The effect of different salt contents (2.50%, 2.00%, 1.75% and 1.50%) on the flavor characteristics of air-dried sausages was explored by intelligent sensory technologies (electronic tongue and electronic nose) and gas chromatography-mass spectrometry (GC-MS). The results showed that the moisture content, water activity and lactic acid bacterial count increased gradually, while pH significantly decreased with the decrease in NaCl level (P < 0.05). The results of electronic tongue and electronic nose showed that the taste and odor characteristics of sausages with 1.75% and 2.00% NaCl were the closest to each other. Additionally, the contents of volatile compounds were significantly affected by NaCl level (P < 0.05). On the whole, salt reduction improved the formation of volatile compounds from carbohydrate metabolism and reduced the formation of volatile compounds from esterification. Finally, sensory evaluation indicated that the overall acceptability of sausages with 2.00% and 1.75% NaCl was the highest, but the saltiness of the sausage with 1.75% NaCl was not enough.

The present work was undertaken in order to study the effect and mechanism of different addition schemes of spices on enhancing the flavor of liquid egg products. Based on sensory scores for aroma enhancement, taste enhancement, deodorization and egg flavor retention, 0.15% fennel, 0.15% coriander seed, 0.2% tangerine peel, 0.2% nutmeg and 0.25% purple onion as well as 0.025% tangerine peel + 0.075% purple onion and 0.05% coriander seed + 0.025% tangerine peel + 0.075% purple onion were found to be more effective in enhancing the aroma of liquid egg products. Gas chromatography-ion mobility spectrometry (GC-IMS) analysis showed that the underlying mechanism may not be simple flavor superposition or flavor masking but a series of chemical reactions between the spices and flavor substances in liquid egg, resulting in a significant reduction or even the disappearance of unpleasant flavor components such as glutaraldehyde, 3-methylbutyraldehyde and 3-octanol, as well as the production of organic acids such as isovaleric acid and propionic acid and of esters with good flavor including butyl 3-methylacetate and ethyl acetate.

Compared to the non-covalent complex, the covalent complex between black soybean protein isolate (BSPI) and chlorogenic acid (CA) was found to have higher polyphenol-binding capacity. Fluorescence spectroscopy and circular dichroism (CD) spectroscopy were used to analyze the effect of CA cross-linking on BSPI structure. It was found that after the addition of CA, the secondary and tertiary structures of BSPI were changed. The proportion of α-helix decreased significantly and the proportion of random coil increased significantly. The protein structure became more loose and disordered, and this effect was more obvious for the covalent complex than the non-covalent one. Crosslinking with CA greatly improved the emulsifying capacity and antioxidant activity of BSPI. Nanoemulsions prepared with the BSPI-CA conjugates had smaller mean particle sizes and higher absolute values of zeta-potential than those prepared with native BSPI. The storage stability and oxidative stability of nanoemulsions with the BSPI-CA conjugates were enhanced significantly, and the covalent conjugate was more beneficial to the basic properties and stability of nanoemulsions.

Methyl cellulose (MC) was used to replace salt at different levels (2% salt, 0.4% MC + 1.6% salt, 0.8% MC + 1.2% salt, 1.2% MC + 0.8% salt, and 1.6% MC + 0.4% salt) in the preparation of emulsified meat batters. The cooking loss percentage, color, texture, low-field nuclear magnetic resonance (LF-NMR) transverse relaxation time (T2) and rheological properties of meat batters were measured and the correlation between them was analyzed. Principal component analysis (PCA) was performed to find out the optimal level of MC replacement. The results showed that cooking loss percentage decreased first and then gradually increased with increasing MC level, and the color parameters L* (brightness) and whiteness of low-salt meat gels significantly increased (P < 0.05). In addition, the contents of immobile and moderately bound water initially increased and then decreased, the springiness, chewiness and gumminess of meat gels significantly decreased (P < 0.05), and the storage modulus G’ and the loss modulus G’’ also showed a gradually decreasing trend. There were significant correlations between cooking loss percentage, color, texture and water relaxation characteristics; the higher the cooking loss percentage of meat gels, the higher the content of immobile water and the higher the overall hardness and springiness. The low-salt meat gel with 0.4% MC had the lowest cooking loss percentage, and its hardness was not significantly different compared with the control group with 2% salt (P > 0.05), but higher than that of the other replacement groups. In PCA, the comprehensive evaluation results of the sample with 0.4% MC were similar to those of the high-salt control group, so that we concluded that 0.4% MC was an appropriate level of replacement.

Methylglyoxal and formaldehyde are harmful substances widely existing in foods and in the human body. This work aimed to evaluate the efficacy and mechanism of action of amino acids in eliminate them. At pH 7.0, different amino acids were reacted with methylglyoxal with a molar ratio of 1:1 at 80 ℃ for 4 h, and residual methylglyoxal was determined using high performance liquid chromatography (HPLC) after derivatization. Among the 14 amino acids investigated, cysteine, γ-aminobutyric acid, and lysine showed the highest ability to eliminate methylglyoxal. γ-Aminobutyric acid, more abundant in foods, was found to be more effective in eliminating methylglyoxal at pH 7.0 than pH 2.0, and the presence of formaldehyde increased the elimination rate to 81%. This effect was more pronounced under thermal conditions (160 ℃). Based on the above results, the reaction product of γ-aminobutyric acid with methylglyoxal and formaldehyde was synthetized and purified. By high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), high-resolution mass spectrometry (HRMS), and nuclear magnetic resonance (NMR), the product was identified as an imidazole salt with a molecular mass of 254.133 9 and a maximum absorption wavelength of 220 nm. It was a nitrogen-containing pentabasic cyclic product formed from two molecules of γ-aminobutyric acid, one molecule of methylglyoxal and one molecule of formaldehyde through nucleophilic addition.

In this paper, we explored the relationship between the conformational changes of soybean protein isolate (SPI) caused by charge density modification through succinylation and the improvement in emulsifying properties. Succinic anhydride was used to modify SPI. The conformational changes of SPI with different degrees of succinylation were analyzed by fluorescence spectroscopy, ultraviolet spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The effect of succinylation on the physiochemical properties of SPI was characterized by scanning electron microscopy, zeta potential, surface hydrophobicity, molecular flexibility and emulsification. The results showed through succinylation reaction, succinyl groups were successfully grafted onto SPI, so that the isoelectric point of SPI decreased and the electronegativity increased. Additionally, the microstructure was changed with small holes on the surface of the smooth and irregular sheet structure, and the the molecular mass was increased. The increase in charge density led to unfolding of the tertiary structure of SPI, exposure of tryptophan residues burying and tyrosine residues, and a red shift in the fluorescence and ultraviolet absorption spectra, which proved that succinylated SPI is located in a more hydrophilic environment. The reaction between free amino groups in SPI and succinyl groups transformed the N–H bond into C–N bond, resulting in changes in the amide III band. The surface hydrophobicity of succinylated SPI was decreased, the molecular flexibility was increased, and the emulsification activity and emulsifon stability were improved compared to SPI. This study confirmed that the increase in the charge density of succinylated SPI can affect the spatial conformation of SPI and consequently improve the emulsifying properties significantly.

