In this study, zein-based gluten-free dough (Z dough) was prepared with zein, corn starch, and Artemisia sphaerocephala Krasch gum (ASKG). Also, zein-free dough (NZ dough) was prepared with corn starch and ASKG as control. The effects of adding different amounts of lactic acid solution on farinographic properties of the doughs were compared, indicating that zein crucially affects the farinographic properties of Z dough. Among the Z dough samples, Z2 with a ratio between lactic acid solution and the total amount of raw material (L/F) of 2:50 had the longest stability time, the lowest weakening degree, and the highest farinographic index. It was found that lactic acid could cause the deamidation and hydrolysis of zein in dough, promote the transformation of α-zein diploids to haploids, and change the surface hydrophobicity and secondary structure of zein. Further, Z dough was processed into noodles to investigate the influence of lactic acid content on the cooking quality of zein-based noodles. It was found that the noodles were not easy to break and had the lowest cooking loss and good texture. In summary, an appropriate amount of lactic acid can improve the farinographic properties of zein-based gluten-free dough, increase the surface hydrophobicity of zein and the proportion of β-sheet, and improve the cooking quality of zein-based noodles.

D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), an inhibitor of P-glycoprotein (P-gp) with low toxicity and irritation, and the natural phytochemical quillaja saponin (QS), with a strong emulsifying effect, were selected for mixing with ethoxylated hydrogenated castor oil (RH40) as emulsifiers to prepare TPGS-QS microemulsion with ethyl oleate as an oil phase and isopropanol as a co-emulsifier. The morphology, particle size and zeta potential of emulsion droplets were observed by optical microscopy (OM), transmission electron microscopy (TEM) and laser particle size analyzer. The optimal microemulsion formulation consisted of a mixture of ethyl oleate, 0.02% TPGS, 1.5% QS, RH40 and isopropanol at a ratio of 30:6.6:6.6:39.4:17.5 (m/m). All solutions were prepared with purified water. The microemulsion was yellowish, clear and transparent in appearance with strong fluidity, and it was identified as an O/W-type emulsion with uniform spherical droplets. In addition, its average particle size was (48.89 ± 0.08) nm, and its zeta potential was (–4.513 ± 0.564) mV. The α-glycosidase inhibitory activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) cation radical scavenging capacity and iron reducing power of TPGS-QS microemulsion was tested, and its in vitro cytotoxicity on HepG2 and Caco-2 cells was evaluated through MTT assay. The half-maximal inhibitory concentration against α-glycosidase was 67.15 mg/mL, and the emulsion had antioxidant activity. It hardly affected the normal growth of cells, but even had a promoting effect on cell proliferation within a certain concentration range.

The effect of PEGylation and PEGylation degree on the antigenicity and structure of β-lactoglobulin were investigated by covalent binding of PEG to the carboxyl group of β-lactoglobulin. The results showed that the total modification rate was 82.91%. The PEGylation products were separated and purified using an SP Sepharose Fast Flow cation exchange column into two major fractions with purity of 99.66% and 98.61%. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) the relative molecular weights of the products identified as 23.3 and 28.6 kDa, respectively, indicating that they were mono-PEG-β-LG and di-PEG-β-LG. The half-maximal inhibitory concentration (IC50) values of β-LG, mono-PEG-β-LG and di-PEG-β-LG were 1.90, 2.47 and 10.41 μg/mL, respectively as determined by indirect competitive enzyme-linked immunosorbent assay (IC-ELISA). The IC50 values of mono-PEG-β-LG and di-PEG-β-LG were 1.30 and 5.48 times higher than that of β-LG, respectively, which indicated that the antigenicity of β-LG could be significantly reduced by increasing the PEGylation degree. The free sulfhydryl contents of mono-PEG-β-LG and di-PEG-β-LG were 42.70 and 37.97 μmol/g, respectively, indicating that as the PEGylation degree increased, the masking effect increased. Surface hydrophobicity analysis and intrinsic fluorescence analysis showed changes in tertiary structure only for mono-PEG-β-LG, and in both secondary and tertiary structure for di-PEG-β-LG, indicating that the spatial structure changes of β-LG after PEGylation might be the cause of the destruction of its conformational epitope and the decrease of its antigenicity. The masking of PEG molecules might be another reason for the reduced antigenicity of products. The covalent PEGylation of the carboxyl group of β-LG could significantly reduce its antigenicity, and the antigenicity decreased significantly with the increase of PEGylation degree.

Myofibrillar protein (MP) plays a determinant role in the gel properties and sensory quality of meat products, but it is vulnerable to oxidative attack during processing and storage. In this study, the effect of different concentrations of L-Arg (1, 3, 5 and 10 mmol/L) on the structure and gelling properties of MP was investigated under oxidative conditions induced by a hydroxyl radical-generating?system. After the treatment, the conformational changes of MP were analyzed by sulfhydryl group (–SH) measurement and tintrinsic tryptophan fluorescence spectroscopy, and the cross-linking and aggregation of MP was analyzed in terms of particle size and solubility as well as by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The gelling properties of MP were evaluated using a rheometer, a texture analyzer and a scanning electron microscope (TEM). The secondary structure of protein gels was analyzed by Raman spectroscopy. The experimental results showed L-Arg affected the structural and gelling properties of MP under oxidation conditions in an obvious concentration-dependent manner. L-Arg at concentrations of 1–5 mmol/L had a certain protective effect on the content of –SH groups, while 10 mmol/L L-Arg resulted in significantly decreasing the content of –SH groups. The addition of L-Arg reduced the fluorescence intensity of endogenous tryptophan and increased particle size. SDS-PAGE showed that the oxidation-induced formation of disulfide bonds resulted in protein cross-linking and aggregation, thereby leading to a decrease of solubility. With the increase in L-Arg concentration, the microstructure of MP gels became more compact, accompanied by a gradual decrease of gel strength and whiteness and a gradual increase in gel yield. On the whole, under the oxidative condition, addition of 5 mmol/L L-Arg significantly increased the content of sulfhydryl groups, and decreased cooking loss and gel strength, thus improving the oxidation stability of meat protein and consequently the tenderness and water-holding capacity of meat products.

The effects of different genotypes of milk protein on milk coagulation properties were studied in this work. Blood samples from 1 071 Holstein cows were collected for analyzing the genotypes of κ-casein (κ-CN) and β-lactoglobulin (β-LG), and milk samples were collected to evaluate coagulation traits based on the identified genotypes. On the basis of preliminary screening, milks with good, poor and no coagulation ability with at least 30 samples each were selected for analysis of rheological properties, protein polymorphism and mineral ion distribution. All analyses were performed in three replicates. The differences in coagulation time and the contents of colloidal calcium, magnesium and phosphorus among milks with different coagulation abilities were determined using a dynamic rheometer, inductively coupled plasma mass spectrometry (ICP-MS), capillary electrophoresis and high performance liquid chromatography (HPLC), and the influence of protein polymorphism caused by different genotypes and protein contents on milk coagulation ability was evaluated. The results showed that in all cow groups, β-LG AB genotype (48.48%) was the most common, while milk coagulation ability of cows with β-LG AA genotype (30.97%) was better. Compared with κ-CN AA and AB genotypes, cows with κ-CN BB genotype (12.00%) showed better milk coagulation ability, shorter coagulation time and stronger curd strength. Milk samples with better coagulation ability had higher contents of casein and colloidal calcium as well as lower pH. Milk coagulation time was inversely proportional to κ-CN content, and changes in the composition and gene frequency of casein and whey protein affected milk coagulation properties (MCP).

