive protein cross-linking and aggregation took place, accompanied by a decrease in the comprehensive viscoelasticity. The results of SEM and LCSM showed that the addition of TG made dough microstructure more continuous and compact, significantly improving gluten structure. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that TG induced protein cross-linking and aggregation.

In this paper, different concentrations of polysaccharides extracted from Auricularia cornea Ehrenb. were used to prepare corn starch-polysaccharide blends, and their physicochemical and structural properties were studied. The results showed that compared with those of corn starch, the peak viscosity and peak time of blends was increased, the breakdown and setback was decreased, the peak temperature (TP) was increased significantly, and the enthalpy difference (ΔH) was decreased, indicating improved stability and anti-aging capacity. This effect was more significant with increasing level of polysaccharide addition. After the addition of the polysaccharides, the consistency coefficient K was increased, the fluid index n was decreased, the pseudoplasticity was enhanced leading to the easier occurrence of shear thinning, and the storage and loss moduli were increased. The maximum storage modulus was observed with addition of 0.5% A. cornea Ehrenb. polysaccharides. Scanning electron microscopy (SEM) showed that the polysaccharides reduced the size of pores within the microstructure, and the blends with 0.5% and 1.0% A. cornea Ehrenb. polysaccharides had a more uniform and dense gel structure. Infrared spectroscopy showed that no new groups were formed in the starch-polysaccharide blends. The structural orderliness of starch was improved at an addition level of 0.5% but reduced at 1.0%, 2.0%, 5.0% and 10.0%. This study can provide a reference for the application of A. cornea Ehrenb. polysaccharides in starch-based foods.

In order to improve the dispersibility of microcrystalline cellulose (MCC) in starch (ST) films, modified microcrystalline cellulose (MD-MCC) was prepared by cationic etherification of MCC, and its chemical structure, crystallinity, thermal stability and micromorphology were characterized. The starch/cellulose composite films ST-MCC and ST-MD-MCC were prepared by the solution casting method. The effects of different amounts of MCC and MD-MCC on the physicochemical properties of starch films were investigated. The results showed that the basic chemical structure of MD-MCC was similar to that of MCC, and the basic structure of cellulose was still maintained, but the crystallinity and thermal stability slightly decreased, with porous structures appearing on the surface. With the increase of MCC and MD-MCC concentrations, the surface roughness of the composite films increased, the light transmittance and elongation at break decreased, the water contact angle, moisture content and thickness rose, and the tensile strength and water vapor permeability first increased and then decreased. MD-MCC was dispersed better in the composite films than MCC. The tensile strength and water resistance of ST-MD-MCC films were better than those of ST-MCC films. ST-5% MD-MCC had the maximum tensile strength and the best water resistance.

This study aimed to find a way to obtain the efficiency of traditional deep frying by using an air fryer and to compare the differences between the two frying methods in terms of the eating quality of Coregonus peled meat. By measuring the cooking loss, texture and color of cooked fish, the optimal processing parameters for deep frying were 170 ℃ for 100 s and 180 ℃ for 80 s, and those for air frying were 170 ℃ for 12 min and 180 ℃ for 10 min. Then, we compared the differences in the basic nutrients of C. peled meat processed by the two frying methods. The fat content of deep-fried fish meat ranged between 18.68% and 20.33%, while the fat content of air fried fish meat with sensory quality similar to the former was in the lower range of 16.21%–17.54%. Fish meat processed by the two frying methods displayed similarities in the composition of volatile flavor compounds, free amino acids, nucleotides and sensory evaluation. In summary, air frying can bring about similar effects to deep frying in terms of the appearance, texture, nutrients and sensory quality of C. peled meat while using less oil.

In order to study the influence of night temperature in the greenhouse on the fruit quality of Cabernet Sauvignon, we controlled night temperature in the greenhouse to the high night temperature (HT, the average temperature is 21.8 ℃), the low night temperature (LT, the average temperature is 17.1 ℃), and the natural environment temperature (CK, the average temperature is 18.9 ℃) for 35 consecutive days starting before veraison, and we monitored the temperature and humidity during this period. We measured and compared chemical components and volatile aroma composition of the three treatment groups. The results showed that LT accumulated 11.7%, 51.7% and 27.9% more soluble sugar, anthocyanins and flavonoids in mature grape berries than CK, respectively. LT degraded 16.1% and 16.5% less total acids and tannins than CK, respectively. HT significantly decreased total phenol content, despite having no effect on other quality indexes tested. The night temperature had a significant effect on the composition and proportions of volatile aroma components. A total 103 volatile compounds were detected, 44, 38 and 43 of them being found in LT, HT and CK, respectively. Eleven volatile components were common to all three groups. HT reduced the kinds of volatile compounds, but increased the relative content of aldehydes. LT increased the relative contents of aldehyde, terpenes and esters. HT and LT reduced the relative contents of alcohol compounds. Therefore, these results indicated that LT can improve berry quality while HT has an opposite effect.

In this study, gelatin was extracted from the skin of New Zealand hoki (Macruronus novaezelandiae), and was further hydrolyzed enzymatically to produce peptides. Peptide-selenium complexes were prepared by using sodium selenite as a selenium source and the one with high selenium-binding capacity was selected and structurally characterized. The results indicated that the pepsin hydrolysate had the highest calcium binding capacity (13.61 μg/mg) and was thus used to peptide-selenium complexes. After selenium binding, the UV absorption intensity of the peptides increased, accompanied by a red shift in the maximum wavelength, and the fluorescence absorption peak shifted from 311 to 355 nm together with a weakening of the fluorescence intensity. These phenomena indicated the production of a new complex from selenium binding to the peptides. Based on particle size distribution measurement, atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray diffraction analysis, the peptide-selenium complex had a nanocrystalline structure. The binding reaction of carboxyl and amino groups in the peptides with selenium transformed the secondary protein from β-sheet to α-helix and β-turn, thereby making the structure more compact and orderly. This study provides a new approach for high-value utilization of fish skin.

