In this study, whey protein isolate (WPI) and theanionic polysaccharide xanthan gum (XG) were used as basic raw materials to prepare composite particles. To explore the main factors that affect the formation of composite particles, the effects of preparation conditions such as ionic strength, temperature, and mixing mode on the turbidity, particle size, and zeta potential of the WPI-XG composite system, and the structure of the particles through a laser confocal microscope. The results showed that low ionic strength (≤ 20 mmol/L) could promote the formation of WPI-XG composites; the higher the temperature, the larger the particle size of the composite particles. The particles prepared by heating the WPI solution and then mixing it with the XG solution had larger protein-to-polysaccharide ratio, smaller particle size and greater absolute value of zeta potential; in contrast, shearing could decrease the particle size and the absolute value of zeta potential. Finally, it is concluded that the sheared WPI particles subjected to heat treatment at 75 ℃ and XG could form a more complete “core-shell” structure.

Pickering emulsion gels with high oil-phase volume fraction were prepared with insoluble soy peptide aggregate (ISPA), and the effects of simulated environmental conditions on their properties and stability were analyzed. The results showed that the droplet size of emulsions was decreased and the gel strength was increased with an increase in ISPA mass fraction and oil phase volume fraction, and the emulsion with 1.00% ISPA and 60% oil phase showed stronger gelation potential. Furthermore, it was found that the strength of the emulsion gels was increased at higher NaCl concentrations or lower pH, and the droplet size was changed little after 90 days of storage at room temperature or heating for 60 min at 90 ℃. In conclusion, ISPA has great potential for applications in novel Pickering emulsion stabilizers and food ingredients.

In this study, an ethanol extract of Ilex latifolia Thunb. was fractionated by successive solvent extraction, and the antioxidant, anti-complement and anti-cancer activity of the ethanol extract and its fractions were explored. Furthermore, the fractions with the highest bioactivity activity were further fractionated into monomers, which were subsequently identified. The antioxidant activity was measured by total reducing power, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and superoxide anion scavenging capacity. The anti-complement activity was evaluated by hemolysis assay, and the inhibitory effect on the proliferation of MCF-7 cells was determined by MTT assay. The chemical structures of the purified monomers were identified by mass spectrometry (MS) and nuclear magnetic resonance (NMR). The results showed that the ethanol extract and its fractions all had good antioxidant effect. Among them, the ethyl acetate fraction not only had a strong antioxidant activity in the experimental concentration range, but also had a good anti-complement activity with an inhibition percentage of (79.67 ± 0.99)%. It could inhibit the proliferation of human breast cancer MCF-7 cells with an inhibition percentage of (54.8 ± 0.26)%. A total of 11 monomer compounds were isolated from the ethyl acetate fraction, and most of them were identified as phenols and flavonoids. In conclusion, the ethanol extract of I. latifolia Thunb. and its fractions have antioxidant and anti-complement activities and an inhibitory effect on the proliferation of MCF-7 cells, and the ethyl acetate fraction has the strongest biological activity.

In order to control the formation of fat crystal network structure and optimize the quality of the final product, this work aimed to investigate the effect of lard-based monoacylglycerol (L-MAG) on the isothermal crystallization kinetics, microstructure, thermal behavior, polymorphism and hardness of palm stearin (PS) at different temperatures of 4, 15 and 20 ℃. Our results showed that the types of fatty acids in L-MAG were identical to those in PS, but the contents of fatty acids were different between them. L-MAG could decrease the crystallization rate and extent of PS. However, this effect depended on the concentration of L-MAG and crystallization temperature. The effect of L-MAG on reducing the crystallization rate and the solid fat content value at equilibrium was more significant when the crystallization temperature was higher. Furthermore, this effect was proportional to the concentration of L-MAG in the range of 1% to 4%. Results of differential scanning calorimetry (DSC) and X-Ray diffraction (XRD) suggested that L-MAG could promote the crystallization of low-melting fractions and had little effect on the polymorphism of PS. Moreover, the hardness of PS increased after addition of PS, which could be attributed to the formation of a more compact and orderly crystal network with a high degree of space filling. The crystallization behavior of PS could be modified to improve the quality of the final product by controlling the concentration of L-MAG and crystallization temperature.

To investigate the inhibitory effect of hydrocolloids on the formation of advanced glycation end products (AGEs), four chemical models, bovine serum albumin (BSA)-fructose (Fru), BSA-glucose (Glu), BSA-methylglyoxal (MGO), and BSA-glyoxal (GO), were used to evaluate anti-glycation capacity of nine hydrocolloids. Alginic acid (ALA) and xanthan gum (XG) were selected as the best inhibitors to investigate the effects of hydrocolloid addition (0.25%, 0.5%, 1.0%, 1.5%, and 2.0%) as well as baking temperature and time on the quality properties, AGEs formation and protein oxidation products in sponge cakes. Under the optimum baking conditions (180 ℃/40 min), the addition of 0.5% ALA or 2.0% XG significantly reduced the formation of fluorescent AGEs, non-fluorescent AGEs and protein oxidation products. At the same time, ALA and XG improved the texture and increased the moisture contents of the cakes. ALA and XG are promising natural AGEs inhibitors to reduce AGEs generation in bakery products.

Anti-zearalenone monoclonal antibodies (mAbs) were directionally conjugated on the surface of hydrazide group-functionalized gold nanoparticles because of the nucleophilic addition reaction between the aldehyde groups of the antibody Fc region and the hydrazide groups on gold nanoparticles (AuNPs). Compared with the carbodiimide-mediated covalent coupling method, the proposed directional coupling strategy showed several advantages such as use of less amounts of labeled antibody and shorter reaction time. The hydrazided gold nanoparticles-based immunochromatographic assay (hAuNPs-ICA) showed higher sensitivity for ZEN detection. Additionally, when hAuNPs-ICA was used to analyze ZEN-spiked maize samples, the average recoveries ranged from 83.1% to 118.0% with intra- and inter-batch coefficients of variation ranging from 3.9% to 13.1%, indicating good accuracy and precision.

In this paper, selenized mung bean resistant starch (MB-RS4?Se (IV)) was prepared from mung bean resistant starch (MB-RS4) by the nitric acid-sodium selenite method. Scanning electron microscopy (SEM) revealed that the starch granules were completely collapsed and fragmented after selenization. The structural characteristics of MB-RS4 and MB-RS4?Se (IV) were analyzed by ultraviolet (UV) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR). The results showed that selenization resulted in a red shift of the UV peak and a hyperchromic effect. Additionally, the characteristic peaks of Se=O, C–C (Se)2 and Se–O–C appeared at wavenumbers of 787.88, 730.88 and 654.75 cm-1, respectively, and the crystal structure was destroyed. The molecular mass dropped significantly, and MB-RS4·Se (IV)’s configuration was reversed and the C6 position was substituted compared with MB-RS4. MB-RS4·Se (IV) had a significantly enhanced inhibitory effect on α-glucosidase and α-amylase. The results of the enzymatic reaction kinetics showed that the inhibition of α-glucosidase was competitive type, and the inhibition of α-amylase was mixed anticompetitive type.

