In this study, a method for the simultaneous detection of 5-hydroxymethyl-2-furfural (HMF), 5-methyl furfural (MF) and furfural (FF) was established by ultra-high performance liquid chromatography (UPLC) after enrichment of furfurals in the acid hydrolysate of dextran by solid phase extraction (SPE) using a hydrophilic-lipophilic balance (HLB) column. The effect of different degrees of acid hydrolysis of dextran on the production of HMF, MF and FF was analyzed. The results showed that the proposed UPLC method was rapid, accurate and sensitive. Under incomplete acid hydrolysis conditions (0.5 mol/L H2SO4, 60 ℃), the recovery of monosaccharides from dextran was low and the three furfural compounds were undetectable in the hydrolysate. Under the optimal hydrolysis conditions (2 mol/L H2SO4, 100 ℃), the content of monosaccharides in dextran hydrolysate increased, the formation rate and content of HMF increased significantly, and FF was detected; however, the formation rate and content of FF were lower than those of HMF. Under excessive hydrolysis conditions (4 mol/L H2SO4, 120 ℃), the recovery of monosaccharides was lower than that under the optimal hydrolysis conditions. Meanwhile, the contents of HMF and FF were higher, and MF was not detected during the whole hydrolysis process. The above results show that during the hydrolysis of dextran, the yield of furfural compounds is closely related to the monosaccharide content in the hydrolysate. In addition, more vigorous acid hydrolysis conditions will promote the formation of HMF and FF in dextran hydrolysate, HMF being the easiest to form, followed by FF. The formation of MF requires more vigorous catalytic conditions.

To overcome the limitations of the oral limitations of capsaicin, this study prepared a thiolated chitosan-zein nanoparticle delivery system loaded with capsaicin. The preparation process was optimized based on particle size and loading capacity, and the efficiency of encapsulation was verified by fluorescence spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The stability and release properties of the capsaicin-loaded nanoparticles were also evaluated during in vitro digestion. The results showed that at a thiolated chitosan to zein to capsaicin of 10:10:1, the particle size of the nanoparticles, which were observed to be regular spherical in shape, was (76.05 ± 1.06) nm, and the loading capacity was (36.85 ± 1.22) μg/mg. The nanoparticles were formed through hydrogen bonds and hydrophobic interactions. In addition, the nanoparticles had good pH stability and ionic strength stability, which could effectively delay the release of capsaicin during simulated digestion in vitro, and the release ratio after 4 h digestion was only (40.08 ± 4.28)%. The nanoparticles can be used for oral delivery of capsaicin.

In this study, the effects of different mass fractions of whey protein isolate (WPI) on the physicochemical properties, physical stability, rheological properties and microstructure of Antarctic krill oil (AKO, 30%, m/m)-in-water emulsion were compared and analyzed. The results showed that the mean particle size and zeta potential of AKO emulsion without WPI were 516.67 nm and −14.03 mV, respectively. As the mass fraction of WPI increased from 0% to 6%, the mean particle size of the emulsion decreased by 42.28% (P < 0.05), and the absolute value of zeta potential significantly increased by 18.05% (P < 0.05). The physical stability of the emulsion was obviously improved. Shear rheological test showed that the apparent viscosity of the emulsion increased with an increase in WPI mass fraction. Microrheological test showed that the introduction of WPI in the emulsion system slowed down the droplet movement speed, increased the elastic behavior, and decreased the fluidity. The microstructure observation showed that WPI addition caused the emulsion to form a more complete and uniform network structure, binding more lipid droplets to maintain the stability of the emulsion. The excessive addition (greater than 6%) of WPI caused the flocculation of the emulsion, thereby weakening its stability. Therefore, the addition of appropriate amounts of WPI can effectively improve the stability of AKO emulsion by reducing the particle size, increasing the charge repulsion force of lipid droplets, and enhancing the viscoelasticity and protein network structure binding. This study is expected to provide guidance for constructing high-load and high-stability AKO emulsion system and broadening its application in health foods.

In this study, the effects of soybean oil addition (1%, 3%, 5% and 7%) on the structure of surimi gels during freeze-thaw were investigated, and the first-order Ogden model was used to describe the relationship between the true stress and the true strain of surimi gels with different mass fractions of soybean oil under large compression deformation (stretch ratio of 0.4–1). The results showed that the addition of soybean oil to fresh surimi reduced the gel strength and enlarged the pores of the gel network. It was found that the addition of 5% and 7% soybean oil had a protective effect on the gel network structure of surimi after six freeze-thaw cycles. The gel strength of surimi with 5% and 7% soybean oil (319.30 and 338.64 g · cm, respectively) was significantly higher (P < 0.05) than that (286.04 g · cm) of the control group (without soybean oil), and the gel network structure was more complete than that of the latter. The Ogden model was fitted well to the true stress-strain compression response curves of fresh and freeze-thawed surimi gels with the addition of soybean oil (R2 = 0.916–0.998). The model fitting results showed that the initial shear modulus changes of fresh and freeze-thawed surimi gels were consistent with the gel strength results. This study suggested that the addition of soybean oil at 5% and 7% can reduce the damage caused to the surimi gel structure by freeze-thaw cycles. The Ogden model can well describe the effect of soybean oil addition on the large deformation behavior of fresh and frozen-thawed surimi gels. These findings may provide theoretical and technical support for the quality improvement of surimi products and the control of transportation and storage conditions.

This study addressed the effect of polysaccharide hydrocolloids on the crust characteristics and oil penetration of fried battered and breaded fish nuggets (BBFNs). Fish pieces were battered with a mixture of wheat starch (WS) and wheat gluten (WG) at a ratio of 11:1 (m/m) added with 0.3% sodium carboxymethyl cellulose (CMC-Na), 0.2% guar gum (GG), or 0.2% xanthan gum (XG), breaded, and fried at 170 ℃ for 40 s followed by 190 ℃ for 30 s. The fluorescence intensity, surface hydrophobicity (H0), sulfydryl and disulfide bond contents, and secondary structure of WG and the crystal structure of WS in the crust were determined, and the oil penetration in the crust was evaluated. Results showed that the H0, fluorescence intensity, disulfide bond content, relative contents of β-sheet and β-turn in the crusts with the three polysaccharide hydrocolloids were greater than those in the control (without the addition of any polysaccharide hydrocolloids), while the free sulfydryl content and the relative contents of α-helix and random coil of WG, and the relative crystallinity of WS were lower than those in the control. The H0, fluorescence intensity, sulfydryl content and relative α-helix content of WG and the relative crystallinity of WS were lowest for the crust with XG, followed by CMC-Na and GG, while an opposite trend was observed for the disulfide bond content and relative β-sheet content. Furthermore, Sudan red staining area was largest for the control, and smallest for fried BBFNs with XG (present only in the crust), followed by CMC-Na and GG. These results indicated that due to their high hydrophilicity and unique structures, the three polysaccharide hydrocolloids can interact with WG to improve the stability of the crust, thereby inhibiting the oil penetration of fried BBFNs.

