The effects of the lipophilic emulsifiers glycerol monostearate (GMS), polyglycerol fatty acid esters (PGE) and propylene glycol monostearate (PGMS) on the crystallization of an anhydrous milk fat-based fat blend and the stability of whipped cream were studied. The purpose of this study was to establish the relationship between the crystallization of the fat blend and the stability of whipped cream in order to provide a theoretical basis for regulating the stability of whipped cream. Results demonstrated that GMS, having hydrophilic glyceryl groups, showed the highest onset crystallization temperature. GMS, as a heterogeneous nucleating facilitator, induced heterogeneous nucleation and led to the formation of tiny and homogenous crystals in the fat blend. Owing to the good emulsifying property of GMS, small and uniform fat globules were well dispersed in the emulsion. These crystals and fat globules contributed to the formation of a firm and compact foam structure in whipped cream. PGE, with hydrophilic polyglycerol groups, showed the largest spatial structure, which provided many nucleation sites to form small and uniform crystals in the fat blend during the crystallization process and finally strengthen the emulsifying stability and bubble stability of whipped cream. PGMS, containing hydrophilic propylene glycol groups and having good oil solubility, could easily adsorb onto the surface of the fat blend and induce heterogeneous nucleation. However, PGMS had low onset crystallization temperature, and the heterogeneous crystals formed by PGMS hindered the crystal growth of the fat blend and reduced the interaction between crystals. The tiny but loose network structure of crystals formed in the fat blend resulted in the formation of a weak foam structure in whipped cream.

Total polyphenol-selenium nanoparticles (TP-SeNPs) were prepared with blueberry pomace polyphenols, prepared by ultrasonic assisted aqueous two-phase extraction and purified by using macroporous resin X-5. The structure of TP-SeNPs was characterized by energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD), and the antibacterial activity was measured. The results showed that selenium salt was reduced into elementary selenium, and hydrogen bond-like interactions existed between the O–H groups of polyphenols and nanoselenium atoms. Additionally, TP-SeNPs were stable as an amorphous solid which was nearly spherically dispersed. The inhibitory effect of TP-SeNPs was better against Gram-positive bacteria than against Gram-negative bacteria. The minimum inhibitory concentration (MIC) against Listeria monocytogene was 0.06 mg/mL. TP-SeNPs effectively inhibited the formation of L. monocytogene biofilms, and destroyed the permeability and integrity of the cell wall and membrane, and caused leakage of cell contents, thereby leading to the death of L. monocytogene. This study offers a new idea for the application of blueberry pomace and selenium nanoparticles, and provides a theoretical basis for the development of selenium nanoparticles with antimicrobial activity.

Two anthocyanin monomers were separated from the crude anthocyanin extract from Lycium ruthenicum Murr. (LRM) by sequential preparative medium-pressure liquid chromatography (MPLC) on microporous and gel-type resins, and their structures were identified by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and nuclear magnetic resonance (1H NMR) spectroscopy. Their inhibitory activity against pancreatic lipase was also evaluated. Results indicated that the contents of anthocyanins P1 and P2 in the purified product obtained with macroporous resin D101 were 18.22% and 30.77% and were increased to 84.16% and 81.48% after chromatography on Sephadex LH-20, respectively. P1 and P2 were identified as petunidin 3-O-rutinoside(trans-p-coumarin)-glucoside-5-O-glucoside and petunidin 3-O-rutinoside(trans-p-coumarin)-5-O-glucoside by UPLC-MS/MS and 1H NMR, respectively. Both of them showed an excellent inhibitory activity against pancreatic lipase with half maximal inhibitory concentration (IC50) of 0.250 and 0.224 mg/mL, respectively, which were much lower than that of the crude anthocyanin extract and the macroporous resin D101 purified product. This work provides a basis for further research and utilization of anthocyanins from LRM.

The effect of combined treatment of different mass fractions (0.25%, 0.5%, 0.75% and 1.0%) L-lysine and 0.5% transglutaminase (TGase) on the water-holding capacity (WHC), texture, water mobility and distribution, microstructure and protein conformation of low-salt chicken meat batter (LCMB) gels was studied. The results showed that TGase alone had no significant effect on the WHC (P > 0.05), but significantly increased the hardness of LCMB gels (P < 0.05). In the presence of TGase, the hardness, springiness, cohesiveness and chewiness of LCMB gels showed an increasing trend with increased content L-lysine. The results of low-field nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and Raman spectroscopy indicated that L-lysine combined with TGase could increase the relative content of immobilized water (P21) and decrease the relative content of free water (P22) in LCMB gels, promote the formation of a three-dimensional ordered, compact and continuous gel network structure, and enhance the exposure of tryptophan, tyrosine and aliphatic amino acid residues in meat proteins. In conclusion, L-lysine combined with TGase treatment can improve the gel quality of LCMB by affecting its water distribution, microstructure and protein conformation.

In this study, the inhibitory effect and mechanism of gallic acid on α-amylase and α-glucosidase were investigated in terms of inhibitory rates, inhibition kinetics, ultraviolet (UV) spectra, fluorescence spectra, circular dichroism (CD) spectra, and molecular simulation. The results showed that gallic acid had a good inhibitory effect on α-amylase and α-glucosidase, with half maximum inhibitory concentrations (IC50) of (0.72 ± 0.01) and (0.59 ± 0.02) mmol/L, respectively, and inhibited α-amylase in a non-competitive manner and α-glucosidase in a mixed competitive-non-competitive manner. The results of UV spectroscopy and fluorescence quenching indicated that gallic acid statically quenched the fluorescence of the enzymes by altering the microenvironment around their aromatic amino acid residues. CD spectroscopy showed that gallic acid reduced the α-helix content and increased the β-sheet, β-turn and random coil contents of α-amylase and α-glucosidase, thus leading to changes in the enzymes’ conformation. The molecular docking results showed that gallic acid bound to α-amylase and α-glucosidase mainly through hydrogen bonds and hydrophobic interactions.

This study aimed to investigate the structural characteristics and biological activity of polysaccharides from selenium-enriched Cordyceps militaris. A homogeneous polysaccharide (SeCMP0.2) was isolated and purified from the fruiting bodies of selenium-enriched C. militaris by water extraction and alcohol precipitation, followed by anion exchange column chromatography. The structural characteristics of SeCMP0.2 were characterized by high-performance gel permeation chromatography (HPGPC), high-performance liquid chromatography (HPLC), nuclear magnetic resonance spectroscopy (NMR), and atomic force microscopy (AFM). The immunoregulatory activity of SeCMP0.2 was evaluated by using RAW264.7 mouse macrophages. Results showed that the weight average molecular mass and selenium content of SeCMP0.2 were 440.7 kDa and 49.1 μg/g, respectively. SeCMP0.2, with a triple-helix conformation, was aggregated in aqueous solution. Moreover, it was a heteropolysaccharide mainly composed of galactose (53.1%), glucose (8.2%), and mannose (37.1%), containing both α- and β-type glycosidic linkages. The dominant residues in SeCMP0.2 including T-Galp-(1→, →2)-Galp-(1→, and →6)-Manp-(1→ accounted for 16.6%, 29.4% and 26.9%, respectively. Additionally, the in vitro immunomodulatory assays showed that SeCMP0.2 could significantly upregulate the mRNA expression levels of inducible nitric oxide synthetase (iNOS), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) by activating the mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB) signaling pathways, thereby exerting immunoregulatory activity. These results will lay the foundation for further development and utilization of selenium-enriched C. militaris resources.