In order to reduce the negative effect of nitrite addition on the safety and quality of emulsified sausage, the effects of phosphorylated nitrosohemoglobin (P-NHb) as a sodium nitrite (NaNO2) substitute on the color, antioxidant capacity and sensory quality of emulsified sausage were studied. The results showed that with the extension of storage time, the inhibitory effect of P-NHb on total volatile base nitrogen was not significantly different from that of NaNO2 (P > 0.05). The addition of P-NHb inhibited the decrease in the pH of emulsified sausage. The highest residual nitrite in the P-NHb group was (6.22 ± 0.01) mg/kg. The highest thiobarbituric acid reactive substances (TBARS) values in the P-NHb and NaNO2 groups were (0.62 ± 0.01) mg/kg and (0.67 ± 0.01) mg/kg, respectively, indicating that P-NHb can inhibit lipid oxidation, and its antioxidant effect is better than that of NaNO2. P-NHb endowed emulsified sausage with ideal color. Furthermore, there was no significant difference in the overall acceptability between the P-NHb and NaNO2 groups (P > 0.05). In summary, P-NHb can improve the color of emulsified sausage, reduce its residual nitrite and have a strong antioxidant effect. Therefore, it can be used as a new natural pigment and considered as a NaNO2 substitute in meat products.

In this work, broken rice was pre-gelatinized by a wet heating method followed by roller drying to prepare ready-to-eat cooked rice powder. The effect of pregelatinization time on the water absorption index (WAI), water solubility index (WSI), rheological properties, and microstructure and digestion characteristics of instant rice powder was evaluated. The results showed that the reconstitution characteristics and digestibility of instant rice powder were improved by pregelatinization. Compared to the unpregelatinized sample, pregelatinization for 30 min increased WAI, WSI, gelatinization degree, starch hydrolysis rate and fast digestible starch content by 9%, 50%, 21%, 21% and 57% (P < 0.05), respectively; and decreased caking rate by 1.87%.

In this study, fresh-cut potato chips were soaked in L-cysteine (Cys) aqueous solutions at different concentrations (1, 3, and 5 mg/mL) and then deep-fried. The results showed that the contents of glyoxal (GO), ketoacetaldehyde (MGO), 3-deoxyglucuronone (3-DG) and hydroxymethylfurfural (HMF) in fried potato chips were significantly reduced after Cys immersion, and so was the production of advanced glycation end products (AGEs) from dicarbonyl compounds. Besides, it was found that the acid value, peroxide value and carbonyl value of oil in fried potato chips also showed a downward trend after Cys immersion. Cys also affected the flavor of fried potato chips, increasing the contents of volatile aldehydes and alcohols but decreasing the content of pyrazines. Sensory evaluation by 12 panelists indicated that cysteine-treated potato chips had higher acceptability scores than the control group.

Physicochemical properties, total bacterial counts and volatile flavor compounds of fermented yak meat sausages with 0.0%, 1.5%, 3.0% and 4.5% NaCl were evaluated in this experiment. The results showed that the pH and lightness value of the sausage with 4.5% NaCl were significantly higher than those of the other three groups (P < 0.05). The hardness, adhesiveness and chewiness decreased with decreasing amount of added NaCl, while the storage modulus and total bacterial count increased. Additionally, the water-holding capacity and resilience of the sausage with 3.0% NaCl were significantly higher than those of the other groups (P < 0.05), and the yellowness value was the lowest among the four groups. As NaCl content decreased from 4.5% to 1.5%, the thiobarbituric acid reactive substances (TBARS) value and sulfhydryl content showed an upward trend, and the protein carbonyl content showed a downward trend, while the redness value, elasticity, and cohesiveness did not significantly differ. Seven categories of volatile flavor compounds including aldehydes, alcohols, and acids were detected in fermented yak meat sausages. Three principal components were identified by principal component analysis (PCA), and 12 key volatile flavor compounds with relative odor activity values (ROAV) ≥1) such as hexanal, nonanal, and isovaleraldehyde were obtained. The relative contents of volatile flavor compounds and the key flavor substances of fermented yak meat sausage varied with NaCl level. With decreasing NaCl content from 4.5% to 1.5%, the relative content of aldehydes derived from lipid oxidation increased. Sensory evaluation showed that with the decrease in NaCl content from 3.0% to 0.0%, the appearance, texture, taste, and overall acceptability showed a downward trend, while there was no significant difference in sensory scores between the sausages with 3.0% and 4.5% NaCl.

In this study, the contents of polyphenols and catechins in the spring and summer shoots with one bud and two leaves of the tea cultivars Fuding Dabaicha, Baihaozao, Bixiangzao and Zhuyeqi were determined by the method specified in the national standard GB/T 8313-2018 and high-performance liquid chromatography (HPLC). The relative expression levels of catechin biosynthesis-related genes were determined by real-time polymerase chain reaction (real-time PCR). The results showed that for the four cultivars, the contents of EGC, ECG and EC in summer tea shoots were significantly higher than those in spring tea shoots (P < 0.01). The expression levels of the F3H and DFR genes tended to be higher in spring than in summer. Differential expression levels (|log2 fold change|≥1) of the ANS, C4H, CHS, ANR, UGT84A and flavonoid 3’,5’-hydroxylase (F3’5’H) genes were found between spring tea shoots from Baihaozao and other samples, implying that the gene expression levels could be not only regulated by season, but also affected by cultivar. The relative expression level of F3’5’H was positively correlated with the content of EGCG, which is derived from the hydroxylation of flavanone at the 3’,4’, and 5’ positions of the B ring catalyzed by flavonoid 3’-hydroxylase (F3’H) and F3′5′H. Therefore, F3’5’H may be the key enzyme for EGCG synthesis.

The key enzyme involved in the biotransformation of limonene into α-terpineol by Penicillium digitatum DSM62840 was extracted and purified by sequential ultracentrifugation, ammonium sulfate precipitation, hydroxyapatite chromatography and gel filtration chromatography after high pressure disruption of cells. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed an obvious protein band with a molecular mass of approximatelty 50 kDa. This protein was tentatively identified as dihydrolipoyl dehydrogenase (PDIDSM_08010) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results of this study may provide a basis and reference for α-terpineol production.