In an effort to elucidate the effect of protein oxidation on its water-holding capacity (WHC), yak muscle was treated in a Fenton oxidation system containing 0.1 mol/L NaCl at pH 5.0 or 8.0. The results showed that the contents of malondialdehyde (MDA) and carbonyl groups overall increased with increasing concentration of H2O2 in the Fenton system, and the total sulfhydryl content decreased, which reflects an increase in the degree of oxidation. The contents of MDA and total sulfhydryl groups were higher at pH 5.0 than that at pH 8.0. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) displayed that the oxidation induced backbone breakage and covalent cross-linking by disulfide or non-disulphide bonds of myofibrillar proteins. As a result, the space between muscle structures was reduced and the WHC decreased, which was manifested by an increase in centrifugation loss and cooking loss. Transverse relaxation times (T2) from low-field nuclear magnetic resonance (NMR) and microstructure analysis by scanning electron microscopy (SEM) demonstrated that as the degree of oxidation increased, the content of immobilized water decreased, the content of free water increased, and the microstructure was damaged, causing water loss from the muscle. Under the same oxidation conditions, the centrifugation loss, cooking loss and free water content were lower at pH 8.0 than at pH 5.0, which illustrated that yak muscle had higher WHC at pH 8.0.

Lotus seed protein isolate (LSPI) was used as emulsifier to prepare high internal phase (high load) β-carotene-loaded emulsion (LSPI-BC). The stability and β-carotene retention rate of LSPI-BC were measured, and the mechanism of the changes in LSPI-BC at different stages of in vitro digestion was investigated. The results showed that LSPI-BC had long-term stability at low temperature (4 ℃), and the retention rate of β-carotene was over 85%. However, the stability and β-carotene retention rate of LSPI-BC decreased significantly when the temperature was above 25 ℃. High temperature treatment caused LSPI to unfold and expose hydrophobic groups, forming a spatial network structure that imparts LSPI-BC with good thermal stability and protects the β-carotene from further degradation. In the in vitro digestion experiment, salivary mucin and high concentrations of ions in the oral digestive fluid decreased the magnitude of surface charge on the droplets and then affected the stability of the emulsion. In the gastric phase, flocculation or fusion occurred due to the effect of pH, the potential changed from negative to positive, and the protein aggregates dispersed. In the intestinal phase, the droplet size decreased obviously and the absolute value of potential increased. After hydrolysis, the 1,1-diphenyl-2-picylhydrazyl (DPPH) radical scavenging ability increased significantly. In addition, free fatty acids were released gradually during simulated digestion, and the amount of free fatty acids released increased obviously in the first 30 min of digestion, and then reached 61.94% at 60 min, indicating that LSPI was more suitable for encapsulating active substances. The encapsulated active substance remained stable in acidic medium, its release was delayed during in vitro digestion and its bioavailability was increased to 58.51%. This study may provide a theoretical basis for the development and utilization of LSPI for high loading and sustained release of lipid-soluble active substances.

This study compared the differences in the proximate nutritional quality, organic acid components and structural characteristics of South China 9 (SC9) cassava flour before and after fermentation by five strains. The results showed that fermentation by Saccharomyces cerevisiae significantly increased the protein content of cassava flour to 0.83 g/100 g (P < 0.05), which was 2.2 times higher than that of the control group. However, the cyanide content was significantly reduced by Schwanniomyces occidentalis Klöcker fermentation (P < 0.05), and the degradation rate was 91.82%. After fermentation by Bacillus subtilis, the total content of organic acids was the highest, 10.987 mg/g. In addition, the yield of crude polysaccharide was 1.59% and significantly higher than that of the control group (P < 0.05). The peak viscosity, trough viscosity and final viscosity of cassava flour fermented by B. subtilis were 5 397.5, 3 439.0 and 4 770.0 mPa·s, respectively, and significantly higher than those of the control group (P < 0.05), and the breakdown value was 1 958.5 mPa·s and significantly lower than that of the control group (P < 0.05). The analysis of structural characteristics showed that the size of cassava starch granules became more uniform and significantly smaller after fermentation. Collectively, these findings suggest that fermentation by B. subtilis is beneficial to improve the nutritional quality of cassava flour in terms of fat, organic acid and crude polysaccharide and its processing characteristics.

In order to reduce the content of saturated fat in emulsified sausage, the effects of using flaxseed gum-linseed oil (FG-LO) emulsion to replace pork backfat at different proportions (25%, 50%, 75% and 100%) on the color, cooking loss, emulsion stability, texture, moisture distribution, lipid oxidation, microstructure and sensory quality of emulsified sausage were investigated. The emulsified sausage without fat replacement was used as control. The brightness (L* value) increased significantly (P < 0.05), and the redness (a* value) decreased significantly (P < 0.05) in the fat replacement groups when compared with the control group; however, the yellowness (b* value) did not significantly change (P > 0.05), and there was no obvious difference in the color observed by the naked eye. The lowest cooking loss and water loss were observed at replacement proportions of 100% and 75%, respectively, while the fat loss had no significant changes at different replacement proportions (P > 0.05). As the replacement level of fat increased, the hardness decreased gradually and the texture became soft, indicating that fat replacement improved the texture of emulsified sausage. After adding FG-LO emulsion, emulsified sausage exhibited the conversion of free water to immobilized water, indicating that FG could interact with meat proteins to form a three-dimensional network structure to lock water molecules, thus enhancing the water-holding capacity. The extent of lipid oxidation was enhanced by the addition of FG-LO emulsion. The results of scanning electron microscopy (SEM) showed that the microstructure of the emulsified sausage with a replacement level of 25% was the most uniform and exquisite, with smaller pores. The sensory evaluation results showed that only the 100% replacement group was significantly different from the control group in terms of texture and overall acceptability (P < 0.05). The results of principal component analysis (PCA) showed that the emulsified sausage with 25% fat replacement was the most similar to the control group. Collectively, 75% fat replacement could reduce the cooking loss, increase the water-holding capacity (WHC), and result in the best emulsion stability and softer texture without causing any significant difference in the sensory quality of emulsified sausage.

The effect of addition of mixtures of exopolysaccharide (EPS) from Lactobacillus plantarum JLAU103 with fish gelatin (FG) in different proportions to low-fat yogurt on its quality characteristics was investigated. The results showed that adding 0.1% (m/m) EPS and 0.6% (m/m) FG improved the water retention and pH of low-fat yogurt, reduced the titration acidity, and resulted in viscosity similar to whole-fat yogurt. Addition of EPS and FG made the network structure of low-fat yogurt more compact, reducing the voids in it. The viable bacterial count of low-fat yogurt was significantly increased to 8.40 × 108 CFU/mL after addition of 0.6% FG and 0.1% EPS (P < 0.05). The contents of characteristic volatile flavor substances such as diacetyl, 2-nononone and 2,3-glutaredione increased significantly, the sensory score increased, and the texture was significantly improved. The rheological results showed that addition of EPS reduced the thixotropic loop area of low-fat yogurt, enhanced the stability and total strain, and caused low-fat yogurt to form a more solid gel network. Therefore, L. plantarum JLAU103 EPS combined with FG can significantly improve the quality of low-fat yogurt, and has a good application prospect.

