This work was undertaken to study the effects of abscisic acid (ABA) and sodium tungstate (Na2WoO4) as an ABA synthesis inhibitor on carotenoid synthesis in germinated maize. Yellow maize kernels (cv. ‘Suyu 29’) was soaked in different concentrations of exogenous ABA and germinated. The contents of soluble protein, free amino acids, proline, vitamin C, total phenols and carotenoid, antioxidant enzyme activity, antioxidant capacity, and the expression of the genes associated with carotenoid synthesis in germinated maize were determined. The results showed that ABA increased the contents of soluble protein, free amino acids, proline, vitamin C, total phenols and endogenous ABA in germinated maize compared with the untreated control group. At an ABA concentration of 5 mg/L, the carotenoid content reached the highest level, and the levels of lutein and zeaxanthin increased by 27.6% and 20.1%, respectively, compared with the control group. However, Na2WoO4 inhibited the synthesis of endogenous ABA and reduced the content of carotenoids. Quantitative fluorescence polymerase chain reaction (PCR) results showed that ABA treatment could significantly increase the expression of the genes associated with carotenoid synthesis in germinated maize. Meanwhile, the antioxidant enzyme activity and antioxidant capacity were significantly enhanced. In summary, exogenous ABA treatment can promote endogenous ABA synthesis in germinated maize, and increase the expression of the genes associated with carotenoid synthesis and antioxidant capacity, thus improving nutritional quality.

In order to study the effects of prolylhydroxylase (PHD) on hypoxia inducible factor-1α (HIF-1α) expression, glycolysis and meat quality in yak muscle during postmortem aging, the Longissimus dorsi muscle of yaks was injected postmortem with dimethyloxaloylglycine (DMOG) or normal saline as a control and evaluated for changes in HIF-1α expression, key glycolytic enzyme activities, glycolysis degree and meat quality after different aging periods. The results showed that HIF-1α expression increased first and then decreased with increasing aging time. However, in the DMOG-treated group, HIF-1α expression was significantly increased during the first 12 h postmortem (P < 0.05), suggesting that inhibition of PHD activity can up-regulate HIF-1α expression. The activity of hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) increased first and then decreased with aging time, all of which were significantly higher in the DMOG-treated group than in the control group from 3 to 120 h (P < 0.05). The glycogen content and pH of the DMOG-treated group were significantly lower than those of the control group from 3 to 72 h (P < 0.05), while the lactic acid content was significantly higher than that of the control group (P < 0.05), suggesting that PHD can up-regulate the activity of glycolytic enzymes by mediating HIF-1α expression and consequently accelerate the process of glycolysis. Moreover, the shear force of the DMOG-treated group was significantly higher than that of the control group during 3–72 h (P < 0.05), the L* value was significantly higher than that of the control group during 6–168 h (P < 0.05), and the a* value was significantly higher than that of the control group during the entire aging process (P < 0.05). The muscle fiber diameter and area in the DMOG-treated group were lower than those in the control group, and the gap between muscle fibers was higher but not significantly than that in the control group. These results indicate that PHD affects postmortem meat quality by mediating HIF-1α expression, causing pH changes and consequently changes in shear force and L* value. Nevertheless, the reason for changes in a* value needs to be further explored. In conclusion, PHD can increase the activity of key glycolytic enzymes by up-regulating HIF-1α expression during postmortem aging, thereby accelerating the glycolysis process, resulting in changes in muscle internal environment and ultimately affecting the formation of postmortem meat quality.

Newly harvested corn was stored under constant temperature (15 or 25 ℃) and relative humidity (55%). The structure and physicochemical properties of zein during postharvest ripening of corn were studied, and their relationship was analyzed. During the 56-day postharvest ripening period at 15 and 25 ℃, the free sulfhydryl content, surface hydrophobicity, particle size and polydispersity index (PDI) of zein decreased, while the disulfide bond content and absolute value of zeta-potential increased. The hydrogen bond association decreased, and more ordered β-sheets were transformed into a disordered structure, and the thermal stability and the molecular mass of α-zein subunit decreased. In addition, during postharvest ripening of corn the physicochemical properties of zein significantly changed. The solubility and water-holding capacity of zein reached their maximum on the 42th day at 15 ℃ and on the 28th day at 25 ℃, and the emulsifying and foaming capacity increased significantly after postharvest ripening for 14 days at both temperatures. However, the oil-holding capacity decreased. The improvement in physicochemical properties of zein during postharvest ripening of corn may be related to the reduction in protein aggregation and its flexible structure. These results showed that proper postharvest ripening of corn could modify the structure of zein and consequently improve its physicochemical properties.