Reduced-fat sausages were manufactured with 50% substitution of pork back-fat by either unpre-emulsified or pre-emulsified commercial canola oil combined with green tea extract (100 and 1 000 mg/kg). Textural properties and lipid oxidative stability (expressed as thiobarbituric acid reactive substances value) of cooked products were analyzed. The partial replacement of animal fat with vegetable oil did not compromise the color (lightness and redness), hardness or deformability, and significantly improved oxidative stability (P < 0.05). However, the oil substitution aggravated cooking loss and markedly decreased the breaking force. Pre-emulsification alleviated the texture deterioration induced by fat replacement. Addition of green tea extract, independent of dosage, almost completely inhibited lipid oxidation in sausages during storage. However, green tea extract at 1 000 mg/kg tended to disrupt the texture properties, although no statistically significant difference (P > 0.05) was observed.

In this research, we studied the inhibitory effects of different concentrations (1, 5, 10, 15, and 20 g/L) of hypotaurine (HTU) on the activity of polyphenol oxidase (PPO) from Penaeus vannamei, and further we determined the inhibition type and inhibition constant. Meanwhile, the effects of HTU on PPO conformation were studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD) spectroscopy, surface hydrophobicity measurement and endogenous fluorescence spectroscopy. The results showed that HTU could inhibit 79.38% of PPO activity when its concentration was 20 g/L, and the half-maximum inhibition concentration (IC50) value was 16.09 g/L. The Lineweaver-Burk double reciprocal plot showed that the Vmax remained unchanged while the Km increased. It was presumed that HTU was a competitive inhibitor with an inhibition constant KI of 0.445 mmol/L. SDS-PAGE results showed that the molecular mass of the enzyme did not change significantly with increasing HTU concentration. The results of CD spectroscopy and surface hydrophobicity showed that the secondary structure of the enzyme was transformed from α-helix and β-sheet to β-turn and random coil, and partial unfolding occurred, leading to the exposure of hydrophobic amino acid residues and enhanced surface hydrophobicity. HTU could quench the endogenous fluorescence of PPO and result in a red shift in the maximum emission wavelength. Therefore, it is speculated that HTU may affect the enzymatic activity by changing the spatial structure of PPO.

In this research, gold nanoparticles (AuNPs) were prepared by reducing HAuCl4 with green tea extract as a reducing and protecting agent, which was rapid and environmentally friendly. The AuNPs were more stable compared with those traditionally prepared using citrate sodium as a reducing agent. In the presence of the new AuNPs, vitamin C (VC) reduced AgNO3 to Ag coated on the surface of AuNPs, leading to the formation of core-shell Au@Ag nanoparticles (AuNPs@Ag) and consequently causing changes in the color of the solution and an increase in the absorbance at 410 nm. VC could be analyzed qualitatively by the naked eyes according to the color change and quantitatively by UV-Vis absorption spectroscopy. When the concentration of VC was 2 mg/L, the solution could be observed to change from pale pink to yellow by the naked eyes. The linear range of VC was from 0.4 to 120 mg/L and the limit of detection (LOD) was 0.14 mg/L. This colorimetric assay was successfully applied to detect VC in VC tablets and drinks with spiked recoveries ranging from 92.2% to 115.0%.

In this study, a strain with the capability of producing a high yield of protease, named CL-10, was isolated from the sewage of a canteen in Nanchang University and was identified as Bacillus amyloliquefaciens through physiological and biochemical tests and 16S rRNA sequencing. Rapeseed meal was used as a cheap nitrogen source to produce protease by the strain. The selection and optimization of medium constituents as well as their levels for improved production of protease were carried out using one-factor-at-a-time (OFAT) method combined with response surface methodology (RSM). Rapeseed meal, corn meal and wheat bran levels were selected as independent variables for Box-Behnken design. As a result, the optimal levels for rapeseed meal, corn flour, wheat bran, Tween 20 and ZnSO4·7H2O were determined as 6.1%, 4.4%, 3.2%, 0.7% (V/V), and 0.2%, respectively. Confirmatory experiments performed under these conditions yielded a maximum protease activity of 6 385.1 U/mL, which was increased 2.35-fold compared with the basal fermentation medium, accompanied by a 54.6% reduction in the average cost of nitrogen source. The established process had the advantages of producing high enzymatic activity, low cost, and simple operation. Our results can guide the resource utilization of rapeseed meal for the production of protease.

In this study, the effects of fructooligosaccharides (FOS) on the chemical, microbiological and antioxidant properties of tamarind juice fermented by Lactobacillus plantarum A33 during fermentation and storage were investigated. FOS significantly increased the production of lactic acid and acetic acid during fermentation, with maximum yields of 3.12 and 0.34 g/L, which were 2.5 and 9 times higher than that of the blank group, respectively. FOS significantly increased the viable bacterial count up to 9.59 (lg(CFU/mL)), about 5.3 times higher than those of the blank group, and the total polyphenol content and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity to 156.75 μmol/100 mL and 37.96 μmol Trolox equivalent (TE)/100 mL, respectively. During storage, the viable cell count decreased significantly in the control group, while it remained above 106 CFU/mL in the FOS group after 28 d of storage. FOS significantly improved the DPPH radical scavenging capacity of fermented tamarind juice during cold storage, resulting in the highest DPPH radical scavenging capacity of 44 μmol TE/100 mL on day 14. A total of 90 kinds of volatile components were found in the fruit juice, and 10 kinds of new volatile components were produced after 36 h of fermentation. The contents of most of the volatile components were decreased after 21 days of cold storage, while the content of characteristic substances in the juice was relatively stable, imparting a unique flavor to tamarind juice. The content of ethyl acetate continued to rise, making the flavor more refreshing. Our findings suggested that the flavor, viable cell count and antioxidant capacity of fermented tamarind juice could be improved by adding FOS before inoculation.