Resveratrol was esterified by 9c,11t-conjugated linoleic acid (CLA), and complexed with beeswax to prepare oleogel rich in resveratrol conjugated linoleate using peanut oil as the base oil. The effects of the concentration of beeswax-resveratrol conjugated linoleate mixture (BRE), mass ratio between beeswax and resveratrol conjugated linoleate, heating temperature, heating time and cooling temperature on the oil retention capacity of oleogel rich in resveratrol conjugated linoleate were discussed, and its basic physicochemical properties, thermal properties, and composition were characterized. The results showed that the preparation conditions that provided maximum oil retention capacity (98.6%) were determined as 12%, 7:3, 70 ℃, 20 min and 4 ℃ for BRE concentration, mass ratio of beeswax to resveratrol conjugated linoleate, heating temperature, heating time and cooling temperature, respectively. Compared with beeswax oleogel, the viscosity of the obtained product was reduced by 30%, and the brightness and the α-type crystals were also reduced. Furthermore, it was found that oleogel rich in resveratrol conjugated linoleate had no trans fatty acid.

In an effort to investigate the effect of addition of different levels (0%, 0.2%, 0.5% and 1.0%) of vacuum freeze-dried (VFD) garlic powder to myofibrillar protein (MP) extracted from yak meat on its emulsification properties in the Fenton oxidation system, MP was evaluated for active sulfhydryl content, protein solubility, and surface hydrophobicity, percentage of interface adsorbed protein, emulsion viscosity, emulsification activity, emulsion stability (clarification index, integrated light transmittance, sedimentation rate) and microstructure after oxidation for 12 h at 4 ℃ in the oxidation system. The results showed that addition of high levels of VFD garlic powder (0.5% and 1.0%) significantly enhanced the emulsification activity, emulsion stability and oil phase distribution uniformity of MP in the Fenton oxidation system (P < 0.05). Adding 0.5% of VFD garlic powder provided good protection for yak meat MP in the Fenton system, resulting in a 2.55-fold increase in active sulfhydryl content, a 19% increased in protein solubility and a 25.41% reduction in surface hydrophobicity. Adding 1.0% of VFD garlic powder significantly improved the emulsification characteristics of yak meat MP in the Fenton oxidation system, increasing the viscosity of yak meat MP emulsion by 2.02 times, and the emulsification activity by 49.80%, and reducing the clarification index, integrated light transmittance and sedimentation speed by 17.06%, 37.44% and 50.79%, respectively. These results suggested that VFD garlic powder significantly improves the emulsification characteristics of yak meat MP in the Fenton oxidation system, and its effect depends on the addition amount of VFD garlic powder. Addition of 1.0% of VFD garlic powder is more effective.

In this paper, zein and gallic acid (GA) were used to prepare zein/gallic acid composite nanoparticles (ZGP) by antisolvent precipitation. Meanwhile, ZGP was used as stabilizer to prepare antioxidant Pickering emulsion. The results showed that ZGP exhibited good dispersivity in the nanometer scale and positive zeta potential. The bonding between Zein and GA was achieved mainly through hydrogen bonds, and X-ray diffraction analysis demonstrated that the resultant complex showed an amorphous structure. Thermodynamic analysis proved that the reaction between Zein and GA was spontaneous and exothermic, the surface hydrophobicitygradually decreased, and the thermal stability of ZGP increased with increasing GA addition. Furthermore, the Pickering emulsion stabilized by ZGP showed a shear thinning phenomenon typical of a non-Newtonian fluid, and the storage modulus (G’) was higher than the loss modulus (G”). During the storage period (50 ℃, 20 d), the amounts of primary and secondary lipid oxidation products both gradually decreased with an increase in GA concentration, indicating that the ZGP stabilized Pickering emulsion has antioxidant capacity and can inhibit lipid oxidation.

In order to improve the utilization value of Agriophyllum squarrosum and the eating quality of rice noodles, the effects of adding different levels (0%, 5%, 15%, 25%, 35% and 45%) of A. squarrosum flour on the pasting, rheological and thermal properties of rice flour as well as the firmness, cooking quality and digestive properties of rice noodles were systematically investigated. The results showed that the supplementation of 25% or above of A. squarrosum flour significantly (P < 0.05) increased the contents of protein, fat, and fiber, and 35% or above of A. squarrosum flour significantly (P < 0.05) decreased the content of carbohydrate in mixed flours compared to pure rice flour. With increasing concentration of A. squarrosum flour equal to or greater than 15%, the peak viscosity of mixed flours decreased significantly (P < 0.05), and the viscoelasticity of gels increased continuously; the cooking loss and resistant starch content of noodles increased significantly (P < 0.05). The addition of more than 25% of A. squarrosum flour deteriorated the cross-sectional compactness and surface flatness of rice noodles. The sensory score of noodles containing less than 15% of A. squarrosum flour was higher than that of pure rice noodles. Therefore, A. squarrosum flour can be used as an ingredient in the production of new rice noodles.

In order to study the effect of ultrasonic pretreatment on the structure of peanut protein isolate microgel particles (PPIMP) and the characteristics of Pickering emulsion stabilized by it, the structural changes of PPIMP after ultrasonic treatment at a 500 W power for 10, 20, 30 and 40 min were evaluated in terms of its particle size, zeta potential, surface hydrophobicity, infrared spectrum, and emulsifying properties and the particle size distribution, stability index and rheological properties of the Pickering emulsion were systematically investigated. The results showed PPIMP pretreated by ultrasonic for 20 min had the smallest particle size, and the largest surface hydrophobicity, emulsifying capacity and emulsion stability. Meanwhile, the relative content of α-helix in PPIMP increased, the relative content of β-sheet decreased, the hydrogen bonds between protein molecules were destroyed, and the protein molecules were unfolded. In addition, Pickering emulsions with oil phase volume fractions of 65%, 70%, 75%, and 80% stabilized by PPIMP exhibited a typical non-Newtonian pseudoplastic behavior, and the Pickering emulsion with 80% phase oil presented the best stability among all prepared Pickering emulsions. The results of this study confirmed that PPIMP can be used as an effective Pickering emulsion stabilizer, which is helpful for the preparation of PPIMP-based Pickering emulsion with high stability and its application in the food industry.