In this work, the effect of the addition of different amounts of chitooligosaccharide (0%, 1%, 2% and 4%) on the gel quality of chicken breast batter subjected to high temperature treatment was investigated. It was found that the addition of chitooligosaccharide significantly increased the hardness and chewiness (P < 0.05), reduced the cooking loss (P < 0.05) and increased water-holding capacity (WHC) of chicken breast gel compared with the control group. Low-field nuclear magnetic resonance (NMR) spectroscopy showed that chitooligosaccharide increased the proportion of immobile water and decreased the proportion of free water within the gel and the transverse relaxation time. Microstructural analysis showed that the gel network structure of chicken breast batter gradually became more regular and homogeneous, with small pores being observed in the gel, as the concentration of added chitooligosaccharide increased from 1% to 4%. Besides, addition of chitooligosaccharide resulted in positive changes in the smell and color of chicken breast gel, with the best overall acceptability being obtained when 4% chitooligosaccharide was added. In conclusion, chitooligosaccharide can be used to improve the quality of chicken breast batter subjected to high temperature treatment.

In order to explore the important role of seasonal temperature in the formation of soy sauce quality, three fermentation temperatures (37, 30 and 15 ℃) were set up to simulate the temperature changes during the four seasons in Guangdong and compared with natural fermentation. During the fermentation process, the dynamic changes of flavor indexes of base soy sauce were measured and sensory evaluation was also carried out to accesses the quality of the product. The results showed that fermentation at 30 ℃ was beneficial for the formation of alcohols, esters and phenols, imparting the highest sensory score and the best overall quality to base soy sauce. Base soy sauce fermented at 37 ℃ had high contents of acid and bitter amino acids and was rich in aldehydes, ketones, furans (ketones) and pyrazines, which formed the basis for soy sauce flavor. Fermentation at 15 ℃ was unfavorable for the formation of acids, bitter amino acids and characteristic flavor compounds in soy sauce, resulting in the lowest sensory score. Moreover, the great temperature changes during natural fermentation were detrimental to the formation of free amino acids and flavor substances. This study provides a theoretical basis for improving the production process and quality stability of Cantonese-style high-salt liquid-state soy sauce.

Malatya cheeses with different cow to goat milk ratios (1:0, 3:1, 1:1, 1:3 and 0:1) were prepared to investigate the effect of blend ratio between cow and goat milk on the yield, physicochemical properties, texture, color, melting temperature, sensory quality, protein hydrolysis and antioxidant properties of traditional Malatya cheese during the ripening process. The results showed that increasing the proportion of cow milk resulted in lower protein content, hardness, chewiness, brightness and whiteness values, and higher moisture content of Malatya cheese. As the ripening time increased, the degree of proteolysis gradually increased, and the antioxidant activity of cheese gradually increased until the 60th day, and then decreased. There was no significant difference in cheese yield between the 50% cow milk addition and the pure goat milk groups (P > 0.05), while the former had the highest sensory evaluation score. Malatya cheese prepared from 50% cow milk and 50% goat milk showed no significant difference in the degree of proteolysis compared with pure goat milk cheese, and in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, superoxide anion radical scavenging capacity, reducing power, or total antioxidant capacity compared with traditional Malatya cheese (P > 0.05). From these results, it was found that the optimal addition level of cow milk in Malatya cheese was 50%, which imparted good quality and antioxidant properties to Malatya cheese.

In order to clarify the influence of Lactiplantibacillus pentosus fermentation on the structure of peanut proteins, changes in the structure of peanut protein isolate (PPI), arachin and conarachin before and after fermentation were studied. The results showed that L. pentosus fermentation significantly increased the free sulfhydryl content, surface hydrophobicity and denaturation temperature, and significantly reduced the β-folding content and denaturation enthalpy of arachin (P < 0.05). It reduced the free sulfhydryl content, surface hydrophobicity, and denaturation enthalpy, and significantly increased the degeneration temperature and α-helix content of PPI and conarachin (P < 0.05). Through particle size, potential and spectral analysis, we found that L. pentosus fermentation significantly improved the particle size and zeta potential of each protein component, and resulted in a red shift in their fluorescence peaks. In contrast to PPI and conarachin, the maximum fluorescence emission wavelength of arachin showed a 1.3 and 2.4 nm red shift, and arachin exhibited a 19.54% and 14.75% higher increase in thermal denaturation temperature, respectively. Thermal properties and scanning electron microscopic (SEM) analysis showed that arachin had maximum structural unfolding and higher thermostability after fermentation, indicating that L. pentosus fermentation is more likely to promote the molecular modification of arachin, and contributes to the gel modification of peanut proteins.

Ginseng residue, the by-product of the extraction of bioactive components from ginseng, is rich in dietary fiber. In this study, ginseng insoluble dietary fiber (IDF) was prepared by ginseng residues fermented with Morchella esculenta, Hericium erinaceus or Armillaria mellea in order to explore the effect of fermentation by edible fungi on the structure and functional properties of IDF. The results of scanning electron microscopy (SEM) showed that a large number of honeycomb pores appeared on the fermented fiber surface and the specific surface area increased compared with that before fermentation. The particle size of fermented fiber decreased. Fourier transform infrared (FTIR) spectroscopy showed that fermentation resulted in partial degradation of cellulose, hemicellulose and lignin in IDF. The results of X-ray diffraction showed that the fermented fiber had a higher degree of crystallinity. The results of differential scanning calorimetry (DSC) showed that the fermented fiber had better thermal stability. The results of functional characteristics showed that compared with unfermented IDF, the water-holding capacity, oil-holding capacity and water-swelling capacity of IDF fermented by Armillaria mellea increased by 74.2%, 93.6% and 124.38%, and all of the increases were higher than those in IDF fermented by the other three strains. Additionally, IDF fermented by Armillaria mellea had the highest glucose adsorption capacity (17.91–83.56 mg/g), glucose dialysis retardation index (GDRI, 30.29%–68.27%), cholesterol adsorption capacity (8.44 mg/g at pH 2.0, and 12.35 mg/g at pH 7.0), sodium cholate adsorption capacity (6.57–12.7 mg/g), nitrite adsorption capacity (1 642.37 μg/g at pH 2.0, and 1 249.13 μg/g at pH 7.0) and cation exchange capacity. In summary, fermentation by edible fungi can effectively improve the functional properties of ginseng insoluble dietary fiber, which will promote its application in foods.

The purpose of this study was to explore the ability of different bifidobacterial species to utilize xylooligosaccharide (XOS). It focused on the mechanism for the efficient utilization of XOS by Bifidobacterium pseudolongum JNFEN6 through cell physiological analysis and transcriptomic analysis. The results showed that XOS had different effects on the growth of different Bifidobacterium species, and it had the most significant effect on the growth and acid-producing capacity of B. pseudolongum JNFEN6. When B. pseudolongum JNFEN6 was cultured for 36 h on XOS as the sole carbon source, the activity of β-xylosidase produced by this strain was 0.97 U/mL, and the concentration of propionic acid in the fermentation system was 85.26 μg/mL. The transcriptomic results showed that a total of 297 differentially expressed genes were identified, including 136 up-regulated genes and 161 down-regulated genes. Among them, the ATP-binding cassette (ABC) transport permease, substrate-binding protein and MFS transporter genes promoted the transport of XOS, while the XOS metabolic hydrolase, acetate kinase and lactate dehydrogenase genes promoted the metabolism of XOS. In summary, B. pseudolongum JNFEN6 can efficiently utilize XOS, which can take in XOS, mainly through the ABC transport system and the MFS transport system, and metabolize XOS through the ‘bifidus shunt’ pathway, finally producing short-chain fatty acids or other organic compounds. This study provides a theoretical basis for the application of XOS as a bifidus factor.

