In this study, the impact of oxidative modification of hemin prosthetic group on the solubility, particle size, emulsifying activity and emulsion stability of myosin was investigated. Meanwhile, the changes in the dynamic rheological properties, gel strength, water-holding capacity, water distribution, intermolecular interaction forces and microstructure of heat-induced myosin gel were analyzed before and after the oxidative modification and the mechanism behind its effect on the water-holding capacity of heat-induced myosin gel was deciphered. The results showed that treatment with low concentrations of hemin prosthetic group had no impact on the solubility, but increased the emulsion stability, heat-induced gel strength and water-holding capacity of myosin, and made the gel network structure more uniform, ordered and compact with smaller holes in it by intermolecular interactions such as disulfide bonding. Besides, the treatment improved the surface hydrophilicity and water-holding capacity of the gel and enhanced the interaction between protein and water, consequently increasing the proportion of immobile water and retaining more water in the gel network structure. By contrast, high concentrations of hemin prosthetic group led to lower solubility, larger particle size, and worse emulsifying activity and emulsion stability of myosin, damaged the gel network structure, flattened the rheological curve, and weakened the water-holding capacity.

In order to investigate the effects of silver carp muscle hydrolysates (SCMHs) on the quality characteristics of frozen dough, the changes in the rheology, microstructure, proofing and baking characteristics of dough with or without 2% of SCMHs after four cycles of freeze-thaw treatment (each consisting of freezing at ?18 ℃ for 18 h and thawing at 4 ℃ for 6 h) were analyzed. Results showed that addition of SCMHs inhibited the increase in the proofing time of frozen-thawed dough and the decrease in the specific volume of the resulting bread, and the most pronounced effect was observed with SCMH at 30 min of hydrolysis (SCMH-30). The proofing time and bread specific volume of the SCMH-30 group were 121 min and 1.72 mL/g compared to 170 min and 1.54 mL/g for the blank control group, respectively, indicating good cryoprotective effect of SCMH-30. Addition of SCMHs decreased the tensile strength but increased the adhesiveness and extensibility of fresh dough, which was likely related to the negative effect of some reducing peptides in SCMHs. Although the tensile strength of dough decreased and the adhesiveness and extensibility increased after four freeze-thaw cycles for all groups, SCMH-30 and trehalose, with good cryoprotective effect, resulted in smaller variations in these parameters. Scanning electron microscopic (SEM) observation indicated that SCMH-30 weakened gluten network formation in dough, but maintained the gluten network structure after four freeze-thaw cycles. The farinographical properties revealed that SCMH-30 significantly decreased dough development and stability time and farinograph quality number (FQN), and increased dough weakness, and this negative effect was ameliorated by addition of glucose oxidase. These findings provide a theoretical guidance for the application of SCMHs to improve the quality of frozen dough.

The effects of punicalagin (P) and sodium pyrophosphate (SPP) and their combination (P + SPP) on the oxidative stability and gel properties of myofibrillar protein (MP) under oxidative stress were studied. The results showed that the addition of P and SPP effectively inhibited the increase of carbonyl content and the decrease of free amino content induced by oxidation, and the combination of P and SPP had the best effect; however, neither single nor combined additives effectively inhibited the decrease of sulfhydryl content induced by oxidation. The addition of P promoted protein unfolding induced by oxidative stress and significantly inhibited the increase of protein particle size (percentage inhibition of 10.50%) induced by oxidation. It had no significant effect on protein solubility or rheological properties during heat-induced gelation, but significantly improved the cooking loss and texture deterioration of heat-induced MP gels under oxidative stress. The addition of SPP also promoted protein unfolding induced by oxidation, inhibited the increase of protein particle size (percentage inhibition of 17.65%), increased the solubility of oxidized MP by 9.78%, significantly changed the rheological behavior of MP during heat-induced gelation, and resulted in a 42.56% reduction in the cooking loss of heat-induced gels, while texture indexes such as gel strength were significantly reduced. The combination of P and SPP had a similar effect on the heat-induced gel properties of MP as the addition of SPP alone. Moreover, the antioxidants used in this study significantly increased the oxidative stability of MP and the water-holding capacity of its heat-induced gel, but the effects on the gel texture characteristics were closely related to the type of antioxidants.

In order to improve the stability of emulsions, gelatin (GE), soybean protein isolate (SPI), chitosan (CS) and gum arabic (GA) were modified with 3.000% nano-SiO2 and used separately as a stabilizer to prepare camellia oil emulsions. The effect of nano-SiO2 on emulsion properties was investigated by considering emulsifying activity, emulsion stability, centrifugal stability, average particle size, rheological properties, microstructure and oil droplet distribution. The results showed that nano-SiO2 enhanced the stability of emulsions. The comprehensive properties of GE-nano-SiO2 composite emulsion were the best. Addition of nano-SiO2 significantly enhanced the emulsifying activity and emulsion stability (P < 0.05), and reduced the centrifugal stability by 68.444%. The resulting emulsion had the smallest particle size and uniform particle size distribution with an average particle size of 8.472 μm, and the emulsion particles were spherical with smooth surface. The emulsion was rheologically characterized as a typical weak gel with good stability. The results of this study could provide a practical basis for the preparation and application of nano-SiO2-modified natural macromolecules in emulsions.

In this study, the Auricularia auriculata polysaccharides extracted using high pressure-shearing extraction method were phosphorylated at different temperatures using sodium trimetaphosphite as a crosslinking agent, and the structure and in vitro hypoglycemic activity of the modified polysaccharides were characterized.?The results showed that the phosphorylated polysaccharides were heteropolysaccharides mainly composed of xylose, fructose, mannose and glucose. With the increase of temperature, the molecular mass of the phosphorylated polysaccharides decreased significantly and a triple-stranded helical structure was observed. Infrared (IR) spectra showed that the characteristic absorption peaks of P＝O and P–O–C appeared at 1 205 and 898 cm-1. Nuclear magnetic resonance (NMR) spectra showed that the phosphorylation mainly occurred on the C6 hydroxyl groups, and the signal peak of P in the phosphate group appeared in the range of δ 0–1.5. Scanning electron microscopic (SEM) results showed that the surface morphology of the modified polysaccharides changed significantly, and it was finer and more broken compared to the original polysaccharides. In addition, 5.0 mg/mL of the phosphorylated polysaccharide PAAP-4 had strong inhibitory effect on α-glucosidase and α-amylase. The inhibitory rate of α-glucosidase was 56.89%, and the in vitro hypoglycemic activity was enhanced compared to that of the original polysaccharides.