In this study, the effect of three self-assembly sequences on the structural properties, three-dimensional (3D) printing characteristics, storage stability and freeze-thaw stability of high internal phase Pickering emulsions (HIPPEs) stabilized by ternary aggregates of lactoferrin, epigallocatechin-3-gallate (EGCG) and low methoxylated pectin was evaluated. The results showed that self-assembly sequence directly affected the ability of ternary aggregates to stabilize HIPPEs. The particle sizes of the ternary aggregates were between 1.7 and 2.9 μm, and they showed different network structures and surface wettabilities (between 55.62° and 68.15°). Optical microrheology and texture analysis showed that the decreasing order of the viscoelasticity, hardness, adhesiveness and chewiness of HIPPEs was lactoferrin-EGCG-low methoxylated pectin > lactoferrin-low methoxylated pectin-EGCG > low methoxylated pectin-EGCG-lactoferrin. The HIPPE stabilized by lactoferrin-EGCG-low methoxylated pectin was solid-like and more suitable for 3D printing. The microstructure showed that these HIPPEs were oil-in-water Pickering emulsions. It is particularly noteworthy that the HIPPE stabilized by lactoferrin-EGCG-low methoxylated pectin showed excellent long-term storage stability and freeze-thaw stability, which is of great significance for its potential application in cold chain logistics. In conclusion, when using ternary complexes to stabilize HIPPEs, self-assembly sequence is an important factor that cannot be ignored.

The effects of adding different levels (0.01%, 0.05% and 0.10%) of banana flower extract (BFE) versus dibutylated hydroxy toluene (BHT) on protein oxidation in naturally fermented yak meat sausages were investigated. lys The carbonyl content, Schiff base content, total sulfhydryl content, active sulfhydryl content, surface hydrophobicity, dimeric tyrosine content, endogenous fluorescence intensity and solubility of myofibrillar proteins (MPs) from fermented yak meat sausage were measured at different fermentation times, and the secondary structure and composition of MPs were characterized by Fourier transform infrared (FTIR) spectroscopy, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that compared with the blank control, the addition of BFE decreased the carbonyl group content, Schiff base content, surface hydrophobicity, dimeric tyrosine content and endogenous tryptophan fluorescence intensity of MPs, and increased the total sulfhydryl group content, active sulfhydryl group content and solubility. FTIR spectroscopy showed that the addition of BFE improved the reveal the more stability of the secondary structure of MPs. SDS-PAGE showed that BFE reduced the diffusion of myosin heavy chain and had a protective effect on myosin. This study showed that BFE inhibited protein oxidation in naturally fermented yak sausage, and this effect was positively correlated with BFE concentration, being most pronounced at 0.10% BFE concentration.

This work investigated the feasibility of partially replacing minced pork with frozen-thawed konjac glucomannan (KGM)-zein composite gels. The effects of adding different levels (20%, 40%, 60%, and 80%) of frozen-thawed composite gels with different ratios between KGM and zein (8:1, 2:1, 1:2, and 1:8) to minced pork on its color, texture properties, and water-holding capacity (WHC) were studied. The results showed that the color, hardness, and springiness of minced pork with 20% frozen-thawed composite gels were not significantly different from those of pure minced pork, and the addition of frozen-thawed composite gels significantly enhanced the WHC. Changing the ratio of KGM to zein had no significant effect on the hardness, springiness or WHC of minced pork with 20% frozen-thawed composite gels. Therefore, the frozen-thawed composite gels have potential to partially replace minced pork in the preparation of low-fat meat products.

In this study, six lipase-producing strains from food sources were screened for their ability to produce lipase. Among them, Staphylococcus epidermidis N30 and Yarrowia lipolytica C11 demonstrated high enzyme activities of 1.07 and 0.84 U/mL, respectively. They had the following enzymatic properties: optimum reaction temperature of 50 ℃ and pH of 8.0. The optimum substrate for S. epidermidis N30 was C4 ester, while that for Y. lipolytica C11 was C8 ester. The inoculation of sour meat with S. epidermidis N30 or Y. lipolytica C11 effectively enhanced the production of flavor substances, especially ethyl butyrate, ethyl caproate, ethyl caprylate, ethyl caprate, nonanal and 1-octen-3-ol, thus promoting the production of fruity, floral, wine-like, mushroom-like and fatty aromas in sour meat.

In this study, the survival of the main serotypes O157:H7 and O26:H11 of Shiga toxin-producing Escherichia coli (STEC) inoculated in fermented sausage during processing was investigated, and the changes of virulence gene expression in the bacteria and the product at different production stages were analyzed by reverse transcription real-time polymerase chain reaction (RT-real-time PCR). The results showed that there was no significant difference in the count of lactic acid bacteria, lactic acid content, pH, or water activity (aw) value between STEC inoculated and uninoculated groups at most production stages. During sausage production, the growth of E. coli O157:H7 and O26:H11 was inhibited significantly (P < 0.05) and decreased by 1.51 and 1.39 (lg (CFU/g)), respectively, but the two strains showed different inhibition processes. After eliminating the difference in bacterial counts, it was found that the virulence gene expression in the bacterial cells was significantly up-regulated (P < 0.05) at the late stage of production. The expression of most virulence genes per unit mass of sausage increased significantly (P < 0.05) at the early stage of fermentation, and all virulence genes were highly expressed in the final product. Therefore, although STEC could be inhibited effectively during fermented sausage production, virulence gene expression was enhanced in the bacterial cells and was at a high level in the final product.

Strains K2, Z7-1 and Z8-4, all of which could produce compounds that contribute to pleasant floral and fruity aromas, were isolated from kefir grains collected from Kumming, Yunnan. Based on genome resequencing, the genome similarity of the strains to Geotrichum candidum LMA-244 was analyzed, showing that the DNA-DNA hybridization values were 99.50%, 99.40% and 99.50%, and the average nucleotide identity was 98.66%, 98.65% and 98.68%, respectively. Based on morphological characteristics and 26S rDNA sequence homology analysis, all the strains were identified as G. candidum. Gene function annotation of G. candidum K2 was carried out using the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and Cluster of Orthologous Group (COG) databases. The results showed that 40.74% of the annotated genes were associated with cellular components, 47.54% with biological processes and 11.73% with molecular functions. KEGG metabolic pathway analysis revealed the presence of genes and pathways related to terpenoid biosynthesis, indicating that G. candidum K2 has the genetic basis for the synthesis of volatile aroma components. By gas chromatography-mass spectrometry (GC-MS), a total of 50 volatile components were detected in the fermentation broth of G. candidum K2. Among them, 3-alkene, α-pinene and p-cymene contributed to the floral aroma, L-α-terpineol was responsible for the pine-like aroma, terpinen-4-ol and (-)-terpinen-4-ol was responsible for the clove-like aroma, and α-terpineol acetate contributed to the fresh and sweet aroma. Therefore, it was inferred that G. candidum greatly contributes to the formation of aroma substances in kefir grains. This study may provide a theoretical basis for the application of G. candidum K2 in fermented dairy products and other fermented foods.

In this study, fermented hot pepper products were prepared using Kluyveromyces lactis Km and Lactobacillus plantarum QB3 singly and in combination. The physicochemical analysis showed that fermented hot peppers inoculated with QB3 consumed the most reducing sugar, resulting in the fastest drop of pH of the fermentation broth, and an increase in the contents of short-chain fatty acids and vitamin A by 62.5% and 13.8%, respectively. QB3 grew dominantly in fermented hot peppers, reducing the α-diversity of microorganisms. A total of 73 volatile compounds were detected in fermented hot peppers, 46 of which may contribute to the flavor. Correlation analysis showed that 148 species of microorganisms may be involved in the synthesis of 71 compounds, and L. plantarum and K. lactis may be involved in the synthesis of 26 volatile compounds. K. lactis was key to the formation of flavor compounds, and the synthesis of most volatile compounds was negatively correlated with L. plantarum. This study may provide a theoretical basis and technical support for the preparation of fermented hot pepper products with various flavors by inoculating lactic acid bacteria and yeast, and provide a reference for the flavor diversification of fermented food.