The effects of the degradation products of fucosylated exopolysaccharide (DFcP) on the infant fecal microflora were evaluated in vitro in this study. The results of single-strain culture showed that DFcP was selectively utilized by Bifidobacterium longum subsp. infantis ATCC 15697, B. breve ATCC 15700 and Lactobacillus plantarum CGMCC 1.19, and promoted the accumulation of short chain fatty acids (SCFAs). Compared with 2’-fucosylactose (2’-FL), DFcP was utilized more quickly by the fecal microbiota and led to higher levels of SCFA production (34.57 mmol/L, P < 0.05) during in vitro fermentation. The results of single-molecule real-time sequencing (SMRT) showed that DFcP increased the proportion of Firmicutes in the fecal microbiota, up-regulated the relative abundance of Enterococcus, Lactobacillus and Bifidobacterium, which was verified by the results of real-time polymerase chain reaction (PCR). In conclusion, DFcP could be rapidly utilized by the infant fecal microbiota, and significantly regulate its structure and promote the accumulation of the beneficial metabolite SCFAs. This study reveals the potential of DFcP as new prebiotics, which provides a theoretical basis for further development of novel fucosylated oligosaccharide resources.

Studies have shown that Geotrichum citri-aurantii can adjust the pH of infection sites to enhance its pathogenicity, and PacC, a key transcription factor in the pH signal transduction pathway, plays an important role in fungal response to environmental pH changes, but the role of PacC in G. citri-aurantii remains unclear. In this study, two candidate PacC genes were annotated from the genome of G. citri-aurantii and analyzed by bioinformatics methods and their expression patterns under different pH conditions were also studied. The results showed that PacC1 and PacC2 belonged to the C2H2 protein family, and were closely related to the PacC of Penicillium digitatum. PacC1 and PacC2 had differences in chromosomal location, protein molecular mass and isoelectric point. Under in vitro conditions, G. citri-aurantii could adapt to a wide range of pH, and the optimal pH value was found to be 3.0. The expression of PacC1 and PacC2 was regulated by pH, and their expression trends were similar. Under in vivo conditions, the pH of sour rot lesions in ‘Miyagawa-wase’ mandarin fruit tissue at pH > 3.0 decreased significantly with the progression of the disease, while the pH of sour rot lesions in Eureka lemon fruit tissue at pH < 3.0 increased significantly, and the relative expression levels of PacC1 and PacC2 showed an increasing trend. In conclusion, it can be seen that the environmental pH affects the growth of G. citri-aurantii, which in turn regulates the environmental pH. Due to the differences in gene structure and physicochemical properties, the degree and mode of pH response are different between the two PacC genes. They play an important role in the wide pH adaptability of G. citri-aurantii and in accelerating its infection process in citrus fruit.

In order to achieve high-valued utilization of algal residue, the present study investigated the preparation and activity of antioxidant peptides from Haematococcus pluvialis. Antioxidant peptides were prepared through 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging activity-guided fractionation of an enzymatic protein hydrolysate from H. pluvialis by using ultrafiltration, preparative high performance liquid chromatography (HPLC) and analytical HPLC. Amino acid sequence was identified by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The antioxidant peptides were screened and confirmed by molecular docking, and the mechanism of action of the antioxidant peptides was clarified. Furthermore, the in vivo antioxidant activity of the antioxidant peptides was evaluated by using Caenorhabditis elegans. The results showed that the antioxidant capacity of the protein hydrolysate from H. pluvialis was enhanced by 2.96-fold after purification, and fraction i, with the strongest free radical scavenging ability (which scavenged (96.97 ± 2.00)% of ABTS radical cation at 0.25 mg/mL) was selected for structural identification. Ten peptide sequences i-1 to i-10 were obtained. The molecular docking results showed that the minimum binding free energy between i-1 and ABTS radical cation was lowest, indicating that i-1 had the strongest antioxidant capacity. Furthermore, the novel antioxidant peptide was identified as KFTPAP. In vivo experiments showed that the peptide significantly improved antioxidant capacity in C. elegans (P < 0.05) in terms of the activities of superoxide dismutase (SOD) and catalase (CAT) and malondialdehyde (MDA) content, the effect being most pronounced at a concentration of 100 μmol/L. The potent antioxidant activity of this peptide may be due to the fact that hydrophobic amino acid residues concentrate at the C-terminus, and it contains phenylalanine residues and derives from chlorophyll proteins. This study provides a reference for the high value-added utilization of H. pluvialis residues and the development of food-derived antioxidants.

Total RNA was extracted from sesame seeds, and the sesame Ses i 3 gene was obtained by using reverse transcription-polymerase chain reaction (RT-PCR). The plasmid pET-22b(+) was used to construct an expression vector, and the recombinant plasmid was transformed into competent Escherichia coli BL21 (DE3) host cells for induced expression. The expressed protein was purified by Ni2+-affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the molecular mass of the expressed protein was approximately 66 kDa. The ability of the recombinant and native Ses i 3 protein to induce sesame allergy in mice was compared by using a BALB/c mouse allergy model, which was found to be similar by measuring specific antibodies (immunoglobulin E (IgE), IgG1, and IgG2a), cytokines (interleukin (IL)-4, IL-5, interferon-γ (IFN-γ) and histamines). Hence, the recombinant Ses i 3 protein can be used for future studies on the allergenicity of sesame.

The aim of this study was to develop primary and secondary models to describe the growth kinetics of Staphylococcus aureus in glutinous rice dough in order to provide a basis for monitoring the growth of S. aureus in raw materials for glutinous rice products. Glutinous rice dough was inoculated with a mixture of two S. aureus strains (ATCC 8095 and NCTC 8325) and cultured at 4, 11, 18, 25, 32 or 37 ℃. The results showed that the growth data of S. aureus in glutinous rice dough at all temperatures except 4 ℃, at which S. aureus grew slowly, could be fitted to three primary growth models (the Baranyi, modified Gompertz and Huang models). However, the modified Gompertz model most accurately fitted the growth data of S. aureus at lower and higher temperatures (11 and 37 ℃). The Akaike information criterion (AIC) and the coefficient of determination (R2) showed that the modified Gompertz model could be used as the optimal primary model for the prediction of S. aureus growth. Thereafter, the effect of temperature on the growth rate of S. aureus was analyzed using the Ratkowsky (RSR) and Huang square-root (HSR) models. The results showed that the RSR model provided more accurate predictions of the lowest (0.049 ℃) and highest (47.135 ℃) growth temperatures than did the HSR model, suggesting the RSR model was a more suitable secondary growth model for S. aureus in glutinous rice dough. The results of this study can provide a scientific basis for food companies and regulatory agencies to predict the growth of S. aureus in glutinous rice products for food safety risk assessment.