The metabolic mechanism of Saccharomyces cerevisiae in response to formic acid stress was studied by non-targeted metabolomics based on liquid chromatography-mass spectrometry (LC-MS) in this work. The data were analyzed by multivariable statistical methods such as principal component analysis (PCA) and orthogonal partial least squares discriminate analysis (OPLS-DA). Totally 226 significantly differential metabolites (P < 0.05) with a variable importance in the projection (VIP) value greater than 1 were identified in Saccharomyces cerevisiae under formic acid stress, mainly including L-tryptophan, L-glutamine, 5-hydroxyindoleacetic acid, indoleacetaldehyde, L-phenylalanine, L-glutamate, oxidized glutathione, and 5’-phosphoribosyl-N-formylglycinamide. The analysis of differential metabolic pathways showed that formic acid stress may cause reactive oxygen species (ROS) accumulation, inducing oxidative stress and excessive ATP consumption, and ultimately inhibiting yeast cell growth. In addition, by increasing the contents of intracellular aromatic amino acids and slowing down the rate of anabolism of some amino acids and nucleotides to reduce energy consumption, yeast cells could protect themselves, thus contributing to the improvement of their tolerance to formic acid. This study provides a scientific theoretical reference for further research on methods to improve cellular tolerance to acid inhibitors.

Fermented sausages were manufactured with Staphylococcus simulans NJ201 as a starter, and naturally fermented sausages were used as a control. The pH, color parameters, texture, peroxide value (POV) and thiobarbituric acid reactive substances (TBARS) value, protein carbonyl content, total sulfhydryl content, and volatile flavor composition in fermented sausages were measured to explore the effect of S. simulans NJ201 on the quality and oxidative stability of fermented sausages. The results showed that inoculation with S. simulans NJ201 significantly lowered the pH value of fermented sausage during its fermentation and maturation (P < 0.05), and improved the color and the texture characteristics. The POV, TBARS value and protein carbonyl content of the inoculated group were significantly lower than those of the control group (P < 0.05), whereas the sulfhydryl content was significantly higher than that of the control group (P < 0.05). The number and amount of volatile flavor substances in the inoculated group were higher than those in the control group. In summary, inoculation with S. simulans NJ201 can improve the taste and enhance the flavor of fermented sausages, effectively inhibit fat oxidation and protein oxidation and increase the oxidative stability of fermented sausages.

This study aimed to compare the effect of different pretreatment methods for DNA extraction on the bacterial community structure in salami for the purpose of selecting appropriate pretreatment methods for a standardized high-throughput sequencing process. We extracted bacterial DNA from salami by three common pretreatment methods: direct extraction (M0), tapping homogenization (M1), and bead beating (M2). We performed MiSeq high-throughput sequencing of the V3-V4 hypervariable region of the bacterial 16S rRNA gene and analyzed the bacterial community structure based on operational taxonomic units (OTUs). The results showed that a total of 319, 206, and 253 OTUs were observed with M0, M1, and M2, respectively; the number of OTUs shared by the three methods was 129, accounting for 31.85% of the total OTUs. For the three methods, the Chao1 index was 177.93 ± 31.02, 120.76 ± 28.60, and 166.96 ± 15.63, respectively, and the Shannon index was 2.79 ± 0.22, 2.95 ± 0.31, and 3.25 ± 0.30, respectively. At the phylum and family level, the bacterial community structure of the samples obtained by different pretreatment methods was similar despite differential abundance; however, different pretreatment methods affected the results of subsequent community structure analysis at the genus level. M0 increased the abundance and diversity of dominant bacteria, and could be applied to detect bacteria in maturing salami samples. M1 and M2 removed free DNA, leaving only bacterial cells with a complete structure, which could better reflect the bacterial community structure in samples. The bacterial community structure and abundance observed with M1 and M2 for homogeneous samples tended to be consistent. In conclusion, this study shows that different pretreatment methods can affect the results of bacterial community structure analysis. A standardized procedure for high-throughput sequencing should be established as soon as possible to ensure data reliability and the comparability of results across studies.

This study aimed to explore the hydrolysis characteristics of Pinctada fucata meat and quick identification of angiotensin-converting enzyme (ACE) inhibitory peptides from its hydrolysates. Hydrolysates at different times (2, 4, 6, 8 and 10 h) were collected to characterize the hydrolyis process by tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and molecular mass distribution measurement, and reversed-phase high performance liquid chromatography (RP-HPLC). In addition, the 10 h hydrolysate was separated and purified, and then the fractions with a high ACE inhibitory activity were identified and screened by molecular docking. Moreover, their activities were verified and their mechanisms of action were elucidated. The results showed that as the hydrolysis proceeded, large-molecular-mass proteins were gradually digested into low-molecular-mass peptides, and that a characteristic peak appeared in the RP-HPLC profile. A total of 54 peptide sequences with high average local confidence (ALC) were obtained from fractions F2 and F3, which had stronger ACE inhibitory activities. Six potential ACE inhibitory peptides were determine by molecular docking and five of them exhibited different ACE inhibitory activities at 1 mg/mL, among which, WFHAVFW and WHAFLW had the strongest ACE inhibitory activity with inhibition percentages of (95.57 ± 0.37)% and (98.59 ± 0.08)%, respectively. The half-maximal inhibition concentration (IC50) value of the hexapeptide WHAFLW was determined to be 52.39 μmol/L. The molecular docking indicated that the peptides could interact with ACE through hydrogen bonding, van der Waals interaction, and Pi-Pi interaction to form a stable peptide-enzyme complex. In conclusion, the combined use of bioactivity-guided fractionation and computer-aided screening can provide a rapid method for screening hydrolysate for strong ACE inhibitory peptides.

Objective: To gain a deep understanding of the taste characteristics of bone peptides from different species of livestock and poultry and the differences between them, and to explore the feasibility of using electronic tongue in their rapid qualitative identification. Methods: Totally 16 samples of yak bone peptides (YBPs), bovine bone peptides (BBPs), pig bone peptides (PBPs) and chicken bone peptides (CBPs), four samples from each species, were collected for analysis of nutritional components and amino acid composition to clarify the material basis of the taste difference between them, and then the data of their taste characteristics were quantitatively discriminated by electronic tongue combined with multivariate statistical analysis. Results: The nutritional composition and amino acid composition of bone peptides from different animal species were different. Principal component analysis (PCA) and discriminant factor analysis (DFA) distinguished bone peptides from different animal species, and DFA was significantly more effective than PCA. Supervised partial least squares discriminant analysis (PLS-DA), orthogonal partial least squares discriminant analysis (OPLS-DA) and Fisher discriminant analysis model all had good discriminant capability for the taste characteristics of bone peptides, and the discriminant accuracy of the Fisher model was 68.8%. Conclusion: The taste characteristics of the four bone peptides differ umami, sweetness and bitterness. Electronic tongue taste detection combined with multivariate statistical analysis can provide a rapid and reliable means for the discrimination of bone peptides from different animal species.