Objective: To understand the relationship between the genetic characteristics and the biofilm formation capability of typical strains of Listeria monocytogenes from fresh livestock and poultry meat in order to provide a basis for the precise control of bacteria in foods. Methods: Ten isolates of L. monocytogenes belonging to eight sequence types (ST) were selected for whole genome sequencing, gene functional annotation, virulence factor identification, analysis of mobile genetic elements (prophage, genome island and plasmid), evolutionary analysis and, identification of genes related to biofilm formation. The biofilm formation capability of these strains was determined by crystal violet staining, and its correlation with their genomic characteristics was analyzed. Results: The virulence islands LIPI-1, LIPI-2 and more than 19 another virulence genes, as well as different numbers of prophages and genome islands, were identified in the genomes of the eight STs. The LIPI-3 genes were only identified in the ST3 isolates, and plasmids were identified in the ST8 and ST1403 isolates. Evolutionary branching coefficients showed that five STs were closely related to the outbreak strains in the database. In addition, the luxS and sigB genes related to biofilm formation were mutated or deleted in six and seven STs, respectively. The ST1403 and ST87 isolates had a stronger ability to form biofilm, while the ST1402 isolates had the weakest biofilm formation capacity. Conclusion: Fresh livestock and poultry meat contains a variety of L. monocytogenes with pathogenic potential and carrying mobile genetic elements may be related to the biofilm formation capability.

Clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9’s main element Cas9 protein is generally expressed by Escherichia coli, but in the process of expression and purification, Cas9 protein is prone to problems such as the formation of insoluble inclusion bodies, high endotoxin content, incorrect protein folding due to too large protein molecules, and low yield. This study aimed to achieve efficient soluble expression of Streptococcus pyogenes Cas9 (SpCas9) protein in E. coli for the purpose of promoting its application and popularizing gene editing technology. The solubility-enhancing tag GB1 was applied to improve the expression level and solubility of Cas9 protein, and a multiple promoter strategy was used to further improve the expression level of Cas9 protein. As a result, the expression of Cas9 protein was increased by 3.52 times. In vitro enzymatic digestion analysis showed that the functional activity of Cas9 protein was not affected by fusion with GB1. Furthermore, a ribonucleoprotein (RNP) complex was assembled and transformed into the host Aspergillus niger, so that the pyrG gene was successfully destroyed.

This study compared the differences in the growth and metabolism of Clostridium celerecrescens JSJ-1, a strain able to produce caproic acid, and Clostridium tyrobutyricum D-1, a stain able to produce butyric acid, when cultured separately or co-cultured in different systems (solid medium, and liquid medium with or without use of dialysis bag). Furthermore, this study investigated the effect and mechanism of co-culture with C. tyrobutyricum on caproic acid metabolism in caproic acid-producing bacteria by culturing JSJ-1 alone in the presence of butyric acid or sodium butyrate at different concentrations. The results showed that when co-cultured on a composite solid medium containing glucose in anaerobic conditions at 34 ℃, D-1 grew better than JSJ-1, and could preferentially utilize glucose for growth. The generation time of caproic acid was three days earlier when D-1 and JSJ-1 were co-cultured in a liquid medium than when JSJ-1 was cultured alone under the same conditions, and the concentration of caproic acid was 9.93 and 9.79 g/L on the 12th day in the two cases, respectively. Glucose had a strong inhibitory effect on the production of caproic acid by JSJ-1, which could be relieved by preferential utilization of by D-1 upon co-culture. The co-culture in the liquid medium with and without use of dialysis bag were compared, revealing that whether there was direct contact between JSJ-1 and D-1 had no effect on the yield of caproic acid. By purely culturing JSJ-1 in the presence of butyric acid or sodium butyrate, it was found that butyric acid generated by D-1 at pH 6–6.5 could promote the synthesis of caproic acid by JSJ-1. During co-culture, the preferential utilization of glucose by D-1 could relieve the inhibitory effect of glucose on the production of caproic acid, and butyric acid produced by D-1 could promote the synthesis of caproic acid.

In order to improve the ability to produce ethyl acetate, Nakazawaea ishiwadae GDMCC 60786 was mutagenized by atmospheric and room-temperature plasma (ARTP), ethyl methanesulfonate (EMS) and nitrosoguanidine (NTG). The mutants were sequentially screened by using a plate medium containing tributyrin, shake flask fermentation and addition of substrate. The genetic stability, hemolytic activity and in vitro drug resistance of the selected mutant were evaluated. Mutant N5, which was found to be able to produce a high yield of ethyl acetate, had good genetic stability and in vitro safety. After five successive passages, the average production of ethyl acetate was 764.54 mg/L, and the glucose conversion rate was 38.22%, which were 2.90 times and 25.03% higher than those observed with the original strain, respectively. When ethanol was used as a supplementary carbon source, the yield of ethyl acetate was 1 426.81 mg/L; however, upon the addition of acetic acid, N5 did not grow and lost the ability to produce esters, indicating that the strain was more tolerant to ethanol than acetic acid. Meanwhile, the activities of esterase, acetyl-CoA and alcohol acyltransferase in N5 cells were measured to reach a maximum value after 24 h. In summary, this study successfully constructed a set of suitable mutagenesis system for this strain.

An extraction and purification method for soluble polyphenol oxidase (sPPO) and membrane-bound polyphenol oxidases (mPPO) from Agaricus bisporus was developed involving temperature-induced phase partitioning, fractional precipitation with ammonium sulfate, and DEAE anion exchange chromatography. The purity, molecular mass and enzymatic reaction kinetics of purified PPO were investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Native-PAGE and Michaelis-Menten equation. The specific activities of sPPO and mPPO toward catechol were 6 912.88 and 19 092.94 U/mg, and increased by 12.20 and 10.86 times, respectively, compared with that of crude PPO. The results of enzymatic reaction kinetics showed that the catalytic activities of sPPO and mPPO toward different substrates were greatly different and were higher toward catechol. mPPO had a stronger affinity to the substrate catechol and a higher reaction rate than sPPO. The optimum pH and temperature for both PPO enzymes were 6.8 and 30 ℃, respectively. This study may lay a foundation for future research on mass spectrometry identification and enzymatic properties two forms of PPOs from A. bisporu and inhibition of enzymatic browning caused by PPO.

This study aimed to investigate the efficient expression of the xylanase gene Pthxyn of Pseudothermotoga thermarum and its application in beer brewing. The recombinant plasmid pET-20b-pthxyn was constructed and expressed in Escherichia coli. Pthxyn was purified. The molecular mass of the recombinant xylanase was 130 kDa, and the optimum reaction pH and temperature were 5.5 and 95 ℃, respectively. It retained 80% and 83% of its activity after incubation at pH 5.0–8.0 for 2 h, and at 75 ℃ for 1 h, respectively. In the saccharification stage of beer brewing, the recombinant xylanase was added to the reaction system consisting of barley or wheat as raw material at 65 ℃, and the products xylose and glucose were detected by high performance liquid chromatography (HPLC). The results showed that when barley was used as raw material, the xylose content increased from 0.017 to 1.25 g/L, and the glucose content increased from 20 to 36.57 g/L. When wheat was used as the raw material, xylose increased from 0.003 g/L to 0.708 g/L, and the glucose content increased from 21.9 g/L to 36.63 g/L. In summary, the recombinant xylanase is tolerant to a wide range of pH and stable to heat treatment, and can synergize with endogenous enzymes to improve its catalytic efficiency in the saccharification stage of beer brewing, making it have good prospects in beer brewing.