In order to study the effect of methyl jasmonate (MeJA) on the size of Agaricus bisporus, different concentrations of MeJA were sprayed on the mushroom before harvest. The results showed that compared to the control group, 50 μmol/L MeJA significantly increased the average mass of individual mushroom bodies and the diameter and thickness of pilei, and advanced the time to reach the harvest size by one day. The activity of cytochrome P450 oxidase significantly increased on day 1 and day 3 (P < 0.05), and the activity of endo-β-1,4-glucanase significantly increased on day 2 (P < 0.05) compared to the control group. According to the transcriptome sequencing, 525 genes in the pilei of MeJA treated A. bisporus were found to be differentially expressed between day 0 and day 1, significantly more than those found in the control and ethanol treated groups (P < 0.05, |log2Fold Change| > 1). Gene ontology (GO) enrichment analysis showed that MeJA may increase the size of A. bisporus by affecting the differential expression of genes enriched in GO items related to growth and development such as cellular process, cell, and catalytic activity. The gene screening results showed that MeJA could up-regulate the gene AGABI2DRAFT_43781, and down-regulate the genes AGABI2DRAFT_136361, AGABI2DRAFT_188444 and AGABI2DRAFT_194024 to increase the size of A. bisporus. This study provides experimental and theoretical basis that MeJA increases the size of A. bisporus.

We aimed to understand the succession of the bacterial communities in Aspergillus-type Douchi during its fermentation and to explore the inherent relation with fermentation environment factors. In this study, The main physicochemical properties were determined, and the composition and succession of the bacterial communities were investigated by high-throughput sequencing and statistical analysis. The results showed that the total amount of microbes, pH, the contents of reducing sugars, total alcohols, and water gradually decreased during the fermentation process, whereas the total amount of acids increased; the temperature increased first and then decreased. Species annotation and diversity analysis revealed that Staphylococcus was the core genus during the entire fermentation process, with relative abundances in the range of 24.16% to 85.97%; the composition (in terms of diversity and uniformity) of the bacterial communities changed significantly, and significant variation in the uniformity was found among fermentation stages (P < 0.05). The correlation analysis showed that the fermentation environment affected the bacterial community succession of Aspergillus-type Douchi, with the main driving factors being reducing sugar content, temperature and pH. Considering the actual situation in the industrial production, temperature may be an important factor to be controlled in the future.

High-efficiency expression of the alginate lyase gene (rFlAlyA) from Flavobacterium sp. in Bacillus subtilis was studied. After high cell-density fermentation for 48 h, the enzymatic activity reached the highest level of 2 550 U/mL with a protein content of 4.5 mg/mL. The rFlAlyA, with a molecular mass of about 30 kDa, was purified to electrophoretic homogeneity after fractionation with (NH4)2SO4 and ion exchange chromatography on SP strong cation exchange column. Maximal enzymatic activity was observed at pH 7.5 and 50 ℃. The enzyme showed good stability at pH 4.0?11.0 and was thermostable up to 50 ℃, retaining over 80% of its activity. The substrate specificity indicated that rFlAlyA was a polymannuronate lyase with trisaccharide being the shortest-chain substrate. For alginate oligosaccharides production, sodium alginate was reacted with rFlAlyA under the optimal conditions for 4 h, giving a final concentration of reducing sugar of 33 mg/mL in the reaction mixture and a conversion rate was 70.1%. Electrospray ionization tandem mass spectrometry showed that the degree of polymerization (DP) of the hydrolysates was 1 to 8 and trisaccharide was the most abundant, which accounted for 34.0% of the total components when the DP was 3. The findings of this study indicated that the recombinant alginate lyase could be applied for the production of alginate oligosaccharides.

In order to establish the correlation between aerobic plate count on the eggshell surface and liquid whole egg’s shelf life, the typical bacterial strains on the eggshell surface were isolated and purified by the gradient dilution and streak plate methods and were identified by morphological observation, physiological and biochemical tests and 16S rRNA gene sequencing. Then the isolated strains were separately inoculated into liquid whole egg, which was subsequently stored at 4 ℃, and their spoilage potential was comparatively evaluated by measuring growth kinetics curves as well as the total volatile basic nitrogen (TVB-N) content, pH, textural properties and sensory evaluation of liquid whole egg. The results showed that microbial contamination on the surface of eggs was an important factor affecting the shelf-life of liquid whole egg (P < 0.05), and the typical strains we obtained included Escherichia coli (E), Bacillus subtilis (B), Kocuria marina (D) and two strains of B. cereus (A and C). All inoculated samples became spoiled after storage at 4 ℃ for 30 h, showing significantly higher TVB-N value than the non-inoculated control. In addition, the pH value, gel hardness and water-holding capacity of the samples were decreased significantly as compared with those of the control samples. By comparing changes in the storage quality of the samples, the spoilage potential of B. cereus was the strongest among the spoilage bacteria, followed sequentially by E. coli, B. subtilis and K. marina.

The aim of this study was to explore the cause of spoilage in the fruit of Chaenomeles speciosa (Sweet) Nakai during storage. The tissue isolation method was used to isolate the microorganisms causing decay of C. speciosa. Two bacterial strains and six mold strains but no yeast strains were obtained. The results of back-inoculation test showed that both the bacterial strains and three of the mold strains caused rot of C. speciosa fruit. These strains were identified by morphological and molecular biology methods as Bacillus megaterium, B. pseudomycoides, Penicillium crustosum, Cladosporium velox and P. expansum, respectively. This study will provide theoretical support for controlling spoilage microorganisms in C. speciosa fruit during storage.

