In this study, three different kinds of milk fat (two butters (A and B) and cream) were hydrolyzed respectively with two lipases (D and E) and two cutinases (F and G), and acid value and volatile compound profile before and after hydrolysis were compared. The results indicated that the variation of acid value after hydrolysis depended on the enzyme used. The largest increase in acid value of over 40 mg/g was observed after hydrolysis of 50% (m/m) butter A by lipase E. Cutinase G, however, very weakly hydrolyzed the milk fat and caused the smallest change in acid value. More volatile compounds were identified in hydrolyzed milk fat. Lipase D produced the highest content of octanic acid when hydrolyzing the butters and 50% (m/m) cream (except when using 93.3% (m/m) cream as substrate). After hydrolysis by lipase E, butyric acid, hexanoic acid, octanic acid and decanoic acid were the major compounds in the hydrolysate of butter A, whereas the most prominent volatile compounds in the hydrlysates of butter B and milk cream were octanic acid and hexanoic acid, respectively. After hydrolysis by cutinase F, hexanoic acid and octanic acid were the major volatile compounds in 93.3% (m/m) cream, while hexanoic acid and decanoic acid were major volatile compounds in the hydrolysates of butters and 50% (m/m) cream, respectively. The results showed that hydrolysis by lipases or cuitnases caused a significant change in the volatile compound profile of milk fat, not only producing new fatty acids, but also increasing the contents of butyric acid, hexanoic acid, octanic acid, and decanoic acid.

In order to explore the affecting mechanism of sodium alginate and calcium chloride on the retrogradation of rice starch, the effect of sodium alginate and calcium chloride on the thermodynamic properties of rice starch retrogradation was investigated using a differential scanning calorimeter and confirmed by thermogravimetric analysis. An Avrami model was used to analyze the kinetic parameters. The results showed that 3 mmol/L calcium chloride, 0.9% sodium alginate and their mixture increased the gelatinization peak temperature by 1.0%, 1.1% and 2.2%, and the gelatinization enthalpy by 4.7%, 14.0% and 21.4%, respectively. There was no significant effect of calcium chloride on the retrogradation of rice starch stored for 21 days (P < 0.05); while 0.6% sodium alginate and its mixture with calcium chloride decreased the retrogradation enthalpy by 23.7% and 27.6%, and the retrogradation rate by 33.9% and 36%, respectively. The crystallization mode of rice starch was transformed from instantaneous nucleation to continuous nucleation in the presence of calcium chloride, sodium alginate (0.9%) or their mixture, and correspondingly, the crystallization rate constant was decreased by 73.0%, 90.1% and 95.3%. The moisture loss rate of retrograded rice starch was decreased by 87.1% with the addition of a mixture of sodium alginate (0.6%) and calcium chloride, confirming the inhibitory effect of the mixture on the retrogradation of rice starch.

The objective of this study was to investigate the effects of tea polyphenols (0, 0.02, 0.2 and 1.0 mg/mL) on the side chain structure, water-holding capacity (WHC) and water distribution state of myofibrillar protein (MP) in hydroxyl radical oxidation system. Results showed that oxidative stress to MP significantly decreased free sulfydryl content and WHC, significantly increased surface hydrophobicity, dityrosine content and free water content, and lowered endogenous tryptophan?fluorescence intensity compared to the non-oxidized control (P < 0.05). Under oxidative conditions, free sulfydryl content and endogenous tryptophan?fluorescence intensity gradually increased, surface hydrophobicity decreased, and WHC of MP gels rose with increasing concentration of tea polyphenols; immobilized water content significantly increased while free water content significantly declined (P < 0.05). Tea polyphenols can protect the side chain structure of MP and improve the WHC of heat-induced gels under oxidative conditions.

This paper focuses on the physicochemical and functional properties of soybean dietary fiber from enzyme-assisted aqueous extraction processing (EAEP) and on its effect on the farinograph properties of wheat flour and the texture of dough as well as its effect in improving the texture and digestibility of biscuits. The results showed that the purity of the dietary fiber was 81.34%, and that the content of soluble dietary fiber accounted for about 50.83% of the total dietary fiber. The farinograph properties of wheat flour and the textural properties of dough were the best when added with the dietary fiber at 30%. The textural properties of the resulting biscuits were better than those of commercial high-fiber biscuits. Additionally, the digestion rate was significantly lower than that of commercial high-fiber biscuits and ordinary biscuits, accompanied by a decrease in rapidly digestible starch content by 17.14% and 42.57% and an increase in slowly digestible starch content by 24.93% and 110.27% as well as in resistant starch content by 0.85% and 21.57%, respectively, and the glycemic index was only 45.99, a value for low-sugar foods. Therefore, the dietary fiber had good physicochemical and functional properties, indicating its great potential in the baked food industry as a new resource of soybean dietary fiber.

The epoxy-modified Fe3O4 magnetic microspheres prepared in our laboratory were used as the carrier to immobilize phospholipase A1 (PLA1). Response surface methodology was used to optimize the immobilization conditions. Furthermore, the properties of the immobilized enzyme were studied. The results showed that the optimal immobilization conditions were determined as follows: buffer pH 4.0, reaction time 1.9 h and enzyme dosage 3.6 mL/g. The activity of the immobilized enzyme obtained under these conditions was 3 675 U/g with an immobilization efficiency of 61.1%. Compared with the free enzyme, the optimal reaction pH was shifted to alkaline pH of 1.0 and the optimal reaction temperature of the immobilized enzyme was increased by 5?℃. The storage stability of the immobilized enzyme was increased as well. And the immobilized enzyme retained about 81.1% of the initial activity after the 8th use for rapeseed oil degumming. Moreover, modern analytical methods such as X-ray diffraction (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the carrier. The results showed that the nano-sized microspheres were successfully prepared with epoxy-modified surfaces.

This study aimed to elucidate the mechanism for the preparation of meat flavorings by thermal reaction of hydrolyzed animal protein (HAP). Four thermal reaction systems, HAP alone, HAP plus oxidized lard (HAP-OL), HAP plus xylose (HAP-Xyl) and HAP plus both oxidized lard plus xylose (HAP-Xyl-OL), were reacted at 120, 130 or 140 ℃ for 120 min. The effect of adding oxidized lard and xylose on the pH, browning degree, molecular mass distribution and taste of reaction products was investigated. The results showed that the pH decline, absorbance at 294 and 420 nm, and chroma of the reaction products from HAP-Xyl were much higher than those of HAP-OL, and the?values?of?these parameters?were?highest?in the reaction products of HAP-Xyl-OL. The changes in absorbance at 420 nm and chroma at the early stage of reaction followed zero-order kinetics for all four reaction systems. The reaction rate constant and activation energy showed that HAP-Xyl reacted fastest and HAP-Xyl-OL reacted more slowly than HAP-Xyl, suggesting that the presence of OL inhibited the reaction of xylose with HAP. The molecular mass distribution of the reaction products with better taste was determined by high-performance gel chromatography (HPGC). It was shown that the addition of xylose decreased the fractions with molecular mass < 1 kDa, while oxidized lard had little effect on the molecular mass distribution. Furthermore, sensory evaluation showed that the addition of xylose enhanced the umami and meaty taste, the addition of oxidized lard increased the kokumi, continuity and mouthfulness, and the addition of both oxidized lard and xylose increased the umami, meaty taste, kokumi, continuity and mouthfulness.