The objective of this study was to investigate the effects of different frozen storage conditions (freezing at ?18 and ?60 ℃, and quick freezing at ?60 ℃; 60 and 180 days) through measuring the contents of fat, non-esterified fatty acids (NEFA), and lipid peroxide (LPO), fatty acid composition, the microstructure of milk fat globules and volatile compounds in human milk. The results showed that the fat content decreased significantly, whereas NEFA and LPO contents increased significantly after frozen storage at ?18 ℃ for 60 and 180 days; the content of unsaturated fatty acid (UFA) decreased after 180 days; the milk fat globule membrane was destroyed and lipid accumulation was observed; the contents of off-odor compounds such as aldehydes and acids increased significantly during frozen storage. Storage at ?60 ℃ and at ?60 ℃ with quick freezing had less impact on fat composition compared to ?18 ℃. For instance, no significant difference in fat content was found compared to fresh human milk, despite a slight increase in the contents of NEFA, LPO, and off-odor compounds, and a slight increase in the content of long chain polyunsaturated fatty acids after storage at ?60 ℃ for 180 days. Furthermore, the structure of milk fat globules was damaged much less at ?60 ℃ than ?18 ℃, and the increase in the contents of off-odor compounds was slowed down. Storage at ?60 ℃ with quick freezing was more effective in maintaining the original flavor of human milk than ?60 ℃. Therefore, we concluded that fast freezing at ultra-low constant temperature has little effect on the fatty acid composition of human milk and protects the physiological properties of lipids, ensuring the quality of human milk feeding, and thus can be considered as the best choice for human milk storage.

A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) pretreatment method combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of seven cucurbitacins in oriental melon. The samples were extracted with acetonitrile. After centrifugation, 1 mL of the supernatant was cleaned up with 50 mg of primary secondary amine (PSA) and 50 mg of octadecylsilane (C18). The separation was performed on a Waters XBridge C18 column with gradient elution using acetonitrile as mobile phase A and 0.1% formic acid in 5 mmol/L ammonium acetate aqueous solution as mobile phase B. The detection was accomplished by multiple-reaction monitoring scanning in a positive/negative ion-switching electrospray ionization mode. The cucurbitacin compounds were separated within 16 min. Good linearity was achieved for all analytes in the concentration range of 0.1–1 500 μg/L with correlation coefficients greater than 0.99. The recoveries at spiked levels of 20.0, 100.0 and 500.0 μg/kg were between 75.7% and 118.3%, and the precision, expressed as relative standard deviation (RSD), ranged between 0.5% and 13.6%. The limits of detection (LOD) were between 0.16 and 4.33 μg/kg, and the limits of quantitation (LOQ) were between 0.27 and 13.11 μg/kg. We concluded that this method has the advantages of simple pretreatment, high sensitivity, precision and accuracy, and short analysis time, and is suitable for simultaneous determination of the seven cucurbitacins in oriental melon.

In order to investigate the changes in the chemical composition of black tea during storage, we analyzed sun-dried black tea stored for 0, 1, 3 and 4 years by metabolomics based on ultra-high performance liquid chromatography-quadrupole orbitrap mass spectrometry (UPLC-Q-Orbitrap/MS). A total of 82 compounds were identified, including six catechins, nine dimeric catechins, five amino acids, eight alkaloids, eight phenolic acids, three organic acids, two aroma precursors, six N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSF), twenty flavonol/flavone glycosides, ten lipids and five other compounds. Partial least squares discriminant analysis (PLS-DA) and heatmap analysis showed that the chemical composition of sun-dried black tea of different ages was greatly different, with 66 significantly differential compounds being identified between groups (P < 0.05). The contents of catechins, dimeric catechins, amino acids and most flavonol-O-glycosides decreased after storage, while the contents of caffeine, flavone glycosides and six EPSF compounds increased. The Pearson correlation coefficients of the contents of EPSF compounds with storage time were 0.802–0.986, indicating that the contents of EPSF compounds increased in a linear manner during storage. This study can provide a theoretical basis for the elucidation of the chemical composition of sun-dried black tea and for its scientific storage.

Objective: The polysaccharides from Spirulina platensis were extracted, purified and thermally degraded. The chemical properties and fine composition of different polysaccharide fractions were analyzed and compared. Methods: Five polysaccharide fractions (P0, P0.2, P0.4, P0.6 and P0.8) and their degradation products were obtained by sequential protease hydrolysis, alcohol precipitation, anion exchange chromatography and thermal degradation. High performance size exclusion chromatography (HPSEC), ion chromatography (IC), high performance liquid chromatography (HPLC) and hydrophilic interaction liquid chromatography-Fourier transform mass spectrometry (HILIC-FTMS) were used to analyze the chemical properties and fine composition of different polysaccharide fractions. Results: The content of sulfated groups in P0, P0.2, P0.4 and P0.6 ranged from 6% to 7%, lower than that in P0.8 (14.46%). The monosaccharide composition analysis showed that P0 was a glucan. P0.2 was a heteropolysaccharide mainly composed of glucose, galactose, rhamnose, fucose and other neutral sugars, while P0.4, P0.6 and P0.8 were mainly composed of rhamnose, glucuronic acid, glucose, xylose and galactose. Through HILIC-FTMS analysis, it was found that the oligosaccharides derived from the thermal degradation of P0.2 were mainly composed of hexose monosaccharide, pentose oligosaccharides, deoxyhexose-pentose oligosaccharides and deoxyhexose-uronic acid oligosaccharides with sulfate groups being in the deoxyhexose, pentose and hexose moieties, and that the composition of the oligosaccharide chain was complicated. However, the composition of P0.4 and P0.6 was very similar, mainly composed of rhamnose-pentose oligosaccharides, rhamnose-glucuronic acid oligosaccharides, pentose disaccharides and trisaccharides with sulfate groups being in the rhamnose and pentose moieties. Conclusion: There are many complex sulfated polysaccharides with different structures in S. platensis, including sulfated glucouronic acid-rhamnan as a unique sulfate polysaccharide.

The volatile composition of whole wheat flour and quick-frozen pre-fried whole wheat Youtiao before and after different reheating methods was analyzed comparatively using electronic nose and headspace solid phase microextraction combined with gas chromatography and mass spectrometry (HS-SPME-GC-MS). Meanwhile, the effect of different reheating methods on polyphenolic contents and antioxidant properties of quick-frozen pre-fried Youtiao was explored. It was found that different characteristic flavor substances were produced after different reheating methods. During the pre-frying and reheating processes, some flavor substances in whole wheat flour disappeared. The relative peak area of aldehydes in quick-frozen pre-fried Youtiao was 50%, which indicates that aldehydes may be the major flavor component of Youtiao. Among the three reheating methods evaluated, refrying produced the largest number of aldehydes and heterocyclic compounds. The contents of acids and hydrocarbons increased in the microwaved sample, and the highest content of aldehydes mostly non-flavor-active saturated aldehydes was observed in the steamed sample. Moreover, all three reheating processes reduced the content of polyphenols in Youtiao, and the loss of polyphenols in pre-fried and reheated Youtiao was ranked in decreasing order of steaming > microwave > pre-frying > refrying, while the opposite was observed for the antioxidant properties.