In this work, nano fish bone (NFB) was prepared from silver carp bones and added to silver carp myosin. The speciation changes and distribution of calcium in NFB (NFB-Ca) during myosin gelation were investigated by measurement of various calcium species, surface element analysis, microstructure examination and low-filed nuclear magnetic resonance (LF-NMR). Results showed that the Ca content of myosin with the addition of NFB significantly increased compared to that without added NFB. NFB-Ca existed mainly in an insoluble form in myosin (> 95%). Heating treatment at 40 ℃ significantly increased the ionic Ca content; however, ionic-Ca was transformed into other forms at 90 ℃. Therefore, it was suggested that part of the soluble Ca released from NFB participated in the formation of salt bridges and consequently was transformed into insoluble calcium, facilitating myosin cross-linking. As a result, a continuous and uniform gel network structure was observed under laser confocal scanning microscopy (LCSM). Meanwhile, LF-NMR showed that the compact microstructure could help to hold more water and decrease water mobility. In addition, the surface Ca of myosin with NFB increased, and the distribution uniformity of Ca was improved after heating treatment.

A variety of spectroscopic techniques were used to study the inhibitory effect and mechanism of rutin and quercetin on starch-digesting enzymes and their combined effect. The results showed that the types of inhibition of rutin and quercetin on α-amylase were competitive, mainly driven by hydrophobic interactions and hydrogen bonds, and the half maximum inhibitory concentrations (IC50) were 0.36 and 0.22 mg/mL, respectively. The inhibition of α-glucosidase by rutin and quercetin was of mixed type, driven by hydrogen bonds, and the IC50 were 1.30 and 0.362 mg/mL, respectively. Moreover, both flavonoids could combine with α-amylase and α-glucosidase at only one/kind of action site to form a complex, thus inhibiting the activity of the enzymes, and their combinations in different proportions had a synergistic inhibitory effect on α-amylase and α-glucosidase. When the concentration ratio between rutin and quercetin was 7:1 and 3.6:18, the combination index for α-amylase and α-glucosidase was 0.20 and 0.22, respectively, showing the best synergistic inhibitory effect. This study provides a theoretical basis for further research on the interaction mechanism between flavonoids and starch-digesting enzymes, is meaningful for guiding the processing and utilization of edible and medicinal plants rich in flavonoids, and helps to promote the virtuous cycle of the tartary buckwheat industry.

To improve the loading rate and stability of ferulic acid, ferulic acid-loaded hydrogel based on amyloid fibrils, formed by heat treatment of hen egg white lysozyme under acidic conditions, was prepared by self assembly. The effects of amyloid fibril concentration, polyphenol addition, and pH on the loading rate of ferulic acid were investigated to optimize the hydrogel preparation conditions. The structural changes of the protein and the microstructure and gel properties of the hydrogel were explored by infrared (IR) spectroscopy, endogenous fluorescence spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and rheometry, and the effects of polyphenol addition on the structure and properties of the hydrogel were evaluated. Ultra-high performance liquid chromatography (UPLC) was used to test the stability of ferulic acid loaded in the hydrogel under thermal and light conditions. A simulated digestion system was established to investigate the in vitro slow release profile of ferulic acid from the hydrogel network. The results indicated that the optimum preparation conditions that provided maximum ferulic acid loading of 6.99% were determined as 70 g/L, 0.6% and pH 5 for concentration of amylose fibril, addition of ferulic acid and pH, respectively. Moreover, the hydrogel could effectively reduce the degradation of ferulic acid under different thermal and light conditions. Compared with lysozyme, the proportion of α-helix and β-sheet in the amyloid fibril increased and the tertiary structure formed an aggregation precursor state, which was more favorable for binding to polyphenols to form structurally stable hydrogels. The amyloid fibril-based hydrogel loaded with 0.6% ferulic acid had the gelation performance, tightest intermolecular structure, highest storage modulus (1 655.5 Pa), and lowest swelling rate (160%), and best slow-release performance in vitro.