In order to develop a new biodegradable antimicrobial packaging material, four typical essential oils including oregano oil, thyme oil, rosemary oil and cinnamon oil were screened for antimicrobial activity, and we investigated the effect of incorporating different concentrations of cinnamon oil on mechanical, optical and antimicrobial properties and water vapor permeability of composite films prepared using corn starch, chitosan and konjac glucomannan (KGM) as film forming materials, glycerol as a plasticizer and Tween-80 as a surfactant. The antibacterial activity against Staphylococcus aureus, Escherichia coli and Salmonella enterica of the essential oils was in the descending order of cinnamon oil > oregano oil > thyme oil > rosemary oil. Tensile strength (TS) and water vapor permeability of composite films decreased, while elongation at break (EAB) and opacity increased with the increase of cinnamon oil. The color parameter a* value did not vary significantly (P > 0.05), whereas L* value significantly decreased and b* and ΔE values significantly increased with increasing cinnamon oil concentration from 15.0 to 20.0 g/L (P < 0.05). The antimicrobial properties of composite films were improved significantly with the incorporation of cinnamon oil (P < 0.05). The combination of Tween-80 and cinnamon oil demonstrated synergistic antimicrobial activity against Gram-negative E. coli, while an antagonistic effect against Gram-positive S. aureus was observed. The film with 20.0 g/L cinnamon oil had good physical and antimicrobial properties. However, further studies are needed to optimize the preparation of biodegradable antimicrobial cinnamon oil/corn starch-based films.

Deep-fried twisted dough sticks or Youtiao in Chinese were made from aluminum-free premix flour for deep-fried twisted dough sticks incorporated with different amounts (0%, 3%, 6%, 9% and 12%) of green wheat flour using different yeast starters: instant dry yeast H-1 (high sugar-tolerant Saccharomyces cerevisiae var. ellipsoideus), instant high-active dry yeast H-2 (high sugar-tolerant Saccharomyces cerevisiae var. ellisoideu), high-active dry yeast L-1 (low sugar-tolerant Saccharomyces cerevisiae var. willanus), and instant dry yeast L-2 (low sugar-tolerant Saccharomyces cerevisiae var. bayanus EC-1118). We studied the fermentation and rheological properties of doughs and the specific volume, texture characteristics and sensory quality of the resulting Youtiao. The results showed that H-2 had the best fermentation characteristics in terms of high elastic and viscous modulus and good viscoelasticity among four yeast strains. For each addition level of green wheat flour, the specific volume and elasticity of Youtiao made with H-2 was larger than those of Youtiao made with the other strains. The specific volume and texture quality of Youtiao made with 6% green wheat flour added were moderate; the sensory score was similar to that of the blank control while the contents of carbohydrate and dietary fiber were higher. Therefore, Youtiao made from H-2 fermented dough with 6% green wheat flour added had good sensory quality and was nutritious.

An in vitro immune cell model was used for bioactivity-guided fractionation of the crude polysaccharides ultrasonically extracted from Haematococcus pluvialis residue left after the extraction of astaxanthin by sequential DEAE-52 anion exchange and Sephacryl S400 column chromatographies. The molecular masses of the isolated polysaccharides were determined by high performance gel permeation chromatography (HPGPC). The results showed that five polysaccharides, named HPP-c1, HPP-c2, HPP-c3, HPP-c4 and HPP-c5, were obtained by DEAE-52 column chromatography. Of these, HPP-c3 had the highest immunological activity. Further, HPP-c3-s1, HPP-c3-s2, and HPP-c3-s3 were isolated from HPP-c3 by Sephacryl S400 column chromatography. HPP-c3-s1 could significantly stimulate the proliferation of spleen cells (P < 0.01) in the concentration range of 0–250 μg/mL in a dose-dependent fashion. HPP-c3-s1 had the highest stimulation index (SI) of 1.34 among the HPP-c3 fractions. The purity of HPP-c3-s1 was found to be homologous with a molecular mass of 23 413 kDa. These results provide a valuable guidance for the high-value comprehensive utilization of H. pluvialis.

In this work, the effect of adding different amounts of ultrasonic-assisted acid-modified wheat bran powder on the farinographic properties and gelatinization characteristics of wheat flour as well as the tensile and texture properties of dough was investigated. The results indicated that dough water absorption rate and development time (DDT) increased, and dough stability time (DST) and farinographic quality number (FQN) increased initially and then decreased with increasing addition of acid modified superfine wheat bran; maximum resistance to extension, resistance to extension (R) and ratio of resistance to extension to extensibility (R/E) increased, while extensibility (E) and extension area decreased. These variations suggested that the modified wheat bran powder showed both?positive?and?negative effects on the tensile properties. In addition, peak viscosity, trough viscosity, breakdown, final viscosity, setback, peak time and gelatinization temperature all increased firstly and then decreased. The same trend was observed for texture properties such as hardness, springiness, adhesiveness, chewiness, cohesiveness and resilience. Overall, it was concluded that the application of acid modified wheat bran powder in the range of 6%–9% could improve flour quality and dough texture properties.

Lactobacillus plantarum K25, isolated from Tibetan Kefir, was pretreated at low (4, 10 or 20 ℃) and high temperatures (45, 50 or 55 ℃) for different times (0.5, 1.5, 3, 5, 8, 18 or 24 h). Subsequently, the survivability of L. plantarum K25 was determined after 1, 15 and 30 days of storage at ?20 ℃. L. plantarum K25 without any treatment was used as a control. The results showed that after pretreatments at 4 ℃ for 18 h and at 55 ℃ for 0.5 h the viable counts were 12 and 15 times higher than those of the control after 30 days of storage at ?20 ℃. Fermented ice cream using K25 (control), C-K25 (pretreated at 4 ℃ for 18 h) and H-K25 (pretreated at 55 ℃ for 0.5 h) with or without chocolate were prepared. The acidity of the C-K25 and H-K25 fermented ice cream was lower than that of the control, whereas the viscosity and firmness were significantly increased as compared to those of the control (P < 0.05). In addition, melting rate and overrun were improved in the C-K25 and H-K25 fermented ice cream. The viable counts of the control, H-K25 and C-K25 ice cream were 5.63, 7.26 and 7.32 (lg(CFU/mL)), respectively after 60 days of storage at ?20 ℃, indicating that cold and heat pretreatments facilitated bacterial survival in the frozen environment. The highest viable count (7.56 (lg(CFU/mL))) was found in the C-K25-fermented ice cream with chocolate, indicating that chocolate provided protection for L. plantarum K25 against cold damage. Finally, after storage at ?20 ℃ for 30 days, all the experimental groups showed no significant decrease in the survival rate of L. plantarum K25 upon mimic gastric acid and bile salt stress (P > 0.05).

This study was aimed at the composition of lactic acid bacteria and the relationship between changes in the flavor characteristics and the microbial diversity in naturally fermented Jinzhou pickle for the purpose of laying the basis for its industrial production. The contents of total acid, amino nitrogen, nitrite and NaCl and the total number of colonies were determined in 27 samples, and the differences among samples from different locations were analyzed. All investigated chemical components of pickle brines significantly varied with producing areas, fermentation conditions and methods (P < 0.05). We also found a direct association between changes in the flavor characteristics and changes in the bacterial community during the fermentation process. A total of 24 strains suspected of being lactic acid bacteria were isolated from 7 representative samples in terms of the chemical components. All these strains were identified as lactic acid bacteria by 16S rDNA sequence analysis, including 10 strains of Lactobacillus, 8 strains of Enterococcus, 3 strains of Streptococcus, and 3 strains of Weissella.