In this study, lupin proteins were extracted from lupin seeds by two different methods, namely, micellization and alkali dissolution followed by acid precipitation, and their physicochemical properties were evaluated. The molecular mass distribution of lupin proteins was mainly in the range of 18–90 kDa and consisted of proteins with various molecular masses. The total amino acid content of lupin proteins extracted by sequential alkali dissolution and acid precipitation (66.2%) was significantly higher (P < 0.05) than that obtained by micellization (27.8%). The isoelectric point (pI) of lupin proteins extracted by the two extraction methods was close to 5.0. The water-holding capacity of lupin protein extracted by micellization was significantly higher (P < 0.05) than that obtained by alkali dissolution followed by acid precipitation, but there was no significant difference (P > 0.05) in oil-holding capacity between the two methods. The foaming capacity of lupin protein extracted by sequential alkali dissolution and acid precipitation decreased significantly at pH 2.0–6.0, and was the lowest at pH 6.0, and the trend of foam stability was similar to that of foaming capacity. However, pH had no significant effect (P > 0.05) on the foaming ability of lupin protein extracted by micellization. The emulsifying capacity of lupin protein extracted by micellization was the lowest at pH 4.0, and then increased with the increase of pH. The emulsifying capacity of lupin proteins extracted by the two extraction methods was the highest at pH 10.0. The solubility of lupin protein extracted by alkali dissolution followed by acid precipitation was the lowest at pH 4.0, and increased rapidly with the increase of pH from 4.0 to 10.0. The solubility of lupin protein extracted by micellization increased with the increase of pH from 2.0 to 10.0. The results of this study can provide theoretical and technical support for the development and application of lupin proteins in the food industry.

This study is aimed to explore the effects of different full drying methods (far infrared, microwave, re-drying, carding, and rotary pot full drying) on the color and chlorophyll degradation of green tea. A method for the analysis of chlorophylls and their degradation derivatives in tea was established based on ultra-high performance liquid chromatography quadrupole orbitrap high resolution mass spectrometry (UPLC-Q-Exactive Orbitrap-MS). A total of 19 chlorophylls and degradation derivatives were detected within 20 min, and six pairs of epimeric chlorophylls and chlorophyll derivatives were well separated with simple sample pretreatments. For the purpose of the present study, this method was applied to analyze chlorophylls and their degradation products in green tea samples manufactured by the five different full drying methods, and the data were analyzed by orthogonal partial least square-discriminant analysis (OPLS-DA) and one-way analysis of variance (ANOVA). The results showed that compared to the other full drying methods, green tea prepared by microwave full drying had better sensory color and quality. The contents of chlorophyll a (Chl a), chlorophyll b (Chl b), chlorophyll a’ (Chl a’) and chlorophyll b’ (Chl b’) were the highest in green tea prepared by microwave full drying, while the contents of pyropheophorbide a (PyrPo a), pyropheophorbide b (PyrPo b), pyropheophytin a (PyrPhe a) and pyropheophytin b (PyrPhe b) were the lowest, indicating that microwave full drying resulted in the lowest degree of isomerization, magnesium removal and degradation reaction and decarboxymethylation. Therefore, microwave full drying is more beneficial to the protection of chlorophylls in green tea. This study can provide a theoretical basis and technical guidance for quality improvement and directed processing of green tea.

The objective of the present study was to investigate the influence of cooking water on the taste characteristics of hand-grasped mutton. Hand-grasped mutton was made from mutton chops from Ningxia Yanchi Tan sheep with domestic water in Yanchi County, Ningxia; domestic water in Fengtai District, Beijing; or superpure water. The results showed that cooking water had a significant effect on the taste characteristics of hand-grasped mutton. The index of protein degradation and the contents of glutamic acid and 5’-inosinic acid in hand-grasped mutton made with superpure water were remarkably higher than those in the other two samples, while the contents of alanine and glycine in hand-grasped mutton made with Yanchi domestic water were markedly higher than in the other two samples. The umami intensity of hand-grasped mutton made with superpure water was the highest, while that of hand-grasped mutton made with Fengtai domestic water was the lowest. Collectively, the results of electronic tongue and sensory analysis indicated that there were significant differences in taste characteristics between the three samples of hand-grasped mutton, which was related to the types and contents of trace metal elements in cooking water.

In order to solve the problems of quality decline in spring roll wrappers (SRW) caused by water loss during frozen storage and the high oil content of fried SRW, the effects of addition of different levels (0%, 0.3%, 0.6% and 0.9%) of soluble soybean polysaccharide (SSPS) on the processing properties and eating quality of SRW repeatedly frozen and thawed 0, 4, 8, 12 and 24 times were investigated. The results showed that SSPS significantly enhanced the water content of SRW (P < 0.05), decreased the water loss during freeze-thaw cycles, and improved the textural properties and freeze-thaw resistance. Besides, SSPS maintained the microstructural integrity and compactness of SRW, significantly decreased the oil content of fried SRW (P < 0.05), and improved the crispness and color. Meanwhile, SSPS increased the sensory score of fried SRW, indicating that SSPS can be used as an effective quality improver for SRW.

In this study, the effect of heat treatment at different temperatures (60–100 ℃) on the stability of liver ferritin from Acipenser baerii (ABLF) was investigated by electrophoresis, ultraviolet (UV) absorption spectroscopy, dynamic light scattering (DLS), Fourier transform infrared (FTIR) spectroscopy. Besides, the effect of heat treatment temperatures of 25–65 ℃ on the rate of iron release from ABLF and the storage stability of ABLF at 4 and 25 ℃ were explored. The results showed that the solubility and iron content of ABLF gradually decreased, and the content of protein aggregates increased with increasing heat treatment temperature (60–100 ℃). The FTIR spectroscopic results showed that the relative content of α-helix structure gradually decreased, and the relative content of random coil structure generally increased with increasing heat treatment temperature, especially in the range of 80–100 ℃, while little changes were observed in the range of 60–80 ℃ indicating that ABLF had good stability at 60–80 ℃. The rate of iron release from ABLF increased with increasing heat treatment temperature (25–65 ℃). ABLF was more stable when stored at 4 ℃ than at 25 ℃. The results of this research will provide a theoretical basis for the processing and utilization of ABLF.

In this study, based on the codon preference of Escherichia coli BL21 (DE3), base optimization was carried out on the?tannase?encoding?gene CsTanA of Camellia sinensis. In the optimized gene, the GC content was 51.9%, the codon adaption index (CAI) value was 0.8, and the consistency of the gene sequence before and after optimization was 77.8%. Recombinant expression and enzymatic characterization of the optimized gene using?expression?vector?pET30a were investigated. The recombinant strain, with an A600 nm value of approximately 0.6, was cultured at 30 ℃ in the presence of the inducer isopropyl-β-D-thiogalactoside (IPTG). In the supernatant from the broken cells, the recombinant tannase rCsTanA had a specific activity of 0.35 U/mg, and it was purified 4.4 folds by Ni-NTA affinity chromatography with a specific activity of 1.53 U/mg. The apparent molecular mass of the purified rCsTanA was about 39 kDa, and its optimal reaction temperature and pH were 40 ℃ and 7.0, respectively. The effects of different metal ion concentrations on the enzyme activity were different. At low concentration (1 mmol/L), K+ enhanced the enzyme activity of rCsTanA by 37.28%, while Ag+, Cu2+ and Fe3+ reduced the enzyme activity by more than 80%. At high concentration (5 mmol/L), Cu2+ completely inhibited the activity of rCsTanA. The surfactants sodium dodecyl sulfate (SDS), Tween-80 and cetyltrimethyl ammonium bromide (CTAB), and the polar solvents methanol, ethanol, glycerin, isopropanol and acetone had strong inhibitory effects on rCsTanA activity. The results of this study can provide theoretical support for the further application of plant tannase.