For the purpose of enhancing the stability and antibacterial activity of eucalyptus leaf essential oil, a eucalyptus oil Pickering emulsion was fabricated using a mixture of sodium oleate modified attapulgite nanoparticles (M-APT) and carboxymethyl chitosan (CMCS) as a stabilizer. The effects of M-APT, CMCS and essential oil concentration on the emulsion’s stability were evaluated in terms of creaming behavior, micromorphology and rheological?properties. The results showed that the modification of APT with sodium oleate increased its contact angles (θ) from 15.2° to 83.7°, which facilitated irreversible adsorption of M-APT nanoparticles onto the surface of oil droplets. The droplet diameter of the emulsion decreased with an increase in M-APT concentration. The hydrophilic CMCS chains were self-assembled to form a 3D network, which encapsulated the M-APT-adsorbed oil droplets. The storage modulus (G’) of the emulsion increased with increasing CMCS concentration, and so did the stability against creaming. Furthermore, the diameters of inhibition zone of the Pickering emulsion against Staphylococcus aureus and Bacillus subtillis were slightly larger than those of eucalyptus essential oil as determined by the agar diffusion method. This could be attributed to the fact that M-APT adsorption onto the oil droplet surface allows for encapsulation of the essential oil, reducing its volatility. The results of bacterial growth kinetics proved the synergistic effect of M-APT and CMCS in encapsulating the essential oil for improved stability and sustained-released antibacterial activity, which is great significance to expand the application of plant essential oil as a biological antibacterial agent.

This study aimed to explore the effects of adding different proportions of whole wheat flour into Xinjiang Oil Naan dough on its farinographic properties, tensile properties, gelatinization properties, solvent retention capacity (SRC), moisture distribution and gluten secondary structure. The results showed that the processing quality of dough deteriorated with increasing level of whole wheat flour. The water absorption rate increased from 65.18% to 80.30%, the dough development time increased from 4.13 to 5.34 min, the peak viscosity, trough viscosity, setback and breakdown showed a downward trend, and the gelatinization temperature continued to increase; the tensile fracture energy decreased from 87 to 30 cm2, the elongation decreased from 156 to 92 mm, and the tensile resistance decreased from 302 to 242 EU. Compared with refined wheat flour, the SRC in sodium carbonate solution, sucrose solution and water of whole wheat flour increased by 20.56%, 18.69% and 34.94%, respectively, while the SRC in lactic acid solution decreased by 23.47%. The magnetic resonance imaging (MRI) results showed that the percentage peak area A21/A2 of transverse relaxation time increased, and the percentage peak area A22/A2 and A23/A2 decreased with increasing level of whole wheat flour replacement. The Fourier transform infrared spectroscopic (FTIR) analysis showed that the total content of α-helix and β-sheet in gluten decreased from 68.57% to 50.89%, and the random coil content increased by 31.5% indicating deterioration of gluten protein structure.

Gelation of native oat protein and oat protein glycosylated with lactose was induced by heat or transglutaminase (TGase) treatment in order to investigate the effects of different induction methods on the gel properties and structure of oat protein. The results showed that compared with the heat-induced gel of oat protein, the elasticity, hardness, and water-holding capacity of three other oat protein gels were significantly improved (P < 0.05). The texture properties (elasticity, hardness and viscosity) and water-holding capacity of the TGase-induced gels were better than those of the heat-induced gels, and the texture properties and water-holding capacity of the glycosylated protein gels were significantly higher than that of the non-glycosylated protein gels (P < 0.05). The surface hydrophobicity of enzyme induced protein gel was higher than that of 2 kinds of heat-induced protein gel, respectively; the surface hydrophobicity of glycosylated modified protein gel was lower than that of non-glycosylated modified protein gel. Furthermore, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy and microstructure analysis proved that TGase could cause intermolecular or intramolecular cross-linking of oat protein to form macromolecules, and the TGase-induced gel had a denser three-dimensional network microstructure. This study shows that TGase can induce native and glycosylated oat protein more effectively compared with heat treatment, which provides a theoretical basis for the diversified development of oat flour.