In the present work, the effects of different addition levels (0.015%, 0.030% and 0.045%) of Zanthoxylum bungeanum Maxim. leaf extract (ZME) on the formation of heterocyclic amines (HAs) in roast beef patties were investigated. The results showed that compared with the control group, the generation of total HAs was significantly inhibited by ZME (P < 0.05), with a maximum inhibition rate of 39.87%. However, it had different effects on the formation of different types of HAs. The formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazole[4,5-f]quinoline (MeIQ), 1-methyl-9H-pyrido[3,4-b]indole (Harman) and 2-amino-9H-pyrido[2,3-b]indole (AαC) was 71.76%, 78.02%, 49.07%, 35.82% and 100% inhibited by addition of 0.045% ZME, respectively. On the other hand, it significantly promoted the formation of 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (8-MeIQx) and 9H-pyrido[3,4-b]indole (Norharman) (P < 0.05). Further analysis of the effects of ZME on HA precursors in roast beef patties showed that the consumption of precursors exhibited a decreasing trend with increasing addition level of ZME. Significant correlations were found between the formation of HAs and the consumption of free amino acids. All results indicated that ZME could significantly inhibit HAs formation of roast beef patties, which may provide a theoretical basis for improving the safety of processed foods and for wider application of ZME.

Polysaccharides (NHP) extracted from Nymphaea hybrid by ultrasonic-assisted hot water extraction were degraded with a combination of ascorbic acid and H2O2 into three low-molecular-mass polysaccharides (DNHP-1, DNHP-2 and DNHP-3). The structural, rheological, functional and antioxidant properties of the polysaccharides were studied. The results showed that although the monosaccharide types of NHP kept unchanged after degradation, the molar percentages of galacturonic acid and mannose decreased and the molar percentage of rhamnose increased. Fourier transform infrared (FTIR) spectroscopic analysis revealed that the primary structures of the polysaccharides were not affected after degradation. Congo red test showed that none of the four polysaccharides had triple helix structures. Rheological analysis demonstrated that DNHP solutions displayed lower apparent viscosity than NHP solution at the same concentration, while the elasticity of DNHP was improved compared with that of NHP. DNHP had better water-holding capacity and weaker oil-holding and emulsifying capacity. Furthermore, DNHP-2 collected after 60 minutes of degradation had stronger antioxidant activity in terms of scavenging capacity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, 2,2’-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical cation and hydroxyl radicals. The results of this study may provide a theoretical basis for the application of N. hybrid polysaccharides in foods, cosmetics and medicines.

In this study, the effect of modifying the pectin content of freeze-dried reconstituted apple cubes by adding either pectin or pectinase on its hardness, crispness, microstructure, and hygroscopic properties was addressed. The results showed that apple cubes with 0.5%–4% of pectin exhibited a typical honeycomb-like porous structure, whose hardness and brittleness increased by 2.01–5.41 folds and 1.17–1.27 folds, whose breaking rate during oscillation decreased by 38.97%–55.78% compared with the control sample. In contrast, the microstructure of apple cubes treated with pectinase was disordered with big pores, the hardness decreased by 34.03%, the brittleness increased by 1.13 times, and the breaking rate during oscillation was increased by 1.24 times relative to the control sample. In addition, the addition of pectin reduced the hygroscopicity of the cubes, and caused desorption hysteresis in 70%–90% relative humidity. The cubes treated with pectinase showed a greater mass change and consequently increased moisture absorption when reaching adsorption equilibrium. In summary, manipulation of the pectin content in apple puree can be used as an effective approach to modify the texture and hygroscopic characteristics of reconstituted apple cubes, which can provide a theoretical reference for further research to improve the texture quality of freeze-dried plant-based foods.

This research aimed at investigating the structure and diversity of the bacterial community in Guizhou shui-douchi at three different fermentation stages by Illumina MiSeq high-throughput sequencing technology and also at isolating and identifying the dominant bacteria. The results showed that a total of 296 063 valid data and 1 124 operational taxonomic units (OTU) were obtained from the three samples. A total of six phyla and 21 genera were annotated. At the phylum level, the abundance of Firmicutes increased with the increase in fermentation time, while the abundance of Proteobacteria decreased. At the genus level, the abundance of Bacillus increased. Due to the addition of antibacterial ingredients such as salt and spices, the number of bacterial species presented a declining trend after post-fermention for 24 hours. In addition, four strains with high protease activity were obtained using an automated?mass spectrometry microbial identification system?(VITEK MS) and were identified as Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus cereus, respectively. This study may provide a guidance for the standardization and safety control of Guizhou shui-douchi.

The gene of single-chain variable fragment (scFv) against 3-amino-2-oxazolidinone (AOZ) derivatives was constructed and physicochemical properties and structure of its encoded protein were predicted in this study. First, total RNA was extracted from hybridoma cell line 1D2 that can secrete a monoclonal antibody (mAb) with high activity and specificity against AOZ derivatives and the heavy and light chain variable region encoding genes (VH and VL) were amplified and connected with each other via a (G4S)3 peptide linker by gene splicing overlap extension-polymerase chain reaction (SOE-PCR) to construct the scFv gene against AOZ derivatives. Then the sequence of amino acids in the antibody was deduced and bioinformatic analysis was carried out after gene sequencing. Finally, the scFv gene was inserted into the expression vector Plip6/GN for expression and the activity of the expressed protein was identified by direct competitive enzyme-linked immunosorbent assay (dcELISA). The results showed that the full length of the scFv gene was 750 bp, encoding a protein of 250 amino acids with a molecular mass of 27 012.20 and a theoretical pI of 9.13. The predicted secondary structure showed that the antibody contained 20 α-helixes, 25 β-turns, 114 random coli and 91 extension bands. The front top view of the tertiary structure prediction showed that the heavy and light chains were connected with each other by linkers to form a circular bucket-like structure, and the side view showed a pocket-like structure, which was consistent with the structural characteristics of natural scFv. The dcELISA results showed that the antibody had good antigen-binding activity. This study will lay a foundation for the establishment of immunoassay methods for AOZ residue detection and the modification of scFv against AOZ derivatives in the future.