Tenebrio molitor rennet (TMR) was prepared and the effects of preheating milk at different temperatures on its coagulation behavior and hydrolytic properties were evaluated, and the structure of milk curds was characterized by Fourier transform infrared (FTIR) spectroscopy and laser scanning confocal microscopy (LSCM). The results showed that the water-holding capacity of curds increased significantly with the increase in preheating temperature (P < 0.05), while the particle size, apparent viscosity and storage modulus G′ increased initially and then decreased (P < 0.05); the particle size and apparent viscosity reached their maximum of 15.07 and 0.51 at 45 ℃, respectively. The production of casein glycomacropeptide (CGMP) and the degree of hydrolysis (DH) were not significantly changed with increasing temperature from 45 to 55 ℃ (P > 0.05). The secondary structure and microstructure indicated that the flexibility, stability and compactness of curds were the best at 45 ℃. At this temperature, the water-holding capacity and whey OD value of TMR-coagulated curd tended to be stable when compared with that coagulated by commercial rennet (CR), and the particle size significantly increased. Meanwhile, TMR-coagulated curd exhibited a continuous, irregular and compact network structure, indicating good coagulation properties. Therefore, the optimum coagulation temperature for TMR was 45 ℃. This study provides a theoretical basis and reference for the development and application of new insect-derived rennet.

The enhancing effect of low concentrations of exogenous acetic acid on the fermentation of acetic acid by Acetobacter pasteurianus CICC 20001 was evaluated, and the underlying molecular mechanism was investigated using transcriptomics. The results showed that the acid production efficiency was significantly improved by addition of 0.5% acetic acid to the culture medium. A total of 482 significantly differentially expressed genes between the fermentations with and without 0.5% acetic acid were identified, of which 424 were up-regulated and 58 were down-regulated. In total 412 and 70 significantly differentially expressed genes were observed on days 1 and 7 of fermentation, respectively. Addition of 0.5% acetic acid to the culture medium could enhance the tolerance of A. pasteurianus to acetic acid by urea metabolism, propionic acid metabolism and acetic acid assimilation metabolism, reduce the toxic effect of acetic acid on the bacterium, and ultimately improve the acid production efficiency. In addition, strengthening the signal transduction, membrane transport and energy metabolism in A. pasteurianus may be important for nutrient transport and energy transformation in acetic acid fermentation. These results will provide new insights into the mechanism by which exogenous acetic acid enhances acid production by A. pasteurianus and provide a theoretical basis for improving the efficiency of acetic acid fermentation.

The present study was designed to evaluate the effect of the chymosin from Bacillus licheniformis on the proteolysis of Cheddar cheese during ripening. The chymosin was used to produce cheddar cheese (CDF) and Cheddar cheese analogue (CD3), and a commercial milk-clotting enzyme preparation was also used to prepare Cheddar cheese (CCF). The variation of proteolysis indexes was analyzed during cheese ripening. The results showed that the contents of casein, soluble nitrogen at pH 4.6 (pH 4.6-SN), 12% trichloroacetic acid-soluble?nitrogen (12% TCA-SN), 5% phosphotungstic acid-soluble?nitrogen (PTA-SN) and total free amino acid in CDF, CD3 and CCF increased significantly with maturation time, and were significantly higher in CDF than in CCF during maturation (P < 0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the degree of hydrolysis of α-casein (α-CN) was higher in CDF. The results of pH 4.6-SN analysis showed that the total peptide content increased first and then decreased with ripening time, but the ratio of hydrophobic peptide to hydrophilic peptide showed a continuous downward trend. At the sixth month of ripening, the ratios of hydrophobic peptide to hydrophilic peptide in CDF, CD3 and CCF were 2.668, 2.822 and 3.788, respectively. Principal component analysis (PCA) showed that for all three cheeses, the proteolysis degree was positively correlated with maturity, but negatively correlated with the ratio of hydrophobic peptides to hydrophilic peptides. The above results showed that cheese produced with Bacillus licheniformis chymosin had higher degree of proteolysis, but smaller proportion of hydrophobic peptides. Our findings could provide a theoretical basis for the application of Bacillus licheniformis chymosin in cheese production.

To elucidate the differential milk fat globule membrane (MFGM) proteins between donkey colostrum (DC) and mature milk (DM), a comparative analysis was performed using proteomics. A total of 216 and 215 MFGM proteins were characterized in DC and DM, respectively. Among them, 15 differentially expressed and 25 specifically expressed MFGM proteins were identified. Bioinformatics analysis showed that the significantly differentially expressed MFGM proteins were mainly involved in cellular components including extracellular exosome, extracellular vesicle, and extracellular organelle compartments, and participated in biological processes such as external stimuli, cell proliferation, and blood vessel morphogenesis, and molecular functions such as metal ion binding, cation binding, and calcium ion binding. Additionally, these significantly differentially expressed MFGM proteins were mainly involved in metabolic pathways such as the complement and coagulation cascades and intestinal immune network for IgA production. Furthermore, some key protein factors with high connectivity, as determined by protein network interaction analysis, were identified as differently expressed MFGM proteins. This study provides a better understanding of the biological properties of donkey MFGM proteins and paves the way for future research of MFGM protein nutrition and for the development of formula milk powder.

A virulent phage P65, one of whose hosts is methicillin-resistant Staphylococcus aureus (MRSA), was isolated from the sewage of dairy cow farm. The transmission electron microscopic (TEM) observation showed that the head of the phage was polyhedral, belonging to the long-tailed Siphoviridae family. Its optimal multiplicity of infection (MOI) was 0.01. The one-step growth curve showed that the latent period of the phage was 10 min, the lysis period was 90 min, and the burst size was 35.46 PFU/cell. Its lytic activity remained stable at pH 4–10 and 30–45 ℃. After 70 min of UV irradiation, the titer of the phage decreased from 1.91 × 108 to 2.65 × 104 PFU/mL. After 48 hours of phage treatment, the biofilm clearance rates of strains MRSA 2 and MRSA 24 were 91.3% and 92.2%, respectively. At 25 ℃, P65 had an antibacterial effect in milk and beef contamination models. The results showed that phage P65 has a wide host spectrum and stable lytic activity, and thus has potential for the removal of biofilm and food preservation.?

Totally 46 strains suspected of being lactic acid bacterial were isolated from three samples of sour bamboo shoot collected in Liuzhou, and their probiotic and anti-inflammatory properties were evaluated by acid resistance, bile salt resistance, simulated gastrointestinal digestion, in vitro HT-29 cell adhesion and NO release tests. Strain SS-31 was selected as an excellent anti-inflammatory strain and it was identified as Lactobacillus fermentum by 16S rRNA gene sequencing. The results showed that SS-31 had high acid resistance, and the number of viable cells remained above 107 CFU/mL with a survival rate of over 90.02% after 3 h of treatment with 0.1% bovine bile salt. Its survival rate was 80.28% after 2 h incubation in artificial gastric juice, but only 3.63% in simulated artificial gastric juice. SS-31 had strong adhesion to HT-29 cells with an adhesion rate of 4.47%, which was just slightly lower than that of the control strain Lactobacillus rhamnosus LGG (4.95%). Compared with the model group, SS-31 significantly reduced the secretion level of NO in the culture supernatant of lipopolysaccharide (LPS)-simulated RAW264.7 cells (P < 0.05), and pro-inflammatory cytokines such as IL-1β and IL-6 (P < 0.05). The results proved that Lactobacillus fermentum SS-31 has potential for the treatment of inflammation.