Headspace solid phase microextraction coupled with gas chromatography (HS-SPME-GC-MS) was applied to identify the volatile flavor components of two traditional fermentation starters (Baiqu and Hongqu) for Hongqu glutinous rice wine. The characteristic aroma components were determined by principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). Also, MiSeq high throughput sequencing technology was used to analyze the structure of microbial flora in the two fermentation starters. Results showed that a total of 70 volatile components were detected in the fermentation starters, and that there was a significant difference in the volatile profiles of Hongqu and Baiqu. The dominant microorganisms in Hongqu were Bacillus sp., Weasella sp., Staphylococcus sp., Aspergillus niger, A. oryzae and A. flavus, while the dominant microorganisms in Baiqu were Pantoea sp., Enterobacter sp., Weasella sp., Saccharomyces cerevisiae, Rhizopus arrhizus and Mucor indicus. The research results provide a theoretical basis for elucidating the mechanism of aroma production and for improving the flavor quality of Hongqu glutinous rice wine.

The present study was conducted in order to investigate the relationship between the diversity of the bacterial community in four naturally fermented sour meat products and their flavor qualities. The bacterial community composition was investigated by 16S rDNA V3-V4 region high throughput sequencing using Ion S5 XL sequencing platform. Meanwhile, these samples were subjected to electronic nose evaluation and solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) analysis. The results revealed that the average number of sequences per sample was 110 395. The overall bacterial community compositions of the four samples were quite complicated, including 11 phyla, among which, Firmicutes was absolutely dominant, accounting for 83.73%–98.92% of the total number, followed by Proteobacteria and Actinobacteria. The dominant genera were Lactobacillus, Weissella and Lactococcus. A total of 126 volatile compounds were identified from four naturally fermented sour meats, including acids, alcohols, aldehydes, esters, ketones and terpenes. There were differences in the abundance of bacterial species among the four samples and the microfloral community was closely to the production process. The bacterial diversity involved in the fermentation process was one of the most important factors shaping the flavor characteristics of traditional sour meat products. Compared to traditional methods, the information about bacterial community diversity provided by high-throughput sequencing method was closer to the microecology of the samples, which were helpful to better understand the microfloral composition of sour meat and might provide a scientific support for the modernization of the traditional food industry and food quality and safety control.

Objective: This study aimed to evaluate the stress resistance and malolactic fermentation ability of an acid-tolerance mutant strain of Oenococcus oeni for the purpose of providing a basis for the development of commercial wine fermentation starters. Methods: A acid-tolerant mutant b1, obtained by N+ ion implantation mutagenesis, was tested for the effect of various environmental stress factors and their combinations as well as wine-model conditions on its growth, L-malic acid degradation rate and β-glycosidase activity. Furthermore, we assessed the malolactic fermentation (MLF) ability of mutant b1. Results: The L-malic acid degradation rate and β-glycosidase activity of b1 were higher than those of the other strains under the conditions: pH 3.0, alcohol concentration of 14% and malic acid concentration of 3 g/L. pH had the greatest influence on the growth, L-malic acid degradation rate and β-glycosidase activity of b1, alcohol concentration was in the middle, and L-malic acid concentration was least effective. When the alcohol concentration of the model wine was 14%, the L-malic acid consumption of strain b1 was 1.493 2 g/L, which was 1.41 and 1.26 times as high as that of O. oeni SX-1b and 31-DH, respectively, and it had the highest β-glucosidase activity. Conclusion: Acid-tolerant mutant b1 has good stress resistance and malolactic fermentation ability. Therefore, it has the potential to be used as a commercial starter .

This study aimed to develop an effective and safe biological control agent and to sufficiently explore and make use of beneficial microorganisms. One bacterial strain named CF-2, which was separated from fermented bean curd and showed inhibitory effect on postharvest diseases of honey peaches, was identified based on morphological features, physiological and biochemical characteristics, and 16S rDNA sequence homology analysis. The growth curve of CF-2 and its optimal growth conditions were determined. Subsequently, the antimicrobial activity of CF-2 and its metabolites against four main postharvest fungal pathogens of honey peach (Alternaria alternata, Monilinia fructicola, Cephalothecium sp. and Rhizoctonia sp.) was assessed by plate confrontation method and in vivo experiments. The results showed that strain CF-2 was identified as Bacillus subtilis. At 24-48 h of culture, the growth rate of CF-2 reached a peak, and the optimal pH and temperature for its growth were determined as 7.0 and 37 ℃, respectively. CF-2 showed inhibitory effect on the four fungal pathogens in vitro with an average percentage inhibition of (38.70 ± 9.22)%, and it exhibited the strongest inhibitory effect on Cephalothecium sp. with a percentage inhibition of (52.30 ± 3.67)%. The 24 h fermented broth and its cell-free filtrate and cell suspension also had strong inhibitory effect on all four pathogenic fungi. The average percentage inhibition of the cell-free filtrate was (68.76 ± 5.77)% and it showed the strongest inhibitory effect on A. alternata with a percentage inhibition of (77.41 ± 1.91)%. Compared to the control group, treatment with the cell-free filtrate delayed spore germination of the fungal pathogens by 62-64 h and decreased spore?germination rate by 87.93% on average after 12 d. In in vivo experiments, the 24 h fermented broth of CF-2 and its cell-free filtrate and cell suspension all increased the percentage of marketable fruit compared to the control group, especially the cell-free filtrate, which showed the strongest effect, increasing the percentage of marketable fruit by 29% after 6 d. The above findings indicated that CF-2 and its metabolites had strong inhibitory effect on four main fungal pathogens in honey peach.

Four hybridomas secreting monoclonal antibody (McAb) against bovine immunoglobulin G (IgG) were developed by fusion of spleen cells from immunized BALB/C mice with SP2/0 myeloma cells, and they were named as 2F6, 5E3, 9C6 and 9H8. The McAbs secreted by all four hybridomas were identified as IgG1 subtype with a titer of 5.12 × 106. Both 5E3 and 9H8 recognized the heavy chain Fc fragment of bovine IgG. 2F6 recognized the light chain Fab fragment of bovine IgG, and 9C6 recognized the heavy chain Fab fragment of bovine IgG. The McAb from 9C6 could react with both IgG1 and IgG2. The cross-reactivity between 9C6 and goat IgG, sheep IgG, rabbit IgG, bovine IgM, casein, β-lacto globulin, lactoferrin, bovine serum albumin, ovalbumin or fish gel was less than 1%. The affinity constant of 9C6 was 8.92 × 108 L/mol.

Microbial amylases play a crucial role in the hydrolysis of rice starch (the starch content of rice is more than 70%) during the brewing of Hongqu glutinous rice wine, which influences or even determines the conversion of the raw material and therefore the product quality of Chinese Hongqu glutinous rice wine. Two Bacillus strains able to hydrolyze starch, numbered BHQ03 and BHQ06, were isolated from a fermentation starter for Hongqu glutinous rice wine. The strains were identified using molecular biological methods, and 4 type I pullulanase encoding genes, namely pulL1 and pulL2, pulL3 and pulL4, were cloned from each strain. pulL1 and pulL3 each encoded 713 amino acids and showed a sequence similarity of 96.31%, while pulL2 and pulL4 each encoded 852 amino acids and had a sequence similarity of 99.77%. The proteins PulL1 and PulL2 both belonged to the G13 subfamily, and had 4 characteristic conservative regions. PulL2 contained a signal peptide of 32 amino acids at the N-terminal, and exhibited a mutation at the catalytic site (D407G). Based on previous studies combined with 3D structure homologous modeling, the catalytic process of the pullulanase was analyzed. The above results provide a basis for scientific understanding of the hydrolysis process of starch during the brewing of Chinese Hongqu glutinous rice wine.