In this study, we investigated the bacterial community composition and structure during the fermentation process of traditional light-flavor baijiu using PacBio SMRT sequencing technology, and further explored the mechanism of bacterial community self-assembly during the fermentation process using a framework to quantitatively infer community assembly mechanisms by phylogenetic bin-based null model analysis (iCAMP). The results showed that the bacterial diversity decreased and then increased during the fermentation process. Lactobacillus, Acetobacter, Pediococcus and Weissella were identified as the dominant genera, and L. pontis, L. paralimentarius, L. brevis and L. acetotolerans as the dominant species. According to the differences among bacterial communities at different fermentation times, the whole fermentation process could be divided into three stages: I (0 days), II (3–10 days) and III (12–28 days). Acetobacter malorum, L. paralimentarius and L. pontis were the differential species in stages I, II and III, respectively, and there were a significant negative correlation between the differential species in different stages and a significant positive correlation between the differential species in the same fermentation stage. In addition, turnover was the major process responsible for bacterial community changes, and drift during stoichiometry was the most important process driving bacterial community self-assembly. Meanwhile, starch content, temperature and moisture content may be the main factors influencing bacterial community self-assembly during fermentation. The above results provide insight into the bacterial species composition, community succession patterns and self-assembly mechanisms during the fermentation of traditional light-flavor baijiu, which can provide a theoretical basis for regulating the microbial communities in the baijiu brewing process and further optimizing the role of multiple microorganisms in the mixed fermentation process.

In order to study the effects of different functional strains on alleviating protein oxidation and enhancing flavor in fermented sausage, Lactiplantibacillus plantarum NJAU-01 (LpN), with excellent antioxidant activity, L. plantarum CGMCC 18217 (Lp10), with the ability to improve the flavor of fermented sausage, and Staphylococcus saprophytic CGMCC 3475 (Ss), with high protease activity, were selected for use in a multi-strain starter culture for fermented sausage. The degree of protein degradation and oxidation in fermented sausage during fermentation and the final flavor of the product were evaluated. The results showed that the Lp10 + LpN + Ss starter culture could reduce the degree of protein oxidation in fermented sausage and increase the types and contents of volatile flavor substances, while endowing fermented sausage with better color and improving its texture characteristics, and the fermented product had high sensory scores. This study showed that the combination of Lp10, LpN and Ss could improve the quality and flavor of fermented sausage while delaying the oxidation of protein.

A modular metabolic engineering for Escherichia coli was designed for efficient production of β-nicotinamide mononucleotide (β-NMN). First, eight enzymes involved in the shunt metabolic pathways of nicotinamide (NAM) and β-NMN were inactivated to reduce the additional consumption of precursors and products by chassis cells. Second, by introducing BcNaiP, BmPnuC, 5-phosphoribosyl-1-pyrophosphate synthetase (Prs) and nicotinamide phosphoribosyl transferase (Nampt) and deleting the regulatory protein PurR, an engineered strain N12’ was obtained, which could accumulate 0.34 g/L β-NMN in shake-flask fermentation. Then, we found that the Nampt enzyme from Comamonadaceae bacterium had higher activity and caused less burden on the chassis cells. By further strengthening the expression levels of BmPnuC and Prs, the β-NMN titer of the engineered strain N18 was increased to 1.36 g/L in shake-flask fermentation. Finally, after fed-batch fermentation for 38 h, the β-NMN titer reached 10.2 g/L, and the molar conversion rate of NAM to β-NMN was 74.5%. This engineered strain has the advantages of clear genetic background, no nutritional defects, and no need for induction and therefore, has a good prospect for industrial application.

A bacterial strain with high efficiency of zearalenone (ZEN) removal was isolated from wheat samples by enrichment culture method using ZEN as a major carbon source. By morphological observation, 16S rDNA sequence and gyrase B (gyrB) sequence analysis, the strain was identified and named as Bacillus safensis M7L4. ZEN at a concentration of 10 μg/mL could be completely degraded by viable cells of strain M7L4 in 24 hours when cultured in minimal salt medium. By ultra-high performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UPLC-QTOF-MS/MS), the transformation product of ZEN was identified as zearalenone-phosphate (ZEN-P) with a mass-to-charge ratio (m/z) of 397.1. The phosphoenolpyruvate (PEP)-utilizing enzyme gene of Bacillus safensis (named BsaPUE) was amplified from M7L4 and inserted into the pET-28(+) vector. The recombinant Escherichia coli BL21(DE3) harboring the plasmid pET-28a(+)-BsaPUE was induced with isopropyl-beta-D-thiogalactopyranoside (ITPG) and the expressed protein was purified by Ni-NTA chromatography. The recombinant BsaPUE exhibited phosphotransferase activity, which could entirely transform ZEN (10 μg/mL) to ZEN-P in the presence of ATP and Mg2+ within 30 minutes. Strain M7L4 and its phosphotransferase are promising resources for the biodetoxification of ZEN.

The purpose of this study was to obtain microbial strains capable of high-efficiency degradation of T-2 toxin and to investigate their mechanism of action. T-2 toxin-degrading microorganisms were isolated from wheat and identified and their degradation characteristics were explored; their metabolites and mechanism of action were analyzed by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). The results showed that two efficient T-2 toxin degrading strains, AFJ-2 and AFJ-3, were screened from 50 wheat samples and identified respectively as Curtobacterium sp. and Bacillus sp. by morphological observation and 16S rDNA sequence analysis. T-2 toxin at 5 μg/mL was completely degraded within 7 and 12 h by strains AFJ-2 and AFJ-3, respectively, and intracellular enzymes from them could significantly degrade T-2 toxin (P < 0.05) without adsorption. Strain AFJ-2 was able to convert T-2 toxin to HT-2 toxin and T-2 triol, while strain AFJ-3 could degrade T-2 toxin to produce neosolaniol (NEO). Based on the predicted degradation sites, it was hypothesized that the two strains could work together to degrade T-2 toxin to produce a new product, 4-deacetyl-NEO. The research results enrich the strain resource bank for the biodegradation of T-2 toxin, and provide a reference for the separation and purification of T-2 toxin-degrading enzymes and the excavation of functional genes.

In order to produce enzyme cocktails with an advantage in hemicellulose degradation for enzymatic hydrolysis of corn bran fiber (CBF) to produce oligoarabinoxylan, Aspergillus niger and Phanerochaete carnosa were cultured on CBF (containing 50.97% xylose and 28.47% arabinose) under submerged fermentation. The maximum xylanase activity of A. niger and P. carnosa during fermentation was found to be 246.58 (72 h) and 367.21 U/mL (60 h), and the highest activity of α-L-arabinofuranosidase of A. niger and P. carnosa was 57.90 (144 h) and 8.26 U/mL (192 h), respectively. Label-free proteomic analysis revealed that a total of 109 and 105 proteins were identified from the fermentation broths of P. carnosa and A. niger, respectively. The number of glycoside hydrolases secreted by A. niger (82) was more than that produced by P. carnosa (53), and there was also a great difference in the distribution of the glycoside hydrolase family between the two strains, while the number of oxidases secreted by P. carnosa (6) was higher than that secreted by A. niger (2). The results showed that A. niger and P. carnosa could grow on CBF as a carbon source and secrete enzyme cocktails with different compositions but similar catalytic function and efficiency, suggesting that A. niger and P. carnosa use different multi-enzyme synergetic strategies to degrade CBF.