In this study, Q Exactive quadrupole Orbitrap mass spectrometry with Proteome Discoverer 2.2 software was used to identify the signature peptides of heat load from α-lactalbumin and β-lactoglobulin in heat-treated cow milk, and the effect of heating temperature on their contents was studied. The results showed that there was a correlation between the degree of whey protein denaturation and the contents of the signature peptides. With increasing heating temperature and time, the contents of the signature peptides increased significantly, and then remained unchanged when the heating temperature exceeded the denaturation temperature of whey protein. After heating at temperatures exceeding 80 ℃, the content of peptide 3# increased obviously, and it was found that the contents of peptides 1#–6# were significantly different between pasteurized milk and ultra high temperature (UHT) milk (P < 0.01). Therefore, based on ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and principal component analysis (PCA), this study can provide technical support for quality control and evaluation of thermally treated milk.

In order to figure out the function of the chaperone Hfq in Shewanella baltica SB-19 isolated from large yellow croaker, a hfq-knockout (KO) strain and a wild type (WT) strain of this spoilage bacterium were investigated for differences in their growth rate, quorum sensing, stress resistance, and ability to spoil sterilized fish juice. There was only one hfq gene in S. baltica SB-19, and its expression level increased with the increase of cell density. Although the growth rates of the WT and KO strains were similar at 30 ℃, the KO strain was significantly delayed and the cell density at the stationary phase was much lower at 4 ℃. Both strains had similar ability to produce the quorum sensing (QS) signal molecules of diketopiperazines (DKPs) and autoinducer-2 (AI-2), but the KO strain showed lower biofilm formation ability and extracellular protease activity, and sterilized fish juice inoculated with the KO strain produced less total volatile basic nitrogen (TVB-N) and trimethylamine (TMA). Besides, the KO strain was more susceptible to salt, nutritional, heavy metal, and disinfectant stress. The above results showed that Hfq was involved in regulating a variety of metabolic pathways in S. baltica SB-19, and affected the growth, quorum sensing, spoilage ability, and adaptability to environmental stress of the bacterium. Therefore, Hfq is a global regulatory factor that can regulate many physiological activities of S. baltica SB-19. This study provides a theoretical basis for the biological research of S. baltica and understanding the spoilage mechanism of seafood.

In order to study the effect of fermentation by Lactobacillus paracasei NXU-19004 on the quality characteristics of goji juice, non-targeted metabolomics based on gas chromatography-mass spectrometry (GC-MS) was used to identify and analyze the differential metabolites of fermented goji juice samples at four different fermentation times, and principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were used to distinguish the four samples. Then the metabolic pathways of the differential metabolites were annotated in the KEGG database to identify the key metabolites. The results showed that a total of 63 differential non-volatile metabolites were detected in the four samples. Among them, the average relative abundance of amino acids, organic acids and lipids in fermented goji juice showed an overall increasing trend with fermentation time. The results of multivariate statistical analysis showed that there were significant differences between the samples, and an obvious clustering area was observed for each sample, indicating that the samples can be discriminated based on the differential metabolites. A total of 47 metabolic pathways were identified, and 9 key pathways through which more differential metabolites could be enriched were observed, most of which were involved in amino acid metabolism. It could be concluded that fermentation time had the greatest influence on the metabolism of amino acids in fermented goji juice. It was further confirmed that the key metabolites were alanine, limonene, benzaldehyde, benzoic acid, nicotinamide, niacin, squalene, proline, sarcosine and 2-phenylacetamide. The results of this study provide a theoretical basis for further studies on the factors affecting the formation of differential metabolites in goji juice during lactic acid bacteria fermentation.

The bacterial community structure in different fermentation rounds in Maotai town was analyzed by MiSeq high-throughput sequencing combined with SPSS statistical software 26.0 and the environmental effect on it was evaluated. A total of 33 bacterial classes, 153 families and 396 genera were identified, among which, the dominant classes were Gammaproteobacteria, Bacilli, Sphingobacteriia, Alphaproteobacteria, Actinobacteria, Flavobacteriia and Betaproteobacteria. Totally 19 dominant families were found, including Enterobacteriaceae, Sphingobacteriaceae, Bacillaceae, Flavobacteriaceae, Thermoactinomycetaceae, and Planococcaceae. Among them, Flavobacteriaceae, Planococcaceae, Bacteroidales_S24-7_group, Microbacteriaceae and Brucellaceae were considered as the dominant bacterial families for the first time in baijiu-making environments. A total of 22 dominant genera were identified, including Sphingobacterium, Enterobacter, Pantoea, Acinetobacter, Oceanobacillus and Pseudomonas. The correlation of environmental factors (temperature, humidity, precipitation, sunlight and atmospheric pressure) with the alpha diversity and the 48 dominant bacterial classes, families and genera was analyzed by t-test combined with Spearman correlation analysis. The results showed that the alpha diversity was significantly correlated with environmental factors, and the environmental bacterial communities in the 2nd and 3rd rounds of fermentation had a significant correlation with temperature and humidity. In addition, 35 dominant bacteria had a significant correlation with environmental factors; among them, Gammaproteobacteria and Bacilli as well as their respective subclasses were significantly correlated with the five environmental factors, especially temperature, humidity and sunlight. Alphaproteobacteria and its subclasses had a significantly positive correlation with environmental temperature. Sphingobacteriia, and its Sphingobacterium genus had a significant correlation with temperature and precipitation. Actinobacteria and its subclasses were significantly positively correlated with light duration. Betaproteobacteria and Flavobacterium as well as their respective subclasses were almost not affected by environmental factors. The results of this study provide a basic theoretical and disciplinary basis for the in-depth understanding of the microbial community structure characteristics in the brewing environment of Maotai town and their correlation with environmental factors.

In order to explore the changes in the bacterial community structure and diversity in sea buckthorn jiaosu during natural fermentation, Illumina-MiSeq high-throughput sequencing technology was used to study the bacterial diversity of sea buckthorn jiaosu liquid at different fermentation stages. The results showed that a total of 601 species belonging to 422 genera, 239 families, 149 orders, 57 classes and 25 phyla were obtained by the analysis of operational taxonomic unit (OTU). Cyanobacteria, Proteobacteria, unclassified_k__norank_d__Bacteria, Acidobacteriota, Firmicutes were the five dominant phyla in sea buckthorn jiaosu. Among them, Cyanobacteria was the absolute dominant phylum and its relative abundance at three fermentation stages, namely F22_Q (72 h), F22_Z (624 h) and F22_H (1 584 h) were 93.28%, 66.59% and 35.40%, respectively. Norank_f__norank_o__Chloroplast, Ralstonia, unclassified_k__norank_d__Bacteria, norank_f__Mitochondria, Burkholderia-Caballeronia-Paraburkholderia were the dominant genera. Among them, norank_f__norank_o__Chloroplast was the absolute dominant genus and its relative abundance ranged from 35.39% to 93.28%. The three fermentation stages were clustered into two groups by sample cluster analysis and principal component analysis (PCA); one group consisted of the early stage (F22_Q) and middle stage (F22_Z), and the other group consisted of the late stage (F22_H). The results from this study could provide a theoretical basis for sea buckthorn jiaosu fermentation.