In this study, the gastric digestibility of dialyzed and non-dialyzed soybean protein was investigated using a static digestion model and a semi-dynamic digestion model. The results from the static model suggested that dialysis had no effect on the gastric digestion process of soy protein. However, in the semi-dynamic model, the pH, dry matter mass of emptied digesta and free amino group content of the non-dialyzed soy protein (SP-ND) differed somewhat from those of the dialyzed soy protein (SP-D) indicating that the SP-ND retained more components in soybeans, resulting in a greater buffering capacity, delayed gastric emptying and slower protein digestion. In addition, the static and semi-dynamic digestion models had different advantages, so they can be used for different research purposes. This work could provide new insights into the development and health effects of soy protein-based products.

Chitosan-based composite film incorporated with soybean protein isolate and Auricularia auricular polysaccharide (SPI/CS/AAP) was modified by ultrasonic, microwave, ultraviolet (UV) or their combination to evaluate the effect of different modification methods on the film’s properties. The results showed that the mechanical properties and barrier properties of the film were improved by ultrasonic, microwave and UV modification treatments. Among them, the effect of ultrasonic-microwave synergistic modification was the most pronounced, resulting in the highest tensile strength (TS) and elongation at break (EAB) (21.67 MPa and 78.02%, respectively) and lowest water vapor permeability (WVP) and oxygen permeability (OP) (1.34 × 10-12 g/(cm·s·Pa) and 0.47 × 10-2 g/(m2·d), respectively). Furthermore, the synergistic modification could significantly increase the brightness, whiteness and light transmittance of the film. The composite film was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), revealing that the hydrogen bonding between the film matrix molecules was strengthened by ultrasonic, microwave and UV treatments, and the modified film exhibited a dense and stable network structure and improved thermal stability.

In this study, the effects of different tea polyphenol treatments, direct addition of antioxidant on the surface of dried scallop (traditional) and after antioxidant addition allowing it to stand, leaving antioxidant both on the surface and inside of dried scallop (improved), on the oxidation stability of dried scallops were evaluated in terms of oxygen consumption, primary oxidation products, secondary oxidation products, free radical intensity and oxidation-induced substrate loss. A shelf-life prediction model of dried scallops was established to evaluate the effect of different tea polyphenol treatments on the predicted shelf life of dried scallops. The results showed that compared with the traditional one, the improved treatment significantly prolonged the induction period of oxidation of dried scallop, and effectively reduced peroxide value (PV), thiobarbituric acid reactive substances (TBARS) value, free radical intensity, and the loss of eicosapentaenoic acid and docosahexaenoic acid contents, and it could extend the shelf life of dried scallop by up to 10.23 days. This study provides a theoretical basis and methodological guidance for the development of high-efficiency antioxidants for and maintaining the nutritional quality of dried marine animal products.

The purpose of this study was to develop a dynamic prediction model of Listeria monocytogenes growth in fresh pork. Pork samples inoculated with a three-strain cocktail of L. monocytogenes were incubated under three groups of dynamic temperature conditions (1–45 ℃) to observe the growth of L. monocytogenes. The growth data of L. monocytogenes were analyzed by the one-step method and fitted to two different primary models, Baranyi and two-compartment models and then to the Cardinal secondary model. The results showed that both Baranyi-Cardinal model and Two-compartment-Cardinal model were equally suitable to describe the growth of L. monocytogenes in pork. The minimum, optimum and maximum growth temperatures of L. monocytogenes estimated by the Baranyi-Cardinal model were 0.94, 38.37 and 45.36 ℃, and those estimated by the Two-compartment-Cardinal model were 1.03, 37.96, 45.58 ℃, respectively. The optimum growth rate and the maximum growth density estimated by the Baranyi-Cardinal model were 0.891 and 0.858 h-1, and those estimated by the Two-compartment-Cardinal model were 9.07 and 9.09 (lg(CFU/g)), respectively. Model validation was conducted by using another four groups of dynamic growth experiments and three groups of isothermal growth experiments (4, 20 or 37 ℃). The obtained results showed the models could accurately predict the growth behavior of L. monocytogenes under both dynamic temperature and isothermal conditions. The root mean square error (RMSE) was between 0.13 and 0.48 (lg(CFU/g)), and the residual error obeyed the normal distribution with a mean value of ?0.02 (lg(CFU/g)) and a standard deviation of 0.29 (lg(CFU/g)). At last, numerical simulation of the growth of L. monocytogenes in fresh pork under cold storage in a household refrigerator was conducted, showing the application potential of the models. The results of this study are useful for growth prediction and risk assessment of L. monocytogenes in fresh pork.