In order to study how polyphenol oxidase regulates the progression of Agaricus bisporus browning, we performed mRNA sequencing using the RNA-seq technique on the pilei of A. bisporus collected on day 1, 7 and 14 of postharvest storage. A total of 168 607 212 high-quality reads were obtained; 727 and 1 524 differentially expressed genes were identified on day 7 and 14 compared with day 1 of storage, respectively. These differentially expressed genes were classified into 180 metabolic pathways after gene ontology and pathway enrichment analysis; of them, five polyphenol oxidase genes (PPO1, PPO3, PPO5, LAC1 and LAC4) were screened out and their relationships with browning were investigated. These results provide a theoretical basis for mining of functional genes and quality improvement of A. bisporus.

Response surface methodology was employed to optimize the solid-state fermentation process of Fusarium oxysporum LD105, isolated from maca rhizosphere soil in Kunming, Yunnan Province, for improved production of antibacterial polysaccharides. Polysaccharide yield and antibacterial activity were used as response variables. Using one-factor-at-a-time method, fermentation time, initial moisture content, sucrose and KH2PO4 concentration were identified as main factors that significantly influence the responses. The three-dimensional response surfaces were generated to study the interaction among the four factors. The results showed that the optimal fermentation conditions were as follows: fermentation time 5 d; sucrose concentration 3%; fermentation temperature 28 ℃, initial moisture content 54%, KH2PO4 concentration 0.3%, inoculum size 10%, initial medium pH 6, peptone concentration 1.5%, and 10 g of medium contained in a 250 mL conical flask. Under these conditions, the percentage inhibition of Escherichia coli and the polysaccharide yield were 37.6% and 30.2 mg/g, which were increased by 2.8 and 2.5 folds as compared to that obtained using the unoptimized medium, respectively.

Ten strains of lactic acid bacteria from different sources including fermented fruit were screened for tolerance to stress conditions. Lactobacillus plantarum ZG2 and Lactobacillus casei GG8 were selected as the best for the fermentation of pear juice. We compared the fermentation performance of the two strains by measuring the viable count, pH value, organic acids and volatile components of pear juice during the fermentation process. The results showed that the viable count of ZG2 decreased rapidly during the early part of the fermentation process, lasting for a short time of period. The pH value at the end of fermentation for GG8 was lower than that for ZG2. The organic acid compositions of the two fermented juices were similar although ZG2 exerted stronger lactic acid-producing ability while GG8 produced larger amounts of citric acid and total acids. The primary flavor compounds of pear juice changed little before and after fermentation, 2-methoxy-3-methylpyrazine, linalool and terpineol. Both strains produced the most abundant volatile compounds during the middle stage of fermentation, and GG8 also produced abundant volatile compounds during the late stage. Compared with L. plantarum ZG2, L. casei GG8 has greater potential for research and application.

This study aimed to clone and express the gene encoding antimicrobial peptide PlnF from Lactobacillus plantarum in Lactococcus lactis for the purpose of obtaining a recombinant strain which can be applied directly in in food preservation and preservation. The plnF gene was cloned and inserted into plasmid vector pNZ8149. The resulting recombinant plasmid was transformed by electroporation into competent cells of L. lactis NZ3900 under the conditions: resistance 200 Ω and capacitance 25 μF. The recombinant strain was screened out using a bromocresol purple-supplemented medium, confirmed by PCR and sequenced. The expression was induced by 1 ng/mL nisin for 6 h. The culture supernatant was found to be active against Staphylococcus aureus with an inhibition diameter of (14.03 ± 0.23) mm and it displayed a protein band of 5.8–7.8 kDa as determined by Tricine-SDS-PAGE, which was consistent with the predicted value. Furthermore, the extracellular expression of recombinant PlnF was confirmed by nano LC-ESI-MS/MS.

The aim of this study was to evaluate the changes in microbial and physicochemical characteristics (acidity, pH, VC and organic acid contents and color) during the fermentation of the fruit juice of Citrus paradisi cv. Changshan Huyou by either Lactobacillus plantarum L1 or Lactobacillus fermentum L2. Besides, we also examined the effect of different Lactobacillus strains on the contents of total phenol, total flavonoids and antioxidant activity of fermented Huyou juice. Results indicated that the two lactic acid bacteria grew rapidly in Huyou juice and attained a viable bacterial population of 108 CFU/mL. During their growth, the pH decreased significantly whereas the acidity and VC content greatly increased. In addition, significant changes were observed in the color parameters; L* value decreased whereas a* and b* values increased. The contents of organic acids also changed considerably; the contents of tartaric acid, citric acid, acetic acid and lactic acid increased significantly, whereas the opposite was observed for oxalic acid, malic acid and succinic acid. Acetic acid, lactic acid and malic acid were changed most obviously among all organic acids. The antioxidant activity of the fermented fruit juice was greatly higher than that of the unfermented control; the scavenging capacity against DPPH, superoxide anion and hydroxy radicals were increased by 4.3%, 15.9% and 0.7%, respectively. The contents of total phenol and total flavonoids increased after fermentation. The quality and antioxidant activity were improved significantly by fermentation with the two lactic acid bacteria. This study can provide the theoretical basis for probiotic fermentation of Huyou juice and for the development of probiotic fermented fruit juice.

This study aimed at the molecular investigation of the gene loci that control the main quality traits of steamed bread. A total of 205 wheat cultivars were used for genome-wide association analysis of the specific volume, color and texture properties of steamed bread with 24 355 single nucleotide polymorphism (SNP) markers covering the whole genome of wheat. A total of 8 SNPs were found to be significantly associated with specific volume (P < 0.000 1) and they were also found to highly contribute to the variation in specific volume (R2 > 10%); two SNPs associated with specific volume exhibited stable expression in at least two environments. A total of 23 SNPs were significantly associated with color, 30 SNPs highly contributed to the variation in color and 9 SNPs associated with color showed stable expression in more than two environments. A total of 31 SNPs were significantly associated with texture properties, 46 SNPs highly contributed to texture properties and 11 SNPs associated with texture properties were stably expressed in more than two environments. Furthermore, 5 main gene loci that control texture properties were identified, such as BS00000020_51 associated with gumminess on chromosome 5D. These SNPs can provide a valuable basis for molecular breeding of wheat for improved quality of steamed bread.