The metabolite profile of low-salt shrimp paste during low-temperature fermentation was investigated by metabolomics based on gas chromatography-mass spectrometry (GC-MS), and the differential metabolites were selected by multivariate statistical analysis combined with t-test and variable importance in projection (VIP) analysis. The results showed that the orthogonal partial least squares discriminant analysis (OPLS-DA) model clearly discriminated the metabolite profiles of shrimp paste samples fermented at 10 (low temperature) and 20 (control) ℃. A total of 44 metabolites were identified in the two samples, including 16 amino acids, 6 fatty acids, 2 amines, 8 organic acids, 3 alcohols, 3 nucleotides and 6 other compounds. By considering P < 0.05 and VIP > 1, 30 differential metabolites were obtained, including 7 amino acids, 2 esters, 2 purines, 8 organic acids, 2 alcohols and 9 other metabolites. The levels of L-serine, L-threonine, xanthine, hypoxanthine and L-glutamine in the low-temperature group were significantly higher than those in the control group, while the levels of nerazine acetate, zeaxanthin and melatonin were significantly lower (P < 0.01). These results provide a theoretical basis for further improving the production process of low-salt shrimp paste.

The objective of the current study was to isolate and identify lactic acid bacteria from a series of Guizhou-style fermented cured meat products, such as Jinping sour pork, Rongjiang sour pork, Kaili sausage, Zunyi sausage, Weining dry-cured ham, Panxian dry-cured ham, Kaili air-dried meat, Zunyi air-dried meat, and Bijie air-dried meat, as well as to illustrate their protein degradation capacity, physiological and biochemical characteristics, practical applicability, and safety. A strain named SJ-4, with strong protein degradation capacity and the potential to be used as a meat starter culture, was selected from the isolated strains, and was used as an inoculum to produce fermented loin ham. Effects of the starter culture on the color, texture, electronic tongue response value and flavor of fermented lion ham were examined using naturally fermented lion ham as a control. The results showed that the strain was tolerant to 6 g/100 mL NaCl and 150 mg/kg NaNO2, did not produce NH3, H2S or H2O2, had no amino acid decarboxylase activity, and had the ability to decompose protein but not fat. Under the optimum growth conditions of 37 ℃ and pH 6.0, the strain entered the logarithmic growth phase after 4 h cultivation, and the pH dropped to 3.80 after 18 h, proving that it can be used as a meat starter culture. Strain SJ-4 was identified as Lactobacillus plantarum according to its morphological, physiological and biochemical characteristics and 16S rDNA sequence alignment. Inoculation with SJ-4 significantly affected the color, hardness and cohesiveness of fermented loin ham (P < 0.05), and was beneficial for the formation of flavor compounds, increasing the contents of key flavor components such as nonanal and 3-hydroxy-2-butanone. Therefore, Lactobacillus plantarum SJ-4 can be developed as a high-activity meat starter culture.

The volatile components of virgin olive oils from the representative varieties (Laixing and Ezhi 8) grown in Longnan, Gansu province and a mixed extra virgin olive oil popular with consumer were comparatively analyzed by gas chromatography-mass spectrometry (GC-MS). In addition, their aroma compounds were identified by gas chromatography-olfactometry (GC-O), and the contribution of these aroma compounds to the flavor profile of olive oil was analyzed by OAV in order to identify the key aroma-active compounds in each sample. Totally 35, 30 and 25 volatile components were identified in Laixing, Ezhi 8 and mixed virgin olive oils, respectively. The contents of hexanol, 3-hexen-1-ol, (E)-2-hexen-1-ol and (E)-2-hexenal were the highest in all samples. In addition, 13, 15 and 12 aroma compounds were identified in the three samples, including C6 compounds with grassy notes, and heptanal and (E,E)-2,4-decadienal with fatty aroma notes. In total, 12, 13 and 11 compounds whose OAV were higher than or equal to 1 were identified as the key aroma-active compounds in the three samples. The OAVs of 1-octen-3-ol, linalool, (E)-2-hexenal and (E,E)-2,4-decadienal were higher, indicating that these compounds were important to the flavor quality. The results of this study can provide a theoretical basis for improving the flavor quality of virgin olive oil.

The volatile components of the seed oils from canola (Brassica napus) and Indian mustard (Brassica juncea) extracted under the same conditions were determined by solvent-assisted flavor evaporation (SAFE) combined with gas chromatography-mass spectrometry (GC-MS). Based on odor activity value (OAV), partial least squares discriminant analysis (PLS-DA) was used to identify the key volatile flavor components to discriminate the two oils according to their sensory flavor. The results showed that 82 volatile components of 12 kinds and 90 volatile components of 11 kinds were detected in canola and rapeseed oil in a total quantity of 22 377.88 and 157 512.98 μg/kg, respectively. Meanwhile, the total amounts of thioside degradation products were 3 311.07 and 146 492.82 μg/kg, and the total amounts of phenolic substances were 12 125.47 and 4 613.03 μg/kg, respectively. The 13 most important characteristic flavor substances were identified using PLS-DA in combination with OAV, namely 6-methylthiohexanenitrile, 5-(methylthio)-valeronitrile, benzenepropionitrile, 3-butenyl isothiocyanate, benzeneacetonitrile, trans-2-decenal, n-hexanol, linalool, ethylbenzene, phenylethanol, gamma-nonanolactone, 4-vinyl-2,6-dimethoxy-phenol, and 3-methylcrotononitrile. 6-Methylthiohexanenitrile, phenylacetonitrile, linalool, 5-(methylthio)-valeronitrile, benzyl propionitrile, and 3-butenyl isothiocyanate all contributed to the unique pungent flavor of rapeseed oil, and phenyl acetonitrile and linalool were detected only in traditional rapeseed oil; n-hexanol, phenylethanol, and gamma-nonanolactone were more abundant in canola oil and had an important effect on the sweetness of rapeseed oil. The results of sensory evaluation showed that the sweetness of canola oil was better than traditional rapeseed oil, while the pungency of traditional rapeseed oil was stronger. Erucic acid was not detected in canola oil, while the content of erucic acid in traditional rapeseed oil was 30.25%. The total content of vitamin E and sterols in canola oil was higher than that in traditional rapeseed oil. The results of this study offer support for the selection of raw materials and odor markers for the production of different aroma types of rapeseed oil.