Flammulina velutipes polysaccharide (FVP) was added to soy protein isolate (SPI) hydrogels and subjected to heat treatment to improve the gel strength, water-holding capacity and thermal stability. The stability of FVP-SPI hydrogels was further analyzed in terms of their secondary and tertiary structures and intermolecular forces. The results showed that heat treatment and addition of FVP significantly improved the water-holding capacity of SPI hydrogels, and increased the enthalpy change of denaturation (ΔH) by 25.46%, thereby significantly improving hydrogel stability. Hydrophobic interactions, disulfide bonds and electrostatic interactions were the major driving forces for the formation of heat-induced FVP-SPI hydrogels. The addition of FVP improved the electrostatic interactions and caused transformation of α-helix into β-sheets in the hydrogels, surface exposure of the tryptophan residues in SPI and enhanced hydrophobicity. The enhancement of SPI hydrogels by FVP provides a reference for the development and application of SPI hydrogels.

In order to explore the retardant effect of adding oleic acid and maltitol mixtures on the retrogradation properties of corn starch, rapid viscosity analysis (RVA), differential scanning calorimetric analysis (DSC), texture analysis, dynamic rheological analysis, low-field nuclear magnetic resonance (LF-NMR), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to evaluate the gelatinization, retrogradation, rheological, texture and crystallization structure properties of corn starch gels with different proportions of oleic acid and maltitol mixtures. The results suggested that adding oleic acid and maltitol mixtures could increase the gelatinization temperature, and decrease the setback value and retrogradation rate of corn starch. Upon addition of a 0.5:1.5 mixture of oleic acid and maltitol, the gelatinization temperature was the highest (77.80 ℃), while the setback value was the lowest (1 218 cP). The retrogradation rate of corn starch gels decreased by 60% lower than that of native starch gel. Adding oleic acid and maltitol increased the tangent of loss angle and transverse relaxation time (T2) of corn starch gels, which resulted in the formation of a weak gel structure as well as a reduction in the firmness, short-range order and relative crystallinity of corn starch gels. The 0.5:1.5 mixture had a synergistic effect on retarding the retrogradation of corn starch. These results may be related to the fact that maltitol could inhibit water molecule movement in starch system and that oleic acid could form a complex with starch to prevent the recrystallization of starch. The present study provides a theoretical basis for improving the processing properties of corn starch and the quality of starch-based foods.

In order to improve the utilization rate of hawthorn, hawthorn powder (HP) was included in the formulation of cake as a dietary fiber and source of bioactive substance. The physicochemical properties and microstructure of whole hawthorn powder (WHP) and peeled hawthorn powder (PHP), and the influence of HP on the quality characteristics, microstructure, antioxidant properties and sensory quality of wheat cake were studied. The results showed that the physicochemical and antioxidant properties, bioactive components and X-ray diffraction crystal structures of the two kinds of HP were different, and HP affected the physicochemical, texture, sensory and antioxidant properties, bioactive substances and microstructure of cake. The shrinkage, baking loss, pH, elasticity, cohesion, brightness and overall acceptability of cake decreased with HP addition, and the density, hardness, viscosity, chewability, redness and yellowness values, total polyphenol and total flavonoid contents and antioxidant properties increased. WHP and PHP could be added into cake at levels up to 15%. The sensory characteristics of the cake with HP, with a unique hawthorn-like flavor, were not significantly different from those of the control group.

The objective of this study was to explore the formation process, molecular interactions, and microstructure of whey protein concentrate (WPC) gels by a dynamic rheometer, a microrheometer, a circular dichroism spectrometer, a fluorescence spectrophotometer and a scanning electron microscope (SEM). Furthermore, the mechanisms for the effects of heating temperature (60 and 85 ℃) and pH (2.0, 4.5, 7.0 and 9.0) on the properties and microstructures of WPC gels were discussed. The results indicated that pH affected the gel structure by changing the charge density of WPC. After heat treatment at 85 ℃, the protein molecules were unfolded more sufficiently and exhibited a lower content of α-helix structure. In addition, the wavelength of maximum endogenous fluorescence intensity was red-shifted. The WPC gel formed at 85 ℃ showed higher elastic and viscous moduli as well as elasticity index and macroscopic viscosity index, and lower solid-liquid balance value. In addition, higher temperature could promote the formation of hydrogen bonds, disulfide bonds and hydrophobic interactions, thus improving the properties and microstructure of WPC gels.

The interaction between Escherichia coli O157:H7 and the common food spoilage bacterium Pseudomonas spp. on their motility and biofilm-producing ability was investigated when cultured together. Furthermore, reverse transcription real-time quantitative polymerase chain reaction was used to analyze the changes of virulence genes (stx1, stx2, hly and eae) expression in representative strains of E. coli O157:H7 during mixed species biofilm formation. The results showed that the motility of the three tested strains of E. coli O157:H7 was lower than that of the four strains of Pseudomonas when they were cultured separately (P < 0.05). When co-cultured with E. coli O157:H7, the swimming motility of Pseudomonas was inhibited considerably. The selective culture results showed that the two species did not promote each other’s biofilm-producing ability when co-culturing for 72 h. Instead, biofilm formation by the four Pseudomonas strains was significantly inhibited by the three strains of E. coli O157:H7 (P < 0.05). Furthermore, it was found that the expression of four virulence genes of E. coli O157:H7 CICC21530 per unit volume in the mixed culture and per until area in the mixed biofilm were lower than that in the single culture and the single biofilm, respectively (P < 0.05), and the same was true for that per unit cell number, indicating that the expression of virulence genes in E. coli O157:H7 was inhibited by Pseudomonas during mixed culture and mixed biofilm formation. It was also found that the expression of the four virulence genes in the biofilm was higher than that in planktonic cells (P < 0.05), indicating that the virulence of the bacterial cells increased after biofilm formation. This study can provide a scientific basis for revealing the interaction between food-borne pathogens and spoilage bacteria during mixed biofilm formation and for risk assessment, prevention and control.

In this study, phage display technology combined with bioinformatics was used to identify the B cell epitopes of α-lactalbumin and β-lactoglobulin from bovine whey. The amino acid composition and spatial distribution of different types of epitopes was analyzed. The results showed that some linear epitopes were part of the conformational epitopes. IgE and IgG-binding epitopes shared some common sequences. At the same time, we identified a new linear IgE-binding epitope in β-lactoglobulin. The epitopes we obtained are candidate biomarkers for the diagnosis and prognosis of milk allergy, and can be used for guiding the development of hypoallergenic dairy products.

This study was designed in order to scientifically evaluate the health benefits of Porphyra haitanensis harvested at different times and its phenolic compounds. The bioaccessibility and antioxidant activities of phenolic compounds in P. haitanensis harvested at different growth stages (early, middle and late) were evaluated after being cooked and subjected to in vitro oral and gastrointestinal digestion and the modulatory effect of cooked P. haitanensis on the gut microbiota in vitro was investigated. The results showed that the bioaccessibility of total polyphenols and total flavonoids were 104.80%–117.03% and 35.21%–59.60% after in vitro digestion, respectively, and the content and release after digestion of polyphenols in P. haitanensis at the early growth stage were higher than those at the middle and late stages. In vitro colonic fermentation of P. haitanensis could promote the production of propionic acid and n-butyric acid, and effectively inhibit the production of isobutyric acid and isovaleric acid. According to 16S rRNA gene sequencing, P. haitanensis could promote the growth of Bacteroidetes, Megamonas, Lactobacillus and other beneficial bacteria. In conclusion, P. haitanensis is a good source of polyphenols, and polyphenols in P. haitanensis still have good antioxidant activity and bioaccessibility after digestion in gastrointestinal tract. P. haitanensis has a significant regulatory effect on the gut microbiota. Young P. haitanensis seems to be a better choice for consumers.