In this study, two common cereal polysaccharides, arabinoxylan (HBAX) and β-glucan (HBBG), were prepared from the bran and endosperm of highland barley, respectively. The inhibitory effects, modes and types of the two polysaccharides on pancreatic α-amylase and their interactions with the enzyme were investigated by enzymatic kinetics and fluorescence quenching analysis. The results showed that both HBAX and HBBG effectively inhibited the activity of pancreatic α-amylase, the former being significantly more effective. Their inhibitory effects were both reversible, but their inhibitory types were different. HBAX presented mixed competitive and non-competitive inhibition, indicating that it not only can bind to the active sites of the enzyme, but also can form an enzyme-starch-inhibitor complex to block the enzymatic reaction. HBBG exhibited a mixed type of anti-competitive and non-competitive inhibition, suggesting that HBBG could only bind to the inactive sites of the enzyme to form an enzyme-starch-inhibitor complex. The fluorescence quenching results revealed that both HBAX and HBBG could interact with pancreatic α-amylase and quench its endogenous fluorescence statically. However, HBAX showed significantly higher affinity to the enzyme than HBBG, and could affect the polarity of the internal hydrophobic environment of pancreatic α-amylase, and in turn affect its microstructure. In conclusion, the differences in the inhibitory effects of HBAX and HBBG on the activity of pancreatic α-amylase might be related to their different inhibitory types and affinities to the enzyme. This study will provide a theoretical basis for the application of highland barley polysaccharides in the regulation of starch digestion and in low glycemic index foods.

This study aimed at the epitope mapping and allergencity reduction of the wheat non-gluten allergen α-amylase inhibitor. Its linear epitopes were predicted by using bioinformatic prediction tools DNAstar, IMED, and IEDB. Six candidate epitopes were obtained by comprehensive analysis, and four linear epitopes were verified by using indirect competition enzyme-linked immunosorbent assay (ic-ELISA). The allergenicity of the allergen was reduced by interaction with polyphenols, A non-covalent complex of α-amylase inhibitor and epigallocatechin gallate (EGCG) was prepared and characterized by fluorescence spectroscopy, circular dichroism (CD) spectroscopy and ultraviolet (UV) spectroscopy, and the efficiency of allergenicity reduction was investigated by ic-ELISA. Results showed that the complex with a molar ratio of α-amylase inhibitor to EGCG of 1:30 had the lowest IgE-binding capacity. The binding capacity was reduced by 22.7%. Molecular docking simulations by using Autodock software further demonstrated that the allergenicity reduction was due to the interactions of the linear epitopes of α-amylase inhibitor and their nearby residues with EGCG. This study can provide a reference for the epitope mapping of wheat non-gluten allergens and the preparation of polyphenols to reduce their allergenicity.

The dynamic changes of moisture, acidity, amino nitrogen content, fermentation power, esterification power, liquefaction power, saccharification power and acid protease activity were measured during the traditional and mechanized production of Chixiangxing Baijiu Qu, the structural characteristics of bacterial communities were analyzed by high-throughput sequencing technology, and the correlations among bacterial communities and those between them and physicochemical factors were predicted by Pearson’s statistical method. The results showed that moisture content, amino nitrogen content, saccharifying power, esterification power and fermentation power were significantly higher and acidity was significantly lower at the end of the traditional fermentation process than mechanized fermentation. However, there was no significant difference in liquefaction power or acid protease activity between the two fermentation processes. A total of 18 bacterial genera with relative abundance greater than 1% were identified during traditional and mechanical fermentation, including Lactobacillus, Bacillus, Pediococcus, Weissella, Ralstonia, Leuconostoc, Acetobacter, Exiguobacterium Staphylococcus, Kurthia, Acinetobacter, Enterococcus, Glutamicibacter, Thermobifida, Streptomyces, Enterobacter, Gemmobacter, and Oceanobacillus, among which Lactobacillus, Bacillus, Pediococcus and Weissella were the core ones for both traditional and mechanical fermentation, but their proportions were significantly different between the two fermentation processes. Bacillus was dominant in mechanized fermentation and its abundance was significantly higher in mechanized than traditional fermentation, while Lactobacillus was dominant in traditional fermentation; its abundance was significantly higher in traditional than mechanical fermentation, and so was the abundance of Pediococcus and Weissella. The correlation analysis revealed that Bacillus was in competition with Lactobacillus; Pediococcus and Weissella, and Lactobacillus were positively correlated with amino nitrogen content, fermentation power, esterification power, saccharifying power and acid protease activity, and Bacillus was positively correlated with acidity, amino nitrogen content and liquefaction power. Moreover, there were differences in the texture of traditional and mechanized Qu samples and the amount of oxygen in contact with Qu during the making process, which may be related to the addition of wheat bran in the mechanized process and the environmental difference between the two processes. Appropriate control of environmental oxygen concentration and stabilization of environmental changes in the mechanized process can be conducive to the balanced growth of core functional aerobic and anaerobic microorganisms, thereby improving Qu quality. This study provides a scientific theoretical basis for advancing the development of the mechanized fermentation of Chixiangxing Baijiu Qu.

To improve the efficiency of nisin synthesis by Lactococcus lactis HB03, the oxidative stress effect and the pattern of changes in the concentration of extracellular amino acids during the growth and fermentation of this strain were determined. Then, the differences in gene expression related to the peptide hydrolase system, UMP de novo synthesis, and peptidoglycan anabolism at the transcriptome level were analyzed. As a result, deficiencies of cysteine (Cys) and arginine (Arg) were identified as the limiting factors for nisin synthesis at the mid to late logarithmic phase. The optimal fed-batch culture strategy in a 10 L fermentor was obtained as follows: addition of 0.15 mmol/L Cys at 11, 13.5, 17, and 19.5 h, addition of 15 g/L peptone at 12 h, addition of sucrose at a flow rate of 1.5 g/(L·h) during 10 to 24 h, and addition of Arg at a flow rate of 0.25 g/(L·h) during 12 to 21 h. Under these conditions, nisin production was increased to 8 963 IU/mL, which was 28.2% higher than that obtained by adding only Cys (6 993 IU/mL). These results provide an important reference for the industrial fermentation of nisin.

The pattern and cause of changes in microbial community structure and metabolic activities were explored during the long-term storage of Nongxiangxing Baiju Daqu. The microbial community composition on and in Daqu was determined by high-throughput sequencing technology, and changes in saccharification power and liquefaction power were analyzed. Volatile flavor substances were studied by headspace-solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS), and the formation mechanism of Daqu microbial flora and the cause of metabolite changes during storage were explored by constructing a phylogenetic null model as well as using multivariate statistical analysis. The results showed that during the storage of Nongxiangxing Baijiu Daqu, the microbial community was rebalanced, and enzyme activities and volatile compounds were further enriched and transformed. The development of microbial communities was governed by stochastic processes, and also affected by deterministic processes, in which heterogeneous selection played a major role, and niche width differences also had a certain impact on it. The changes in saccharifying power, liquefaction power and flavor substances of Daqu were closely related to the succession of microbial community. These results provide a theoretical basis for the quality control of Daqu.

In this study, in order to investigate the metabolic pathway of semicarbazide, a metabolite of nitrofurazone, in crustacean aquatic products, the accumulation of nitrofurazone and its metabolites in Procambarus clarkii was evaluated at different time points, and the metabolomics characteristics of semicarbazide were analyzed by ultra-high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry (UPLC-Q-Exactive-MS). Meanwhile, substances that may be related to semicarbazide production in the metabolic pathway were examined through in vitro simulation test. The results showed that the semicarbazide content in the muscle tissue of P. clarkii increased with increasing nitrofurazone stress period, while the nitrofurazone content initially increased, then decreased and finally increased again. Metabolomics demonstrated that a total of 39 differential metabolites were annotated in samples treated with nitrofurazone for 24 h compared to 4 h, of which 22 metabolites were up-regulated while the remaining 17 were down-regulated. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis suggested that nitrofurazone exposure could affect pathways associated with taurine and hypotaurine metabolism, arginine biosynthesis, alanine, aspartate and glutamate metabolism, and D-glutamine and D-glutamate metabolism. Validation tests confirmed that taurine, arginine, alanine and glutamine might be crucial in the metabolic pathway of semicarbazide.