The key aroma compounds in heated sheep tallow were analyzed by solvent-assisted flavor evaporation (SAFE) combined with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). Based on NIST2011 database search, retention index, and comparison with authentic standards, 58 volatiles were identified by GC-MS, among which 2,3-butanediol, acetic acid, acetoin, propanoic acid, hexanoic acid, and 2-hexanol were more abundant. A total of 37 odor activity regions were found by aroma extract dilution analysis (AEDA) combined with GC-O. Totally, 37 odorants were identified, among which (E,E)-2,4-heptadienal, (E)-2-nonenal, (E,E)-2,4-octadienal, (E)-2-decenal, (E,Z)-2,4-decadienal, (E,E)-2,4-decadienal, 2-heptanol, trimethylpyrazine, 4-methylthiazole, 3-(methylthio)propanal, dihydro-5-methyl-2(3H)-furanone, and 4-ethylphenol, with higher flavor dilution (FD) values (log2FD ≥ 4), were considered to be the key aroma compounds in sheep tallow. These results can provide a basis for the utilization of sheep tallow in the food industry and the preparation of mutton flavorings.

To clarify the quality characteristics of natural dry red wine from the Eastern Foothill of Helan Mountain, the physicochemical indexes, flavor substances and sensory profile of naturally fermented ‘Merlot’ dry red wines produced at three different regions in the Eastern Foothill of Helan Mountain were analyzed. The results showed that there was no significant difference in the basic oenological parameters such as alcohol content, residual sugar, dry extract, total acid, or pH between the naturally fermented wine and that prepared by the traditional process, while the former had lower contents of glycerol and malic acid and higher amounts of volatile acids and lactic acid. The concentrations of total phenols, tannins and anthocyanins were relatively lower in the naturally fermented wine, and the chroma and red hue were weaker, whereas the yellow hue and hue angle were not significantly different from those of the traditional one. The total amount of aroma compounds and the contents of esters of medium- and short-chain fatty acids in the natural wine were lower than those in the traditional one, while the proportions of higher alcohols, long-chain fatty acid esters with more than ten carbon atoms and phenols were slightly higher in the natural wine. Moreover, clustering analysis on aromatic components clearly distinguished the natural wine from the traditional one. In terms of olfactory properties, the chroma of the natural wine was slightly weaker, but no significant difference in taste was found. Despite having weaker fruity aroma, the natural wine had more complex flavors such as almond-like, pepper-like and vanilla-like aromas and had a higher overall score. In summary, the natural dry red wine has more prominent sensory quality and a unique style.

The aim of this study is to explore the yield and flavor characteristics of essential oils extracted from black pepper, white pepper, green pepper, and fresh pepper fruit. The essential oils were extracted by steam distillation, and the extraction yields of different pepper essential oils were compared. The flavor characteristics of different pepper essential oils were analyzed by gas chromatography-mass spectrometry (GC-MS), electronic nose and quantitative descriptive sensory analysis. The results showed that the extraction yield of essential oil from fresh pepper fruit was 3.229 mL/100 g, which was significantly higher than that from white pepper, black pepper, and green pepper (1.718, 1.867, and 1.487 mL/100 g, respectively). A total of 48 volatile substances were identified from the four pepper essential oils, the main ones being β-caryophyllene, 3-carene, D-limonene, β-pinene, δ-elemene, and β-myrcene. The electronic nose data confirmed that discriminant function analysis (DFA) distinguished different pepper essential oils better than principal component analysis (PCA). The sensory evaluation showed that the pepper-like aroma of the essential oil of fresh pepper fruit was stronger than the other three essential oils and had higher acceptance. The results of partial least squares regression (PLSR) analysis showed that the aromatic?plant-like, herbal, and pepper-like aroma properties were positively correlated with (+)-α-pinene components. The experimental results provide a reference for the development and upgrading of pepper essential oil products.

Dried sea bass samples were prepared with endogenous enzymatic transformation + light heat treatment (S1), endogenous enzymatic transformation + high-intensity heat treatment (S2), light heat treatment (S3) and high-intensity heat treatment (S4), and their flavor was analyzed by sensory evaluation, solid phase microextraction combined with gas chromatography-mass spectrometry (GC-MS). The correlation between volatile components and sensory attributes was investigated by partial least squares regression (PLSR). Sensory analysis showed that there were significant differences in flavor profiles between samples S1, S2, S3, and S4. The results of GC-MS showed that n-hexanal, nonanal, n-octanal, butyl phenol, 1-octene-3-ol, 2,3-octanedione, caryophyllene, and 2,6-di-tert-butyl-p-cresol were the major volatile components in dried sea bass. The volatile components of S1, S2, S3, and S4 were significantly different, and the content of volatile components in S1 and S2 was significantly higher than that in S3 and S4. PLSR analysis showed that benzaldehyde, kunienal, n-octanal, acetophenone, heptanol, and 2-ethyl hexanol were correlated with the sensory properties of dried sea perch. The contents of these substances were significantly different among the four samples. The comparison revealed that hexanal, acetophenone, and benzaldehyde in S1 and S2, enhancing the grassy and sweet aroma, were produced by the reaction between fat and amino acids under the action of endogenous enzymes. In S3 and S4, heat treatment promoted the oxidative degradation of triglycerides to produce octanal, 2-ethylhexanol, decenal and trans-2-octenal, enhancing the orange and fatty aroma. In addition, the enzymatic activity of cathepsin B was much higher in S1 and S2 than in S3 and S4. The results of this study provide a theoretical reference for optimizing the preparation process of dried sea bass and further understanding of the mechanism of the flavor formation of aquatic foods.

The volatile compounds of 25 brands of fragrant vinegar, rice vinegar and aged vinegar were detected by ultra-fast gas chromatography-electronic nose and were analyzed qualitatively and quantitatively by retention index and external standard method. A flavor wheel for vinegar was developed based on the odor activity values (OAV) of volatile compounds, and the volatile aroma profiles of the different kinds of vinegar were compared and their relationship with the content of volatile compounds was evaluated. Linear discriminant analysis (LDA) and random forest (RF) were used to investigate the difference in the composition of volatile compounds of different kinds of vinegar in order to distinguish them. The results showed that in total 44 volatile compounds were detected in the three kinds of vinegar, mainly including alcohols, esters, aldehydes, ketones, acids, alkanes and heterocycles, the most abundant ones being acids, followed in decreasing order by alcohols, aldehydes and alkanes. The OAVs and odor radar chart of vinegar samples showed that acetic acid, 3-methylbutyraldehyde, phenylacetaldehyde, 5-methylfurfural and guaiacol contributed a lot to the aroma. The sourness, and fruity and cocoa-like aroma of fragrant vinegar were higher than those of rice vinegar and aged vinegar, but the flowery aroma of aged vinegar was higher than that of the other two types. The results of LDA showed that there were significant differences among different brands and types of vinegar. Using random forest machine learning, the three types of vinegar were discriminated with an accuracy of 100%, and 3-methylbutanol, guaiacol, benzaldehyde and acetone were selected as important compounds to distinguish different kinds of vinegar.