Ripened Pu’er tea was made from the sun-dried leave of large-leaf tea (Camellia sinensis (Linn.) var. assamica (Masters) Kitamura) by natural fermentation, pure culture fermentation with Rhizopus arrhizus, or mixed culture fermentation with Saccharomyces cerevisiae, R. arrhizus and Aspergillus niger in proportions of 2:1:2, 2:2:2 and 2:3:2. The composition and content of aroma substances in Pu’er tea were analyzed by simultaneous distillation extraction (SDE) coupled with gas chromatography-mass spectrometry (GC-MS). The results showed that there were significant differences in the types and relative contents of aroma substances among all tea samples. The relative contents of terpenols in the three co-fermented Pu’er tea samples were higher than that in the naturally or R. arrhizus fermented ones, and had unique flowery, fruity and caramel-like aromas. The relative content of alcohols in the co-fermented Pu’er tea with yeast, R. arrhizus and A. niger in a ratio of 2:1:2 was 47.32%, which was significantly higher than that in the other samples (P < 0.05). The relative content of methoxybenzene in Pu’er tea obtained by natural fermentation and pure culture fermentation, having an aged aroma, were higher than that obtained by the three collaborative fermentation methods. The relative content of methoxybenzene in Pu’er tea fermented with pure R. arrhizus was as high as 31.24%, which was significantly higher than that obtained by the other fermentation methods (P < 0.05). Therefore, co-fermentation with beneficial microorganisms can improve the quality of Pu’er tea and endow it with unique flowery and fruity aromas.

The purpose of this study is to select lactic acid bacteria with a strong ability to inhibit oral pathogens, high safety and strong oral colonization capacity. Firstly, the strains that could inhibit Streptococcus mutans and Streptococcus gordonii were screened from lactic acid bacteria resource bank in the laboratory by Oxford cup diffusion method. The 28 selected strains were evaluated for hemolytic activity. The results showed that seven of the 28 strains showed α-hemolysis while the remaining 21 did not. The antibacterial metabolites of 16 strains without hemolysis and with a diameter of inhibition zone ≥ 10 mm against S. mutans and S. gordonii were determined by neutralization, catalase and protease susceptibility assays. Then seven strains with strong bacteriostatic capacity and the potential to produce non-organic acid antimicrobial metabolites were selected. The safety evaluation results showed that all seven strains had low acid production ability and caused low corrosion to teeth. The highest tolerable concentration of lysozyme for strain JZ14-1 was 1.6 mg/mL, while that for the other six strains was 1.2 mg/mL, indicating that all seven strains could tolerate lysozyme. Strain HB13-2 was most susceptible to antibiotics. The oral colonization capacity evaluation of strain HB13-2 showed the following results: the highest hydrophobicity of 44.00%, surface acid charge of 20.16%, surface base charge of 49.44%, and content of exopolysaccharides of 0.283 mg/mL. This strain could easily colonize in oral cavity and had low biofilm formation capacity and good self-aggregation capacity, and the maximum inhibition percentage against S. mutans biofilm was 59.72%. Moreover, strain HB13-2 had strong copolymerization capacity with S. mutans, and the copolymerization capacity was 67.40% at 24 h. In conclusion, strain HB13-2 has good antibacterial activity, high safety and strong oral colonization capacity. It is identified as Lactiplantibacillus plantarum by 16S rDNA sequencing.

Three walnut peptides with different molecular masses were prepared from walnut meal protein by sequential enzymatic hydrolysis and ultrafiltration, and separately glycosylated with five sugars (glucose, sucrose, lactose, maltodextrin and dextran). The reaction conditions were optimized based on emulsifying properties and anti-lipid oxidation capacity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared (FTIR) spectroscopy and circular dichroism (CD) spectroscopy were used to characterize the glycosylated peptides, their physicochemical properties were studied, and their emulsion stability was determined by laser confocal microscopy (LCM). The results showed that the optimal conditions for the glycosylation reaction between walnut peptide with molecular mass greater than 30 kDa and maltodextrin were as follows: ratio of walnut peptide to maltodextrin 1:2, reaction time 8 h, reaction temperature 80 ℃, and peptide concentration 15 mg/mL. SDS-PAGE confirmed the formation of a covalent complex between the walnut peptide and maltodextrin through glycosylation reaction. FTIR spectroscopy showed that sugar molecules were connected to walnut peptide molecules by covalent bonds. CD spectroscopy showed that the peptide’s structure changed. The proportion of α-helix increased from 4.85% to 6.43%, the proportion of antiparallelism increased from 30.16% to 35.91%, the proportion of parallelism increased from 3.28% to 4.33%, the proportion of β-turn decreased from 23.21% to 20.77%, and the proportion of random coil decreased from 33.59% to 31.22%. The glycosylation modification did not improve the Fe2+ chelating capacity, but increased the solubility, emulsifying capacity to (83.24 ± 1.64) m2/g, emulsion stability to (218.49 ± 3.55) min, water absorption capacity to (3.92 ± 0.36) g/g, oil absorption capacity to (3.17 ± 0.24) g/g, surface hydrophobicity to 251.05 ± 6.91, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacity to (86.74 ± 2.14)%, and anti-lipid oxidation capacity to (62.17 ± 3.51)%. The results of LCM showed that the encapsulation capacity of walnut peptides for walnut oil was enhanced after glycosylation, suggesting a potential application for improving the stability of emulsions. The glycosylation modification of walnut peptides provides a new idea for the processing and utilization of walnut meal by-products and provides a reference for the application of glycosylation modification in food development.

A filamentous fungus producing polygalacturonase (29.2 U/mL) was isolated from orchard soil in northern Guangxi, and identified as Trichoderma koningiopsis. Using polygalacturonic acid as the substrate, the optimum reaction temperature of the enzyme was 50 ℃, and it maintained more than 70% of the maximum activity at 50 ℃ for 1 h, which was identified as a medium-high temperature tolerant enzyme. The enzyme had unique weakly acidic catalytic characteristics. The optimum reaction pH was 5.0, and it retained 73% of its maximum activity at pH 6.0, and was tolerant to pH 2.5–8.0. Zn2+ partially activated the enzyme activity, while Mn2+ inhibited the enzyme. It could depectinize five weakly acid fruit pulps (papaya, banana, banana, and white- and red-fleshed pitaya) but to different extents. The yield of juice of banana pulp increased by 24.4%, the viscosity of papaya pulp decreased by 82.5%, and the transmittance of red-fleshed pitaya pulp increased by 31.9%, indicating good depectinization efficiency for the three fruits. The polygalacturonase-producing strain has good prospects for its application in juice production from tropical and subtropical perishable fruits.

In this study, the antihypertensive peptide WQVLPNAVPAK was selected for the synthesis of the gene encoding the hexameric peptide angiotensin I-converting enzyme inhibitory peptide (ACEIP) based on the codon preference of Escherichia coli. The synthetic gene was cloned into the expression vector pET30a to construct recombinant plasmid pET30a-ACEIP. The recombinant plasmid was identified by double digestion with restriction endonucleases NdeI and HindIII and polymerase chain reaction (PCR), and transformed into competent E. coli BL21 (DE3) cells to construct the expression system E. coli BL21(DE3)/pET30a-ACEIP, which was induced with isopropyl-β-D-thiogalactopyranoside (IPTG) at a final concentration of 0.8 mmol/L. A clear band of 8.7 kDa was seen on Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The hexameric peptide ACEIP was purified by Ni2+ affinity chromatography and the expression of the fusion protein was 61.30 mg/L. The expression of ACEIP was 57.84 mg/L. The half-maximal inhibitory concentration (IC50) of the hexameric peptide was 6.39 mg/mL after trypsin digestion, whose ACE inhibitory activity was higher than that of the monomeric peptide WQVLPNAVPAK (IC50 of 12.34 mg/mL).