In this paper, the structural characteristics of bacterial communities in Daqu of Maotai-flavor liquor produced in different brewing areas of Maotai town were systematically studied by high-throughput sequencing combined with mathematical analysis. A total of 532 genera of bacteria belonging to 21 phyla were detected. Aneurinibacillus, Rummeliibacillus, Morganella, Prauserella, Olivibacter, Kurthia, Janibacter, Bartonella, Myroides, and unclassified_o__Corynebacteriales and Parapusillimonas were first detected in Daqu of Maotai-flavor liquor. It was found that the bacterial diversities of Daqu from all brewing regions were rich and varied, despite high similarity in the composition of the dominant phyla, dominant genera and core genera. The dominant phyla included Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. The dominant genera included Lentibacillus, Kroppenstedtia, Pantoea, Oceanobacillus and Enterobacter. Bacillus was the core bacterial genus. This similarity suggested enhanced stability of brewing microecological structure and could be considered as an important contributor to the stable production of Maotai-flavor liquor in Maotai town. The structure of bacterial communities in Daqu varied significantly more among fermentation rounds in the same brewing region than among brewing regions. The inter-regional variation was mainly in functional bacteria with low abundance. The results of this study lay a foundation for related research and provide theoretical reference and guidance for monitoring Maotai-flavor liquor production and enterprise site selection.

A simple and sensitive high performance liquid chromatography (HPLC) method was established for simultaneous determination of seven organic acids in order to investigate the effects of organic acid metabolism on the cottony softening and quality of wax apple during postharvest storage. An Atlanis T3 chromatographic column (4.6 mm × 250 mm, 5 μm) was used to separate the organic acids. The mobile phase was a mixture of 0.02 mol/L phosphate solution (pH 2.2) and methanol at a ?ow rate of 0.5 mL/min. The column temperature and UV detection wavelength were set as 25 ℃ and 213 nm, respectively. The seven organic acids were successfully separated and detected under the above experimental conditions. The method displayed a wide linear range with correlation coefficients all above 0.999 5. The limits of detection (LODs) were in the range of 0.001–0.014 mg/g and the limits of quantitation (LOQs) were in the range of 0.003–0.042 mg/g. The spiked recoveries ranged from 86.84% to 98.86%, with relative standard deviation (RSD) less than 5%. This method proved to be a suitable, efficient, quick, accurate and sensitive method for the determination of the seven organic acids in wax apple fruit. The measured contents of organic acids during storage were as follows: pyruvic acid 0.395–0.975 mg/g, malic acid 6.951–10.059 mg/g, ascorbic acid 0.013–0.172 mg/g, lactic acid 0.030–0.735 mg/g, acetic acid 0.263–0.702 mg/g, citric acid 1.658–5.370 mg/g, and fumaric acid 0.269–0.518 mg/g.

The phospholipids in pasteurized milk samples were analyzed and identified by ultra-high performance liquid chromatography-triple quadrupole-time of flight tandem mass spectrometry (UPLC-Triple-TOF MS/MS). The chromatographic separation was performed on an ACQUITY UPLC? BEH C18 (2.1 mm × 100 mm, 1.7 μm) column using gradient elution with water/methanol/acetonitrile (1:1:1, V/V) as mobile phase A and isopropanol/acetonitrile (1:1, V/V) as mobile phase B. Data acquisition was done in the positive ion mode using electrospray ionization (ESI). According to the high-resolution mass spectral data of retention time, quasi-molecular ions and secondary fragments combined with information on the mass spectral fragmentation pathways of reference standards, a total of 68 phospholipid molecules were identified including 22 phosphatidylcholine (PC, 7.98%), 17 phosphatidylethanolamine (PE, 56.60%), 10 phosphatidylserine (PS, 1.70%), 7 phosphatidylinositol (PI, 1.33%), and 12 sphingomyelin (SM, 32.39%). This study achieved comprehensive qualitative and quantitative determination of phospholipids in milk by using the UPLC-Triple-TOF MS/MS method with high sensitivity, precision and stability. This method could detect more phospholipids in milk than other detection techniques and thus provide more basic data for research on milk phospholipids.

In order to obtain well-flavored blue clam hydrolysates, single-enzyme hydrolysis was carried out using protamex, papain, bromelain, alkaline protease and neutral protease. The flavor characteristics of the resulting hydrolysates were comprehensively evaluated by solid phase microextraction combined with gas chromatography-mass spectrometry (SPME-GC-MS), electronic nose (EN), electronic tongue (ET) and automatic amino acid analyzer. The taste activity value (TAV) was used to assess the contribution of the taste-active compounds to the main tastes. The results showed that the highest hydrolysis degree of of 28.02% was observed for the protamex hydrolysate. The flavor profiles of the five hydrolysates were significantly different from one another. EN and ET could clearly distinguish the odor and taste patterns of these hydrolysates. Umami and sweetness were the main taste characteristics for all blue clam hydrolysates. The total amount of free amino acids and the total amount of umami and sweet amino acids were the highest in the protamex hydrolysate and alkaline protease hydrolysate, respectively. A total of 50 volatile components were identified, among which, aldehydes and alcohols were the most abundant. The relative contents of the aldehydes responsible for the fishy odor were the highest in the alkaline protease hydrolysate, and the lowest in the protamex and neutral protease hydrolysates. The flavor compounds 2-ethyl-furan and 2-pentyl-furan were the most abundant in the protamex hydrolysate, which exhibited the best flavor.