This study aimed to establish a quantitative method for detecting Bifidobacterium in infant formula by using droplet digital polymerase chain reaction (ddPCR). A pair of specific primers and probes were designed targeting the single copy gene rpsL of Bifidobacterium. The reaction conditions of ddPCR were optimized, and the specificity, sensitivity and repeatability of the developed method were investigated and compared with those of the plate counting method. The limit of detection (LOD) was 296 CFU/mL for pure bacterial culture, and 7 300 CFU/g for a simulated sample, respectively. There was no cross-reaction with 10 related species of Lactobacillus, and this method had good repeatability. When Bifidobacteria in commercial infant formula samples were detected by ddPCR and the plate counting method, the deviation between the results of the two methods was less than 10%, indicating good agreement. The ddPCR method can detect Bifidobacteria in infant formula milk powder more quickly, sensitively and accurately than the plate counting method, and it thus has good application prospects.

To explore the microbial community and special spoilage bacteria in pallet-packaged giant salamander (Andrias davidianus) meat during cold storage, the total volatile basic nitrogen (TVB-N) content and total bacterial count of giant salamander meat were evaluated after different refrigeration durations (0, 2, 4, 6 and 8 d) at 4 ℃, and the changes and diversity of the microbial flora were explored by Illumina MiSeq sequencing. The results showed that the total count of bacteria and TVB-N levels in salamander meat showed an upward trend during refrigeration, and exceeded the safety limit on the 6th and 8th days, respectively. The results of high-throughput sequencing showed that the microbial abundance in giant salamander meat decreased with storage time. The dominant phyla of bacteria were Bacteroidetes and Firmicutes during the early storage period (0 and 2 d), and Proteobacteria during the middle (4 d) and late (6 and 8 d) storage periods. The dominant genera were Bacteroidetes and Faecalibacterium during the early storage period, and Pseudomonas, Aeromonas, Hafnia-Obesumbacterium and Serrella during the middle and late storage periods. Principal coordinate analysis showed that there were great differences in microbial community structure between the three storage periods, and the degree of superposed interpretation of the two principal coordinates was 80.92%. Linear discriminant analysis effect size (LEfSe) analysis showed that Proteobacteria, Actinobacteria, Bacteroides, Fibrinobacteria and Firmicutes were the major bacterial phyla that significantly changed during cold storage. The main bacterial genera that significantly changed during storage were Pseudoxanthomonas, Bauldia, Serrella, Acinetobacter, Aeromonas, Pseudomonas, ambiguous_taxa, Hafnia-Obesumbacterium, Rikenellaceae_RC9_gut_group, Prevotella_9, Bacteroides, Fibrobacter, Lachnospira, Faecalibacterium, Clostridium_sensu_stricto_1. Evolutionary analysis showed that there was a strong correlation between the succession of microflora and storage time. Overall, the dominant spoilage microorganisms in giant salamander meat are Pseudomonas, Aeromonas, Hafnia-Obesumbacterium and Serrella. This study provides a reference for the targeted bacteriostasis of spoilage bacteria in giant salamander meat during cold storage to extend its shelf life in the future.

In order to analyze the differential metabolites between brown rice and white rice and related metabolic pathways, high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS)-based non-targeted metabolomics was used to analyze the metabolites of brown rice and white rice, and multivariate statistical analyses including principal component analysis (PCA), partial least square discriminant analysis (PLS-DA) and cluster analysis were conducted. Based on the significant changes with multiple difference ≥ 1.2 or ≤ 0.833 3, P < 0.05 and variable importance in the projection (VIP) ≥ 1, 460 differential metabolites including 300 up-regulated metabolites and 160 down-regulated metabolites were detected between brown rice and white rice in the positive ion mode, and 579 differential metabolites including 383 up-regulated metabolites and 196 down-regulated metabolites in the negative ion mode. In the positive mode, two metabolic pathways (phenylalanine, tyrosine and tryptophan biosynthesis, and histidine metabolism) with the involvement of four metabolites were determined. In the negative mode, five metabolic pathways (betalain biosynthesis, C5-branched dibasic acid metabolism, purine metabolism, zeatin biosynthesis and carbon metabolism) with the involvement of 10 metabolites were determined. These results showed that the differential metabolites were mainly up-regulated in brown rice compared with polished rice, and they regulated the contents of amino acids, polyphenols, and fatty acids in rice bran and embryos by affecting metabolic pathways such as amino acid metabolism, carbon metabolism, purine metabolism, zeatin metabolism, and betaine biosynthesis, thereby improving the nutritional quality of rice. This study provides a theoretical basis for the nutritional evaluation of brown rice, and the development of brown rice processing technologies and products.

A high-purity antioxidant peptide SHP-1 was purified from enzymatically hydrolyzed soybean protein prepared under previously optimized conditions by high-efficiency strong anion exchange column (HiTrap Q HP), fast weak anion exchange column (HiTrap DEAE-FF) and preparative liquid chromatography. The molecular mass of the peptide was determined to be 741.41 Da by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The amino acid composition of SHP-1 was analyzed by an amino acid analyzer, revealing that it is composed of five amino acids. By using LC-MS/MS as well as comparison to the soybean protein database, the amino acid sequence of SHP-1 was determined to be IPPGVPY, which is derived from the G4 subunit of glycinin.

This study was conducted in order to explore the fermentation capacity and glycosidase activity of indigenous non-Saccharomyces isolated from naturally fermented grape juice from the eastern foothill of Helan Mountain using WL medium and esculin medium. The activity of β-D-glucosinase, β-D-xylosidase, α-L-rhamnosidase, and α-L-arabinosidase of the isolates were determined and compared using the p-nitrophenol method. The growth kinetics and glycosidase activity of six selected strains were monitored during the fermentation of synthetic grape must by each of them. The results showed that the six non-Saccharomyces strains with high glycosidase activity were identified as Hanseniaspora opuntiae, Metschnikowia pulcherrima, Hanseniaspora uvarum, and Torulaspora delbrueckii through sequence analysis of the D1/D2 domain of 26S rDNA, but their glycosidase activities were different. T. delbrueckii showed better fermentation capacity for synthetic grape must and higher cumulative glycosidase activity (94.10–127.70 mU/mL) than the other strains, which was 1.96–2.30 folds higher than the control strain. M. pulcherrima had high α-L-rhamnosidase and α-L-arabinosidase activity, while H. opuntiae and H. uvarum-3 showed high β-D-xylosidase and α-L-arabinosidase activity. In conclusion, these strains of non-Saccharomyces yeast have high glycosidase activity and possess good application potential for wine aroma enhancement.