To clarify the taste differences between surimi products from different fish species and establish a taste fingerprint of surimi products, three species of marine fish (hairtail, red sea snapper, and golden thread) and three species of freshwater fish (silver carp, grass carp, and black carp) were used to produce surimi gels. The taste profiles of the gels were analyzed by an electronic tongue, high performance liquid chromatography and gas chromatography, and a taste fingerprint of surimi was established by significance analysis of microarray (SAM), cluster analysis, and heatmap analysis. The results showed that the taste characteristics of the six surimi products were significantly different. Hairtail surimi contained high levels of glutamate (2.37 mg/100 g) and aspartic acid (1.32 mg/100 g). Golden thread surimi showed the lowest contents of glutamate and aspartic acid. In addition, grass carp surimi contained relatively high contents of proline (tasting sweet) and histidine (tasting bitter). The proportion of polyunsaturated fatty acids in marine surimi was about twice as high as that in freshwater surimi. Among the freshwater surimi products, the proportion of polyunsaturated fatty acids was relatively higher in silver carp surimi. Compared with freshwater surimi, marine fish surimi had a higher content of betaine, inosine 5’-monophosphate (IMP) and guanosine 5’-monophosphate (GMP), and a lower content of hyperxanthine (Hx). Through SAM, a total of 46 differential substances were selected between the six surimi products, and the taste fingerprint constructed based on these differential substances by heatmap analysis could directly reflect the taste differences and major differential substances between freshwater and marine fish surimi.

In order to analyze the aroma characteristics and composition of tolu balsam, tolu balsam extracts prepared with five different concentrations of ethanol were separated by pervaporation. The retentate and permeate were evaluated by sensory evaluation and their volatile and semi volatile components were analyzed by solid-phase supported liquid-liquid extraction coupled with gas chromatography-mass spectrometry (SLE-GC-MS). Chemometrics was adopted to explore the difference in target components and the correlation between sensory properties and components. The results showed that the major aroma characteristics of both retentate and permeate were ointment-like and sweet, followed by resin-like, fruity, fresh, and spicy aromas as well as weak creamy, floral, bean-like, and woody aroma notes. A total of 92 components were identified by GC-MS, with esters and alcohols being the predominant ones, accounting for more than 55% of the total, followed by acids, aldehydes, phenols, others and olefins, together with relatively low levels of ketones. Principal component analysis (PCA) and cluster heatmap analysis indicated that tolu balsam extracts obtained with low and medium ethanol concentrations were distinguished from that obtained with high ethanol concentration, and the contents of the identified compounds were overall higher in the former than in the latter. By orthogonal partial least squares discriminant analysis (OPLS-DA), 43 differential compounds were selected. Partial least square regression (PLSR) showed that the characteristic aroma substances of tolu balsam extracts had significant positive correlation with ointment-like, resin-like, fresh and spicy aromas, but had no significant correlation with sweet, fruity, creamy, floral, bean-like or woody aroma. The results of this study may provide a theoretical basis for research on the sensory quality and fine processing of tolu balsam.

The study aimed to investigate the dynamic changes of metabolites in beef high rib with different dry-aging periods by non-targeted metabolomics based on ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS). Multivariate statistical analysis and metabolic pathway analysis were performed on the metabolites. The results showed that 41 differential metabolites were identified in dry-aged beef, including 21 amino acids, 16 fatty acids, 2 nucleotides and 2 other metabolites. The types and relative contents of differential metabolites increased significantly with prolonged aging time. Five key metabolic pathways were identified, including purine metabolism; fatty acid degradation; alanine, aspartate and glutamate metabolism; arginine and proline metabolism; and the tricarboxylic acid (TCA) cycle, which could promote the formation of flavor and nutrients in dry-aged beef.

Gas chromatography-mass spectrometry (GC-MS) and electronic nose combined with chemometrics were used to analyze the volatile components and overall odor of Osmanthus fragrans extracts from four different varieties. The results showed that a total of 65 volatile components from eight chemical classes were identified, including 28 alcohols, 6 ketones, 4 aldehydes, 4 phenols, 4 acids, 5 alkanes, 8 esters and 6 other substances. Alcohols, ketones and esters were the main volatile components in O. fragrans extracts. Venn diagram and cluster heatmap showed that the types and contents of volatile components in the four O. fragrans extracts were significantly different. By partial least squares discriminant analysis (PLS-DA), nine differential volatile components between these O. fragrans extracts were identified, namely, tetracontane, propanoic acid, 1-cyclohexene-1-propanol, 1-octacosanol, palmitic acid, 9,12-tetradecadien-1-ol, cyclohexanol, 2-butanone, and stigmasterol. The results of electronic nose showed that W2W, W2S, W1W, W1S and W5S were the main sensors to distinguish the odors of different O. fragrans extracts. The overall odors of the four O. fragrans extracts were discriminated well. The volatile components of Liuyang Luteus Group and Liuyang Albus Group extracts were more similar, while those of Xianning Luteus Group and Liuyang Aurantiacus Group extracts were significantly different, which was consistent with the results from GC-MS and cluster analysis. The research findings showed that it was feasible to distinguish O. fragrans extracts from different varieties based on volatile substances.

An automated solid phase extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of 26 endogenous components in chaste, acacia and rape honey. The samples were extracted with phosphate buffer solution, purified by solid-phase extraction using an Oasis HLB cartridge, and separated on an Agilent Eclipse Plus RRHD C18 column (2.1 mm × 100 mm, 1.8 µm) by gradient elution using a mobile phase comprising of 0.03% formic acid in water and acetonitrile. The analytes were detected by using an electrospray ion source in the negative ion mode with dynamic multiple reaction monitoring (dMRM), and quantified by an external standard method. Results showed that good linear relationships were obtained for the 26 analytes in their respective concentration ranges with correlation coefficients (r2) greater than 0.996. The limits of detection (LOD) and quantitation (LOQ) ranged from 1.0 to 10.0 and 2.5 to 25.0 μg/kg, respectively. The average recoveries from spiked samples were between 81.9% and 101%, with relative standard deviations (RSD) of 3.4%–9.8%. The UPLC-MS/MS method has the advantages of rapidity as well as high efficiency and accuracy, which can provide technical support for the quality control and identification of honey.

In this study, the differences in total phenol content and metabolite profile among arabic gum, karaya gum and peach gum were analyzed. The results showed that there was a significant difference in total phenol content among the three gums. Peach gum had the highest total phenol content (19.93 μmol/g), followed by arabic gum (4.06 μmol/g) and karaya gum (1.36 μmol/g). Metabolomics analysis showed that all these gums were rich in small molecular metabolites, such as amino acids, organic acids, flavonoids, and lipids. However, there were significant differences in the species and abundance of small molecular metabolites among the gums, which may be associated with producer species and flowing method. The contents of flavonoids and total phenols in peach gum were significantly higher than those in arabic Gum and karaya gum. In addition, the contents of amino acids and organic acids in karaya gum and arabic gum were significantly higher than those in peach gum. The content of lipids in karaya gum was significantly higher than that in arabic gum and peach gum. The metabolic pathways of differential metabolites among the different gums mainly included the pathways of flavonoid biosynthesis, isoquinoline alkaloid biosynthesis, amino acid synthesis and metabolism, and linoleic acid metabolism. The results from our present study may provide technical support for gum quality analysis and the discovery of its functional components.