An ultra-high performance liquid chromatography quadrupole/orbitrap high resolution mass spectrometry (UPLC-Q-Orbitrap HRMS)-based lipidomics approach was developed for evaluating lipids in milk fermented by Streptococcus thermophilus. HRMS scan information dependent acquisition-product ion scan was performed using an electrospray ionization (ESI) source in the positive and negative ion modes to acquire mass spectra. The lipid composition of the fermented milk was analyzed in detail at the molecular level. A total of 1 716 lipids were detected in the sample, including 861 glycerides, 540 phospholipids, 282 sphingolipids and 33 glycolipids. Under the positive mode, the contents of glycerolipids, phospholipids and sphingolipids were determined to be 95.84%, 3.08% and 1.08%, respectively, and triacylglycerols (TG) 16:0/6:0/14:0, 4:0/14:0/16:1, and 10:0/10:0/12:0 were the dominant lipid components (> 5%). Under the negative mode, the contents of phospholipids, sphingolipids and glycolipids were determined to be 35.34%, 28.15% and 36.51%, respectively, and monogalactosylmonoacylglycerol (MGMG, 2:0) was the main lipid component ( > 5%). Good detection performance was observed on glycerides in the positive ion mode, and on phospholipids, sphingolipids and glycolipids in the negative ion mode. MS analysis in the positive and negative ion modes could provide a full understanding the composition of lipid components in milk fermented by S. thermophilus. The proposed method for lipid analysis had the characteristics of high throughput, high sensitivity and high accuracy. It provides a reliable method for analysis of lipids in fermented milk and lays the foundation for enriching research on the biological functions of dairy lipids.

We investigated changes in the phenolic composition of Dongfanliang millet produced in Shanxi province before and after being cooked into porridge. The cooking process was optimized by orthogonal array design. Phenolic compounds were extracted from raw millet and millet porridge and analyzed by widely-targeted metabolomics, and their antioxidant capacities were determined. The results showed that the optimal parameters were as follows: cooking time 15 min, cooking power 700 W, and solid-to-liquid ratio 1:25 (g/mL). Compared with raw millet, the contents of free phenol and bound phenol in millet porridge decreased by 53% and 10%, respectively. The free and bound phenolic compounds from millet porridge scavenged 75.41% and 56.54% of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, and their total antioxidant activities were 14.72 and 9.58 U/mL, respectively. A total of 37 polyphenols were identified by ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS). Nineteen of these were found to be differential between the samples and 10 metabolic pathways were identified by KEGG pathway enrichment analysis. After being cooked, the contents of free and bound phenolics changed, and the latter was relatively stable, indicating that it may play a more important role in the body.

The flavor quality of Jiuqu Hongmei tea processed by a new technology has been demonstrated to be better than that of the one processed by the traditional procedure, but the flavor chemistry characteristics of the new product are not clear yet. In this study, new Jiuqu Hongmei tea samples of different quality grades and traditional Jiuqu Hongmei tea samples were prepared for sensory evaluation following the national standard of China and for measurement of the contents of non-volatile compounds such as water extract, tea polyphenols, free amino acids, caffeine, theaflavins, thearubigins and theabrownins. Also, we analyzed the volatile composition by gas chromatography and mass spectrometry (GC-MS). The results showed that the new tea had a sweet and mellow taste and a high and fresh aroma and it contained less free amino acids and caffeine than the traditional one. Free amino acids, theaflavins, thearubigins and theabrownins were found to be the key taste compounds to differentiate different grades of Jiuqu Hongmei tea. A total of 39 volatile compounds were identified from Jiuqu Hongmei tea, among which dominant were geraniol, linalool, phenylethyl alcohol, benzyl alcohol, benzene acetaldehyde, benzaldehyde, trans,trans-2,4-heptadienal, β-ionone, methyl salicylate, cis-hexanoic acid, 3-hexenyl ester and geranic acid. As the quality grade of new Jiuqu Hongmei tea dropped, the contents of geraniol, nerol, benzene acetaldehyde, nonanal, 3,5-octadien-2-one, 3-octen-2-one and trans-β-ocimene were decreased while the contents of benzyl alcohol, nerolidol, hotrienol, trans-linalol oxide IV, β-cyclocitral, decanal, trans-2-hexenal, cis-jasmone and dihydro actinidiolide were increased. Therefore, Jiuqu Hongmei tea of different quality grades should be manufactured by the new technology of oxygen-supply fermentation according to the characteristics of raw materials.

In this study, we established a quantitative method for the detection of casein in dairy products using 31P nuclear magnetic resonance (NMR) combined with the interpolation method. The results showed that the limit of detection (LOD) of this method was 0.38 g/L (RSN = 3), and the limit of quantitation (LOQ) was 1.25 g/L (RSN = 10). Good linearity was observed within the concentration range of 5.00–35.00 g/L, with correlation coefficient R2 greater than 0.999. The spiked recoveries were in the range of 91.94%–105.10%. The intra-day and inter-day precisions (relative standard deviation, RSD) were in the range of 0.65%–1.40% and 1.40%–1.80%, respectively. The casein contents of different dairy products on the market were detected by this method and the current national standard method (GB 31638-?2016). The error between the two methods was within ± 5%, which met the requirements for comparative analysis and validation of feasibility. Compared with the conventional method, this method had the advantages of simpler sample pretreatment, higher quantitative accuracy, greatly shorter detection time and wider applicability. Therefore, it could be suitable for rapid determination of casein content in dairy products.