The objective of this work was to analyze the changes in metabolites during the inoculated fermentation of grape Jiaosu. The changes of total acids, organic acids, ethanol, total phenolic compounds, major enzymes (SOD and β-glucosidase) and aroma components during the sequential fermentation process of yeast, acetic acid bacteria and lactic acid bacteria were analyzed. The results showed that the total acid concentration increased first and then decreased during the fermentation process, reaching a maximum value of 19.37 g/L on the 34th day. The organic acids produced during yeast fermentation (0–6 days) were mainly citric acid, malic acid and tartaric acid. Ethanol was also mainly produced at this stage. During fermentation with acetic acid bacteria (6–27 days), acetic acid was produced. During fermentation with lactic acid bacteria (27–41 days), lactic acid and citric acid gradually increased to a maximum value of 102.09 and 67.70 mg/L, respectively, while malic acid decreased. Moreover, ethanol content decreased to a minimum value of 0.47% and then tended to be stable. The trends of total phenol content and β-glucosidase activity were consistent, both of which were mainly produced during yeast and at the late stage of lactic acid bacterial fermentation (34–41 days). The activity of SOD showed a fluctuating increase. The volatile compounds produced during grape Jiaosu fermentation were mainly alcohols, acids and esters. These results can provide a theoretical basis for precise preparation and quality optimization of grape Jiaosu.

This work was undertaken to study the regulatory effects of the Agr and LuxS/AI-2 quorum sensing systems on biofilm formation by Listeria monocytogenes (Lm). The agrD and luxS genes of LMB33426 were knocked out by homologous recombination, and the biofilm formation characteristics of the wild-type and mutant strains were investigated comparatively. The results showed that the biofilm formation ability of ΔagrD and ΔluxS was reduced compared with that of the wild-type strain. The hydrophobicity of ΔagrD decreased significantly, and its swimming mobility was higher than that of the wild-type strain at 37 ℃. However, no significant difference was found in drug resistance between the wild-type and mutant strains. This study provides a basis for further research on the regulatory mechanism of quorum sensing systems on biofilm formation by Lm and more broadly, for the development of novel strategies for the prevention and control of Lm infections.

In order to systematically explore the effect of starter on the antioxidant activity of peptides from fermented sausage, the in vitro antioxidant activity of crude peptides extracted from naturally and starter fermented sausage were assessed. The results showed that the peptides from starter fermented sausage had a stronger ability to chelate metal ions and scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals, which increased by 13%, 10% and 20%, respectively, compared with the control group, while the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity was weaker than that of the peptides from naturally fermented sausage. Furthermore, the in vivo antioxidant activity of the peptides from starter fermented sausage was evaluated using a mouse model of D-galactose-induced aging. The results of growth performance showed that the crude peptides could promote the growth of mice and increase visceral indices. Moreover, the crude peptides significantly increased the activities of various antioxidant enzymes in the mouse serum and liver tissue including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) as well as total antioxidant capacity (T-AOC) and reduced malondialdehyde (MDA) content, restoring the antioxidant capacity to normal and even higher than normal levels. This study has shown that the crude peptides from starter fermented sausage have outstanding antioxidant activity, and thus can provide another option for the development of protein-derived antioxidant peptides.