In this study, four yeast strains with good fermentation ability were isolated and purified from wild Hippophaer hamnoides collected from Longzi country, Tibet. All of these strains were identified as Saccharomyces cerevisiae by 26S rDNA gene sequence analysis. Their growth characteristics, tolerance and fermentation characteristics were evaluated in comparison with those of Saccharomyces cerevisiae ATCC9763. The results showed that the 18% ethanol tolerance of strain Nysj-7 was higher than that of Nysj-4, Nysj-9 and ATCC9763, but the same as that of Nysj-1, and the SO2 tolerance of Nysj-7 was higher than that of the other strains. Nysj-4, Nysj-7, Nysj-9 and ATCC9763 could tolerate 500 g/L glucose concentration, which was higher than that observed for Nysj-1. The four strains could grow at pH 2.5. The ethanol production capacity of Nysj-7, Nysj-1, Nysj-4 and ATCC9763 was the same as that of Saccharomyces cerevisiae ATCC9763, and higher than that of Nysj-9. Nysj-7 exhibited the highest ester production capacity and lowest H2S production capacity, and its β-glucosidase production capacity was higher than that of ATCC9763 and lower than that of Nysj-4, but not significantly different from that of Nysj-1 and Nysj-9. By gas chromatography-mass spectrometry (GC-MS), a total of 524 volatile substances were detected in seabuckthorn wine fermented by Nysj-7, and 95 differential metabolites were identified compared with that fermented by ATCC9763 including 69 significantly up-regulated volatile substances and 26 significantly down-regulated volatile substances; the relative content of the former was higher than that of the latter. Principal components analysis (PCA) indicated that there was an obvious difference in the expression of volatile substances by Nysj-7 compared with ATCC 9763. In conclusion, strain Nysj-7 has good tolerance and fermentation characteristics and can be used for fruit wine brewing.

In this study, microbial proteins were extracted by Tris/phenol extraction-methanol/ammonium acetate precipitation from fermented grains for nongxiangxing baijiu production pretreated by centrifugation-ultrasonic disruption (C-UD) or liquid nitrogen grinding-ultrasonic disruption (LNG-UD) and the structure of the microbial communities obtained by the two pretreatment methods was evaluated by using label-free quantitative proteomics. The results showed that there was no significant difference between the protein contents extracted by both pretreatment methods. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the C-UD extract contained more and clearer protein bands. The number of identified peptides and proteins obtained by C-UD was higher than that obtained by LNG-UD, and the Score Sequest HT of protein identification was higher. The microbial species and community structure obtained by the two pretreatment methods were significantly different, and both were significantly different from the results obtained by genomic amplicon sequencing for the same samples, implying the importance of multi-omic designs for studying the microbial community in fermented grains. The results of the present study will help to optimize the extraction of microbial proteins from fermented grains for baijiu production, and lay a foundation for further understanding baijiu fermentation and improving baijing quality.

The characteristic aroma-active compounds of seven samples of red jujube slices during hot air drying were detected and characterized by headspace solid phase microextraction-gas chromatography-olfactometry-mass spectrometry (HS-SPME-GC-O-MS) combined with sensory analysis and partial least squares regression (PLSR) analysis. The results revealed that the major volatile components in dried jujube slices were esters (19), ketones (15), acids (15), aldehydes (12), alcohols (9), hydrocarbons (6) and furan compounds (2). A total of 18 aroma compounds (with odor activity value, OAV > 1) were identified, including esters (3), alcohols (1), acids (2), aldehydes (4), ketones (7) and furan compound (1). Sensory evaluation revealed that the major aroma characteristics of dried jujube slices were caramel-like, roasted, sweet, bitter and burnt. A positive correlation between sensory attributes and aroma-active compounds were clearly elaborated by PLSR. The PLSR results indicated that 2,3-butanedione and 3-hydroxy-2-oxobutane were significantly and positively correlated with the roasted sweet attribute, while γ-butyrolactone, 4-cyclopentene-1,3-dione and 2,5-dimethyl-4-hydroxy-3(2H)-furanone had a significantly positive impact on the caramel-like attribute. 5-Methyl furfural and 5-methyl-2(5H)-furanone were positively correlated with the bitter attribute. 5-Hydroxymethylfurfural was the most powerful odor-active compound that contributed to the burnt flavor. 3-Hydroxy-2-methyl-4H-pyran-4-one, 4H-pyran-4-one and 2,3-dihydro-3,5-dihydroxy-6-methyl were the major sources of the burnt and bitter flavor. These results were verified by the flavor obtained from sensory evaluation with gas chromatography olfactometry.

Solvent-assisted flavor evaporation (SAFE) or simultaneous distillation extraction (SDE) combined with gas chromatography-mass spectrometry (GC-MS) was used to evaluate and determine the types and contents of volatile components in fragrant peanut oils prepared from high-oleic acid and ordinary peanuts under the same conditions. The quality differences between the two kinds of peanuts and between the two kinds of peanut oils were analyzed in terms of sensory evaluation, fatty acid composition, amino acid composition, basic physicochemical properties, and nutritional composition. In addition, the difference between the volatile contents determined using SAFE and SDE was analyzed. Results indicated that the two kinds of peanuts significantly differed with respect to fatty and amino acid composition. The extraction efficiency of SAFE for volatiles was obviously higher than of SDE. Using SAFE combined with GC-MS, 112 and 127 volatile components were detected from high-oleic acid and ordinary peanut oil, at a total amount of 33 945.28 and 46 700.22 μg/kg, respectively, and the two kinds of peanut oils had significant differences in the contents of volatile components such as aldehydes, phenols, furans and pyrazines. The contents of all volatile components except pyrroles were significantly higher in high-oleic acid peanut oil than in ordinary peanut oil. Partial least squares discriminant analysis (PLS-DA) combined with odor activity value (OAV) was used to identify 18 characteristic volatile flavor components that contributed to the sensory difference between the two kinds of peanut oils, which were detected in both oil samples and at higher levels in regular peanut oil. Further analysis revealed that furanone had the most significant influence on the flavor of the two kinds of peanut oils, and made an important contribution to the sweetness of peanut oil. Furthermore, eight pyrazines such as 2,5-dimethylpyrazine, 3,5-diethyl-2-methyl-pyrazine, 2,5-diethyl-pyrazine, 2-ethyl-6-methyl-pyrazine, 2,3-diethyl-5-methyl-pyrazine, 2-methyl-pyrazine, 2,3-dimethyl-5-ethyl-pyrazine, and 2-vinyl-5-methyl-pyrazine had important effects on the difference in the characteristic nutty or roasted flavor of peanut oil. Four aldehydes, including trans-2-octenal, n-hexenal, n-octenal and heptanal, contributed to the difference in the fatty flavor of two kinds of peanut oil. Dimethyl trisulfide, 2,3-pentanedione, N-methyl-2-pyrrole formaldehyde, 2-pentylfuran, and n-tridecane were important contributors to the difference in the sweetness and pungency of both kinds of peanut oils. The results of sensory evaluation showed that each sensory attribute of regular peanut oil was significantly stronger than that of high-oleic peanut oil, which is consistent with the results of volatile components. These results can provide support for precise flavor control in the production of fragrant peanut oil.