In order to clarify the biochemical and volatile constituents of foam formed during the aerobic fermentation of black tea juice, foam was collected at different stages of aeration and analyzed for non-volatile compounds such as tea polyphenols, amino acids, tea saponins, catchins and theaflavins by spectrophotometry and high performance liquid chromatography (HPLC), and for volatile compounds by head space solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). The results showed that the concentrations of tea saponins, tea polyphenols, caffeine, catechins and theaflavins in the foam formed during tea leaf homogenization and aeration were higher than those in the residual tea juice. The total amount of volatile compounds; the contents of decanoic aldehyde, citral, linalool, geraniol and β-ionone, responsible for the sweet and flowery aroma; and the contents of hexanolaldehyde, 1-octyl-3-alcohol, phenylacetaldehyde, methy salicylate and (E)-2-hexenal, responsible for the green aroma, were also higher than those in the residual tea juice, indicating that the foam took away many quality components. In order to retain the quality components, an antifoaming agent was added in black tea juice to prevent foam formation. It was found that 0.2% of the defoamer effectively controlled foam formation while having no significant effect on tea polyphenols or amino acids, and no adverse effect on the fermentation process, and promoted the release of volatile compounds in black tea juice.

Black jujube was prepared from fresh jujube (Zizyphus jujuba cv. Huping) fruit by five different processes, namely three cycles of steaming and roasting (1), soaking in Maillard reaction products (MRPs) solution, incubation under constant temperature and humidity conditions and roasting (2), soaking in MRPs solution and three cycles of steaming and roasting (3), soaking in polyphenol oxidase (PPO) solution, incubation under constant temperature and humidity conditions and roasting (4), and three cycles of steaming and roasting, soaking in PPO solution, incubation under constant temperature and humidity conditions and roasting (5). The volatile components of black jujube were determined by gas chromatography-ion mobility spectrometry (GC-IMS) and headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and the data were analyzed by principal component analysis (PCA) and cluster analysis (CA) to evaluate the effect of different processes on the flavor quality of black jujube. The results showed that the major volatile components of the as-prepared samples were different. The types of basic flavor substances detected by GC-MS and GC-IMS were basically the same, and 6–10 flavor substances were detected by both methods. Furfural, heptanal, nonal, n-octanal and glacial acetic acid were detected in all black jujube samples. Three cycles of steaming and roasting could enhance the flavor of black jujube. Furthermore, this study demonstrates that GC-IMS can be used to quickly identify and analyze the volatile components of different black jujube samples, which provides a theoretical basis for improving the processing technology of black jujube and understanding its browning mechanism.

To investigate the effect of high-temperature and long-time final roasting on the aroma quality of roasted green tea, tea samples processed with different final roasting temperatures and durations were evaluated by sensory evaluation and characterized by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry for their sensory aroma and volatile organic compounds (VOCs). The result of sensory evaluation showed that the eight tea samples were classified into four categories according to their characteristic odors, which suggests that final roasting temperature and duration influenced the aroma of roasted green tea. Totally 58 VOCs were identified among all samples, 45 of which were aroma components shared by these samples. The sample distribution patterns generated by unsupervised clustering analysis on the basis of the 58 VOCs were consistent with those based on sensory evaluation. In addition, 32 VOCs were selected as the key contributors to the aroma differences among samples by one-way analysis of variance (ANOVA) and partial least squares-discriminant analysis (PLS-DA). Two-way ANOVA was further applied to investigate the effect of roasting temperature and duration on the contents of the 32 key VOCs. It was found that the contents of 17 key aroma compounds were significantly affected by roasting temperature, duration and the interaction between them (P < 0.05). The contents of 12 key compounds were significantly affected by roasting temperature and duration (P < 0.05). The contents of α-cubebene and δ-cadinene were significantly affected by the interaction between roasting duration and temperature (P < 0.05), while the content of α-calacorene was significantly affected only by roasting temperature (P < 0.05).

In the current study, bioactivity-guided separation of the eight key antioxidant components of beer with Yuan’an yellow tea was accomplished by sequential alcohol precipitation, solvent extraction, macroporous resin absorption, and semi-preparative liquid chromatography. These antioxidant compounds were identified as (?)-epigallocatechin (EGC), caffeine, (?)-epigallocatechin gallate (EGCG), epicatechin (EC), 1,2,6-tri-O-galloyl-β-D-glucopyranose, (?)-epicatechin gallate (ECG), corilagin (Cor), and tryptophan (Trp) by ultra-high performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry (UPLC-Q-TOF-MS). Furthermore, EGC, EGCG, EC, ECG and Cor were the main antioxidant substances in beer with Yuan’an yellow tea, which collectively contributed up to 54.61% of its antioxidant activity. The contribution of EGCG was the highest, followed by EGC, ECG, EC and Cor. This study provides technical support for identifying the key antioxidant components in beer with tea and developing novel beer products with high antioxidant activity.

Based on ultra-high performance liquid chromatography-triple quadrupole-tandem mass spectrometry (UPLC-QQQ-MS/MS), a high throughput, sensitive and specific method to quantify three classes of phenolic compounds in tea samples was developed and validated. This method possessed good linearity, accuracy and precision, and was successfully applied to the simultaneous quantification of 90 phenolic compounds (catechins, phenolic acids, flavonoids and their glycosides) in four types of Yunnan large-leaf tea. As a result, most phenolic components were more abundant in unfermented tea (green tea and Pu’erh raw tea), while free phenolic acids, flavonoid aglycones and theaflavins were more abundant in fermented tea (black tea and Pu’erh ripe tea). By partial least squares-discriminant analysis (PLS-DA), different types of tea were clearly discriminated according to their phenolic components, and a series of chemical markers were identified.

Pepper (Zanthoxylum bungeanum) oil was produced by deep-frying using 17 Chinese red pepper samples from different geographical origins as raw materials, and sensory evaluation and high performance liquid chromatography-mass spectrometry (HPLC-MS) were used to determine the temporal dynamic curves of numb taste intensity and the content and composition of numb taste-active substances, respectively. The numb taste characteristics of pepper oil from different production areas were investigated by partial least squares-discriminant analysis (PLS-DA) and systematic cluster analysis (CA). The results showed that the numb taste characteristics and the composition of numb taste-active components of pepper oil from different production areas were significantly different (P < 0.05). In addition, the 17 oil samples were clustered into four clusters. Cluster I included the cultivars Fujiao and Mianjiao from Gansu, and Dahongpao from Maoxian and Wenchuan of Sichuan. Cluster II included the cultivar Nanjiao from Sichuan. Cluster III included the cultivar Dahongpao from Shaanxi, Shanxi and Hebei. Cluster IV included small- and large-sized peppers from unknown cultivars.

In this study, the aroma quality and volatile components of Dancong tea were analyzed by sensory evaluation and gas chromatography-mass spectrometry (GC-MS), respectively, and the aroma components were identified using a variety of statistical analyses. The results showed that the most important volatile substances in Dancong tea were indole, dehydrolinalool, linalool, jasmine lactone, safflower aldehyde and β-cyclic citral, followed by neroliol and benzylacetonitrile and α,4-dimethyl-3-cyclohexene-1-acetaldehyde. Among these volatile components, alcohols mainly contributing to the floral and fruity aroma were the most abundant, followed by nitrogen-containing compounds. In correlation analysis and cluster analysis, the honeysuckle-like and osmanthus-like aroma types of Dancong tea had unique volatile composition. The honey-like and floral aroma types were well classified by principal component analysis (PCA) and orthogonal partial least square-discriminant analysis (OPLS-DA). The applicability and testing results of the established OPLS-DA model were good. These results provide a scientific basis for evaluating the aroma quality of Dancong tea and improving product quality.