Four “Golden Flower” fungi were isolated from the pile-fermentation process of Liupao tea, and named LB-22, LB-32, LB-35 and LB-55, respectively. Based on colony morphological characteristics, optical microscopic structural characteristics, internal transcribed spacer (ITS) sequence alignment and analysis and phylogenetic analysis, the four strains were identified as Penicillium manginii, Aspergillus ruber, A. intermedius and A. amstelodami. The four “Golden Flower” fungi were separately inoculated into sterilized raw Liupao tea from the Cangwu variety group for solid-state fermentation. The effects of these fungi on the sensory quality and major physicochemical properties of fermented Liupao tea were investigated through sensory evaluation, biochemical component detection and principal component analysis (PCA). The results showed that the taste of Liupao tea changed from heavy and strong to mellow and thick after fermentation by “Golden Flower” fungi, the aroma changed from coarse-fired to stale, woody and arohid, and the color of tea infusion changed from bright yellow-green to bright, intense red. PCA and hierarchical cluster analysis (HCA) showed clear distinction between “Golden Flower” fungi fermented tea and the unfermented control. Compared with the control group, the contents of flavonoids, total free amino acids, tea polyphenols, thearubigin, catechin (EC, CG, C, EGCG, GCG and ECG) and total catechin significantly decreased in the fermented groups (P < 0.01), whereas the contents of theabrownins significantly increased (P < 0.01). This study provides a reference for the application of “Golden Flower” fungi in Liupao tea, and offers a theoretical basis for research on the industrialization and product development of “Golden Flower” fungi fermented Liupao tea.

In this study, multi-dimensional characterization of different layers of alcoholic fermentative material in Maotai-flavor baijiu cellar in the fifth round of fermentation from a certain region in Hubei was carried out by route analysis, culturable methods, metagenomics, and bionic methods. The results showed that there was no significant difference in the counts of total bacteria, lactic acid bacteria, or yeast and mold among different layers of alcoholic fermentative material (P > 0.05). However, acidity, alcohol content, starch content and reducing sugar content were significantly higher in the middle than lower layer (P < 0.05). Sensory evaluation showed that the lower layer had a stronger bitter taste and bitter aftertaste as well as higher concentrations of nitrogen oxides and methane. The analysis of sequencing data from the MG-RAST database for the fourth round of fermentation showed that the major genera in alcoholic fermentative material were Acetilactobacillus and Sarocladium, whose relative abundance in alcoholic fermentative material was significantly different between the fourth and fifth rounds of fermentation (P < 0.05). Also, there was a significant difference in the microbial community structure of alcoholic fermentative material between the two rounds (P < 0.05), while the difference in the microbial community structure among different layers of alcoholic fermentative material was relatively small. Correlation analysis showed that there was a close relationship between microorganisms in alcoholic fermentative material and its sensory and physicochemical quality.

A commercial yeast strain (L) and five yeast strains (Y-1, Y-2, Y-3, Y-4 and Y-5) isolated from different specialty sourdoughs were checked for their ability to metabolize sugars and organic acids and their effects on volatile flavor substances and sensory quality of sourdough and bread. The results showed that yeast Y-1, Y-3, Y-4 and Y-5 all showed good sugar metabolism ability and were able to produce high yields of malic acid, lactic acid and succinic acid. In terms of sensory quality, the sourdough fermented by each of the five yeast strains had good flavor; sourdoughs Y-3 and Y-4 had better sensory characteristics than other samples. It was found that the hardness of bread made with sourdough Y-3 was reduced by 16.77% and adhesiveness by 72.39% in comparison to commercial yeast L. The sensory score for fermented flavor of bread Y-3 was the highest, 7.74 points, indicating that yeast Y-3 could obviously improve the texture and flavor of bread. The results of headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) showed that the relative contents of alcohols in sourdoughs and breads made with L, Y-3 or Y-4 were the highest, ranging from 72% to 81%. Also, esters were the main flavor substances in sourdough, while aldehydes were predominant in bread. Moreover, the principal component analysis (PCA) of volatiles showed good discrimination among the three sourdoughs as well the three breads; ethyl hexanoate and ethyl caprylate contributed significantly to the flavor of sourdough Y-3, while hexanal and trans-2-nonenal were the key flavor components of bread Y-3. These substances provided rich aromas to sourdough and bread. In conclusion, yeast Y-3 plays a positive role in improving the taste quality of bread.

To investigate the effect of enhanced fermentation with different species of Aspergillus on the flavor of Douchi, the quality differences between enhanced fermentation by A. flavus 7214, A. flavus 7622 or A. oryzae and natural fermentation were compared. The results showed that enhanced fermentation with A. flavus promoted an increase in the total amount of free amino acids and organic acids, particularly glutamic and acetic acids, in Douchi. A total of nine classes of compounds including esters (20), acids (11), aldehydes (12), ketones (9), alcohols (7), pyrazines (8), alkanes (10), phenols (7) and other compounds (8) were identified by gas chromatography-mass spectrometry (GC-MS). While higher levels of pyrazine and phenolic compounds were observed in naturally fermented Douchi, enhanced fermented Douchi had more acids and aldehydes. In addition, some new volatile components, such as methyl phenyl acetate and ethyl linoleate, were formed by enhanced fermentation. Electronic nose analysis revealed that the flavor of A. flavus 7622 fermented Douchi was closest to that of naturally fermented Douchi, while the largest flavor differences were found between A. flavus 7214 fermented and naturally fermented Douchi. Furthermore, A. flavus 7214-fermented Douchi had better overall flavor in sensory evaluation, mainly in terms of aroma, sourness, sweetness, and umami. To summarize, enhanced fermentation promoted the release of free amino acids, organic acids, and volatile compounds, thereby having a significant impact on sweetness, umami, and aroma. These results could provide theoretical guidance for the industrial production of Liuyang Douchi.

In order to reveal the differences in the biosynthesis and metabolism of the major bioactive composition in sea buckthorn berry pulp during ripening, non-targeted metabolomics based on ultra-high performance liquid chromatography coupled to mass spectrometry (UPLC-MS) was used to analyze the metabolites of sea buckthorn berry pulp from two strains at different developmental stages (green and orange pulp). The results showed that the four sample groups had significant metabolic differences. A total of 124 significantly differential metabolites were detected among the four groups based on variable importance in the projection (VIP) > 1 and t-test P < 0.05, including organic acids, carbohydrates, lipids, flavonoids and secondary metabolites. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, 15, 7 and 4 significantly differential metabolites associated with lipid, flavonoid and serotonin metabolism were identified, respectively, and eight significantly differential metabolites involved in anticancer function were selected. The significant up-regulation of phosphatidylcholine (PC) (16:0/16:0) and glycerophosphocholine could be the reason for the high accumulation of lipids in sea buckthorn berry pulp. The significant upregulation of isorhamnetin was key for the high flavonoid content in sea buckthorn berry pulp. Relatively high contents of N-acetylserotonin, capecitabine, γ-aminobutyric acid (GABA) and other bioactive composition involved in anticancer function were shown in sea buckthorn berry pulp during its development. These results provide a scientific basis for revealing the metabolic mechanism of bioactive composition of sea buckthorn berries and developing related functional products.