In order to elucidate the characteristics of mineral elements in the seed kernels of Chinese chinquapin (Castanea henryi), the contents of nine mineral elements including N, P, K, Ca, Mg, Fe, Mn, Zn and Cu in 30 major varieties were determined using a discontinuous autoanalyzer and atom absorption spectrometry and they were analyzed by correlation analysis, factor analysis and cluster analysis. The results were showed that the contents of all 9 mineral elements obeyed normal distribution by Kolmogorov-Smirnov test. The average contents followed the descending order of N (6 873.74 mg/kg) > K (4 402.32 mg/kg) > P (1 619.16 mg/kg) > Ca (471.18 mg/kg)> Mg (394.59 mg/kg) > Mn (115.80 mg/kg) > Fe (16.22 mg/kg) > Zn (8.68 mg/kg) > Cu (7.59 mg/kg). As far as the macroelements were concerned, N, K and P were significantly different from Ca and Mg (P < 0.05); as for the microelements, Mn was significantly different from Fe, Zn and Cu (P < 0.05). The coefficients of variation varied from 8.29% (Zn) to 54.43% (Fe). Correlation analysis showed that there was a complex correlation among these elements. The results of factor analysis showed that N, P, Mn, K, Cu and Fe were the characteristic elements of Chinese chinquapin, and that the cumulative variance contribution rate of six common factors extracted was 90.572%. The cumulative variance contribution rate of the first common factor (F1) was 22.400%, representing N, P and Mn. The cumulative variance contribution rate of the second common factor (F2) was 15.572%, representing K and Cu. The cumulative variance contribution rate of the third common factor (F3) was 14.701%, representing Fe. The cumulative variance contribution rate of the fourth common factor (F4) was 14.614%, representing Mg. The cumulative variance contribution rate of the fifth common factor (F5) was 11.936%, representing Ca. The cumulative variance contribution rate of the sixth common factor (F6) was 11.349%, representing Zn. The top five varieties with the highest synthetic scores were ‘Manzhen’, ‘Changmangzi’, ‘Zhongjianzui’, ‘Caizhen’, ‘Xiaojianzui’. The 30 Chinese chinquapin varieties were classified into 6 groups by cluster analysis. The results of this study can provide basic data for evaluating nutritional properties of Chinese chinquapin, breeding new varieties and developing Chinese chinquapin-based foods.

The effect of the deep-frying process on the flavor compounds of Shanghai smoked fish was investigated. The volatile compounds were determined by solid phase micro-extraction-gas chromatography-mass spectrometry (SPME-GC-MS), the nucleotide composition was analyzed by high performance liquid chromatography (HPLC) and the amino acid composition was studied using an amino acid analyzer. Additionally, sensory evaluation was performed. The results showed that a total of 58, 64, 79, 78, 75 and 76 volatile compounds were detected in grass carp deep-fried at 140, 155, 170, 185 and 200 ℃ for 8 min, and 75, 75, 78, 74 and 74 volatile compounds in those deep-fried at 170 ℃ for 4, 6, 8, 10 and 12 min, respectively. The contents of 1-octen-3-ol, hexanal and other earthy odor compounds decreased with increasing oil temperature and frying time. 1-Octen-3-ol, hexanal, nonanal, decanal, 2-nonenal, 2-decenal, 2,4-nonadienal, and 2,4-decadienal were identified as key flavor compounds. The contents of adenosine monophosphate (AMP) and inosine monphosphate (IMP) increased, and the content of hypoxanthine (Hx) decreased in grass carp after deep drying. Moreover, the contents of sweet-tasting amino acids increased, and the contents of bitter-tasting amino acids decreased after deep frying. Deep frying at 185 ℃ for 10 min resulted in higher contents of AMP and IMP and lower content of hypoxanthine (Hx) as well as the highest taste intensity of glutamic acid and histidine and the highest total amount of taste-active amino acids, better preserving the taste of grass carp. The deep-fried fish showed the highest sensory score with a good taste and a strong aroma as well as a golden surface.

The fruit characters, juice and flesh nutrient components and seed oil composition of two new varieties (Yingyu and Nuozhong) of Phyllanthus emblica L. cultivated in Chuxiong, Yunnan province were analyzed in comparison with those of cultivated ungrafted Phyllanthus emblica L. (CUPE) and wild Phyllanthus emblica L. (WPE). The results indicated significant differences in fruit characters between the new varieties, CUPE and WPE; the new varieties showed greater single fruit mass with a more bright and transparent appearance. Despite a decrease in the levels of VC and phenols, the flesh percentage and water content of the new varieties were significantly higher than those of WPE, accompanied by an increase in the contents of protein and starch in flesh. The types and amounts of volatile components in four fresh samples were significantly different, which indicates that the new varieties have their own unique flavor. Furthermore, we found that the seeds of Yingyu and WPE contained lesser amounts of oil and that the degree of unsaturation of seed oils was lower than that of two other samples, suggesting that Yingyu and WPE are not suitable for oil production. Based on all these results, the new varieties Yingyu and Nuozhong have greater potential for development and utilization in term of fruit size, yield and taste.

The volatile compounds of cooked minced pork with different water-bath reheating times (0, 5, 20, 35, and 65 min), were investigated by dynamic headspace combined with gas chromatography-olfactometry-mass spectrometry. A total of 54 volatile compounds were identified, with 36 of these being common to all samples. Aldehydes accounted for the highest proportion of the total volatile compounds in the samples heated for 5-20 min, and acid contents significantly increased after 35-65 min of reheating. The contents of pentanal, hexanal, octanal, and (E,E)-2,4-nonadienal were increased firstly and then decreased with increasing reheating time. 1-Octene-3-ol and 2-pentyl furan contents were not affected significantly by reheating time (P > 0.05). Odor activity value (OAV) analysis and principal component analysis (PCA) suggested that reheating had a significant effect on the flavor of cooked minced pork. The proportion of warmed-off flavor (WOF) in cooked minced pork was decreased slightly with reheating time, when using pentanal, hexanal, octanal and (E,E)-2,4-decadienal as WOF markers. Therefore, lipid oxidation may be the main formation pathway for reheating flavor in cooked minced pork, and WOF is more easily formed in a shorter reheating time.

Deep-fried grass carp was prepared by sequentially marinating and deep frying fresh grass carp (Ctenopharyngodon idellus). The contents of water-soluble taste compounds, reducing sugars and volatile flavor compounds in fresh, marinated and deep-fried fish samples were determined and compared by high performance liquid chromatography, an amino acid auto-analyzer and headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry (GC-MS), respectively. The results showed that marination and deep frying could enhance the umami taste and that the taste activity value (TAV) of Glu in the intermediate and finished products was greater than one. There was no significant difference in IMP contents between the deep-fried and fresh grass carp, suggesting retention of the original umami taste. The contents of reducing sugars in the deep-fried sample were significantly reduced as compared to the fresh sample. GC-MS analysis demonstrated that there were 72 volatile compounds in the deep-fried grass carp mainly including aldehydes and alkanes. Based on their odor activity values (OAVs), 2,4-decadienal, 1-octen-3-ol, nonanal, hexanal, 2-decenal, decanal and 3-methyl-butanal made an important contribution to the overall flavor of deep-fried grass carp.

The purposes of this study were to establish an enantiomeric separation method for aleuritic acid by high performance liquid chromatography with evaporative light-scattering detection (HPLC-ELSD) and to explore the thermodynamic pattern of the chiral resolution process. The optimum chromatographic conditions were determined by investigated the effect of mobile phase composition and column temperature. The best separation was achieved on a DAICEL CHIRAL PAK IF column (25 cm × 0.46 cm i.d., 5 μm) held at 30 ℃ using a mobile phase composed of a mixture of 0.1% formic acid solution and acetonitrile (40:60, V/V) at a flow rate of 0.5 mL/min. The optimum parameters of ELSD were determined as 70 ℃, 60 ℃ and 1.6 L/min for evaporator temperature, drift tube temperature and carrier gas (high purity nitrogen) flow rate, respectively. The results showed that aleuritic acid obtained by strong alkali saponification was a mixture of two threo-enantiomers (65.5:34.5) with an enantiomeric excess (ee) value of 31%. Thermodynamic analysis indicated that there was a good linear relationship between lnα, lnk1 and lnk2 and 1/T with correlation coefficients (R2) of 0.997 2, 0.995 1 and 0.998 0, respectively. The difference of enthalpy change (ΔΔH) between two enantiomers was ?3 453.0 J/mol and the difference of entropy change (ΔΔS) was ?7.677 6 J/mol, suggesting that the resolution process was controlled by entropy change.