In order to provide a novel enzyme source for the high-efficiency synthesis of galacto-oligosaccharides (GOS), novel lactic acid bacteria (LAB) strains capable of producing β-galactosidase with high transglycosylation activity were screened from camel milk in the present study. The primary screening was performed using MRS plates with lactose as the carbon source supplemented with 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-Gal). The secondary screening was carried out through thin layer chromatographic (TLC) analysis of the products of transglycosylation catalyzed by microbial β-galactosidase. The conditions for enzyme production and transglycosylation reaction were optimized by one-factor-at-a-time method. The β-galactosidase was partially purified by fractional precipitation with ammonium sulfate and its enzymatic properties were characterized preliminarily. Twenty LAB strains producing β-galactosidase with transglycosylation activity were obtained, among which strain L6 produced β-galactosidase with the highest transglycosylation activity and it was identified as Lactobacillus kefiri by physiological, biochemical and molecular biological approaches. The optimal culture conditions that provided maximum activity level of (3.81 ± 0.02) U/mL were determined as follows: concentration of carbon source (lactose) 2 g/100 mL, concentration of nitrogen source (peptone, beef extract, and yeast extract) 1 g/100 mL, initial pH 5.5, and culture at 37 ℃ for 20 h. The β-galactosidase produced by L6 had a broad reactive temperature range of 45–70 ℃ with more than 50% activity being retained. After 4 h reaction at 65 ℃ and pH 7.0 with 45 g/100 mL of lactose as the substrate, the β-galactosidase could produce GOS-2, GOS-3 and other GOS with a yield of 13.51%, 13.85% and 4.15% (m/m), respectively.

In order to explore the change of bacterial community structure during the processing of western-style low-sodium fermented ham, the V3-V4 hypervariable region of the bacterial 16S rRNA gene was sequenced by Illumina MiSeq high-throughput sequencing technology. Taxonomic analysis showed that the bacterial community in all samples consisted of 31 phyla and 664 genera. Firmicutes was the most dominant phylum in the low-sodium fermented ham and Staphylococcus was the most dominant genus. Physicochemical analysis showed that salt content, water content and pH had significant effects on the bacterial community structure. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated differences in amino acid metabolism, lipid metabolism and human disease-related metabolism pathways between the low-sodium and control groups on the 290th day of fermentation. These results will provide a reference for the development of microbial starters to improve the quality of low-sodium meat products and increase the fermentation efficiency.

Objective: To explore the fungal diversity and the change in the fungal community structure in stored rice under different environmental conditions. Methods: The fungal community structure and dominant genera in fresh rice and rice stored at different temperatures (10, 20, 25, 30 and 40 ℃) and relative humidities (43%, 75% and 85%) in Hengyang, Hunan were analyzed by Illumina HiSeq high throughput sequencing. Results: According to the species classification analysis based on operational taxonomic units (OTU), the fungal communities in all samples included 6 phylum, 24 classes, 67 orders, 160 families, 285 genera and 406 species. Ascomycetes was the dominant phylum with a relative abundance of 2.53%–96.86%. followed by Basidiomycetes with a relative abundance of 0.02%–9.39%. The dominant genera included Beauveria, Ophiosphaerella, Aspergillus, Gibberella, Alternaria, Phaeosphaeria, Nigrospora, Microdochium and Candida. The dominant species included B. bassiana, O. agrostidis, A. flavus, A. ochraceus, A. niger, G. intricans, A. longissima, P. microscopica and N. oryzae. Through Venn diagram analysis and principal component analysis (PCA), it was found that there were significant differences in the fungal community diversity between fresh and stored rice samples, and between stored rice samples. There were also differences in the fungal community diversity of rice samples under different temperature and humidity conditions. Conclusion: Relative humidity was the most important factor affecting the relative abundance of A. flavus with the maximum value being observed at 85% relative humidity. To sum up, this study provides theoretical support for the optimization of safe storage conditions for rice.

In our present study, virtual enzymatic hydrolysis of α-lactalbumin was investigated using online bioinformatic tools. The activity, toxicity, and physicochemical properties of the resulting bioactive peptides were predicted. A novel angiotensin I-converting enzyme (ACE) inhibitory peptide, Pro-Glu-Trp (PEW), was selected by molecular docking. PEW was synthesized by the solid phase method and its activity was verified in vitro, showing a half-maximal inhibitory concentration (IC50) value of 3 130 μmol/L. The molecular docking simulation results showed that the interaction between PEW and ACE’s active-site pocket S1 may be the major reason for its ACE inhibitory activity. Hydrogen bonding, hydrophobic force, and electrostatic force were the major forces maintaining their mutual binding. Compared with traditional methods, the protocol presented in this study could quickly and efficiently screen ACE inhibitory peptides, which may provide a new idea for the rapid screening of food-derived bioactive peptides.

This study was undertaken in order to investigate the application potential of Schizosaccharomyces pombe and the best mixed culture of S. pombe and Saccharomyces cerevisiae for dry red wine production. The biomass change during alcoholic fermentation and physicochemical properties, color parameters, and the contents of malic acid and major volatile aroma compounds in ‘Pinot Noir’ wines fermented with mixed cultures of S. pombe (SP1260) and a commercial strain of S. cerevisiae, Vintage Red (VR), or sequential inoculation of VR for alcoholic fermentation and Oenococcus oeni for malolactic fermentation as a control were determined. Moreover, sensory analysis was performed to evaluate the effect of co-inoculation with S. pombe and S. cerevisiae on the quality of ‘Pinot Noir’ dry red wine. The results showed that S. cerevisiae had little effect on the growth of SP1260 when co-inoculated at a mixing ratio of 1 000:1. After completion of alcohol fermentation, the biomass of SP1260 was 106 CFU/mL. Malic acid was degraded completely during the fermentation process, and the content of malic acid was not significantly different between the two wines. The chroma value and total anthocyanin content of the simultaneous inoculation group were significantly higher than those of the control group. In addition, the contents of aroma components such as higher alcohols and fatty acids were lower significantly, the contents of isoamyl acetate, methyl octanoate, ethyl decanoate and eugenol were higher, and the fruity and flowery aroma were stronger compared with the control group. The sensory evaluation results showed that the wine inoculated with a 1 000:1 mixture of SP1260 and VR was deep ruby red in color, transparent and clear, and possessed a well balance sweet and sour flavor with a long aftertaste and a strong and rich aroma, having the best sensory quality. To sum up, simultaneous fermentation with SP1260 and VR at 1 000:1 ratio has the potential to replace malolactic fermentation, which can improve the color and taste, and increase the fruity and floral aroma of dry red wine.

Monascus isolated in our laboratory was used in soft white mold cheese in this study. Physiochemical parameters, texture and rheological properties of white mold cheese with and without Monascus were evaluated using a color difference meter, a texture analyzer, a rheometer, high performance liquid chromatography (HPLC), and the impact of Monascus on cheese ripening was investigated. The results showed that added Monascus changed the color of cheese, producing red pigments giving a* values in the range of 7.81–19.05. The contents of protein and dietary fiber were increased in white mold cheese with Monascus, while the content of fat was not obviously increased compared to the control sample without Monascus. Additionally, rheological and textural measurements showed that white mold cheese with Monascus had had better elasticity (90.35–92.15), higher storage modulus (G′) and smaller tanδ. Chemical analysis indicated that Mevinolin (0.05–2.21 mg/kg) and γ-aminobutyric acid (0.54–0.70 mg/kg) were detected in white mold cheese with Monascus, accompanied by a small amount of citrinin which was lower than the international limits. This study will provide theoretical support for the application of Monascus in dairy products.