The key free and glycosidically bound aroma compounds of ‘Shuanghong’ red wine were identified by liquid-liquid extraction-solvent assisted flavor evaporation (LLE-SAFE) combined with gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and odor activity value (OAV) analysis. The results showed that 37 free aroma compounds with flavor dilution (FD) factors higher than 8, and 23 free aroma compounds with OAVs higher than 1 were identified. Based on the results from aroma reconstitution and quantitative descriptive sensory analysis, there was no significant difference in the intensity of hawthorn-like, smoky/animal-like, fatty, and cooked vegetable-like aromas between the original wine and reconstituted wine prepared by mixing 42 aroma compounds, but the intensity of green and black berry-like aromas in the latter was significantly lower than that in the former. Aroma omission tests confirmed that fatty acid ethyl esters, β-damascenone, C6 alcohols, and volatile phenolic compounds had significant effects on the overall aroma of ‘Shuanghong’ wine.

Comprehensive evaluation of the free amino acid composition of 28 different varieties of lotus rhizomes was carried out by correlation analysis, principal component analysis (PCA) and cluster analysis. Results showed that a total of 17 free amino acids were identified. The average contents of essential amino acids, non-essential amino acid and total free amino acids were 2.05, 12.27 and 14.33 mg/g, respectively. PCA showed that the first three principal components accounted for 80.16% of the total variance, really reflecting comprehensive information on free amino acids in lotus rhizomes. The top five varieties with the highest comprehensive scores were ‘Jinhuawuziou’, ‘Xibo’, ‘E’lian 5’, ‘Wuyibaimushiyong’ou’ and ‘Jinhuahonglian’. Cluster analysis showed the 28 cultivars were divided into three groups, which was consistent with the results of PCA. This study can provide a theoretical basis for further lotus breeding, quality improvement, processing and storage.

An ultra-high performance liquid chromatography (UPLC) method was developed for the simultaneous determination of 19 free amino acids and taurine in formulas for special medical purpose intended for infants. The samples were hydrolyzed by α-amylase, and purified by precipitating proteins and other impurities through pH adjustment. The method was based on pre-column derivatization with 6-aminoquinolinyl-N-hydroxysuccinimidate (AQC). Formic acid-ammonium formate (20 mmol/L, pH 2.25), formic acid-ammonium formate (20 mmol/L, pH 3.00), and acetonitrile were used as mobile phases A, B and C for gradient elution, respectively. The analytes were separated on an AccQ-Tag Ultra C18 column, detected with a diode-array detector and quantified by an external standard method. Good linearity was observed for cystine in the range of 5–125 μmol/L and 18 other amino acids and taurine in the range of 10–250 μmol/L with correlation coef?cients higher than 0.999. The limit of detection (LOD) was 1.5 μmol/L for cystine, and 3 μmol/L for the other analytes. The limit of quantitation (LOQ) was 5 μmol/L for cystine, and 10 μmol/L for the other analytes. The average recoveries of the method were in the range of 90.16%–109.84% with relative standard deviation (RSD) not more than 4.77%. The method was easy to operate, accurate and highly reproducible, and could be suitable for the determination of 19 amino acids and taurine in formulas for special medical purpose intended for infants, providing strong technical support for enterprise quality control and government regulation.

The contents of basic chemical components in the whole fruit, pulp and seeds of two cultivars of Idesia polycarpa var. vestita Diels, Chongqing 1 and 2, at different growth periods were compared, and the composition and proportion of fatty acids in whole fruit oils were analyzed by gas chromatography (GC). The results showed that for both cultivars, there was a significant difference in the contents of crude fat, protein, total sugar, ash, total phenols, total flavonoids and other components among different growth periods and fruit parts (P < 0.05). The optimal harvest times for the two cultivars for oil production were about 198 and 182 days after full bloom, respectively. The main fatty acids in the oil of each part of the fruit were palmitic acid (C16:0), palmitoleic acid (C16:1 cis), and stearic acid (C18:0), oleic acid (C18:1 cis), linoleic acid (C18:2 cis), α-linolenic acid (C18:3 n3), γ-linolenic acid (C18:3 n6) and arachidic acid (C20:0). The relative contents of linoleic acid, unsaturated fatty acid and polyunsaturated fatty acid all showed the following decreasing order: seeds > fruit > pulp, and the relative content of linoleic acid in seeds was 75%. The results of principal component analysis (PCA) showed that the seeds had a relatively high comprehensive score and thus could be suitable for comprehensive utilization.

The volatile flavor components of fried Zanthoxylum bungeanum oil from 17 geographical origins were identified by headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). The results showed that a total of 55 volatile flavor components (18 of which were common to all oil samples) were identified, including 22 hydrocarbons, 17 aldehydes and ketones, 9 alcohols, 5 esters and 2 other substances. Odor activity value (OAV) analysis showed that linalool, eucalyptol, myrcene and limonene were the key aroma substances in fried Z. bungeanum oil. Through principal component analysis (PCA) and partial least squares discrimination analysis (PLS-DA), a discriminant model for the classification of fried Z. bungeanum oil samples according to geographical origin was established, and eight key differential flavor substances were selected using the model, namely phellandrene, ocimene, linalool, eucalyptol, linalyl acetate, (-)-β-pinene, p-cymene and myrcene. The 17 oil samples were divided into four categories according to the aroma substances. Production area and cultivar were important factors for the difference in the aroma of fried Z. bungeanum oil. The results of this study will provide a theoretical reference for the quality evaluation and geographical origin discrimination of Z. bungeanum oil on the market.

This study aimed to determine changes in volatile components and phenols from lemon peels at different ripening stages. Volatile components in the peels of two disease-resistant cultivars, ‘Xiangshui’ and ‘Taichui’ during fruit ripening were determined by solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS), and phenols by high-performance liquid chromatography (HPLC). Results showed that a total of 86 volatile components were identified, mainly including terpenes, aldehydes and alcohols, with sesquiterpenes and aldehydes being the predominant ones in the peel of ‘Xiangshui’ lemon, and monoterpenes and alcohols being the major ones in the peel of ‘Taichui’ lemon. The contents of monoterpenes and sesquiterpenes in the peel of ‘Xiangshui’ lemon decreased first, then increased and then decreased, whereas the contents of aldehydes gradually increased. The contents of all three aroma compounds in the peel of ‘Taichui’ lemon decreased first and increased subsequently. In addition, 26 and 22 characteristic aroma components were observed in the peels of ‘Xiangshui’ and ‘Taichui’ lemon, respectively, based on their odor activity values (OVA). Decanal, dodecanal, geranial, linalool and neral were the most important contributors to the aroma quality of ‘Xiangshui’ lemon peel. Decanal, linalool, citronellal, β-myrcene and citronellyl acetate were the most important contributors to the aroma quality of ‘Taichui’ lemon peel. Totally 12 and 15 phenolic compounds were detected in the peels of ‘Xiangshui’ lemon and ‘Taichui’ lemon, respectively. The total content of phenolic acids was not obviously different between the two samples, while the total content of flavonoids in the peel of ‘Taichui’ lemon was significantly higher than that in ‘Xiangshui’ lemon, with a 20.94 to 118.75-fold increase being observed in the content of polymethoxylated flavones. The contents of total phenolic acids and total flavonoids in the peels of both cultivars decreased with ripening. The results of this study provides support for the utilization of lemon fruit and the development of new disease-resistant germplasm resources.