Polysaccharides from the fruit of sea buckthorn (Hippophae rhamnoides) (SBP) were isolated and purified, and their monosaccharide composition, structural characteristics and antioxidant activities in vitro were analyzed. The crude polysaccharides, prepared by sequential water extraction, alcohol precipitation and protein removal by the Sevag method, were fractionated by DEAE-52 cellulose column chromatography into three fractions: neutral polysaccharide SBP-I and acidic polysaccharide SBP-II and SBP-III. The results of monosaccharide composition analysis showed that SBP-I was composed of arabinose, xylose, mannose, glucose and galactose with a molar ratio of 1.18:1:2.20:32.17:1.45, SBP-II was composed of xylose, mannose, glucose and galactose with a molar ratio of 1:0.28:1.02:0.20, and SBP-III was composed of xylose, glucose and galactose with a molar ratio of 1:2.15:0.28. Infrared spectroscopy showed that all of them had the characteristic absorption peaks of polysaccharides. Antioxidant tests in vitro showed that the crude polysaccharides and the three purified polysaccharides exhibited strong antioxidant activity in a concentration-dependent manner, ranked in decreasing order of antioxidant activity as follows: VC > SBP-III > SBP-II > SBP-I > crude polysaccharides.

Based on the results of high performance liquid chromatography (HPLC) analysis combined with sensory evaluation, a Fisher discriminant analysis (FDA) model to grade the pungency intensity of spicy hot pot seasonings was developed using the Statistical Product and Service Solutions (SPSS) software. Changes in capsaicinoid content during the boiling of spicy hot pot seasonings were monitored to determine its influence on pungency grading. The results showed that pungency grading simply by sensory evaluation was greatly influenced by the sensory appraisers, resulting in low accuracy. When the content of capsaicinoid was used as the criterion, the pungency was graded into five levels with a hit ratio of 24% > 20%, and the proposed model was found to be reasonable. The boiling process could affect the migration of capsaicinoids, and the capsaicinoids were maintained in a dynamic equilibrium between the oil phase and the water phase. In addition, the capsaicinoids in the seasoning migrated gradually into the soup, resulting in constant change in the pungency level. This research concluded that HPLC combined with sensory evaluation could allow clear discrimination of the pungency levels of spicy hot pot seasonings, which will guide consumers to select the most suitable product.

Objective: To establish a high performance liquid chromatography (HPLC) method for the simultaneous determination of 18 polyphenol compounds (protocatechuic acid, gentisic acid, p-hydroxybenzoic acid, syringic acid, chlorogenic acid p-coumaric acid, ferulic acid, m-coumaric acid, o-coumaric acid, t-cinnamic acid, naringin, catechin, naringenin, formononetin, maltol, hesperetin, vanillin, and resveratrol) in different parts of ginseng produced in China. Methods: The contents of total phenolic and individual compounds in Radix Ginseng rubra (red ginseng), dried ginseng, ginseng stems, leaves, flowers and tassels were determined. The chromatographic separation was achieved on a Symmetry?C18 column (4.6 mm × 150 mm, 5 μm) using a mobile phase consisting of 0.1% phosphoric acid (A) and acetonitrile (B), and the detection wavelength was set as 230 nm. Results: The 18 phenolic compounds were separated within 35 min, with good repeatability (relative standard deviation (RSD) ≤ 3.49%), high precision (RSD ≤ 3.02%), good stability (RSD ≤ 2.58%) and reliable recovery (average recoveries ranging from 84% to 99%, RSD ≤ 5%). Significant differences in the contents of total phenolic and individual compounds were found among different parts of ginseng (P < 0.05), and the contents of maltol and catechin were high in all samples. The contents of total polyphenols in red ginseng, dried ginseng, ginseng stems, leaves, flowers and tassels were (69.47 ± 3.25), (95.04 ± 5.03), (175.19 ± 3.26), (256.91 ± 2.81), (174.40 ± 6.26), and (99.31 ± 2.90) mg/100 g, respectively. Conclusion: The method is simple, efficient, accurate and reliable, and can be used for quality control of polyphenols in ginseng.

In this study, Chinese jujube fruit from three varieties (Linzexiaozao, Xiaokouzao and Minqinyuanzao) produced in Gansu province were used to brew jujube wine. The physicochemical parameters, volatile components and sensory properties were analyzed, aiming to provide technical support for jujube wine production and quality analysis. The results showed that physiochemical parameters of all wine samples met the requirements of the national standard of China. Among these, Linzexiaozao jujube wine contained the highest total acid content and highest chroma value. Volatile composition analysis and aroma profile analysis displayed that the contents of esters, alcohols and terpenes were higher in Xiaokouzao wine while the contents of acids, aldehydes and ketons were higher in Minqinyuanzao wine. Damascenone, phenyl acetaldehyde, hexanoate ethyl, acetate isoamyl, butyrate ethyl and isoamyl alcohol could be the main compounds which contribute to the floral, fruity and solvent-like aroma notes of jujube wine. Sensory evaluation indicated that Xiaokouzao wine presented the most intense and elegant aroma, while Linzexiaozao wine showed better color and typicality, and both wines had good sensory quality. The two varieties could be used for the production of domestic jujube wine in Gansu province.

A method for the quantitation of nucleotides (cytidine 5’-monophosphate, uridine 5’-monophosphate, adenosine 5’-monophosphate, inosine 5’-monophosphate, and guanosine 5’-monophosphate) in infant formula was developed by sulfoalkyl betaine-based zwitterionic hydrophilic interaction liquid chromatography. The nucleotides in samples were extracted by two-dimensional solid-phase extraction with weak anion exchange and strong cation exchange, data acquisition was achieved using a UV detector. Chromatographic separation was performed by isocratic elution with a mobile phase consisting of 0.001% formic acid-acetonitrile and 10 mmol/L sodium dihydrogen phosphate solution at pH 5. Under the optimized conditions, good linearity was observed for these nucleotides, with a limit of quantification in the range of 0.10 to 0.15 mg/100 g. The method recovery was above 95% and the precision (expressed as relative standard deviation, RSD) was within 10%. This method was fast, sensitive and accurate and could be applied for the determination of nucleotides in infant formula samples.