In order to rapidly detect the moisture content in tea leaves during green tea fixation, a quantitative prediction model for moisture content changes during green tea fixation was constructed by using machine vision and near infrared spectroscopy. Spectral and image information of samples at different stage of fixation was collected. The characteristic wavelengths were extracted by four different variable selection methods, competitive adaptive reweighted sampling (CARS), variable combination population analysis (VCPA), variable combination population analysis, iterative retained information variable algorithm (VCPA-IRIV), and random frog (RF) algorithm, and the prediction models were developed by using linear partial least squares regression (PLSR) or non-linear support vector regression (SVR) as well as fusing 15 color and texture features in the image. The results showed that the model based on data fusion had improved prediction accuracy compared with that based on single data. The SVR model developed based on the spectral feature wavelengths extracted by CARS algorithm and fusion of 15 color feature using normalization pretreatment combined with principal component analysis (PCA) was the best among all established models. The correlation coefficient of the calibration set (Rc) for the model was 0.974 2, prediction set correlation coefficient (Rp) value 0.971 9, and relative percent deviation (RPD) value 4.154 6, indicating the model had excellent prediction performance. In conclusion, this study proved the feasibility of integrating spectroscopy and imaging technology to predict the moisture content during the process of green tea fixation, which overcomes the problem of the low prediction accuracy of a single sensor, and lays a theoretical foundation for rapid nondestructive detection of the moisture content of fixed tea leaves for green tea and accurately controlling tea fixation quality.

Zhangping Shuixian tea cakes were baked at different temperatures (80-70-60 ℃, 90-80-70 ℃, 100-90-80 ℃, and 110-100-90 ℃). Unbaked samples were used as a control. The effects of different baking temperatures on the flavor quality of Zhangping Shuixian tea cake were investigated by sensory evaluation and biochemical analysis. The results showed that the mellow and sweet taste of Zhangping Shuixian tea cake increased initially and then decreased with increasing baking temperature, and so did the floral aroma. In addition, the aroma changed from strong orchid-like to sweet and burnt. The contents of tea polyphenols, free amino acids, water extract, thearubigins, soluble sugar, theabrownin and caffeine were the key factors affecting the difference in taste. The contents of hexanol, 2-methylbutyraldehyde, 2-methyl furan, dehydrolinalool, 1-pentene-3-ol, cis-2-pentanol, α-farnesene, cis-3-hexenyl acetate, 1-ethyl-1H-pyrrole, linalool, phenethyl ethanol, β-caryophyllene, and 3,4-dihydro-4-methyl-2H-pyran were the key factors affecting the difference in aroma. The tea sample baked at 90-80-70 ℃ had the best flavor quality. Under this condition, the contents of water extract, soluble sugar and theaflavins increased, and the contents of caffeine and theabrownin decreased, thus improving the mellow taste and the sweet aftertaste. Moreover, the content of cis-2-pentenol decreased, and the contents of dehydrolinalool, linalool, β-caryophylene, 1-pentene-3-ol, α-farnene, hexanol, 2-methylbutyraldehyde, 1-ethyl-1h-pyrrole and 2-methylfuran increased, thereby promoting the formation of lingering orchid-like and sweet aromas. In conclusion, this study will provide a reference for research on the optimization of the baking process and the improvement of the flavor quality of Zhangping Shuixian tea.

Stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS) was used to detect the volatile composition of 20 Anjibaicha samples, and gas chromatography-olfactometry-mass spectrometry (GC-O-MS) combined with relative odor activity value (ROAV) was utilized to identify its key aroma-active compounds. Results showed that 109 volatile compounds were detected in the tea samples. Among them, geraniol, diisobutyl phthalate, phytol, methyl salicylate, cis-jasmone, linolenic acid, and linalool were the most abundant components. It was found that the contents of volatile components in different grades of Anjibaicha varied greatly. Moreover, a total of 34 common characteristic peaks were selected to establish a fingerprint of the volatile components of Anjibaicha. Sixteen compounds were identified as key aroma-active compounds of Anjibaicha, including trans-β-ionone, geraniol, linalool, hexanal, heptanal, (E)-2-heptenal, α-ionone, and (Z)-3-hexenyl hexanoate.

In order to avoid environmental pollution and health hazards caused by the use of organic solvents in Soxhlet extraction, and improve the detection efficiency of fat content in pork, a method for determining fat content in pork based on low-field nuclear magnetic resonance (LF-NMR) was proposed. Signal acquisition parameters (echo time and number of scanning cycles), sample mass, drying time and detection temperature were optimized, and the repeatability and precision of the method were verified. When 4 g of minced pork was dried for 6 h in an oven and detected under the following conditions: temperature, 50 ℃; echo time, 0.3 ms; and number scanning cycles, 64, good results were obtained using lard as a standard sample. The correlation coefficient (R2) of the standard calibration curve established was 0.999 9. The repeatability relative standard deviation (RSD) of the proposed method was 1.69%–2.72%, and the intra-day and intra-day precision (RSDs) were 3.07% and 2.57%, respectively. The correlation coefficient between the LF-NMR method and the Soxhlet extraction method specified in the national standard (GB 5009.6–2016) was 0.999 5. Therefore, the LF-NMR method can accurately determine fat content in pork and other meats.

In this study, a delicious mixed mushroom sauce was developed using the rare mushroom Oudemansiella raphanipes and the common oyster mushroom Pleurotus ostreatus as raw materials. Using principal component analysis (PCA) and partial least squares-discrimination analysis (PLS-DA), the flavor changes of mixed mushroom sauces with different mixing ratios were examined as a function of cooking time. The results showed that at a cooking time of 4 min and a 4:6 mixing ratio between oyster mushroom and O. raphanipies, the umami taste of the mushroom sauce was the strongest (m/m). At a cooking time of 4–5 min and a 4:6 ratio, the aroma quality was the best. Fourteen compounds, including glutamate and geraniyl acetone, resulted in significant differences in the umami and aroma of the product at different cooking times. This study will provide a theoretical basis for improving the flavor quality of mixed mushroom sauce, and, more broadly, promote the development of the edible mushroom processing industry.