Three forms of soluble phenolics, free phenolics (FP), esterified-bound phenolics (EP) and glycoside-bound phenolics (GP), were extracted from Sargassum pallidum, and their chemical composition was identified by ultra-high performance liquid chromatography-quadrupole-time of flight-tandem mass spectrometry (UPLC-QTOF-MS/MS). Their antioxidant and α-glucosidase inhibitory activities in vitro were evaluated. Results demonstrated that the soluble phenolics in S. pallidum mainly existed in a bound form, GP and EP fractions contained the highest contents of total phenolics (68.30 mg/g) and flavonoids (83.49 mg/g), respectively. A total of 22 compounds were identified in the three phenolic fractions, including three simple phenolics, four flavonoids and two phenolic acids. Biological activity tests indicated GP had the highest cellular antioxidant activity (CAA value = 18.18 μmol/g), 1,1-dipheny1-2-picrylhydrazyl (DPPH) radical scavenging activity (IC50 = 84.6 μg/mL) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging activity (IC50 = 127.01 μg/mL), while EP had the strongest oxygen radical absorbance capacity (5 322.85 μmol/g) and α-glucosidase inhibitory activity with IC50 value of 27.09 μg/mL. The hypoglycemic activity of EP was significantly higher than that of acarbose. Inhibition kinetics analysis showed that the inhibition mode of α-glucosidase by the three phenolic fractions was a mixed type. In conclusion, bound phenolics from Sargassum pallidum have excellent antioxidant and α-glucosidase inhibitory activities, which will provide a scientific basis for the development of natural antioxidants and hypoglycemic foods.

Sensory quantitative descriptive analysis (SQDA) was used to analyze the flavor structure of nine samples of three aroma types (Nongxiangxing, Jiang-flavor and Zhima-flavor) of Shanzhuang Laojiu, and the results showed that there were significant differences in flavor and taste attributes among the aroma types. Liquid-liquid extraction coupled with gas chromatography-mass spectrometry (LLE-GC-MS) was used to analyze the composition of volatile compounds in these samples, and a total of 74 volatile flavor compounds were identified at high concentrations, manly including esters, alcohols and acids. Based on their aroma activity values (OAVs), 10 characteristic compounds contributing to the aroma of Shanzhuang Laojiu were identified. Partial least squares (PLS) analysis and correlation analysis were used to study the correlation between the sensory attributes and the characteristic aroma compounds, and the results showed that the Jiang, Qu and empty-cup aromas all had good correlation with acetic acid; ethyl butyrate, ethyl caproate, ethyl octanoate, butyric acid and capric acid were the main flavor compounds responsible for the alcoholic, ester, grain-like, sweet and fruity aromas; and the caramel-like and burnt aromas were highly correlated with ethyl myristate, ethyl oleate, ethyl linoleate and 2,3-butanediol. This study may lay the foundation for future research of the flavor formation mechanism of the three aroma types of baijiu.

In order to investigate the changes of metabolite profile during the fermentation of ‘Golden Flower’ Eucommia ulmoides leaf tea, quantitative, qualitative and differential analyses of small molecule metabolites in tea samples at different fermentation times (0, 2, 4, 6, 8 and 10 days) were carried out using ultra-high performance liquid chromatography-quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS). The results showed that 172 significantly differential metabolites, belonging to 13 chemical classes, were identified during the entire fermentation process, including 46 flavonoids, 44 fatty acids, 16 amino acids and 11 organic acids. Furthermore, by selecting significantly differential metabolites at different fermentation times, it was found that the bioactive substances whose contents significantly increased after fermentation included flavonoids, fatty acids and organic acids. These metabolites played an important role in enhancing the taste and aroma of the tea. After fermentation, the contents of the differential metabolites L-glutamine, 20-hydroxyeicosatetraenoic acid, glucuronic acid, trans-ferulic acid, norvaline and auriculoside increased. The fermented tea had health functions such as antioxidant, hypotensive, detoxicating, anti-inflammatory and immunoenhancing effects compared with the unfermented tea. Therefore, fermentation can significantly alter the metabolite profile of E. ulmoides leaf tea, which plays an important role in the formation of the taste and aroma quality and antioxidants of fermented E. ulmoides leaf tea.

Polysaccharides from Semen Astragali complanati (SACP) were obtained by hot water extraction followed by ethanol precipitation and separated by fractional precipitation with 20% and 25% ethanol into two fractions: SACP-20 and SACP-25, which was the major one with higher purity. Their physicochemical properties were determined by colorimetric methods, and their molecular mass distribution, conformation in solution and monosaccharide composition were analyzed by size exclusion chromatography coupled with muti-angle laser light scattering (SEC-MALLS) and high-performance anion exchange chromatography coupled with pulsed amperometric detection (HPLC-PAD). Results indicated that SACP-25 was a homogenous polysaccharide with total sugar content of 87.40% and was composed of galactose (42.92%) and mannose (57.08%). Meanwhile, it showed a random coil conformation in 0.1 mol/L NaNO3. Analysis by methylation combined with gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy revealed that the main chain of SACP-25 was composed of β-1,4-linked-mannopyranose (Manp) with galactopyranose (Galp) side chains attached to C-6 of the Manp residues. This study indicated that Semen A. complanati is good natural source of galactomannans as a water-soluble dietary fiber. The results of this study may provide theoretical support for the ordered structure of polysaccharides and also provide a theoretical foundation for the development and application of SACP in the functional food and pharmaceutical industries.

The basic physicochemical indicators, phenolic composition and aroma composition of fruits from five-year-old ‘Cabernet Sauvignon’ grapevines with four shoot densities of 15, 20, 25, and 30/m from the wine production area of the Qingtong Gorge at the eastern foothill of Helan Mountain in Ningxia were analyzed, and principal component analysis (PCA) was used to investigate monomeric anthocyanin contents and comprehensive fruit quality. The results showed that there were differences in the physical indicators of grape bunches and individual grapes and the chemical indicators such as sugar, acid, phenolics, and aroma substances among different shoot densities (P < 0.05). The contents of total monomeric anthocyanins and total aroma compounds were negatively correlated with shoot density, and the basic physicochemical indicators, phenolic composition and overall aroma quality of grapes with lower shoot density (15–20 m) were better. The PCA performed on monomeric anthocyanin contents showed a clear distinguishment between the different treatments, and the shoot density of 15/m had more obvious effect on monomeric anthocyanin contents. The decreasing order of the comprehensive fruit scores was 15 > 20 > 30 > 25/m. In conclusion, for ‘Cabernet Sauvignon’ grapes in the wine production area of the Qingtong Gorge, the comprehensive fruit quality was best at a shoot density of 15–20/m.