Vomitoxin, also known as DON, is a secondary metabolite produced by several Fusarium sp. In order to select microorganisms capable of degrading DON, high-throughput sequencing was used to analyze DON-degrading bacteria in bacterial consortia. In this study, bacterial consortium LG-6 with DON-degrading capacity was obtained from soil, and it was found that the effect varied depending on the dilution ratio of the bacterial consortium. LG-6 diluted by a factor of 10-7 (denoted as LG-6-7) but not 10-8 (denoted as LG-6-8) could completely degrade DON. The analysis of microbial diversity demonstrated that LG-6-7 included Pseudochrobactrum, Pseudomonas, Delftia, Devosia, and Achromobacter, while LG-6-8 included only Pseudochrobactrum and Achromobacte, indicating that Pseudomonas, Devosia and Delftia are essential for the degradation of DON. In addition, DON was completely degraded within 48 h by a bacterial consortium of Pseudomonas sp. B6-24 and Devosia A6-243. The optimal culture conditions for the bacterial consortium were 37 ℃, pH 7.0, and MMT medium. Moreover, microbial enzymes from the consortium were responsible for the degradation of DON. In conclusion, a bacterial consortium of Pseudomonas sp. B6-24 and Devosia A6-243 can degrade DON completely, which will lay a foundation for the research and development of biological detoxifying agents for vomiting toxin.

The effects of fermentation conditions, namely fermentation temperature, inoculum amount and starter culture composition on physicochemical properties and sensory quality of pork jerky made from the rump meat of Hill-Black pigs was explored by determining pH, water activity (aw), total free amino acids, histamine, nitrite residue, protein composition, color, texture and sensory scores during the fermentation process. The results showed that the content of free amino acids, L* and a* increased gradually (P < 0.05) with the increase in the proportion of Staphylococcus xylose in the starter culture. With the increase in the proportion of Lactobacillus sakei subsp. sakei, pH and aw decreased, while hardness and chewability increased (P < 0.05). In the case of jerky fermented for 32 h, the increasing trend of histamine content slowed down, nitrite residue and elasticity decreased (P < 0.05), and hardness, chewability and a* increased gradually with the increase in inoculum amount (P < 0.05). Pork jerky with an inoculum amount of 107 CFU/g had the best sensory quality. Moreover, with the increase in fermentation temperature, pH, aw and nitrite residue showed a trend of first decreasing and then increasing, while the opposite trend was found for free amino acids, hardness, chewability, L* and a*. Therefore, the selection of suitable fermentation conditions can improve the color and texture of fermented pork jerky, increase the content of free amino acids, reduce nitrite residue and improve the safety of the product.

Porphyra haitanensis protein (PHP) was simultaneously hydrolyzed with papain and chymotrypsin to prepare antihypertensive peptides. The hydrolyate was fractionated by ultrafiltration, and the resulting fractions were evaluated for scavenging capacity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radicals, ferric ion reducing antioxidant power (FRAP) and angiotensin converting enzyme (ACE) inhibitory activity. The bioactive peptides were identified by mass spectrometry (MS) as well as through search in the bioactive peptides (BIOPEP) and antihypertensive peptides (AHTPDB) databases, and their ACE inhibitory mechanism was elucidated by molecular docking. Additionally, the kinetics of enzymatic hydrolysis of PHP was studied. The results showed that among the eight fractions obtained after ultrafiltration, the fraction with molecular mass less than 0.5 kDa had the highest DPPH and ABTS cation radical scavenging capacity, the fraction with molecular mass less than 1 kDa had the highest FRAP value, and the fraction with molecular mass in the range of 500–1 000 Da had the lowest half-maximal inhibitory concentration (IC50) value ((2.21 ± 0.28) mg/mL). Totally, 14 bioactive peptides were identified, four of which were selected for molecular docking analysis, indicating that their amino acid sequences were and docking energy were AVP (?5.87 kJ/mol), GPL (?6.13 kJ/mol), LDY (?7.65 kJ/mol) and LGYL (?7.78 kJ/mol), respectively. The relative error between the hydrolysis degree of PHP predicted by the kinetic model of enzymatic hydrolysis and the experimental values was less than 10%. This study can provide reference for the preparation of bioactive peptides.

This research explored the use of immobilized lipase Novozym 435 to catalyze selective synthesis of 6,6’-O-acyltrehalose diesters through the transesterification of trehalose with fatty acid vinyl esters of different carbon chain lengths (C6–C18) at a molar ratio of 1:4 in a mixed solvent of tert-butanol and pyridine (11:9, V/V). The chemical structures of the products were identified by nuclear magnetic resonance (NMR) and mass spectrometry (MS), the hydrophilic lipophilic balance (HLB), foaming properties and thermostability were determined, and the cytotoxicity was evaluated by the methyl thiazolyl tetrazolium (MTT) assay. It turned out that a series of trehalose fatty acid diesters were formed, with a yield between 43% and 75%. The trehalose didecanoate and trehalose dilaurate had good foaming properties (foamability of 101.00% and 142.67%, and foam stability (within 80 min) of 40%–60% and 50%–70%, respectively). The trehalose dioleate had the best thermal stability with a retention rate of 60.58% at 350 ℃. Moreover, it was found that these trehalose fatty acid esters were safe and lowly toxic. To conclude, this study may point out a new direction for the development of new types of value-added, non-ionic surfactants for the food industry.

In this study, the difference in the nutritional composition of the fruit bodies of Fomitopsis pinicola from different geographical regions (Jilin 1, Heilongjiang 1 and Yunnan 1) as well as its cultured mycelia was investigated by using various analytical methods. The results showed that the contents of carbohydrates, proteins, amino acids, fatty acids and mineral elements greatly differed among fruit bodies and cultured mycelia, and the contents of carbohydrates and fat in fruit bodies were higher than those in mycelia, whereas the opposite was seen for the contents of proteins and ash. These four samples were rich in amino acids, unsaturated fatty acids and trace elements (Zn, Fe, Mn and Cu). The contents of essential amino acids were ranked in the decreasing order of mycelia > Heilongjiang 1 > Yunnan 1 > Jilin 1, the proportions of unsaturated fatty acids in the decreasing order of Heilongjiang 1 > mycelia > Jilin 1 > Yunnan 1, and the contents of trace elements in the decreasing order of Heilongjiang 1 > Jilin 1 > mycelia > Yunnan 1.