A method for the analysis of tocopherols, sterols and triterpenoids in Moutai distiller’s grains was established using ultrasound assisted extraction (UAE) combined with gas chromatography-mass spectrometry (GC-MS). The influence of solvent type and solid-to-liquid ratio on the extraction efficiency of the target analytes was investigated. Under the optimal conditions, five tocopherols, nine sterols and four triterpenoids were identified, and seven tocopherols and sterols were quantitatively analyzed with good linearity (R2 > 0.99), good stability (relative standard deviation not more than 6.40%) and high accuracy (spiked recovery between 88.9% and 102.3%). Through the traceability analysis of 18 bioactive substances in Moutai distiller’s grains, the brewing raw materials were identified as their main source.

A new aptamer-adsorbed gold nanoparticles-based colorimetric method was developed for sensitive detection of histamine, by taking advantage of the facts: 1) histamine can specifically recognize histamine aptamer, leading to exposure of the surface of gold nanoparticles (AuNPs); 2) the imidazole structure of excess histamine can replace the citrate ions on the surface of AuNPs, and destroy the electrostatic interaction between the AuNPs, thereby leading to an aggregation phenomenon that causes a color change from red to blue. Based on the changes in the absorbance of AuNPs solutions, the limit of detection (LOD) was calculated to be 8.89 nmol/L, and the linear range was 50 nmol/L–1.2 μmol/L (R2 = 0.999). Meanwhile, a smart phone was used to take photos of the sample solutions, and the values of red (R), green (G) and blue (B) channels were obtained by the Image J software. Using G/R ratio as the detection signal, the LOD of the RGB method was 24.91 nmol/L, and good linearity was observed in the range from 150 nmol/L to 1.0 μmol/L (R2 = 0.997). In addition, this method has good selectivity to histamine. The recoveries of the spectrophotometric and RGB methods were 91.82%–102.27% and 98.96%–102.89% for spiked water samples and 89.77%–108.92% and 88.96%–109.82% for spiked fish samples, respectively. Both methods are simple, rapid and sensitive. Particularly, the RGB method, which can meet the requirements of on-site real-time detection without the need for any sophisticated instrumentation, is expected to be applied for sensitive monitoring of the freshness of animal-derived foods.

A high performance liquid chromatography coupled to quadrupole-orbitrap high-resolution mass spectrometry method was developed for the simultaneous determination of six amino-carboline heterocyclic aromatic amines (HAAs) in pan-fried pork patties. The effects of processing conditions on the formation of these HAAs were also investigated. Results showed that the optimum extraction and purification conditions were as follows: 1.0 g of the sample was extracted with 10 mL of 1 mol/L NaOH solution-acetonitrile (4:6, V/V) added with 1.5 g of NaCl, purified on a StrataTM-X-C column and eluted with methanol-ammonium hydroxide (90:10, V/V). The calibration curves for the six HAAs were linear in their respective concentration ranges with correlation coefficients greater than 0.996. The detection limit and quantification limit of the developed method were 0.02–0.15 μg/kg and 0.05–0.5 μg/kg, respectively. The recoveries of these HAAs were in the range of 64%–91%. The content of these six HAAs in pork patty pan-fried for 5 min was 9.50 μg/kg. Pan-fried pork patties cooked with rapeseed oil, composite-coating pot, and patty thickness of 4 cm had the highest contents of HAAs, which were 47.62, 76.83 and 29.33 μg/kg, respectively.

Extra virgin olive oil and refined olive oil were evaluated by multi-element analysis combined with chemometrics. The results showed that principal component analysis (PCA) successfully distinguished extra virgin olive oil from refined olive oil, and a reliable orthogonal partial least squares discriminant analysis (OPLS-DA) model was established to identify the grade of olive oil. The results of OPLS-DA were consistent with those of PCA, and good clustering performance was observed on each grade of olive oil; cluster analysis also effectively discriminated the two grades of olive oil. Eight characteristic elements including Al, Fe, Cu, Ba, V, Sc, La and Zn were selected to distinguish them. Therefore, multi-element analysis combined with chemometrics can be used to discriminate extra virgin olive oil from refined olive oil.

A method to accurately and quickly determine milk-derived ingredients in infant formula was developed by the combined use of a genetic detection method for rapid screening and two-dimensional electrophoresis for confirmation, and its sensitivity and accuracy were evaluated. The one-step DNA extraction method based on thermophilic protease allowed the obtainment of DNA just through a temperature-controlled reaction within 17 min, which greatly reduced the sample pretreatment time. The fast real-time polymerase chain reaction (real-time PCR) program took only 28 minutes and 26 seconds. The limit of detection of the method was 10–100 pg/μL DNA for cow, buffalo, yak milk-derived ingredients using the universal primer, for goat and sheep milk-derived ingredients using the universal and specific primers as well as for mammalian milk internal reference, while the sensitivity was 1% (m/m) for bovine milk-derived ingredients in mixed samples. Then the samples that tested positive for bovine genes were examined by two-dimensional electrophoresis for whether they contained bovine caseins or whey proteins in order to determine their authenticity. The combination of the two methods can solve the bottleneck problem of difficult identification of milk-derived ingredients in infant formula by conventional testing methods, due to the complex ingredient composition of infant formula.

In this study, 18 quality indexes of winter jujube collected from five major production areas were determined. Quality evaluation and determination of the key indexes were carried out using multiple comparison, correlation analysis, principal component analysis, cluster analysis and Fisher discriminant analysis. Then, the feasibility of tracing the geographical origin of winter jujube was discussed according to the key quality indexes. The comprehensive analysis of principal component scores indicated that Xinjiang’s Hotan and Shandong’s Zhanhua were superior production areas. Further cluster analysis showed that the 18 quality indexes of winter jujube could be represented by eight key indexes, including soluble solid content, potassium, manganese, individual fruit mass, hardness, ethanol, color and water content. Fisher discriminant analysis showed that the eight key indexes could be used to trace the geographical origin of winter jujube with an overall discrimination accuracy of 100.0%, and a discrimination accuracy for cross-validation of 97.2%. This study provides a theoretical basis for the quality evaluation and key quality index determination of winter jujube from different production areas, which will be of great significance for the geographical origin traceability and production of winter jujube.

Based on transition metal nickel-based basic carbonate (Ni-CHs) grown in situ on carbon paper (Ni-CHs/CP), prepared by one-step hydrothermal method, a highly sensitive and selective enzyme-free sensor to detect glucose was developed. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to identify the phase and characterize the morphology of the material. Cyclic voltammetry (CV) and time-current curve were used to evaluate the performance of the sensor. The results showed that Ni-CHs/CP had the best detection ability for glucose at a low potential of 0.5 V, and the oxidation peak current of the sensor showed an excellent linear relationship with glucose concentration in the range of 0.95 μmol/L–2.623 mmol/L, with a correlation coefficient of 0.998. The detection limit was 0.31 μmol/L (RSN = 3) and response time was 3.5 s. This sensor has good stability and has been successfully used in the detection of actual samples with spiked recoveries of 95.65%–105.56%.