An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established for the analysis of seven phenolic acids in wax apple fruit. The separation was performed on a Waters CORTECD? T3 (2.1 mm × 100 mm, 2.7 μm) column, and the column temperature was set at 30 ℃. The mobile phase consisted of 0.1% formic acid aqueous solution and acetonitrile at a 0.3 mL/min flow rate. The samples were extracted twice with acetonitrile, and the external standard method was used for quantitative detection of the phenolic acids. Results showed that the standard calibration curves had a good linear relationship in the range of 5.0–1 000 ng/mL with correlation coefficients equal to or larger than 0.996 1. The recoveries of spiked samples ranged from 93.6% to 98.8%, with relative standard deviation (RSD) from 1.9% to 7.5%. The limits of detection were 0.3–2.7 μg/kg, and the limits of quantification were 1.0–5.0 μg/kg. This method was used to determine phenolic acids in wax apple fruit, and the obtained data were analyzed by principal component analysis (PCA). Three principal components were obtained and used as the independent variables for proposing a mathematical model. The comprehensive F value was negative on the 6th day of storage, indicating that a large number of phenolic acids had begun to decompose. In conclusion, the established method is simple, sensitive, stable, reliable, and suitable for the quality evaluation of wax apple.

In order to reveal the differences in the nutritional value and flavor of different genders and tissues of scallop (Patinopecten yessoensis), free amino acids, 5’-nucleotides and lipids in the samples were analyzed by targeted and non-targeted metabolomics based on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and ultra-high performance liquid chromatography-Q-Exactive Orbitrap tandem mass spectrometry (UPLC-Q-Exactive Orbitrap-MS). Results showed that glutamic acid and glycine were the main free amino acids in scallop. The contents of glutamic acid and glycine in the adductor muscle were 132.98 and 280.37 μg/g, respectively and were little affected by gender. Adenosine 5’-monophosphate (AMP) was abundant in the adductor muscle and mantle, and the content of AMP in the adductor muscle of female scallops was about twice higher than that in male scallops. A total of 188 lipids were detected in the tissues of scallop, including phospholipids and glycerides. The content of phospholipids in the adductor muscle of male scallops was higher than that in female scallops, while the opposite was true for the content of phospholipids in the gonads. The digestive gland was an important part for storing glycerides, accounting for 49.36% and 33.11% of the total glycerides in male and female scallops, respectively. These results are of great significance for guiding the development of scallop products and the comprehensive processing and utilization of scallop by-products.

The volatile components and aroma active components in physalis fruits were identified, the contribution of individual volatile components to the overall aroma was comprehensively evaluated, and the key aroma components were determined by solid phase microextraction extraction (SPME) and gas chromatography-mass spectrometry (GC-MS) combined with gas chromatography-olfactometry (GC-O) based on odor activity values (OAVs). The results showed that a total of 43 volatile components were determined in physalis fruits. Ten main aroma active substances (OAV > 1) were identified, including four aldehydes and ketones (n-hexanal, methylthiopropionaldehyde, trans-2-cis-6-nonadienal, and 1-octene-3-one), whose aromas are described as grassy, potato chip-like, cucumber-like, and mushroom-like, respectively; five ester compounds (methyl-2-methyl methyl propionate, methyl butyrate, methyl 2-methyl butyrate, methyl ethyl butyrate, and methyl decanoate), whose aroma are described as floral, fruity, apple-like, stimulating fruity, and wine-like, respectively; and one furan compound (2-pentylfuran), whose aroma is described as caramel-like. In the GC-O method, four trained judges mainly identified the “apple-like aroma” of methyl 2-methylbutyrate, the “potato chip-like flavor” of methylthiopropionaldehyde and the “grass flavor” hexanal. Through the qualitative and sensory quantitative descriptive analysis, it was found that methyl 2-methylbutyrate, methylthiopropionaldehyde and hexanal were the main aroma components.

A novel paramagnetic ions-mediated magnetic relaxation switching biosensor was developed to detect hypoxanthine and histamine for the evaluation of fish freshness and quality. With the catalysis of xanthine oxidase or diamine oxidase, hypoxanthine and histamine can be decomposed to generate hydrogen peroxide. Hydrogen peroxide can act as a reductant or oxidant to induce the conversion of paramagnetic ions of different valence (Mn (VII)/Mn (II) and Fe (II)/Fe (III)), leading to an obvious change in magnetic signals. Herein, paramagnetic ions and hydrogen peroxide were employed to fabricate a magnetic signal readout system for the quantitative analysis of hypoxanthine and histamine. As a result, this biosensor allowed highly sensitive detection of hypoxanthine and histamine. The linear ranges for hypoxanthine and histamine were 0.525–1 050 and 5–1 000 μmol/L, the limits of detection were 0.17 and 2.34 μmol/L, respectively. The results of this biosensor for crucian carp samples were in good agreement with those of high performance liquid chromatography (HPLC). The proposed biosensor is sensitive, rapid, low cost and promising for fish freshness detection and quality control.

Objective: To develop a quantitative detection method for norovirus (NoV) in foods based on digital PCR. Methods: Three sets of specific primers and probes were selected to establish one-step reverse transcriptase droplet digital polymerase chain reaction (RT-ddPCR) assays for NoV genotype I (GI), genotype II (GII) and MS2 phage, respectively. The specificity of these RT-ddPCR assays was verified. Their limit of quantitation, accuracy and repeatability were analyzed using NoV RNA reference materials and MS2 phage RNA. Artificially positive samples were prepared to analyze the influence of MS2 phage on the results of NoV detection. Results: The three RT-ddPCR assays had satisfactory specificity, accuracy and repeatability. The limit of quantitation of NoV RT-ddPCR was at five orders of magnitude from 104 to 100 copies/μL and close to that of MS2 phage RT-ddPCR. There was no significant difference between the quantitative results for artificially positive samples with and without added MS2 phage (P ≥ 0.05). Conclusion: NoV RNA could be accurately quantified by the NoV RT-ddPCR assay. MS2 phage did not affect the quantitative results of NoV, and could be added as a process control model virus to indicate virus recovery and calculate the content of NoV particles in foods.

An ultra-performance convergence chromatography (UPC2) method was established for the separation and determination of the residues of florfenicol enantiomers and its metabolite florfenicol amine in fish meat. The samples were extracted with alkalized ethyl acetate, purified on a solid phase extraction column (MCX), and separated on a CHIRALPAK AD-3 column (150 mm × 3.0 mm, 3 μm) by gradient elution using a mobile phase consisting of supercritical CO2 (A) and aqueous ammonia-methanol in water (0.5:99.5, V/V) (B). The system’s back pressure and the column temperature were set at 13.8 MPa and 40 ℃, respectively. The linear correlation coefficients were greater than 0.999 3 in the range of 1.0–20.0 mg/L for the two florfenicol enantiomers and 2.0–40.0 mg/L for florfenicol amine, and the limits of quantification (RSN = 10) were 0.1 and 0.2 mg/kg, respectively. The recoveries of the florfenicol enantiomers and florfenicol amine from spiked fish in the range of 0.1–1.0 mg/kg were 81.5%–108.0%, with relative standard deviations (RSDs) of 5.3%–9.3%. This method is suitable for the separation and determination of the residues of florfenicol enantiomers and its metabolite in fish meat.