The purpose of this study was to investigate the formation of and changes and differences in volatile flavor compounds in diced Tan sheep meat during stir-frying, shallow-frying and deep-frying. Headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze the volatile compounds and partial least squares-discrimination analysis (PLS-DA) was used to identify the composition of volatile components in meat samples cooked by the three methods at different processing stages. The results showed that an electronic nose could discriminate the odors of cooked meat samples at different processing stages. For stir-frying, shallow-frying and deep-frying, the strongest response values of electronic nose occurred in the rendering phase, after 1 min and after 3 min, respectively. Totally 273 volatile compounds were identified from the three cooked meat samples by GC-MS, 174, 158 and 134 of which were identified in the stir-fried, shallow-fried and deep-fried samples, respectively. A large number of volatile flavor compounds were produced at the early stage of shallow-frying and deep-frying and at the later stage of stir-frying. PLS-DA score scatter plots discriminated the volatile compounds in raw meat and the cooked samples, with each having obvious odor characteristics. Aldehydes were the main volatile compounds in the three cooked meat samples, with hexanal being the most abundant one. The number and amount of volatile flavor compounds in stir-fried meat were increased in the rendering stage, which contributed the most to the overall flavor, especially to acids, esters and heterocyclic compounds.

In order to investigate the influence of different salt contents on the quality of pickled peppers, this study compared the sensory quality, amino nitrogen, organic acid and total acid contents and volatile composition as determined by gas chromatography-ion mobility spectroscopy (GC-IMS) of one-year-old pickled peppers with different salt contents (6%, 9%, 12%, 15%, and 18%). The results showed that the sensory scores of the five pickled peppers were 5.75, 7.66, 8.51, 7.99, and 7.78 points, respectively. The contents of total acids in them were (5.431 ± 0.014), (4.575 ± 0.009), (4.227 ± 0.012), (4.125 ± 0.013), and (3.882 ± 0.005) g/kg, respectively, indicating a significant difference from each other (P < 0.05). The contents of amino nitrogen were (0.165 5 ± 0.000 5)%, (0.128 5 ± 0.001 2)%, (0.086 2 ± 0.000 8)%, (0.056 3 ± 0.001 0)%, and (0.033 6 ± 0.000 5)%, respectively, with a significant difference from each other (P < 0.05). A total of six organic acids were detected in all samples by high performance liquid chromatography (HPLC), namely oxalic acid, tartaric acid, lactic acid, malic acid, acetic acid, and citric acid. The contents of organic acids continued to decrease with the increase in salt content. Among them, the content of oxalic acid was the highest. Tartaric acid was not detected in the sample with salt contents equal to or greater than 12%. GC-IMS was used to analyze the difference in the volatile fingerprints of all samples, showing that higher contents of ethyl lactate, ethyl 2-hydroxy-4-methylpentanoate, isoamyl acetate, ethyl acetate, and 4-hydroxyl were found in the sample with 6% salt content. As the salt content increased, the amounts of the above substances decreased, while the amounts of other flavor substances such as ethyl acetate, ethyl 2-methylpropionate, 3-methyl-3-buten-1-ol, ethyl 2-methylbutanoate, 2-octanol, 3-methyl-1-pentanol, n-pentanol, 2,3-butanedione, 3-pentanone and 2-pentylfuran gradually increased, so that an obvious flavor difference occurred. Compared with those with other salt contents, pickled peppers with salt contents of 9%–12% had better flavor quality and could be directly used for the processing and seasoning of chopped hot pepper. The results of this study may be meaningful for guiding the processing of hot pepper.

In this study, the volatile components and key aroma-active compounds of Gongmei white tea were comprehensively analyzed using two-dimensional gas chromatography-time-of-flight-mass spectrometry (GC × GC-TOFMS) combined with gas chromatography-olfactometry-mass spectrometry (GC-O-MS). A total of 236 volatile compounds were identified, mainly including aldehydes (38.46%) and alcohols (25.58%), and the major volatile components were benzaldehyde (147.27‰), (E)-2-hexenal (90.14‰), linalool (79.80‰), phenethyl alcohol (50.76‰), 2-pentyl-furan (46.23‰), geraniol (39.06‰), methyl salicylate (37.80‰), dimethyl sulfide (36.69‰), decane (31.68‰), hexanal (29.39‰), phenethyl alcohol (25.06‰), and benzyl alcohol (22.15‰). GC-O-MS analysis revealed 26 aroma-active compounds, of which 21 compounds were identified, including nine alcohols, five aldehydes, four ketones, two esters and one aromatic hydrocarbon; and these odorants mostly presented clean (green), fresh, floral, fruity, or sweet aromas. Taken together, the GC × GC-TOFMS and GC-O-MS results showed that high proportions of alcohols and aldehydes responsible for natural green, fresh, floral, fruity, or sweet aromas could form the basis for the aroma characteristics of Gongmei. The results in this study will contribute to in-depth understanding of the aroma quality chemistry of Gongmei, and provide a theoretical guidance for improving the aroma quality of Gongmei in processing practices.

The volatile components and fatty acids in biceps femoris, longissimus dorsi and triceps brachii muscles from Tan sheep slaughtered at six months of age were determined. The volatile flavor compounds in lamb meat were analyzed by gas chromatography-ion mobility spectrometry (GC-IMS) and a fingerprint was established. The results showed that a total of 44 volatile compounds were identified, including 15 aldehydes, 11 alcohols, 9 ketones, 6 esters, 2 thiazoles and 1 furan, with hexanal, nonanal, 1-octen-3-ol, 3-hydroxy-2-butanone and ethyl acetate being the major ones. Based on the information of the fingerprint, principal component analysis could clearly discriminate lamb muscles according to characteristic flavor compounds, with the first two principal components together explaining 90% of the total variance. The saturated fatty acid/unsaturated fatty acid ratios in longissimus dorsi, biceps femoris and triceps brachii were 0.84, 0.92 and 0.93, respectively, which were close to the value of 1:1 recommended by Chinese Nutrition Society. The content of polyunsaturated fatty acids in longissimus dorsi was higher than that in triceps brachi. The abundant content of unsaturated fatty acids could contribute to the flavor of lamb.

The metabolites in two different varieties of foxtail millets from the same geographical origin were studied by metabonomics based on gas chromatography-mass spectrometry (GC-MS). The polar metabolites were extracted using methanol solution and then derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide prior to analysis by GC-MS. The results showed that a total of 53 metabolites were identified, 48 of which were found in ‘Gulong’ millet, the dominant ones being linoleic acid and 2-linolacyl-rac-glycerol; and 32 in ‘Heshen’ millet, the dominant ones being linoleic acid and glycerol. There were 21 differential metabolites identified in ‘Gulong’ millet and five differential metabolites in ‘Heshen’ millet. The metabolic pathways of the differential metabolites were also studied. It was found that the glucose, fatty acid, amino acid metabolism pathways and the tricarboxylic acid cycle in ‘Gulong’ millet were more active than those in Hesen millet. It was speculated that the increase in the number of metabolites in ‘Gulong’ millet may be because its metabolic rate was faster than that of ‘Heshen’ millet.

Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was performed to analyze the volatile organic compounds (VOCs) of the tenderloin, belly and rump of commercially reared pigs, the rump of black pigs and the rump of Chinese indigenous pigs. Further, we investigated the difference in the characteristic flavors of pork meat among carcass locations and breeds. The results showed that a total of 41 compounds were identified from the different meat cuts, mainly including aldehydes, ketones and alcohols. A total of 29 compounds were identified from the rumps of different breeds, mainly including aldehydes, ketones, alcohols and pyrazoles. The characteristic chromatographic regions of the tenderloin included 2,3-butanedione, 2,3-pentadione and 2-butanone. The belly contained some unique aldehydes and alcohols at high concentrations as well as higher levels of shared aldehydes and alcohols compared to the other four samples, and its characteristic chromatographic regions included trans-2-octenal, trans-2-heptenal, furfuryl alcohol, 3-octanol, octanal, nonaldehyde and trans-2-hexene-1-alcohol. Few unique VOCs were detected in the rump, with only 2-methylpyrazine and 2,5-dimethylpyrazine being the major ones. Pyrazines were more abundant in the rumps of black pigs and Chinese indigenous pigs than in commercially reared pigs. Based on the established fingerprint combined with principal component analysis (PCA), the five pork samples could be clearly distinguished from each other. GC-IMS is a simple, rapid and non-destructive analytic technique, and its application can provide a reference and theoretical basis for the identification of volatile flavor components and adulteration in as well as breed discrimination of pork samples.

In order to develop a nutritious and healthy probiotic fermented kiwifruit juice with a strong fruity aroma, the aroma components of fermented kiwifruit juices inoculated with single and mixed (1:1) cultures of Lactobacillus plantarum and L. paracasei were comparatively analyzed by headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS). Non-fermented juice was used as control. The results showed that a total of 74 aroma components were identified from the four juice samples, including 17 alcohols, 8 ketones, 19 esters, 12 aldehydes, 8 alkanes, 4 acids, and 6 other compounds. The types and contents of aroma compounds and the aroma values of kiwifruit juices fermented with mixed and single cultures were significantly different (P < 0.05), and the types and contents of alcohols, esters and other aroma substances were significantly (P < 0.05) higher in kiwifruit juices fermented with the mixed culture than with the single cultures, giving a stronger floral and fruity aroma. Therefore, mixed probiotic strains are suitable for the production of fermented kiwi juice.

This study aimed to explore the key chemical components that can affect the brightness of Congou black tea infusions. Firstly, 26 Congou black tea infusions were classified into three groups (high-brightness, mid-brightness and dark) based on the brightness evaluated by a professional sensory panel. Then, 24 components in tea infusions were quantitatively analyzed, and the small molecular compounds significantly related to the brightness of tea infusions were selected by means of statistical analysis. Finally, the tea infusions were fractionated by ultrafiltration and the macromolecular fractions affecting the brightness of tea infusions were determined and further validated by reconstitution and addition experiments. The results of multivariate analysis and one-way analysis of variance (ANOVA) showed that theaflavin-3-gallate (TF-3-G), gallocatechingallate (GCG) and caffeine (CAF) were significantly increased in tea infusions with high brightness, while gallocatechin (GC) was significantly decreased. Moreover, it was found that the macromolecular fraction greater than molecular mass cut-off (MMCO) of 100 kDa negatively affected the formation of bright tea infusions. The results of this study will be of theoretical significance for guiding the quality control and directional processing of Congou black tea in the future.

The nutritional value of proteins in apricot seed kernels from ten cultivars planted in Xinjiang was systematically evaluated in terms of essential amino acid index (EAAI) and score of ratio coefficient of amino acid (SRC). Comprehensive quality evaluation was using principal component analysis (PCA) and cluster analysis (CA). The results showed that the total amino acid content of apricot seed kernels ranged from 16.7% to 23.12%, the ratio of essential amino acids to total amino acids varied from 32.18% to 33.75%, the EAAI were more than 100, and the SRC was less than 100. There were great differences among cultivars in these parameters. The restricted amino acids were sulfur-containing amino acids and Lys. Three principal components were extracted by principal component analysis (PCA), which cumulatively explained 90.295% of the total variance. The reconstructed comprehensive evaluation model based on the variance contribution rate of each principal component better reflected the comprehensive information of apricot seed kernel protein, and could be used to rank the ten cultivars according to their quality. Cluster analysis divided these cultivars into four categories, which was consistent with principal component analysis.

In this study, the characteristic flavor components of ginger samples produced in Tongling, Shucheng and Linquan in Anhui were analyzed by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). The fingerprint for ginger from each region was constructed by using the software Laboratory Analytical Viewer (LAV). The difference in the characteristic flavor compounds of ginger samples from different regions were compared, and the major characteristic flavor compounds and their contents were determined. The results showed that isoamyl acetate, bornyl acetate and myrcene were identified as characteristic flavor compounds of Tongling-grown ginger; 1-hexanol, 2-hexenol, citronellol, heptanal, nonanal, 2-heptanone, 2-nonanone, pentyl butanoate and 3,4-dimethylanisole were identified as characteristic flavor compounds of Linquan-grown ginger; and linalool, ethanol, citral, (E)-2-octenal, pentanal, benzaldehyde, ethyl acetate, propyl hexanoate, octanoic acid, 2-acetylfuran, methylpyrazine and 2-propanone were identified as characteristic flavor compounds of Shucheng-grown ginger. By similarity analysis and principal component analysis (PCA), ginger samples from different geographic origins were clearly distinguished from each other, indicating that GC-IMS can be used for tracing the geographical origin and evaluating the quality of ginger.

In order to ascertain the major quality characteristics of macadamia nuts produced in Guangxi so as to establish a comprehensive evaluation method for its economic characteristics, 14 samples of macadamia nuts from major production areas in Guangxi were selected to determine indicators of superior nuts and quality indexes including the composition and content of fatty acids, amino acids and mineral elements in kernels. The quality of macadamia nuts was comprehensively evaluated by factor analysis (FA), cluster analysis (CA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). The results showed that there were significant differences in the quality of macadamia nuts from different producing areas, and marketable fruit percentage was less than 97% for 42.9% of orchards in Guangxi, suggesting the necessity of strengthening orchard management. The main unsaturated fatty acids were oleic acid and palmitoleic acid, the main amino acids in hydrolyzed macadamia nuts were medicinal amino acids, and the contents of phosphorus and calcium were relatively higher than other mineral elements. Systematic cluster analysis showed that the 14 samples could be divided into three categories, and that 22 indicators including marketable fruit percentage, fat, protein, palmitic acid, heptadecanoic acid, stearic acid, arachidic acid, oleic acid, linolenic acid, eicosatrienoic acid, aspartic acid, threonine, serine, glutamic acid, alanine, valine, isoleucine, leucine, tyrosine, phenylalanine, lysine, and phosphorus were found to be useful to discriminate samples from different geographical origins. Factor analysis was used to establish the evaluation model for the economic traits of macadamia nuts, which had very high predictive accuracy verified by stepwise regression analysis. Category 3 (containing samples 12 and 14) had the best quality, followed sequentially by category 1 (containing samples 1, 2, 3, 6, 7, 8, 9, 10, 11, and 13), and category 2 (containing samples 4 and 5). This study can provide a basis for accurate evaluation of macadamia nut quality, establishment of quality evaluation criteria and quality control of macadamia nut produced in Guangxi.