A method for the determination of vitamins A (VA), D (VD) and E (VE) in health foods by column-switching two-dimensional liquid chromatography was established. According to the sample pretreatment method specified in the national standard GB 5009.82-2016, VA and four isomers of VE were separated on an Agilent Poroshell 120 PFP column (4.6 mm × 100 mm, 2.7 μm) as one-dimensional chromatographic column using a mobile phase consisting of methanol and water by gradient elution, and VD2 and VD3 were separated on an Agilent Zorbax Eclipse PAH column (2.1 mm × 100 mm, 3.5 μm) by gradient elution using a mobile phase composed of methanol and acetonitrile. VD was captured on an Agilent Poroshell 120 EC C18 column (4.6 mm × 5 mm, 4 μm). According to the peak time of VD on the one-dimensional chromatographic column, the column switching time was determined. The one-dimensional detection wavelengths were 325 and 294 nm, and the two-dimensional detection wavelength was 264 nm. The analytes were quantified by external standard method. Results indicated that the calibration curves were linear in the range of 2.50-50.0 μg/mL for VA, and 0.10-2.00 μg/mL for VD, and 5.00-100.0 μg/mL for VE, and the correlation coefficients were all more than 0.999. The recoveries were 86%–102%, with relative standard deviations (RSD) of 1.5%–4.0%. The results suggest that the developed method is accurate and suitable for the determination of VA, VD and VE in health foods.

In this paper, the composition and content of carotenoids in fresh tea leaves and intermediate products of Congou black tea manufacturing were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the dynamic changes of different types of carotenoids during the manufacturing process were analyzed. Results showed that a total of 24 carotenoids were detected in all studied samples, including 3 carotenes, 10 lutein and 11 carotenoid esters. The contents of different types of carotenoids greatly differed, with the predominant ones being lutein, (126.000 0 ± 3.605 6)–(317.666 7 ± 12.662 3) μg/g, and β-carotene, (31.533 3 ± 1.365 0)–(70.166 7 ± 1.650 3) μg/g. The contents of some carotenoids components varied greatly during tea processing, and the variation coefficient of lutein palmitate content was the largest (130.85%) among them. Meanwhile, the contents of different carotenoids showed three overall trends, and the rates of change in lutein at the fermentation and drying stages were the largest, which were 10.25 and 58.33 μg/(g·h), respectively. In addition, continuous moderate temperature, enzymatic oxidation and intense moisture-heat conditions were found to be the major triggers for changes in carotenoid contents, but they had different impacts on different carotenoids. The results of this study will provide an important scientific basis for the formation of black tea flavor quality.

The aroma components of 11 raw Pu-erh tea samples of different ages made from ancient tea trees growing in three tea-producing areas in Xishuangbanna prefecture, Yunnan province were analyzed using headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS), and their sensory characteristics were evaluated by professional tea tasters. Orthogonal partial least squares discriminant analysis (OPLS-DA) with variable importance in the projection (VIP) was used to identify the major differential aroma components. Results showed that fresh raw Pu-erh tea had a clean aroma with methylbenzene, 1-octene-3-ol, D-limonene, cis linalool oxide (furan) and linalool being the major aroma components. After a long period (more than six years) of storage, the aroma turned stale, showing the characteristic flavor of aged Pu-erh tea. The contents of D-limonene, hexaldehyde, and alcohols, such as α-terpineol, 4-terpineol, dehydrolinalool, and nerolidol, methylbenzene, 1-isopropyl-3-methylbenzene and methoxybenzenes increased with prolonged storage time, whereas the contents of 1-octene-3-ol, cis linalool oxide (furan), and linalool decreased. We concluded that sensory properties of raw Pu-erh tea from ancient tea trees could be improved with prolonged storage (more than 6 years), which may be related to the decrease in alcohols with floral and fruity flavor and the increase in methoxybenzenes with stale flavor.

An ultra-high performance liquid chromatography coupled to orbitrap high resolution mass spectrometry (UPLC-Orbitrap HRMS) method was developed to characterize the lipid composition of walnut kernel. According to the MS1 and MS2 data acquired in the positive and negative ion modes by electrospray ionization (ESI), a total of 525 lipids belonging to four classes were detected in walnut kernel, including 250 glycerolipids (GL), 221 glycerophospholipids (GP), 36 sphingolipids (SP) and 18 saccharolipids (SL), accounting for 87%, 12.97%, 0.02% and 0.01% of the total lipids, respectively. Diacylglycerols (DG) and triacylglycerols (TG) were the dominant glyceride components, accounting for 45.23% and 41.77% of the total lipids, respectively. TG (18:2/18:2/18:3) was the major TG and DG (18:2/18:2) was the major DG.?Essential fatty acids such as linoleic acid and linolenic acid were the major fatty acids in DG and TG. There were a variety of phospholipids in walnut kernel, including phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidyl serine (PS), phosphatidyl choline (PC), phosphatidyl ethanolamine (PE), phosphatidyl inositol (PI), phosphatidylinositol?diphosphate (PIP), lyso-posphatidyl choline (LPC), lyso-posphatidyl ethanolamine (LPE), lyso-phosphatidylglycerol (LPG), lyso-phosphatidyl inositol (LPI) and cardiolipin (CL). Among them, PA was the most predominant, accounting for 43.88%. The lipid profile constructed in this study can provide a theoretical basis for the functional development of walnut kernel and further research on its nutritional quality.

In order to explore the effect of storage containers on the aroma components of Fengxiang-type Baijiu, gas chromatography-ion mobility spectrometry (GC-IMS) and electronic nose (E-nose) were used to analyze and compare the flavor components and physicochemical properties such as alcohols, total acids, total esters, soluble solids content (SSC) and pH of Baijiu samples stored in different containers. The results showed that the aroma characteristics of newly produced and stored Baijiu samples were greatly different from each other. Specifically, the aroma characteristics of Baijiu samples stored in a pottery jar were similar to those stored in a stainless-steel vessel, while the aroma characteristics of Juihai-stored Baijiu were unique. By GC-IMS, a total of 66 volatile components were identified in the four Baijiu samples, mainly including esters, aldehydes, ketones and alcohols. Baijiu samples stored in the pottery jar and in the stainless-steel vessel had higher contents of ethanol esters, 2,3-pentanedione and 1-propanol, whereas Jiuhai-stored samples contained higher contents of higher alcohol esters, aldehydes, ketones and some other substances, and had the lowest total acid concentration and the highest SSC, alcohol concentration and pH among the four samples.