In this study, gold nanoclusters templated with unlabeled nucleic acid aptamers were rapidly synthesized for use in combination with gold nanoparticles modified with single-stranded DNA that is partially complementary to the DNA strands of the aptamer in a novel fluorescent composite nano-biosensor for rapid detection of ochratoxin A. The stronger binding force between the target and aptamer brought about fluorescence resonance energy transfer in the Apt-AuNCs@cDNA-AuNPs sensor whose fluorescence had been quenched and consequently recovery of the lost fluorescence intensity, thereby allowing the rapid and accurate detection of ochratoxin A (OTA). The results showed that the peak value of fluorescence intensity (FI) displayed a good linear relationship with the concentration (C) of ochratoxin A within the range from 0.01 to 2.5 ng/mL, which was fitted as FI = 689.84lgC + 8 315.31, with the limit of detection (LOD) of 0.025 ng/mL at signal-to-noise ratio of 3. This new fluorescent composite biosensor has the characteristics of simple synthesis, easy operation, high sensitivity, strong selectivity, good stability and a low LOD, which is expected to provide a new idea and platform for the detection of food safety hazard factors.

In this study, a high performance liquid chromatography (HPLC) method was established for simultaneous determination of 13-hydroxy-9Z,11E-octadecadienoic acid (13-Z,E-HODE), 13-hydroxy-9E,11E-octadecadienoic acid (13-E,E-HODE), 9-hydroxy-10Z,12E-octadecadienoic acid (9-Z,E-HODE) and 9-hydroxy-10E,12E-octadecadienoic acid (9-E,E-HODE) in meat products. The analytes were extracted from samples with methanol, purified by Sep-Pak C18 column, and then separated using isocratic elution on an Absolute SiO2 column (250 mm × 4.6 mm, 5 μm) with a mobile phase consisting of n-hexane, isopropanol and acetic acid (98.3:1.6:0.1, V/V) before being detected at 234 nm using a photo-diode array (PDA). The results indicated that the method displayed a good linearity within the concentration ranges of 0.5–20.0 μg/mL (R2 = 0.999 4) for 13-Z,E-HODE, and 0.25–10.0 μg/mL (R2 = 0.999 2) for 13-E,E-HODE, 0.75–12.5 μg/mL (R2 = 0.999 2) for 9-Z,E-HODE and 0.5–7.5 μg/mL (R2 = 0.999 6) for 9-E,E-HODE, respectively. The detection limits (LODs) for 13-Z,E-HODE, 13-E,E-HODE, 9-Z,E-HODE and 9-E,E-HODE were 0.075, 0.035, 0.090 and 0.060 μg/g, respectively, and the limits of quantification (LOQs) were 0.25, 0.12, 0.32 and 0.20 μg/g, respectively. The average recoveries from spiked samples were 89.03%, 89.03%, 89.33% and 87.93%, respectively. When this method was used to analyze 18 meat products, all the samples contained 13-Z,E-HODE, 13-E,E-HODE, 9-Z,E-HODE and 9-E,E-HODE at levels of 1.73–9.10, 0.56–5.79, 2.37–11.02 and 0.78–5.82 μg/g, respectively. In conclusion, this method was proved to be fast, accurate and reproducible, and could be used for the simultaneous quantitative analysis of 13-Z,E-HODE, 13-E,E-HODE, 9-Z,E-HODE and 9-E,E-HODE in meat products.

In this study, we collected a total of 38 samples of 27 Amanita species and extracted their genomic DNA. Universal primers were used to amplify the internal transcribed spacer (ITS), large ribosomal subunit (LSU), the second-largest subunit of RNA polymerase II (RPB2), and the β-tubulin gene sequences. Sanger bidirectional sequences were obtained, proofread and then submitted to the NCBI GenBank for sequence alignment to identify the species. We calculated the intra-species and inter-species Kimura-2-Parameter (K2P) genetic distance and constructed the phylogenetic tree. The results indicated that β-tubulin and ITS were more suitable than RPB2 and LSU for use in the identification of Amanita species. The combined use of β-tubulin and ITS could be recommended to identify Amanita species, providing early warning of foodborne poisoning caused by poisonous mushrooms. β-tubulin was shorter than LSU, ITS, and RPB2, being suitable for use in the analysis of highly-processed mushroom products and vomits after eating poisonous mushrooms by mistake. Thus, β-tubulin can be used as the optimal barcode to identify and trace Amanita species causing mushroom poisoning.

An analytical method was established for the simultaneous determination of 169 pesticide residues in pepper powder by high performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (HPLC-Q-TOF MS). The samples were soaked in 0.1% (V/V) aqueous acetic acid solution, then extracted with acetonitrile and purified with C18 and Florisil sorbents. The compounds were separated on a C18 column (100 mm × 2.1 mm, 2.6 μm) using gradient elution with a mobile phase composed of 5 mmol/L ammonium formate aqueous solution and methanol, detected in the positive ion mode and quantitated by the matrix matched external standard method. Meanwhile, an accurate mass database and a fragment ion library were created for rapid qualitative and quantitative analysis of the 169 pesticides in pepper samples. The results showed that the method had a good linearity (R2 > 0.95) within the concentration range of 5–100 ng/mL for 136 pesticide compounds. The remaining 33 compounds could only be qualitatively analyzed. The recoveries for the target compounds at three spiked levels ranged from 26% to 140%, with relative standard deviations of 1.5%–36.0%. The method is simple, less time consuming and suitable for rapid and high-throughput screening of pesticide residues in pepper powder samples.