Umami peptides from a decoction of white Hypsizygus marmoreu were separated and purified by sequential ultrafiltration (UF), gel filtration chromatography (GFC) and reversed-phase high performance liquid chromatography (RP-HPLC) combined with sensory evaluation and were identified by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). The identified peptides were synthesized and their taste characteristics were evaluated by sensory evaluation. The results showed that six umami peptides were identified, namely ELELQ, ELQSGNTY, NYNGGY, EAKVY, VANGGGFGAA, and SLLQPL, whose threshold values were 0.16, 0.19, 0.31, 0.38, 0.44, and 0.63 mg/mL, respectively. The molecular masses of the six peptides were all below 1 000 Da. The synthetic peptides had umami-enhancing effects. As seen from the dose-response curves of umami taste for the synthetic peptides in the presence of monosodium glutamate solution, their umami-enhancing effects were significantly different from each other (P < 0.05), among which NYNGGY and ELELQ were prominent umami enhancers. The synthetic peptides were all able to enhance the umami, salty and sweet taste of chicken soup, and ELELQ, NYNGGY and ELQSGNTY were the most effective in improving the taste of chicken soup.

Mixed aqueous solutions of 57 volatile compounds were quantitatively analyzed by headspace solid phase microextraction (SPME), in-tube extraction (ITEX), purge trapping (P&T) or static headspace combined with gas chromatography-mass spectrometry (GC-MS). The results showed that 45 compounds were detected by SPME with a polydimethylsiloxane/divinylbenzene (PDMS/DVB)-coated fiber, 41 compounds were detected by ITEX, 31 compounds were detected by Headspace, and 20 compounds were detected by P&T. In general, ITEX more easily detected aldehydes and hydrocarbons (with a quantitation limit of 20 ng/mL for aldehydes and of 10 ng/mL for hydrocarbons), SPME was more sensitive to alcohols and esters (with a quantitation limit of 20 ng/mL for both), and P&T and headspace were more suitable for the quantification of low boiling point compounds. The food matrix had little effect on SPME or ITEX. A combination of SPME and ITEX could effectively improve the completeness and accuracy of the obtained food aroma fingerprint information. The results of this study may provide an experimental basis for food aroma analysis.

The effects of boiling, microwave cooking and roasting on the volatile flavor compounds of Muscovy duck meat was investigated by electronic nose and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). The results showed that the electronic nose could quickly distinguish the aroma profiles of different cooked samples. A total of 54 volatile compounds were detected by HS-GC-IMS, including 18 aldehydes, 16 alcohols, 11 ketones, 5 esters, 3 furans and 1 olefin, and the relative content of aldehydes was higher than that of other species. Based on relative odor activity values (ROAV), the key flavor substances shared by the three processing methods were decanal, nonanal, octanal, heptanal, valeraldehyde, hexanal, 1-octene-3-one, 3-octanone, 1-octene-3-alcohol, and 2-ethyl furan. Principal component analysis of these key flavor substances showed that three different processing methods could be well separated, and the key flavor substances of each treatment group were different. The findings of this study can provide a theoretical basis for further research on the intensive processing of Muscovy duck meat.

In this study, considering the current market demand for quantitative analysis of adulterated samples, beef samples adulterated with different proportions of pork were analyzed by high-resolution mass spectrometry (HRMS), and the acquired data were evaluated by principal component analysis (PCA), partial least squares-discrimination analysis (PLS-DA), and orthogonal partial least squares-discrimination analysis (OPLS-DA). The results showed that the OPLS-DA model exhibited a better discriminative ability compared with the other methods. By sorting the S-plot values, 25 porcine-derived peptides and 25 bovine-derived peptides were selected. The linear correlation coefficients (R2) for 10 bovine-derived peptides and 6 porcine-derived peptides were above 0.99. Confirmatory experiments showed that the selected peptides could be used to predict the contents of adulterants in real samples. This study has established a method for quantifying the adulteration of beef steak and provided a new idea for screening of significantly differential peptides useful for the quantification of adulteration of meat products.

In this study, a fluorescent probe based on citrate/europium lanthanide coordination polymer nanoparticles (Cit/Eu LCP NPs) was constructed to detect inosine-5’-monophosphate (5’-IMP) in soup. The results showed that 5’-IMP could quench the fluorescence of Cit/Eu LCP NPs. Under the optimal conditions, the fluorescence probe showed a good linear relationship with 5’-IMP in the concentration range of 2.5–200 μg/mL with a detection limit of 0.17 μg/mL. Meanwhile, the fluorescent probe had good anti-interference ability, stability and repeatability. In order to verify its feasibility, Cit/Eu LCP NPs was applied to the determination of 5’-IMP in a real chicken soup sample, indicating that the recoveries of the added 5’-IMP was 97.85%–103.95%. Therefore, the Cit/Eu LCP NPs-based fluorescent probe can be used for the rapid detection of 5’-IMP in soup.

Objective: A novel and rapid method for the detection of Vibrio parahaemolyticus in shrimp products was established by combined use of real-time fluorescent saltatory rolling circle amplification (SRCA) and propidium monoazide (PMA). Methods: Primers were designed and screened based on the V. parahaemolyticus-specific gene toxR. The specificity, sensitivity and detection limit of the PMA-RF-SRCA method were analyzed and compared with those of PMA combined with real-time polymerase chain reaction (PMA-real-time PCR). To evaluate its practicability, the relative sensitivity, relative specificity and relative accuracy of PMA-RF-SRCA were calculated using the national standard method GB 4789.7-2013 as a reference standard when it was used to detect 76 samples. Results: The specificity of the designed primers was excellent, giving positive results for 12 V. parahaemolyticus strains and negative results for 18 non-V. parahaemolytic strains. PMA-RF-SRCA was 100-fold more sensitive than PMA-RF-SRCA with a sensitivity of 3.2 × 100 CFU/mL and a detection limit of 2.08 × 101 CFU/g. Compared with the GB 4789.7-2013 method, the relative sensitivity, relative specificity and relative accuracy of PMA-RF-SRCA were 100.00%, 96.00% and 98.68%, respectively. Conclusion: The PMA-RF-SRCA method has the advantages of strong specificity and high sensitivity, and is suitable for the detection and screening of live V. parahaemolyticus in edible crustaceans.

The triacylglycerols (TAGs) of milks from domesticated dairy animals especially non-bovine mammals were systematically identified and investigated in this research. A total of 31 raw milk samples of Holstein cows, goats, Mongolian horses and Bactrian camels were collected to identify the composition of TAGs by supercritical fluid chromatography-quadruple time-of-flight mass spectrometry (SFC-Q-TOF-MS), and principal component analysis (PCA) was conducted on the data obtained. A total of 145 TAGs were identified from these samples, with molecular mass ranging from 470 to 888, 24–54 total acyl carbons, and 0–9 double bonds. The TAGs were composed of 14 fatty acids (FAs) with 4–20 carbons and 0–3 double bonds. The number of TAGs identified from cow, goat, horse and camel milk was 60, 66, 74 and 44 respectively. The contents of unsaturated TAGs in horse, camel, cow and goat milk were 82.2%, 61.1%, 51.7% and 43.8% respectively. In horse milk, the content of TAGs composed of linolenic acid (Ln) were as high as 45.43%. Fatty acid composition of TAGs in camel milk was the simplest, containing at least one of myristic acid (M), palmitic acid (P), stearic acid (S) and oleic acid (O). The relative content of O-P-O was the highest in Bactrian camel milk fat (5.04%), but lowest in goat milk fat (only 1.8%). The major TAGs of goat milk were composed of saturated fatty acids. Base peak ion chromatograms of the four milks were obviously different from each other. PCA indicated that the four milks were clearly separated, and the distance of clustering was consistent with the taxonomy of species, implying that the TAGs can be applied in modeling for discriminating among milks from different species.