In this study, the flavor components of double-low fragrant rapeseed oils (cv. “Zhongyouza 19”) from nine different planting areas were qualitatively and quantitatively analyzed by headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry coupled with olfactometry (GC-MS-O). The results showed that a total of 63 aroma-active compounds were identified using two columns (polar and non-polar) at a total concentration of 222.0 to 468.9 mg/kg. The total concentration of aroma compounds was highest in the Hunan sample and lowest in the Jiangxi sample. Out of the identified flavor substances, 38 had odor activity value (OAV) greater than 10. The results of partial least squares-discriminant analysis (PLS-DA) and sensory evaluation showed that 2-methylpyrazine, 2,3,5-trimethylpyrazine, and 2-methyl-3,5-diethylpyrazine were the main contributors to roasted aroma notes, 3-butenylisothiocyanate provided spicy notes, and 5-hexenenitrile and 4-methylthionitrile led to green notes. Based on variable important in the projection (VIP) values, nine key differential substances were selected, namely, methanthiol, 2-methylpyrazine, 2,3-diethyl-5-methylpyrazine, dimethyl disulfide, 5-methylthiopentonitrile, 5-hexenenitrile, (E,Z)-2,4-pentadienonitrile, hexanal and dimethyl trisulfide. They could be considered as potential flavor markers for the discrimination of double-low fragrant rapeseed oils from different planting areas. This research can provide a theoretical guide for the screening of raw materials for fragrant rapeseed oils.

In order to study the difference in the encapsulation capacity of different microcapsule wall materials for volatile flavor substances, microcapsules were prepared with seven common wall materials by ultrasonic spray-freeze drying technology and their morphology, encapsulation and slow release capacity for 32 volatiles were evaluated by cold field emission scanning electron microscopy (CFE-SEM), electronic nose (EN), and gas chromatography-mass spectrometry (GC-MS). These results showed that the encapsulation capacity of different wall materials exhibited selectivity for different volatiles. In general, β-cyclodextrin had a stronger encapsulation capacity for the volatile compounds, with a higher encapsulation and release efficiency, so it was an ideal wall material. After 30 minutes of heating, the release profile of volatiles encapsulated by β-cyclodextrin in the EN radar plot was similar to that of free volatiles, indicating that the microcapsules prepared in this study had good slow-release performance. These results provide a theoretical basis for the utilization of microencapsulated products for flavor enhancement and flavor stability improvement in the food field.

In this study, non-targeted metabolomics based on liquid chromatography-mass spectrometry (LC-MS) was used to investigate the changes in the types and contents of metabolites in HN191 purple hot pepper and Erjingtiao at the immature (30 days after anthesis) and mature (60 days after anthesis) stages. The results showed that the four pepper groups were clearly separated without any non-overlapping from one another by principal component analysis (PCA), indicating significant differences in metabolite composition between varieties and mature stages. Taking variable importance in the projection (VIP) > 1, |fold change| > 2 and P < 0.05 as thresholds, 1 065, 1 010 and 1 487 differential metabolites were identified between HN191 and Erjingtiao fruits at 30 day after anthesis, between HN191 and Erjingtiao fruits at 60 days after anthesis, and between HN191 fruits at 30 and 60 days after anthesis, respectively, which were all enriched to flavonoid-related pathways. In the flavonoid biosynthesis and isoflavone biosynthesis pathways, most of the differential flavonoid metabolites were more abundant in HN191 than in Erjingtiao. In addition, in the anthocyanin biosynthesis pathway, seven delphinidin, cyanidin, and pelargonidin derivatives, including delphinidin, delphinidin-3-(P-coumaroyl)-rutinoside-5-glucoside, delphinidin 3-glucoside 5-caffeoyl-glucoside, cyanidin 3-O-rutinoside 5-O-β-D-glucoside, cyanidin 3-O-β-D-sambubioside, pelargonidin 3-glucoside 5-caffeoyl glucoside and pelargonidin 3-O-β-D-sambubioside, were found to be significantly accumulated in immature HN191 fruit, which may be key metabolites related to anthocyanin biosynthesis in HN191.

The aroma components of white tea from the new tea strain ‘Baiyun 0492’ (also known as Baiyun Tezaocha) and ‘Fuyun 6’ as a control were analyzed and compared by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) in an effort to identify the characteristic aroma components of ‘Baiyun 0492’ white tea. A total of 928 aroma compounds were detected in six white tea samples (of three different grades for each type), and nonyl acetate, contributing to floral and fruity aromas, might be an aroma compound unique to ‘Baiyun 0492’ tea. The results of relative odor activity value (ROAV) analysis showed that β-ionone, linalyl acetate, linalool, (Z)-decan-2-enal, damascenone, neral and citral were the key aroma components in both white teas. Based on orthogonal partial least squares-discriminant analysis (OPLS-DA), the contents of linalool, methyl benzoate, hotrienol, nonyl acetate, 3,7-dimethy-6-actenoic acid and geranyl formate in ‘Baiyun 0492’ tea were significantly higher than those in ‘Fuyun 6’ tea (variable important in the projection (VIP) >1, P < 0.05). Linalsol and methyl benzoate were important aroma compounds of ‘Baiyun 0492’ white tea, responsible for pekoe-like, fruity and floral aromas. This study is helpful for a comprehensive understanding of the aroma characteristics of ‘Baiyun 0492’ white tea, and provides a scientific basis for the research and development of ‘Baiyun 0492’ white tea products with distinctive personality.

The overall quality differences among different waxy wheat varieties was studied. Totally 17 waxy wheat varieties approved in China in the past decade and common wheat (hard, mixed and soft) were analyzed for hardness index, dough rheological properties and pasting properties. Comprehensive quality evaluation and classification were carried out by principal component analysis (PCA) and cluster analysis (CA). The results showed that grain hardness index significantly differed among waxy wheat varieties and ranged from 25.2 to 73.82. The proportion of the hard type was 41.18%, the average hardness index was 63.07, with a coefficient of variation of 11.20%. The proportions of the mixed and soft types were both 29.41%. Compared with ordinary wheat flour, waxy wheat flour had a higher protein content (14.78%) and a lower amylose content (1.01%), indicating better processing characteristics. In addition, waxy wheat flour had a high water-absorbing rate (71.1%), good extensibility (157.7 mm), and short gelatinization time (3.59 min), and low setback (290 cP). The results of PCA showed that average particle size of starch granules, volume proportion of type A (≥10 μm) starch granules, final viscosity, setback, and trough viscosity were the major factors affecting the quality difference between soft and hard-type waxy wheat, while gelatinization characteristics, protein content, maximum tensile resistance and starch content were the major factors affecting the quality difference of mixed waxy wheat. The 17 waxy wheat varieties were clustered into three categories by cluster analysis (CA), cluster-I including three varieties of soft and mixed-type wheat with the highest comprehensive score, cluster-II including six hard-type waxy wheat varieties, and cluster-III including eight waxy wheat varieties with low protein content and gelatinization characteristics. This study provides a basis for the quality evaluation, classification and core quality indicator determination of different waxy wheat varieties.

An analytical method was established for the simultaneous detection of five saccharides in tea by multi-plug filtration cleanup (m-PFC) combined with high performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD). An m-PFC cartridge with polyamide powder as sorbent was developed for sample pretreatment. Tea samples were extracted with water while shaking, and then back-extracted with dichloromethane for the removal of impurities. The upper phase was purified using the m-PFC column and detected by HPLC. Quantification was performed by the external standard method. The results showed that the logarithm of the peak areas was linearly related to the logarithm of the concentrations of rhamnose, fructose, glucose, sucrose, and maltose within the linear ranges tested, with correlation coefficients higher than 0.99. The limits of detection (LOD) were in the range of 0.04–0.1 g/100 g, and the limits of quantitation (LOQ) were 0.10–0.20 g/100 g. The average recoveries at three spiked levels were in the range of 91.0%–103%, with relative standard deviations (RSDs) of 1.0%–4.6%. This method has the advantages of simple operation and good purification effect, and is suitable for the quantitation of these five saccharides in tea.