To study the effect of co-culture with Saccharomyces cerevisiae on the metabolism of caproic acid-producing bacteria and its mechanism, a strain of Clostridium celerecrescens JSJ-1 that can produce caproic acid and S. cerevisiae C-1 were cultured separately or co-cultured under different nutrient conditions. We compared the growth and metabolism (number of microbial colonies, glucose, ethanol, butyric acid, caproic acid) of the two strains in monoculture and co-culture. The results showed that S. cerevisiae C-1 grew better than C. celerecrescens JSJ-1 under anaerobic static culture conditions at 34 ℃, and could preferentially utilize glucose in the medium. When glucose was used as the sole carbon source, S. cerevisiae C-1 could utilize glucose to produce ethanol as a substrate for the synthesis of caproic acid by C. celerecrescens JSJ-1. When the medium contained 0.5% glucose and 2% ethanol, the co-culture produced caproic acid four days earlier than C. celerecrescens JSJ-1 alone. Glucose had a strong inhibitory effect on the production of caproic acid by C. celerecrescens JSJ-1. S. cerevisiae C-1 could utilize glucose to relieve its inhibitory effect on the production of caproic acid upon co-culture. During the fermentation of nongxiangxing baijiu, S. cerevisiae can not only provide substrates for caproic acid-producing bacteria to synthesize caproic acid, but also alleviate the inhibitory effect of glucose on caproic acid production.

The GH11 endo-xylanase ScXyn22 from Schizophyllum commune was expressed in Pichia pastoris. Then, its enzymatic properties and its effect on the baking quality of whole wheat bread were characterized. The optimal pH and temperature for the purified recombinant enzyme were 4.5 and 55 ℃, respectively. Under these conditions, the specific activity, Km and Vmax of ScXyn22 were (5 964.1 ± 429.4) U/mg, (3.25 ± 0.27) mg/mL and (1 288 ± 9.14) μmol/(min·mg), respectively. In the reaction system containing 1–5 mol/L NaCl, the activity of ScXyn22 toward birch xylan was significantly enhanced by 1.64, 2.13, 2.31, 2.39 and 2.3 folds, respectively. The activity of ScXyn22 toward wheat arabinoxylan was enhanced by 1.21, 1.46, 1.58, 1.48 and 1.16 folds, respectively. However, the activity of ScXyn22 toward oat β-glucan decreased by 19.31%, 47.72%, 55.97%, 45.99% and 38.18%, respectively, compared with that in the absence of NaCl. In simulated intestinal fluid, the remaining enzyme activity was 81% after 20 min and 65.77% after 120 min. Addition of xylanase had a significant effect on the quality of whole wheat bread. Addition of xylanase at 300 U/kg increased the specific volume of whole wheat bread by 19.7%, and at 150 U/kg decreased its firmness by 57.3%. These results showed that the xylanase has good application potential in whole wheat bread production.

In this study, sweet potato slurry that can be used for starch production was fermented using Lactobacillus plantarum (Lp), Lactobacillus bulgaricus (Lb), Streptococcus thermophilus (St), Pediococcus pentosus (Pp), Lactobacillus casei (Lc) and commercial Lp (SZ), separately, and the effects of different lactic acid bacteria (LAB) starter cultures on the nutritional and functional components (protein, ash, soluble dietary fiber, insoluble dietary fiber, total dietary fiber, total acid, total sugar, lactic acid, short chain fatty acid, total polyphenol, and free amino acid) and sensory characteristics (evaluated by electronic nose, electronic tongue, gas chromatography-mass spectrometry (GC-MS), and sensory evaluation) of sweet potato slurry were compared. The results showed that after fermentation, the contents of protein, sugar, soluble dietary fiber, insoluble dietary fiber and total dietary fiber decreased significantly. All starter cultures showed excellent fermentation performance. After fermentation, the pH of the slurry decreased from 6.62 to 3.67–3.88, the total acid content increased from 0.29 to 2.69–3.67 g/100 mL, and the contents of lactic acid and short chain fatty acids increased significantly. Lb and Lc fermentation significantly increased the content of total polyphenols in the slurry by 18.44% and 17.78%, respectively. Additionally, 16 free amino acids were detected in the fermented slurry, and the content of essential free amino acids increased significantly compared to that in the unfermented slurry. The GC-MS profile showed that lactic acid bacteria fermentation remarkably increased the number and amount of flavor substances in the slurry and improved its flavor and mouthfeel. The slurry fermented by Pp, St and SZ exhibited better overall sensory acceptability than that fermented by the other starter cultures. In conclusion, these findings can provide theoretical support for the research and development of LAB-fermented beverage from sweet potato starch slurry.