In this study, 3-[2-(2-aminoethylamino) ethylamino] propyltrimethoxy functional iron oxide (Fe3O4@SiO2-PAAA) magnetic nanoparticles (MNPs) were prepared by a chemical co-precipitation method and silanization reaction and used to simplify the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method and simultaneously improve the purification efficiency. MNPs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, X-ray photoelectron spectroscopy, and zeta potential analysis. A modified QuEChERS method was developed using Fe3O4@SiO2-PAAA as an adsorbent for detecting seven pesticide residues in fruits and vegetables using gas chromatography-tandem mass spectrometry (GC-MS/MS). Under the optimized conditions, the developed method showed a good linear relationship in the concentration range between 0.007 and 1.000?mg/kg with correlation coefficients (r2) above 0.994. The limits of quantitation (LOQs) for the method were between 0.007 and 0.017?mg/kg. At LOQ, 2?LOQ, and 10?LOQ fortification levels, the recoveries were in the range from 75.2% to 105.4% for the seven pesticides, with relative standard deviations (RSDs) between 3.7% and 15.7%. This method is fast, accurate, effective and sensitive, and can be used as a reference method for the analysis of pesticide residues in fruits and vegetables.

An indirect competitive chemiluminescent enzyme-linked immunosorbent assay (ic-CLEIA) was developed for the rapid detection of amantadine and chloramphenicol residues in poultry meat based on efficient sample pretreatment. The dilution factors of coating antigen, antibody and horseradish peroxidase (HRP)-labeled secondary antibody, and competition time were optimized. The results showed that the half-maximum inhibition concentration (IC50) and the linear range were 0.33 μg/L and 0.06–1.77 μg/L for amantadine, and 0.039 μg/L and 0.010–0.179 μg/L for CAP, respectively. Samples were sequentially extracted with ethyl acetate and potassium carbonate solution, and then the extract was blown to dryness with nitrogen gas and purified by n-hexane extraction before being analyzed. The recoveries of amantadine and chloramphenicol from spiked samples were in the ranges of 92.55%–105.14% and 92.00%–112.50%, respectively, and the coefficients of variation were both less than 10.48%. Furthermore, the results determined by ic-CLEIA were highly correlated with those of instrumental analysis method (R2 > 0.98), which demonstrates that the established ic-CLEIA method has high accuracy and good reliability. This method represents a rapid immunoassay for the detection of veterinary drug residues in poultry meat.

A high performance liquid chromatography-fluorescence detection (HPLC-FLD) method was developed for the qualitative and quantitative analysis of the sialic acids N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) in red meat and its processed products. Single factor experiments were carried out to optimize the derivatization and acid hydrolysis conditions. Besides, ultrasound-assisted acidification was used to shorten the acidification time. It was found that the optimal sample preparation procedure involved ultrasound-assisted acidification time for 30 min with hydrochloric acid as the hydrolysis reagent and derivatization for 120 min with the same volume of 13 mmol/L 4,5-methylenedioxy-1,2-phenylenediamine dihydrochloride (DMB) as the derivatization reagent. The calibration curves for Neu5Ac and Neu5Gc displayed good linearity in the range of 0.1–10 μg/mL. The recoveries were in the range of 91.2%–119.7%. The limits of detection (LODs) for Neu5Ac and Neu5Gc were 0.003 and 0.01 mg/kg, respectively. The precision expressed as relative standard deviations (RSDs) for the two sialic acids was in the range of 0.7%–1.8% and the repeatability RSDs were 1.4% and 1.2%, respectively. The HPLC-FLD method has the characteristics of high sensitivity, short analysis time, and good repeatability and accuracy.

The full length and truncated recombinant outer membrane protein K (OMPK) of Vibrio parahaemolyticus were purified before being used to immunize 6–8-week-old female BALB/c mice. The titer of antisera was measured by an indirect sandwich enzyme linked immunosorbent assay (ELISA). The results showed that the titer of the antiserum against the full-length OMPK recombinant protein was 128-fold higher than that of the antiserum against the truncated OMPK1 recombinant protein. Several monoclonal antibodies (mAbs) were successfully generated by using the full-length OMPK recombinant protein and were used to detect V. parahaemolyticus after being conjugated with biotin and horseradish peroxidase (HRP). Indirect sandwich ELISA results indicated that only biotin conjugated VP3 and VP16 were paired with other mAbs, showing high sensitivity and good specificity to detect various V. parahaemolyticus strains. They showed no cross reactivity with 20 strains of other bacteria. Biotinylated VP16 Fab fragment-VP3 pair showed higher sensitivity to detect V. parahaemolyticus than biotinylated VP16-VP3 pair. By this method with biotinylated VP16-VP3 pair, salmon (about 5–10 CFU/25 g) and blood clam samples were found to be positive for V. parahaemolyticus. Thus, our research successfully developed a rapid, sensitive, and convenient method for V. parahaemolyticus detection by indirect sandwich ELISA.

A novel colorimetric aptamer sensor (aptasensor) was developed for rapid identification of fluoronitrile in egg samples. The assay was based on highly selective aptamer binding to its targets combined with the dual-amplification effect of the EnVision? polymerase chelate (EV) labeled with gold nanoparticles (AuNPs). This method could specifically and sensitively detect ultra-trace amounts of fluoronitrile in egg. EV contained approximately 100 urease molecules which could effectively catalyze decomposition of urea to enrich copper ions to produce basic copper carbonate. Color change of the chromogenic agent of acid copper ion could be generated by basic copper carbonate. In addition, gold nanoparticles could catalyze the deposition of basic copper carbonate to a certain extent. Thus, a dual-amplification effect could be achieved by using the proposed method. The amount of fluoronitrile in samples could be calculated by measuring the change in the absorbance of chromogenic agent-copper ion complex. The results indicated that under optimal conditions, the limit of detection was identified as 0.072 μg/kg and good linearity was observed within the concentration range of 0.1 μg/kg–50 mg/kg with a correlation coefficient of 0.998. This assay was successfully used to analyze fluoronitrile concentrations in egg samples with results consistent with those obtained by a conventional ELISA method.