In this paper, a magnetic separation assisted fluorescence method for the determination of three common organophosphorus pesticides (OPPs) in ‘Shatangju’ mandarin was established. Magnetic beads were synthesized by solvothermal method and modified by polypyrrole (PPy) to form Fe3O4@PPy nanoparticles as a fluorescence quenching agent. This method was based on the use of a 6-carboxyfluorescein (FAM)-labeled aptamer (S4-29) by virtue of its broad-spectrum recognition ability for OPPs. When Fe3O4/PPy nanoparticles mass ratio, Fe3O4@PPy nanoparticles concentration and incubation time were 1:1.5, 0.2 mg/mL, and 120 min, respectivley, the detection limits of phorate, omethoate and profenofos were 4.17 × 10-4, 2.77 × 10-4, and 4.67 × 10-4 μg/kg, and the recoveries ranged from 79.94% to 108.00% with relative standard deviations (RSDs) between 3.05% and 7.39%. In conclusion, this method has strong selectivity and high accuracy and can be used for the analysis of banned OPPs in agricultural products.

Quantitative analysis of beef, chicken in beef products was achieved using species-specific peptides and liquid chromatography-tandem mass spectrometry (LC-MS/MS) in this study. Beef meat was mixed with pork and chicken at ratios of 10%, 50% and 80%, separately. Validation of the species-specific peptides and quantitative analysis of meat products prepared in our laboratory were conducted, showing linear correlation coefficients above 0.99. Meanwhile, 10 commercially available beef products were detected, and a quantitative analysis method based on species-specific peptides was established. The results showed that the developed method allowed quick and effective identification and quantitative analysis of beef products, providing new ideas for the authentication and quantitative analysis of processed meat products.

Here, a rapid method for identifying adulterated Thai jasmine rice was developed using near-infrared spectroscopy combined with backward propagation (BP) neural network. Near-infrared spectra of pure and adulterated rice samples were pretreated by multiplicative scatter correction (MSC) and 48 characteristic wavelengths were selected by competitive adaptive reweighted sampling (CARS). Then, the optimal structure model for BP neural network algorithm was established using absorbance values at these wavelengths as the input layer neurons and Thai jasmine rice contents in samples as the output layer neurons, involving a single hidden layer, seven hidden layer neurons, logsig as the transfer function of hidden layer, tansig as the transfer function of output layer, trainlm as the training function, learngdm as the learning function of the network, and learning rate of 0.35. The model showed an excellent prediction performance with a root mean square error (RMSE) of 0.000 830, correlation coefficient of the calibration set of 0.992 9, correlation coefficient of the verification set of 0.976 1, and correlation coefficient of the test set of 0.975 5.

A method for simultaneous detection of terbufos and its five metabolites in tea by multi-plug filtration cleanup (m-PFC) method combined with liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) was established. The pesticides in tea samples were extracted with acetonitrile after being fully wetted with water. Inorganic salts were added to the system to separate it into organic and aqueous phases. The upper fraction was purified on an m-PFC column before analysis by LC-MS/MS. The accurate quantification was performed by the matrix-matched external standard method. The results showed that the calibration curves for six pesticides (terbufos, terbufos sulfoxide, terbufos sulfone, terbufos-OXON, terbufos-OXON sulfoxide, and terbufos-OXON sulfone) had good linearity in the concentration range of 1–500 μg/L with correlation coefficients higher than 0.999. The detection limits were in the range of 0.001–0.01 mg/kg, and the quantitation limits were 0.002–0.03 mg/kg. The average recoveries at three spiked levels of 0.01, 0.50 and 2.00 mg/kg were in the range of 81.5%–103.9%, with relative standard deviations (RSDs) of 0.9%–10.1%. This method has the advantage of low cost and easy operation, and rapid analysis with good recovery and accuracy, and is suitable for simultaneous determination of the residues of terbufos and its metabolites in tea.

Roast Tan sheep (an indigenous breed in Yanchi County, Ningxia Hui Autonomous Region) meat adulterated with duck meat and pure roast sheep meat were discriminated by an electronic nose. Their volatile composition was analyzed by headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and chemometrics. The results showed that a total of 53 volatile compounds were identified in five adulterated samples, including 12 alcohols, 15 aldehydes, 3 acids, 2 esters, 8 ketones, 8 alkanes, 1 heterocyclic compound and 4 other compounds. Principal component analysis (PCA) clearly distinguished the electronic nose data for the overall odor of adulterated roast mutton samples, and showed that the major differential volatile compounds were alcohol compounds. By partial least squares discriminant analysis (PLS-DA), five characteristic volatile substances were found in adulterated samples, namely 1-octanol, 1-pentanol, hexanal, acetic acid, and dodecane, which will be useful to determine the level of duck meat in adulterated roast mutton samples.

A method was established for the determination of nosiheptide in egg samples using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Egg samples were extracted with acidic acetonitrile, defatted with n-hexane and then purified by solid phase extraction (SPE) on an HLB cartridge. The extract was analyzed by HPLC-MS/MS in the negative electrospray ionization mode using multiple reaction monitoring (MRM). The sample pretreatment?and the experimental conditions were optimized. Fast analysis was achieved when the sample was extracted with 1% formic acid-acetonitrile, cleaned up on an Oasis HLB cartridge, and filtered with a porous polytetrafluoroethylene (PTFE) membrane and ammonium acetate-acetonitrile was used as the mobile phase. A matrix-matched standard calibration curve was prepared and external standard method was used for quantification under the optimal conditions. Good linearity was observed in the concentration range from 1.0 to 20.0 μg/L with a correlation coefficient over 0.998. The limit of detection was 0.3 μg/kg, and the limit of quantification was 1.0 μg/kg. The average recoveries at spiked levels of 1.0, 2.0 and 10 μg/kg were in the range from 83.8% to 96.2%, with relative standard deviations (RSDs) between 6.0% and 8.8%. In conclusion, the developed method is simple, fast, sensitive, accurate, and can be applicable for the detection of nosiheptide in egg samples.

Molecularly imprinted polymers (MIPs) with high selectivity to 29 sulfonylurea pesticides were synthesized by precipitation polymerization, using metsulfuron methyl and chlorsulfuron methyl as the template molecules, 4-vinylpyridine as the function monomer, divinylbenzene as the cross-linking agent and acetonitrile as the porogen, and they were characterized by scanning electron microscopy (SEM) and equilibrium adsorption experiments. The results showed that the MIPs exhibited specific adsorption for the 29 sulfonylurea pesticides, and the maximum apparent binding capacity was 13.21 mg/g. The synthesized polymers were used as solid phase extraction sorbents to develop a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the determination of the 29 sulfonylurea residues in agricultural products. In this method, the peak area of sulfonylurea herbicides had a good linear relationship with their concentration in the range of 2–100 μg/L with a correlation coefficient (R2) of more than 0.999, and the limit of quantitation (LOQ) was 10 μg/kg. At different spiked levels, the recoveries of sulfonylurea herbicides in samples ranged from 74.8% to 110.5% with a relative standard deviation (RSD) of not more than 5.3%.