In this study, the composition and content of vitamin D and its esters in 108 human milk samples from different lactation stages (colostrum on days 0–7, transition milk on days 8–15 , and mature milk after day 16) were analyzed by ultra-high performance liquid chromatography/quadrupole time of flight mass spectrometry (UPLC/Q-TOF-MS). The results showed that human milk contained 4 kinds of vitamin D and 20 kinds of vitamin D esters, 16, 18 and 14 kinds of vitamin D esters being found in colostrum, transition milk and mature milk, respectively. During the whole lactation period, the average contents of vitamin D2 and 25(OH)-D3 in colostrum were highest, 26.83 and 160.67 ng/L, respectively; the average content of vitamin D3 in transition milk was highest, 119.87 ng/L; and the average content of 1,25(OH)2-D3 in mature milk was highest, 1.82 ng/L. The average contents of vitamin D esters in colostrum, transition milk and mature milk were 11.89, 10.73 and 11.47 ng/L, respectively, and the content of vitamin D2 tetradecenoate (C14:1) was highest throughout the lactation period. Through partial least squares-discriminant analysis (PLS-DA), colostrum, transition milk and mature milk could be well separated, indicating that the types and contents of vitamin D and vitamin D esters in human milk change from colostrum to mature milk. There was a correlation between different vitamin D esters. This study could provide data support for the development of infant formula.

The volatile components of three different colored rices were characterized by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). A total of 64 peaks were detected, and 44 volatile compounds were identified. White rice liberated a high concentration of 2-mhyl-2-propenal, 3-methylbutanal, heptanal monomer and four unknown components after cooking. Red rice liberated a high concentration of heptanal (monomer and dimer), pentanal, 2-butylfuran, amyl aldehyde, furan, (E)-2-heptenal (monomer and dimer), octanal (monomer and dimer), (E)-2-octenal, n-nonanal (monomer and dimer), isopentyl alcohol, decanal, ethyl acetate, 2,3-butanedione, 2-pentylfuran, and 10 unknown compounds. Black rice released a high concentration of 2-pentanone, 2-hexenal, 3-butenenitrile, 3-methyl-1-pentanol, 1-octene-3-one, furfuryl alcohol, 2-methyl-ethyl butyrate, benzaldehyde, phenylacetaldehyde, propanedioic acid, dietyl ester, and two unknown components. After cooking, the number of aroma compounds in the three colored rices increased. In conclusion, headspace-gas chromatography-ion migration spectrometry can well characterize the aroma of different colored rices before and after cooking, making it easier for consumers to choose rice.

In order to explore the effect of different distillation methods on the key aroma compounds of whisky, the aroma composition of base whisky produced by two different distillation methods: double distillation in pot stills and continuous distillation in tower stills, and whisky aged with oak chips was detected by headspace-solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The characteristic aroma compounds were determined by odor activity values (OAVs), and the effect of distillation methods on the characteristic aroma of whisky was investigated by sensory evaluation. The results demonstrated that the distillation methods led to significant differences in the raw material-like, fermented and distilled aromas of base whisky. Pot-distilled whisky retained more aroma characteristics of the raw material. The difference in fermented aroma was mainly reflected by the ethyl ester content. More medium-chain and long-chain fatty acid ethyl esters were retained during pot distillation, while more short-chain fatty acid ethyl esters contributing to the fermented aroma were retained during tower distillation. The aroma differences brought about by the distillation methods affected the change of aroma compounds during subsequent aging. After aging, more fermented aroma compounds in pot-distilled whisky were lost, but the distilled aroma and the aged aroma from oak chips were more prominent. Although the aged aroma could attenuate the aroma difference between base whisky produced by different distillation methods, the effect of the distillation methods on the aroma was still evident. The choice of the appropriate distillation process is essential for the production of whisky.

In order to evaluate the influence of season on the fatty acid content of Holstein cow milk in Inner Mongolia, milk samples were collected from 10 large commercial pastures in Inner Mongolia during four seasons (spring, summer, autumn and winter) and analyzed for fatty acid content by gas chromatography (GC). The results showed that: 1) the major fatty acids in Holstein cow milk from Inner Mongolia were palmitic acid, oleic acid, stearic acid, myristic acid and linoleic acid, which did not change due to geographical regions, cow breeds, feeds and processing methods; 2) the proportions of saturated, monounsaturated and polyunsaturated fatty acids in the total fatty acids in cow milk were stable, and so were short-chain, medium-chain and long-chain fatty acids, which was not significantly affected by geographical regions; 3) the major fatty acids in cow milk presented the same trend with season, being at higher levels in spring and at lower levels in summer and autumn; 4) the contents of saturated and polyunsaturated fatty acids differed significantly (P < 0.05) between summer and the other seasons and were lowest in summer, and the content of monounsaturated fatty acids differed significantly (P < 0.05) between spring and summer and were also lowest in summer; and 5) the contents of short-chain and medium-chain fatty acids which have a strong influence on the flavor of milk fat differed significantly (P < 0.05) in summer and autumn compared to the other seasons. This study may provide reliable technical support for product innovation in the dairy industry and the improvement of milk nutritional value.

A method was developed for the simultaneous determination of the residues and migration of 18 polycyclic aromatic hydrocarbons (PAHs) in food contact rubber by gas chromatography-mass spectrometry (GC-MS). The rubber extract was cleaned up by solid phase extraction (SPE) with a silica gel column. The migration solution was extracted with hexane, separated on a DB-EUPAH column (60 m × 250 μm, 0.25 μm), detected in the selective ion monitoring (SIM) mode, and quantified by an internal standard method. The results showed that good chromatographic separation of the 18 PAHs was achieved. The calibration curves showed good linearity in the concentration range of 0.05–0.5 mg/L. The limits of detection (LOD) were less than 0.01 mg/L, and the limits of quantification (LOQ) were less than 0.05 mg/L. The average recoveries for PAHs residues and migration at three spiked levels ranged from 61.3% to 102.2%, and the relative standard deviations (RSDs, n = 6) were 0.5%–9.1%. A total of 16 PAHs were detected in 10 of the 34 batches of food contact rubber tested with total residues ranging from 0.24 to 16.97 mg/kg. No PAHs were found to be migrated from the rubber to 4% acetic acid and 10% ethanol at different experimental temperatures. Many PAHs were found to be migrated to 50% ethanol as a food simulant. The number of PAHs migrated increased with an increase in temperature, and the rate and amount of migration increased significantly. The safety problems caused by the residues of PAHs in food contact rubber and their migration to foods cannot be neglected.

The volatile components in giant salamander oil adulterated with different amounts of peanut oil (0%, 5%, 10%, 20%, 30%, and 100%) were studied by gas chromatography-ion mobility spectroscopy (GC-IMS) combined with chemometrics. The results showed that a total of 41 volatile compounds were identified in all samples, including 21 aldehydes, 6 ketones, 4 alcohols, 4 heterocyclic compounds, 3 esters, 2 sulfur-containing compounds and 1 acid. With increasing adulteration level, the contents of aldehydes, heterocycles, acids and esters increased, while the contents of ketones, alcohols and sulfur compounds decreased. A partial least squares regression (PLSR) model between volatile components and adulteration level was established. The correlation coefficient (R2) values for the calibration and verification sets were 0.992 4 and 0.988 2, respectively, indicating that the reliability of the model. Principal component analysis (PCA) showed that the cumulative contribution rate of the first two principal components (PC) was 94.3%, indicating that the different adulteration levels could be well distinguished by volatile components. Thirteen differential volatile compounds with variable importance for the projection (VIP) scores greater than one, including seven aldehydes, three ketones, one alcohol, one sulfur compound and one ester, were selected by partial least squares-discriminant analysis (PLS-DA). PCA and cluster analysis showed that these differential volatile components could also be used to distinguish the different adulterated salamander oil samples. This study can provide technical support for the nondestructive rapid identification of adulterated giant salamander oil.