A method for the determination of eight nicotine compounds in edible fungi by QuEChERS (quick, easy, cheap, effective, rugged and safe) extraction followed by high performance liquid chromatography-mass spectrometry (HPLC-MS) was developed. The compounds in crushed edible fungi were extracted and purified before being injected into the HPLC-MS system. The chromatographic separation was accomplished on an HILIC column by isometric elution using a mobile phase comprising 10 mmol/L ammonium acetate aqueous solution containing 0.1% formic acid and acetonitrile (20:80, V/V). The chromatographic peaks were detected by electrospray ionization (ESI) in the positive ion mode using multiple reaction monitoring (MRM). Under the optimal conditions, the calibration curve for each analyte was linear over a certain concentration range with a correlation coefficient of greater than 0.99. The limit of quantification (LOQ) and limit of detection (LOD) of the developed method were 0.012–0.12 and 0.004–0.04 μg/kg, respectively. The recoveries of the method were in the range of 78.7%–107.8%. The relative standard deviations for intra-day and inter-day precision were 1.8%–10.3% and 2.8%–11.1%, respectively. The matrix effect rates of the method were 81.5%–106.6%.?In conclusion, this method is simple, rapid, accurate and sensitive, and is suitable for the detection of nicotine compounds in edible fungi.

In this study, a signal amplification enzyme-linked immunosorbent assay (AuNPs-HRP-IgG ic-ELISA) to detect enrofloxacin (ENR) in foods was established using gold nanoparticles (AuNPs) as a signal amplification carrier and horseradish peroxidase (HRP)-labeled secondary antibody as a signal probe. The detection limit (IC15) of this method for ENR was 5 × 10-4 ng/mL, the half maximal inhibitory concentration (IC50) was 0.24 ng/mL, and the detection range was 0.16–500 ng/mL. Compared with the traditional ELISA method (IC50 = 8.76 ng/mL), the sensitivity was significantly improved. The cross-reactivity of this method was less than 0.1% toward ciprofloxacin, ofloxacin, and norfloxacin, indicating good specificity. The feasibility of the AuNPs-HRP-IgG ic-ELISA was validated in terms of spiked recoveries in comparison with a commercial ELISA kit. The recoveries for spiked milk samples was 80.52%–102.66%, suggesting that this method could be suitable for the rapid and sensitive detection of ENR in actual milk samples. This study may also provide a new way to develop detection techniques for other related hazardous substances in foods.

Objective: Herein, a novel fluorescent aptasensor based on fluorescence resonance energy transfer (FRET) was assembled with aptamer and graphene oxide (GO) for simultaneous detection of two mycotoxins. Methods: Fluorescence-labeled aflatoxin B1 (AFB1) aptamers (APT1) and fumonisin B1 (FB1) aptamers (APT2) were adsorbed on the surface of GO by π-π stacking. The fluorescence of the fluorescent groups in aptamers was quenched by GO via FRET. APT1 and ATP2 were combined with AFB1 and FB1, respectively, enabling them to be dissociated from the surface of GO and consequently restoring fluorescence. Results: The aptasensor could provide a fast and sensitive method for the detection of AFB1 and FB1. The detection limit of AFB1 was 0.15 ng/mL, and the detection line of FB1 was 0.12 ng/mL. The recoveries of AFB1 and FB1 in spiked Chinese Baijiu samples were 92.00%–100.81% and 89.00%–99.50%. Conclusion: The fluorescent aptasensor is high sensitive and specific for the simultaneous detection of the two mycotoxins, and it is also suitable for multiplex detection of other mycotoxins.

Based on the regulation of Pb(II) on the enzyme-like activity of carbon dots co-doped with copper and iodine (Cu, I-CDs), a novel, simple and sensitive colorimetric probe was established for the determination of Pb(II) in tea samples. The kinetic parameters of Cu, I-CD peroxidase-like activity were well fitted to the Michaelis-Menten equation. When it was adsorbed on the surface of Cu, I-CDs, Pb(II) could promote the oxidation of the substrate 3,3’,5,5’-tetramethylbenzidine (TMB). The concentration of Pb(II) in the range of 0.27–27.02 mg/L showed a good linear relationship with the formation of oxidized TMB (oxTMB). The detection limit of the developed method was 34.3 μg/L, and the spiked recoveries for actual tea samples were in the range of 92.41%–101.85%. These figures of merit meet the requirements of the national standard GB 5009.12-2017. In conclusion, this method is simple, stable, and specific, and its detection limit is lower than the country’s limit for Pb(II) content in foods.

In this study, based on the CaMV35S promoter, the NOS terminator, Cry1Ab/Ac, HPT and the rice endogenous gene SPS, five different fluorescent probes (FAM, HEX, Taxas Red, Cy5, and Cy5.5) were used to develop and optimize a pentaplex real-time polymerase chain reaction (real-time PCR) method to detect genetically modified rice. For this purpose, a series of experiments was carried out to screen primer combinations, optimize the reaction system, and evaluate the specificity, sensitivity and applicability. The sensitivity of the proposed method was 0.032%. This method has the characteristics of high sensitivity, accuracy and high throughput and allows the rapid and efficient detection of genetically modified components in rice.

In this work, in order to establish a predictive model using TQ analyst software to determine amylose content by attenuated total reflectance-Fourier transform mid-infrared (ATR FT-MIR) spectroscopy, the correlation between amylose content and the spectral variables selected by principal component analysis (PCA) and orthogonal partial least squares (OPLS) was explored and the difference in the interpretation of the selected variables for the models was compared. The results showed that the characteristic waveband selected by OPLS was 969–1 158 cm-1, mainly corresponding to the crystalline and amorphous regions of amylose, and was also the characteristic band of the C–O–C stretching vibration of α-1,4-glycosidic bonds. The prediction performance of the model developed in this region was improved compared with those based on the full-band spectra and in the region of 800–1 200 cm-1, with a correlation coefficient of 0.999 8, a root mean square error for calibration (RMSEC) of 0.587%, a root mean square error for prediction (RMSEP) of 6.26%, and a relative percent deviation (RPD) of 5.177 8. The correlation coefficient between the predicted value and the real value was 0.962 7. Therefore, the variables selected by OPLS could interpret most of the chemical characteristics in the mid-infrared region of amylose, and enhance the analytical capability of the prediction model.