A method was developed for the simultaneous determination of nine mycotoxins in wheat flour by ultra-high performance liquid chromatography-quadrupole/orbitrap high-resolution mass spectrometry (UPLC-Q/Orbitrap HRMS) combined with QuEChERS (quick, easy, cheap, effective, rugged and safe) pretreatment. Samples were extracted with acetonitrile/formic acid solution (98.0:2.0, V/V), salted out with a QuEChERS salt pocket, and then purified with a dispersive solid phase extraction (dSPE) tube. The target compounds were separated by UPLC and detected in the positive ion mode. Measured accurate mass-to-charge ratios of the nine mycotoxins were obtained in the full scan mode with a relative deviation not more than 1.91 × 10-6 compared to the theoretical value, indicating accurate qualitative analysis of these compounds. A tandem mass spectral library for simultaneous screening and quantitation of the mycotoxins was built based on characteristic fragment ions. The linear ranges were 0.25–100 μg/L for all target analytes. The limit of quantification (LOQ) ranged from 0.30 to 3.00 μg/kg. Average recoveries at three spiked levels were in the range of 70.2%-112.0% with relative standard deviation (RSD) of 0.2%–4.5%. This method is useful for the high-throughput screening and confirmation of mycotoxins in wheat flour.

A method for rapid screening and identification of 30 protein assimilation hormones and glucocorticoids in fish was established using ultra-high performance liquid chromatography coupled to quadrupole/orbitrap high-resolution mass spectrometry (UPLC-Q/Orbitrap HRMS). The samples were extracted with 80% acetonitrile aqueous solution (containing 0.2% formic acid), centrifuged, purified by solid phase extraction (SPE) on Oasis PRiME HLB column, and dried with nitrogen blow. The residue was re-dissolved. The chromatographic separation was performed on a Waters Acquity BEH C18 (2.1 mm × 100 mm, 1.7 μm) column through gradient elution using a mobile phase consisting of 20 mmol/L ammonium acetate aqueous solution containing 0.1% formic acid (A) and acetonitrile (B). The target analytes were detected in the positive and negative ion mode using a heated electrospray ionization (HESI) source through primary full scan/data-dependent secondary scan (full MS/dd-MS2) monitoring, and quantitated by matrix-matched external standard method. The results showed that good linearity was observed for the 30 hormones in the concentration range of 0.5–100 ng/mL with correlation coefficients (r) greater than 0.995 0. The limits of detection were between 0.2 and 1.0 μg/kg, and the limits of quantification were between 0.5 and 2.0 μg/kg. The recoveries were 69.7%–103.2% with relative standard deviations (RSDs) of 2.3%–9.4% at three spiked levels for four different fishes (turbot, mandarin fish, mullet and grass carp). The proposed method is efficient, accurate and reliable, and is suitable for the rapid multi-objective screening and quantitative analysis of protein assimilation hormones and glucocorticoids in fish.

In this study, our aim was to establish a sensitive and rapid approach for the visual and point-of-care detection of Staphylococcus aureus using recombinase-aided amplification (RAA) and lateral flow dipstick (LFD). We designed and screened three pairs of specific primers targeting conserved sequences in the nuc gene of S. aureus and optimized reaction conditions. The RAA-LFD assay took 20?min to amplify the target gene with a 200 nmol/L primer concentration at 33 ℃. The specificity analysis exhibited no cross-reaction with other pathogens. The sensitivity of the RAA-LFD method was as low as 4 fg/μL for DNA and 1.83 × 102 CFU/mL for pure cultures. The reliability was verified using artificially contaminated milk samples, showing that the limit of detection (LOD) was 1.83 × 101 CFU/mL after 6 h enrichment. When 64 milk samples were tested for S. aureus using the traditional culture method, polymerase chain reaction (PCR) and the RAA-LFD method, the results of RAA-LFD showed a high total coincidence rate of 95.3% and 98.4% with those of the two former methods respectively. The visual detection method established in this study has the characteristics of high specificity, high sensitivity, rapidity, simple operation, and low requirements for equipment, and can provide a new development direction for the detection of S. aureus in milk.

Using a Kjeldahl distillation apparatus, a method for the simultaneous determination of formaldehyde and sodium diacetate in aquatic products by dual-gradient liquid chromatography (DGLC) with online derivatization was established. Formaldehyde and sodium diacetate in samples were collected by steam distillation using the kjeldahl apparatus after adding phosphoric acid. The distillates were detectd by DGLC. In the left pump system, the content of sodium diacetate in aquatic products was directly detected. In the right pump system, 10 μL of acetonitrile-acetic acid solution containing 2,4-dinitrophenylhydrazine was used as the derivatization agent, and the sample volume was 10 μL. The content of formaldehyde in the distillate was detected after on-line derivatization for 4 min. The linear ranges of formaldehyde and sodium diacetate were 0.5–20.0 and 10–200 mg/L, respectively, with correlation coefficients greater than 0.999. The detection limits of formaldehyde and sodium diacetate were 0.5 and 10 mg/kg, respectively. For the intrabatch repeatability, the recoveries of formaldehyde and sodium diacetate were 81.4%–88.3% and 91.4%–102.9%, respectively, with relative standard deviations (RSDs) of 1.73%–2.68% and 3.08%–4.16%, respectively. For the interbatch repeatability, the recoveries of formaldehyde and sodium diacetate were 80.6%–87.9% and 90.8%–105.1%, respectively, with RSDs of 2.07%–2.72% and 3.44%–4.64%, respectively. The method is rapid and efficient, and is suitable for the simultaneous determination of formaldehyde and sodium diacetate in bulk samples of of aquatic products.

In this study, liver DNA from purebred Ningxia Tan sheep, purebred Xinjiang fine-wool sheep and purebred Tibetan sheep was extracted followed by genomic library construction, amplification, purification and quality control. Simple sequence repeat (SSR) sites in the sequence were detected, and 50 pairs of primers were designed, synthesized and screened for polymerase chain reaction (PCR) amplification. SSR typing was carried out by capillary electrophoresis, and polymorphic primers were selected to detect the genetic polymorphism of the three breeds. The results showed that 10 pairs of SSR primers successfully amplified stable bands. Ten pairs of polymorphic SSR primers were used to analyze the genetic diversity of Ningxia Tan sheep, Xinjiang fine-wool sheep and Tibetan sheep, showing an average number of alleles (Na) of 4.100, 3.100 and 3.600, average number of effective alleles (Ne) of 3.782, 2.747 and 3.193, average observed heterozygosity (Ho) of 1.007, 1.009 and 0.953, average expected heterozygosity (He) of 0.704, 0.615 and 0.660, and average polymorphic information content (PIC) of 0.432, 0.414 and 0.425, respectively. These data indicated that the genetic polymorphism of Ningxia Tan sheep was higher than that of Tibetan sheep and Xinjiang fine-wool sheep. The results of capillary electrophoresis with fluorescence detection showed that the fluorescent primers scaffold632:150-463, scaffold31384:146-461 and scaffold7676:103-270 had excellent specificity for Ningxia Tan, Xinjiang fine-wool and Tibetan sheep, respectively, and they could effectively distinguish the breeds. In conclusion, the gene banks established can allow scientific and accurate identification of Ningxia Tan sheep, Tibetan sheep and Xinjiang Fine-wool sheep.