In order to explore the difference in flavor among yak leg meat roasted at different temperatures, sensory evaluation, gas chromatography-ion mobility spectrometry (GC-IMS), relative odor activity value (ROAV), partial least squares-discriminant analysis (PLS-DA), and principal component analysis (PCA) were used in this study. The results showed that the samples roasted at 240 ℃ for 7 min had the highest (E) sensory evaluation score. A total of 82 compounds were identified by GC-IMS, including 15 aldehydes, 12 alcohols, 24 lipids, 14 ketones, 7 heterocycles, 3 olefins, and 7 other compounds. The total amount of these compounds in sample E (240 ℃) was the highest, followed by samples D (180 ℃) and C (120 ℃). The total amount of these compounds in sample F (300 ℃) was lower than that in sample E (240 ℃). The key flavor compounds of roasted yak meat were ethyl 2-hydroxypropanoate, 4-methylguaiacol, 2-acetyl-1-pyrroline, 5-nonanone, ethyl salicylate, 1-propanol, (E,E)-2,4-heptadienal, 1-penten-3-one, (E)-2-heptenal, linalyl acetate, butanol-D, methional-M, 2-ethyl-6-methylpyrazine, 4-hexen-1-ol, (Z)-4-decenal, 2,4-heptadienal, 2-phenylethanol, and ethyl butyrate. Sample E had roasted meat-like, fatty, flowery and fruity aromas, which was the best among these five samples. The flavor of samples C and D was lower than that of sample E, having nutty, toasty, sweet and smoked aromas.

The contents of total and individual soluble sugar in mature chestnut fruits from the Yanshan-grown varieties (lines) ‘Dabanhong’, ‘Yanbao’, ‘Yanlong’, “Funing12”, “Funing 8” and “Qinglongjuli” were determined by the anthrone colorimetric method and gas chromatography-mass spectrometry (GC-MS), and their biochemical sweetness values were calculated. The differences in the soluble sugar composition among chestnut varieties (lines) were analyzed, and a comprehensive evaluation was carried out using principal component analysis (PCA). The results showed that 24 soluble sugars were detected, with the most abundant ones being inositol, glucose, D-galactose, D-fructose, maltose, sucrose and raffinose, accounting for 98%–99% of all soluble sugar components. The structure of soluble sugar components was basically consistent among different varieties (lines), but there were some differences in the proportion of soluble sugar components. Sucrose accounted for the highest proportion (64.71%–91.11%, with an average of 82.17%) of the total amount of soluble sugar, followed by maltose, which accounted for 3.36%–17.49%, with an average of 8.60%, and monosaccharide composed of inositol and glucose, which accounted for 1.97%–4.14%. The contents of D-galactose, D-fructose and raffinose were relatively low, with an average of 0.52%, 0.42% and 0.77%, respectively. The results of correlation analysis showed that the content of soluble sugars showed a significant positive correlation with sucrose content. D-fructose and inositol contents also showed a significantly positive correlation with each other. D-galactose content showed a significantly negative correlation with biochemical sweetness. According to the results of PCA, the top three varieties (lines) in terms of comprehensive scores were “Funing 12”, ‘Yanlong’ and ‘Yanbao’. The results can provide a scientific reference for the evaluation and sugar quality regulation of Yanshan-grown chestnut resources.

In order to investigate the effect of wrapping-rolling on the quality of Tieguanyin oolong tea, non-volatile and volatile metabolites in rolled tea leaves before and after repeated wrapping-twisting for up to three times were analyzed by widely targeted metabolomics based on headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that a total of 973 non-volatile metabolites belonging to 12 categories were identified, including 468 differential metabolites. The total amount of non-volatile metabolites showed a decreasing trend during the wrapping-twisting process. Particularly, the decrease in the content of differential metabolites such as flavonol glycosides and phenolic acids contributed to the reduction in bitterness and astringency during the wrapping-twisting process. The content of differential lipids increased, which provided favorable conditions for the conversion of volatile fatty acids during the subsequent drying process. A total of 47 volatile components belonging to six categories were identified. During the wrapping-twisting process, the contents of β-red myrcene, heptanal, (E)-2-hexenyl hexanoate and cis-3-hexenyl isobutyrate, responsible for fatty or grassy aroma, decreased, while the contents of methyl jasmonate, benzyl benzoate, geranyl acetone and 3,7-dimethyl-1,5,7-octatrien-3-ol, contributing to floral or fruity aroma, increased. It was noteworthy that the odor activity value (OAV) of the major aroma components in Tieguanyin oolong tea, such as linalool, jasmonolactone, cis-jasmonone, α-farnesene and basilene, were still greater than 1 at the end of the wrapping-twisting process although their contents decreased during this process. It could be seen that the wrapping-twisting process was beneficial to purify the quality of Tieguanyin tea, and provided it with a more mellow taste and more obvious floral and fruit aromas. This study provides new insights into the metabolite changes and the flavor formation of oolong tea during the wrapping-twisting process.

A rapid method was developed and validated for the simultaneous identification and quantitation of the residues of 5-nitroimidazoles and their metabolites in eggs by isotope dilution-ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were extracted with acetonitrile, purified with octadecylsilane-bonded silica gel as sorbent, and defatted with n-hexane. The target compounds were separated in the LC system by gradient elution, and detected using an electrospray ionization (ESI) source in the positive ion mode with multiple reaction monitoring (MRM). Under the optimal conditions, the calibration curves for seven nitroimidazoles were linear in the concentration range of 0.5–20 ng/mL, with correlation coefficient exceeding 0.999. The limits of detection (LOD) and quantification (LOQ) were 0.1–0.25 and 0.3–1.0 μg/kg, respectively. The average recoveries at three spiked levels (0.5, 1.0 and 5.0 μg/kg) were 96.5%–112.7%, with relative standard deviations (RSDs) (n = 6) of 0.82%–8.14%. The proposed method was used for the determination of nitroimidazoles in egg samples from Food Analysis Performance Assessment Scheme (FAPAS) with satisfactory results. The RSDs between the results and the assigned values were less than 10%. This method could accurately detect the seven nitroimidazoles and was validated to be suitable for 38 batches of commercial eggs. The developed method is convenient, sensitive and accurate, and can be applied for daily monitoring of 5-nitroimidazoles and their metabolites in eggs.

A gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (GC-APCI-MS/MS) method was established for the determination of the residues of eight amide herbicides (alachlor, acetochlor, propichlor, butachlor, dichlorochlor, pyrazolam, dimethochlor and metolachlor) in animal-derived foods. The sample pretreatment process involved acetonitrile extraction and enhanced matrix removal (EMR)-lipid cleanup, and ethyl acetate was used to dilute the purified acetonitrile extract instead of solvent conversion. The detection was performed with APCI in the positive ion mode using multi-reaction monitoring (MRM). The results showed that the average recoveries of the eight amide herbicides in spiked pork, pig liver, egg and milk matrices were 63.3%–108%, with relative standard deviation (RSD) 2.51%–13.8%. The limit of detection (LOD) was 0.029–1.3 µg/kg, the limit of quantitation (LOQ) was 0.095–4.2 µg/kg, and the matrix effect was −11%–12%. This method can effectively reduce the matrix effect, and is simple, efficient, accurate, sensitive, and suitable for the rapid quantitative determination of the eight amide herbicides in animal-derived foods.