Based on gas chromatography-mass spectrometry (GC-MS), metabolomic analysis was conducted on rice seeds from the rice-producing area of Jiansanjiang and other areas in Heilongjiang province with the aim of evaluating the effect of the geographical origin on rice metabolites. The XCMS software package was used to process the GC-MS data under the R software platform. Multivariate statistical analysis using principal component analysis (PCA), partial least squares-discriminate analysis (PLS-DA) and orthogonal projection to latent structures discriminate analysis (OPLS-DA) was performed with SIMCA-P software. The results indicated that a total of 173 peaks were detected, and that 44 compounds, including amino acids, fatty acids, saccharide, and polyols, were identified. A total of 23 differential metabolites with significant changes (P < 0.05, VIP ≥ 1) were identified between rice seeds from Jiansanjiang and other areas in Heilongjiang province. The analysis of metabolic pathways showed that amino acid metabolism affected rice quality and varied with the geographical origin. Our data showed that the geographical origin affected both the types and amounts of metabolites in rice. There was a significant difference in the metabolomes of rice from Jiansanjiang and other producing areas. It is feasible to use GC-MS to analyze the effects of the geographical origin on the metabolites of rice seeds and to distinguish between different geographical origins.

The volatile aroma components of dry-cured mutton ham at 0, 30, 60, 90, 120, 150 and 180 d of storage were analyzed using an electronic nose (E-nose) and headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS). E-nose results showed that overall flavor of mutton ham was different at different storage times. GC-MS analysis identified 94 volatile aroma components belonging to 7 classes, with hydrocarbons and aldehydes being significantly more abundant than other flavor compounds. Partial least squares regression (PLSR) analysis indicated that 3-methyl-butanal, pentanal, hexanal, 5-methyl-hexanal, nonanal, benzaldehyde, 2-methyl-2-undecanethiol, 1-pentanol, 1-octen-3-ol, 2-octanone, butanedione, 2-nonanone, acetic acid and 2,6-dimethylpyrazine were identified as characteristic flavor compounds of mutton ham during storage. These research results provide valuable information for understanding the changes in flavor composition during the storage of mutton ham, which is helpful to promote the industrialization of mutton ham.

In this research, electronic nose (E-nose) and headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) were used to evaluate and compare the volatile components of potato bread on day 1 and 6 of storage at room temperature or on day 6 of storage under cold conditions. The results showed that the E-nose could distinguish among the flavors of potato bread after storage at room temperature and under cold conditions for 1 to 9 days. The contribution rates of the principal components and the ?avor discrimination of samples were quanti?ed by principal component analysis (PCA) and linear discriminant analysis (LDA), respectively. The discriminant factor analysis was used to establish a potato bread recognition library model. The results of HS-SPME-GC-MS analysis showed that a total of 28 volatile compounds were identified in potato bread, 17, 4 and 14 of which were found to be present in the 1- and 6-day stored samples at room temperature and the 6-day cold-stored sample, respectively. During storage, the flavor profile changed obviously. Acids, esters, ketones and hydrocarbons disappeared during cold storage. During storage at room temperature, aldehydes and ethers disappeared, while the relative contents of alcohol compounds increased significantly. Conclusively, GC-MS combined with E-nose could be used in comprehensive flavor evaluation of potato bread during storage.

This research studied the qualitative analysis of sea buckthorn seed extract (SBSE), prepared from sea buckthorn seed residue by ethanol extraction and macroporous resin purification, by ultra-performance liquid chromatography coupled with quadruple time-of-flight tandem mass spectrometry (UPLC-QTOF-MS/MS). The bioactive components of SBSE were quantitatively determined by ultra performance liquid chromatography coupled with triple quadruple mass spectrometry (UPLC-QQQ-MS). Meanwhile, the antioxidant effect of SBSE in D-galactose-induced aging mice was studied. The mice were administrated by gavage with SBSE at different dosages for 42 days. Total antioxidant capacity (T-AOC), the activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) and the contents of malondialdehyde (MDA) and lipofuscin (LP) in liver tissue were measured. The results obtained were as follows: A total of 24 compounds were identified by UPLC-QTOF-MS/MS, 14 compounds of which were characterized by comparing with reference substances and quantitatively determined by UPLC-QQQ-MS in the negative ion multiple reaction monitoring (MRM) mode. Kaempferol and its derivatives were the most abundant constituents in SBSE ((667.94 ± 5.61) μg/mL), quercetin and its derivatives were in the middle ((204.01 ± 0.04) μg/mL), and procyanidins were the least abundant ((33.97 ± 0.49) μg/mL). The administration of SBSE to aging mice could increase the activities of GSH-Px, SOD and CAT in liver tissue. Compared with the D-galactose-induced model group, hepatic T-AOC activity in the low-dosage group was significantly increased (P < 0.01), and the levels of MDA and LP were decreased significantly by SBSE at three dosages (P < 0.01).

Quercetin-carboxymethyl sweet potato starch ester was synthesized by covalent attachment of quercetin to carboxymethyl sweet potato starch. The influence of preparation conditions on the degree of substitution (DS) was investigated by the combined use of one-factor-at-a-time (OFAT) method and response surface methodology (RSM). The OFAT results indicated that the DS increased with increasing molar ratio of quercetin to anhydroglucose unit (AGU) of sweet potato starch (Nquercetin/AGU), while it increased then decreased with increasing molar ratio of activating agent to AGU (NEDC/AGU) and reaction pH. Furthermore, the RSM results revealed that both NEDC/AGU and reaction pH had a significant effect on the DS (P < 0.01), while Nquercetin/AGU as well as the quadratic and interactive terms showed no significant effect on the DS (P > 0.05). Finally, the optimal reaction conditions were obtained as follows: carboxymethyl sweet potato starch concentration 51 g/L, Nquercetin/AGU 2:1, NEDC/AGU 1.8:1 and initial pH 7.4. The maximum DS value of 0.114 9 was obtained under the optimized conditions. The covalent linkage of quercetin to carboxymethyl sweet potato starch was confirmed by detectable quercetin release from the product after hydrolysis.

Response surface methodology was employed to optimize the process parameters for enzyme-assisted alkaline extraction of soluble dietary fiber (SDF) from defatted coconut flour. A quadratic polynomial model was built and validated. The yield of SDF was investigated with respect to four variables, enzyme concentration, enzymatic hydrolysis time, alkali concentration and alkaline hydrolysis time. The optimized conditions were as follows: enzyme concentration (α-amylase + glucoamylase, 1:1) 0.5%, enzymatic hydrolysis time 50 min, NaOH concentration 5%, and alkaline hydrolysis time 40 min. Under these conditions, the yield of SDF was 11.78%, and the water-holding capacity, swelling-capacity and oil-holding capacity of the SDF obtained were 3.8 g/g, 3.1 mL/g and 5.2 g/g, respectively. Infrared spectral analysis indicated that there were a large number of hydrogen bonds in the associated state in the SDF. HPLC results indicated that the SDF was composed of 9 monosaccharides, with mannose, galactose, galactosamine and gum sugar being predominant (537.21, 39.48, 40.38 and 15.83 mg/L, respectively).