In this work, a surface-enhanced Raman scattering (SERS) chip based on 4-mercaptoboric acid (4-MPBA) probe was developed by controllable self-assembly for the ultrasensitive quantitation of SO32-. This technique was based on the oxidative transformation of SO32- to SO42- and the Lewis acid-base coordination principle. The quantitative detection of SO32- was based on the ratio of the intensity of the peak at 1 382 cm-1 to that at 1 070 cm-1 (I1 382/I1 070). This ratiometric quantification strategy avoided errors caused by the inhomogeneity of SERS substrates, and effectively improved the reliability of detection signals. The limit of detection (LOD) of this SERS chip was as low as 5 × 10-8 mol/L, and a good linear relationship was obtained over the concentration range of 5 × 10-8 –1 × 10-3 mol/L (R2 = 0.997 4). Using this method, the SO32- content in white sugar was determined to be 1.42 mg/kg and recoveries for spiked white sugar were 98.38%–107.82%, suggesting that this method has good application prospects for the rapid determination of trace levels of SO32- in actual samples.

In this study, a method based on ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-MS-MS) was developed for the simultaneous determination of cannabinol, cannabidiol and Δ9-tetrahydrocannabinol in nine food matrices such as olive oil, beef and bread. The samples were extracted with acetonitrile or methanol and purified using an EMR or HLB solid-phase extraction (SPE) cartridge. The analytes were separated on a BEH C18 column (2.1 mm × 50 mm, 1.7 μm) using methanol and 10 mmol/L ammonium acetate in water as the mobile phase, ionized using an electrospray ionization (ESI) source in the positive ion mode, detected in the multiple reaction monitoring (MRM) mode, and quantified by the internal standard method. The calibration curves for all analytes showed good linearity in the concentration range of 0–200 μg/L, with correlation coefficients greater than 0.998. The limits of detection (at a signal to noise ratio of 3) and quantitation (at a signal to noise ratio of 10) were 3 and 10 μg/kg, respectively. The average recoveries for negative samples spiked at three concentration levels (1, 2, 10 times of the limit of quantitation) were 71.7%–108.5%, with relative standard deviations (RSDs) of 4.6%–12.4% (n = 6). In summary, this method has good stability and high sensitivity, and is suitable for simultaneous determination of the three cannabinoids in common food matrices.

A novel fluorescent coumarin derivatization reagent, 7-(diethylamino)-2-oxo-2H-chromone-3-carboxylic acid (named as L1), was synthesized by condensation-cyclization and hydrolysis reactions using 4-(diethylamino) salicylaldehyde as the raw material. The derivatization reaction system of L1 and fipronil was established and optimized. The optimal reaction conditions were obtained as follows: condensation catalyst, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride/4-dimethylaminopyridine; reaction solvent, dichloromethane; ratio of L1 to fipronil, 11:1; reaction time, 60 min; and derivatization temperature, 45 ℃. The derivative of fipronil, N-(3-cyano-1-(2,6-dichloro-4-(trifluoromethyl)phenyl)-4-(trifluoromethyl) sulfonyl)-1H-pyrazole-5-yl)-7-(diethylamino)-2-oxo-2H-chromone-3-formamide (named as SF1), was isolated and identified. On this basis, a high performance liquid chromatography-fluorescence detection method (HPLC-FLD) based on pre-column derivatization was established for fipronil determination, with a detection limit of 0.01 μg/L and quantitative limit of 0.036 μg/L. In summary, the HPLC-FLD method presented good sensitivity, accuracy and reliability, and therefore could be applied to the detection of fipronil residue in agricultural products.

The geographical traceability of tea from different production areas was studied by gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) based on carbon and nitrogen stable isotope ratios in caffeine and amino acids. The results showed that GC-C-IRMS combined with compound specific stable isotope ratio analysis could be used to trace the geographical origin of tea. Chemometrics analysis showed that this method could effectively distinguish tea from different production areas, with accuracy of prediction and verification more than 85%. BP artificial neural network had the best authentication performance, with accuracy of prediction and verification of 100%. After further screening and identification, two characteristic marker compounds, δ15Nalanine and δ13Ctheanine, were obtained for Xiuya green tea from different production areas. This study can provide some technical support for geographical traceability of tea and help to establish a sound certification system for tea products.

A method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed for the determination of 68 persistent organic pollutants (POPs) including 16 polycyclic aromatic hydrocarbons, 19 phthalate esters, 18 polychlorinated biphenyls and 15 organic chlorines in various teas. Tea samples were crushed and extracted by an accelerated solvent extractor, and the extract was cleaned up by a molecular imprinted polymer solid phase extraction column, and further purified by the QuEChERS method. The analytes were separated on a DB-5ms capillary column and analyzed by GC-MS/MS, where the triple quadrupole mass spectrometer was operated in the multi-reaction monitoring (MRM) mode, effectively reducing the background interference from the tea substrate. In green tea and dark tea samples, the recoveries for the analytes were from 73.1% to 109.5% with a relative standard deviation (RSD) from 0.1% to 9.3% at three spiked concentration levels of limit of quantification (LOQ), 2-fold LOQ and 10-fold LOQ. The limits of detection (LOD) of the proposed method ranged from 0.11 to 4.3 μg/kg. In conclusion, this method can be used for accurate qualitation and quantification of the 68 POPs in tea samples. Moreover, its stability and feasibility have been verified by testing 60 batches of tea samples.

A method based on ultra performance convergence chromatography-tandem mass spectrometry (UPCC-MS/MS) with pass-through solid phase extraction was established for the determination of 19 sex hormones in health foods. The samples were extracted with methanol containing 1% formic acid, and the extract was purified by solid phase extraction using PRiME HLB columns. The chromatographic separation was achieved on a UPCC Torus 2-PIC column (3.0 mm × 100 mm, 1.7 μm) under gradient elution using a mobile phase composed of supercritical carbon dioxide and methanol containing 0.1% formic acid. The separated compounds were analyzed by tandem MS with an electrospray ionization (ESI) source in the positive/negative alternate mode using multiple reaction monitoring. Ninety-seven percent methanol containing 0.2% formic acid and 98% aqueous acetonitrile containing 0.2% ammonia water were used as the auxiliary pump mobile phases. The external standard method was used to quantitatively analyze the sex hormones in sample solutions. Good linear relationship was obtained between the peak area and concentration in the tested concentration ranges (R2 ≥ 0.997 1). The limits of detection and limits of quantification were 0.03?0.85 (RSN = 3) and 0.10?2.5 μg/kg (RSN =10), respectively. The average recoveries (n = 9) at three spiked levels were in the range of 77.8%?111.7% with relative standard deviations (RSDs) between 1.1% and 8.4%. The developed method was successfully used for the determination of actual samples. This method is fast, simple, specific, environmentally friendly and suitable to determine the contents of sex hormones in health foods.