This study investigated the application of an ultrafiltration ceramic membrane (0.04 μm) to refine defecated sugarcane juice. The sugarcane juice was ultrafiltrated for 30 h under the following conditions: transmembrane pressure difference 0.45–0.50 MPa, crossflow velocity 4.0–4.5 m/s, and temperature 75–97 ℃. The membrane permeate flux was decreased from 350.6 to 160.2 L/(m2·h) during the ultrafiltration process and the average flux rate was 177.8 L/(m2·h), which could meet the requirement of industrial production. The apparent purity of sugarcane juice was increased by 2.01 units after ultrafiltration, the percentage removal of pigments was 20.20%, and the clarity was elevated from 79.18% to 99.98%. A fouling layer comp was formed on the membrane surface during the ultrafiltration process, which mainly consisted of organic depositions (e.g., polysaccharides, proteins, aliphatics and phenols) as well as lesser amount of inorganic components such as Na, Mg, Al, Si, P, Cl, K, Ca and Fe. A flux recovery rate of higher than 95.5% was obtained with good repeatability when fouled membrane was successively rinsed with clean industrial water, a mixed solution of 1.0% NaOH and 0.5% NaClO, and 0.5% HNO3 solution, suggesting that this cleaning method was feasible.

An analytical method using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was established for determining multi-elements (Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Cd, Sn, Hg and Pb) in red wine. Samples were filtered through a 0.45 μm pore size cellulose filter, and after acidification with nitric acid, the filtrate was directly analyzed. Instrumental parameters were optimized so that elimination of inferences was achieved via mass-shift reaction of different reaction gases. The limits of detection (LOD) were in the range of 1.4–51.8 ng/L for all analytes. The recoveries for spiked samples were in the range of 94.0%–104.7%, with relative standard deviations (RSDs) no more than 4.0%. The method is simple and fast with low detection limit, good accuracy and high precision, making it suitable for the determination of multi-elements in red wine.

The aim of this study was to determine the virulence genes, phylogenetic groups and antibiotic susceptibility of Escherichia coli isolated from slaughtered pigs. A total of 77 strains of E. coli were isolated from pig samples collected from pig slaughterhouses in Shaanxi province, Chongqing municipality and Henan province for this study. The results showed that iutA was most frequently detected among the virulence genes tested, and group A was the dominant one. Resistance to tetracycline and trimethoprim/sulfamethizole was detected most frequently among 12 selected antibiotics. Overall, most of the isolates (90.91%) were resistant to 3-9 antibiotics, and even some were resistant to up to 11 antibiotics. Our findings indicate that slaughtered pigs carry multidrug-resistant E. coli strains. These strains are likely to enter into the food chain through the pork production process and cause potential health risks to consumers, highlighting the necessity of strengthening food hygiene supervision.

Considering the main cause and positions of quality deterioration and the complexity of detecting newly generated compounds in pork during frozen storage, headspace-gas chromatography-ion mobility spectroscopy (HS-GC-IMS) was chosen as a method for odor deterioration analysis to acquire and analyze the volatile organic compounds (VOCs) generated from lipid oxidation on the surface layer and shallow layer of frozen pork. Dimensionality reduction of the VOCs data of frozen pork stored for different periods was performed by principal component analysis (PCA), and the processed data were applied to establish a discriminant analysis model by K-means algorithm. The model was used to assess frozen pork stored for different periods. The results showed that the VOCs with similar polarity in frozen pork were separated effectively, and the data acquisition and analysis of VOCs were completed within 600 s by HS-GC-IMS. After data screening, 29 VOCs showed obvious changes in ion peak intensity, which?could be displayed in the 2-dimension mode of data visualization. The model developed in this study could classify samples of frozen pork at different storage times into the corresponding clusters.

The volatile organic compounds of wheat with different mildew degrees were detected using gas chromatography-mass spectrometry (GS-MS). Principal components analysis (PCA) of the volatile organic compounds was performed to effectively distinguish the different degrees of moldy wheat in order to provide an experimental basis for visual identification of moldy wheat. Olfactory visualization as a rapid and convenient method was employed to detect fresh and moldy wheat with different mildew degrees, and the data obtained were processed by PCA followed by linear discriminant analysis (LDA) and K-nearest neighbor (KNN) algorithm. The KNN and LDA models gave a recognition rate of 95.83% and 85.40%, respectively. These results conclusively show that olfactory visualization technology can allow fast, non-destructive and accurate detection of moldy wheat.

Objective: To investigate the serotyping, virulence genes and pulsed field gel electrophoresis (PFGE) typing of Staphylococcus aureus in fresh milk for a better understanding of the epidemiological characteristics of S. aureus. Methods: S. aureus strains were isolated from fresh milk samples collected from dairy farms in four regions of Henan province and they were identified by PCR amplification of the thermostable nuclease gene (nuc). The capsular polysaccharide (Cap) serotypes and virulence genes were determined by PCR. The correlation and genetic relatedness among these S. aureu isolates were analyzed by PFGE. Results: A total of 80 S. aureus strains were isolated from 350 fresh milk samples, with a separation rate of 22.86%. Cap5 (60%) was found to be a popular serotype. Of the positive isolates, 62 (77.5%) carried virulence genes, and the prevalence of the virulence genes set, hlb, hld, lukED, ebp, clfA and clfB were 40.00%, 51.25%, 57.50% , 60.00%, 58.75%, 57.50% and 58.75%, respectively. In addition, 47 (58.75%) strains carried at least 6 virulence genes, set-hla-hlb-hld-lukED-cna-ebp-clfA-clfB were found to be the prevalent virulence genotypes. PFGE profiles of 72 strains were obtained. Based on a 90% similarity, they were divided into 12 clusters and 46 PFGE types. The strains in clusters D, G and J were detected to carry some virulence genotypes, suggesting that virulence genes widely existed in a variety of PFGE types of S. aureus isolated from fresh milk in Henan. Conclusions: Fresh milk samples were contaminated by S. aureu to a certain degree. Most of the isolates carried virulence genes, and the virulence genotypes were complicated, posing a potential threat to the health of consumers. The PFGE subtypes were mainly transmitted in the form of clones, and the clone types were diversified and differentiated. Therefore, further clinical studies are needed for serotyping, virulence gene detection and molecular typing of S. aureus in raw milk and dairy products.

The study aimed to develop an approach to quantify pork in adulterated mutton rolls with different fat ratios based on near infrared spectroscopy combined with chemometrics. A total of 324 samples were prepared with different proportions of fat and pork. Spectra were collected by using a near infrared spectrometer. Savitzky-Golay (SG) smoothing, Savitzky-Golay smoothing-first derivation (SG-1st), Savitzky-Golay smoothing-second derivative (SG-2st), multiplicative scatter correction (MSC), centralized correction (Center), and standard normal variate (SNV) were used to preprocess the original spectral data. A prediction model was established by using partial least squares regression (PLSR) method. Based on the prediction parameters, the optimal pretreatment method was SG-1st. Competitive adaptive weighted sampling (CARS) was used to select the optimal wavebands in order to further enhance the prediction capability of the model. The determination coefficients for calibration and validation sets were 0.983 6 and 0.972 5, respectively. The root mean square errors of calibration and validation (RMSEC and RMSEP) were 0.043 7 and 0.057 7, the ratio of performance to standard deviate (RPD) was 7.62, and the correlation coefficient between the CARS model prediction and the experimental data for test set was 0.913 8. The results showed that by using near infrared spectral analysis, the proportion of pork in adulterated mutton rolls with different fat ratios could be rapidly quantified.

For rapid detection of the contamination level of deoxynivalenol (DON) in wheat and its products, a total of 98 samples of wheat, flour and flour products were collected and subjected to attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analysis in the wavenumber range of 4 000 to 600 cm-1. Quantitative models between ATR-FTIR spectra and DON concentration were established by partial least squares regression analysis (PLSR) or stepwise multiple linear regression (SMLR). The results showed that the absorption values of samples with various DON contents were markedly different at 1 740, 1 648, 1 549 and 900–1 300 cm-1. Both PLSR and SMLR models could effectively predict DON contamination in samples. The coefficient of determination for prediction (RP2), root mean square error for prediction (RMSEP) and residual predictive deviation (RPD) of the PLSR model were 0.86, 0.438 mg/kg and 2.6, respectively. The SMLR model built with 9 wavenumbers was found to be optimal, with RP2, RMSEP and RPD of 0.86, 0.426 mg/kg and 2.6, respectively. These results indicated that ATR-FTIR offers the feasibility for rapid determination of wheat samples contaminated by DON.

The aim of the study was to develop a method for the determination of Salmonella by recombinase polymerase amplification (RPA). A specific primer pair was designed based on the conserved sequence of the invasion protein A gene (invA) of Salmonella. The reaction time was optimized and the RPA method was performed successfully at 38 ℃ for 20 min in a water bath: the target fragment was effectively amplified. The RPA reaction could specifically detect Salmonella rather than 26 other foodborne pathogens. The detection limit (LOD) of RPA was 1.1 × 10-3 ng/μL with the genomic DNA of Salmonella as a template, which was consistent with that of real-time PCR. For artificially contaminated lamp, chicken and broccoli samples with a bacterial concentration of 4 CFU/25 g, Salmonella could be detected by RPA after 8 hours of culture. Consistent results were obtained using real-time PCR. The RPA assay was specific, simple and rapid, and could represent a new direction for the detection of foodborne pathogens.

A method was developed for the rapid determination of residues of two pesticides (chlorpyrifos and carbosulfan) and toxic metabolites (carbofuran, 3-hydroxycarbofuran and 3,5,6-trichloro-2-pyridinol (3,5,6-TCP)) in polished rice by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The five analytes were extracted from samples with acidified acetonitrile, purified by solid phase extraction using C18 and primary secondary amine (PSA) sorbents, and separated on an Eclipse XDB-C18 column with gradient elution using a mobile phase composed of a mixture of methanol and 5 mmol/L ammonium formate aqueous solution containing 0.1% (V/V) formic acid. The qualitative analysis was conducted in?the?positive?and?negative?ionization?switching mode using multiple reaction monitoring (MRM). The quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was optimized by comparing the extraction efficiencies of different concentrations of formic acid in order to improve the sensitivity of the method. The correlation coefficients (r) of the calibration curves for all analytes were above 0.998 in the concentration range from 0.2 to 1 000.0 μg/L. The limits of detection (LODs) and quantification (LOQs) of the method ranged from 0.3 to 1.7 μg/kg and from 1.0 to 5.0 μg/kg, respectively. The recoveries from blank samples spiked at three concentration levels (1, 10 and 100 μg/kg for chlorpyrifos, carbosulfan, carbofuran and 3-hydroxycarbofuran as well as 5, 25 and 125 μg/kg for 3,5,6-TCP) ranged from 72.0% to 99.6% with relative standard deviations (RSDs) from 0.6% to 12% (n = 6). The results show that the method is rapid and efficient, and is suitable for rapid determination of chlorpyrifos, carbosulfan and their metabolites in polished rice samples.

A simple and rapid method for the determination of 4 pseudo proteins including melamine, cyromazine, dicyandiamide and biuret in milk and dairy products has been developed by using magnetic molecularly imprinted polymers (MMIPs) extraction combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The MMIPs used for the extraction of 4 pseudo proteins were synthesized by polymerization using biuret-13C2 and cyromazine-D4 as templates and Fe3O4 magnetite as magnetic component. Under the optimized conditions, good linearity was observed for all target analytes in the concentration range of 5–200 ng/mL with correlation coefficient above 0.999. The limits of detection (LODs) for melamine, cyromazine, dicyandiamide and biure were 0.10, 0.02, 0.05 and 0.50 μg/kg in milk samples and 0.25, 0.05, 0.13 and 1.25 μg/kg in powered milk samples, respectively. The recoveries were between 80.5% and 96.1% with relative standard deviations (RSDs) between 1.1% and 9.2%. The developed method was applied with good precision and accuracy to determine real dairy samples.

A method for the determination of fipronil and its metabolites residues in chicken eggs and meat by quick easy cheap effective rugged safe (QuEChERS) extraction coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established. Samples were dispersed in water and extracted with acetonitrile, followed by dehydration with citrate buffer. The extract was diluted before being injected. The analytes were separated on a BEH C18 column with gradient elution using a mobile phase made up of methanol and 5 mmol/L ammonium acetate (containing 0.1% formic acid). The MS analysis was performed using an electrospray ionization (ESI) source in the negative mode with multiple reaction monitoring (MRM). Quantification was performed with matrix-matched?standard?calibration curves. The limits of quantitation (LOQs) of fipronil and 3 metabolites were all 1 μg/kg. In the concentration range of 1 to 100 μg/kg, all the calibration curves showed good linear correlation. The average recoveries for chicken egg and meat at three different spiked levels were 87.6%–117.7%, with relative standard deviations (RSDs) between 3.6% and 9.9%. The method is rapid, sensitive and accurate, and it is suitable for the determination of fipronil and its metabolites residues in animal-derived food s such as chicken eggs and meat.

The paper presents a new method for detecting phospholipid content in soybean oil based on electrochemical analysis and to establish accurate and reliable calibration models. A total of 40 mixed soybean oil samples with different contents of phospholipids were prepared, and the standard values of phospholipid contents were precisely detected by molybdenum blue colorimetry. Considering no electron transfer during the phospholipase hydrolysis process, we developed an electrochemical sensor based on a multiple modified enzyme electrode to obtain electrochemical signals by cyclic voltammetry measurement through an electrochemical workstation. The original electrochemical data were denoised by either Savitzky-Golay smoothing filter or Daubechies (dbN) wavelet series. Through the comparative analysis, it was found that the best denoise was achieved based on db6 wavelet three-layer decomposition. Finally, four methods were used respectively to set up regression models between the electrochemical data and phospholipid concentration, i.e., linear fitting between reductive peak current and phospholipid concentration, principal component regression (PCR) model, partial least squares regression (PLSR) model and support vector machine regression (SVMR) model. Comparison of these methods showed that the prediction accuracy of the SVRR model based on radial basis kernel function was the highest. A good linear relationship was observed in the phospholipid concentration range of 5.87–304.89 mg/L, and the detection limit (LOD) was 1.68 mg/L (RSN = 3). The coefficient of determination (R2), root-mean-square error of prediction (RMSEP) and relative standard deviation (RSD) were 0.998 7, 0.288 9 and 2.55%, respectively, all of which met the requirements of practical detection.