To select plant-derived lactic acid bacteria with probiotic characteristics, 1 000 strains of lactic acid bacteria (LAB) isolated from traditional fermented vegetables were evaluated for acid resistance, bile salt tolerance, bacteriostasis, in vitro antioxidant capacity, drug susceptibility, hemolytic activity and amino acid decarboxylase activity. Furthermore, the selected strains were identified by 16S rDNA gene sequencing. Totally 82 LAB strains were obtained by culturing in MRS medium at pH 3.0, and out of these, 49 strains were selected by culturing in MRS medium with pH 2.5, all of which were tolerant to 0.3% bile salt. Nineteen of the 49 strains were further selected based on their microscopic morphology and plant sources to evaluate their drug sensitivity, hemolytic activity, bacteriostatic effect, amino acid decarboxylase activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. Results showed that the 19 strains were susceptible to most of the 20 antibiotics tested with four of them being susceptible to all the antibiotics. All of the 19 strains had inhibitory activity against the tested pathogenic?bacteria?and had no hemolytic activity. As determined using a commercial amino acid decarboxylase activity kit and polymerase chain reaction (PCR), the 19 strains had no potential risk of producing bioamine, and the in vitro antioxidant capacity of five of these strains was higher than 40%, suggesting the 19 strains have probiotic properties. The results of identification showed that the 19 strains contained seven strains of Lactobacillus fermentorum, six strains of Lactobacillus plantarum, and one strain of Bacillus eneniensis, one strain of Lactococcus pentosus, one strain of Limoxibacter, one strain of Lactobacillus pentosus, one strain of Enterococcus faecium and one strain of Lactobacillus brevis.

In order to study the effect of heat stress on the inner membrane proteins of Clostridium perfringens spores, the physicochemcial changes in the inner membrane proteins after heat treatment at different temperatures (25, 37, 75 or 95 ℃) for 20 minutes were characterized by measuring particle size distribution, surface hydrophobicity, ultraviolet absorption spectrum, endogenous fluorescence spectrum and Raman spectrum. The results showed that heating temperature had a significant effect on C. perfringens spore inner membrane proteins. Compared with the control group (treated at 25 ℃), treatment at 37 ℃ had no significant effect on the inner membrane proteins, and did not cause any significant changes in the particle size distribution, amino acid microenvironment, surface hydrophobicity or secondary structure. After heat stress at 75 ℃, the particle size distribution was uniform and stable, the UV absorption and fluorescence intensity was significantly enhanced, and the surface hydrophobicity was significantly increased. The percentage of α-helix decreased by 3.17%, the percentage of β-sheet decreased by 3.94%, and the proportion of random coil increased by 8.31%. After heat stress at 95 ℃, the proteins’ structure was damaged, the proteins were obviously aggregated or denatured, and the particle size distribution moved significantly to larger particle size. The above results indicated that heat stress at 75 ℃ could effectively affect the physicochemical properties of C. perfringens spore inner membrane proteins, leading to the exposure of hydrophobic sites and amino acid residues and significant secondary structural changes. This study provides a theoretical basis for further research on the effect of heat stress on the functional properties of C. perfringens spore inner membrane proteins.

To explore the antibacterial mechanism of nisin Q13 against Lactobacillus bulgaricus LMG-1, the purity and molecular mass of nisin Q13, produced by Lactococcus lactis Q13 and purified by ammonium sulfate precipitation, ultrafiltration and dextran gel column chromatography, were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the effects of nisin Q13 on the cell membrane permeability, intracellular enzyme activity and cell morphology of L. bulgaricus were evaluated. The results showed that the optimal saturation level of ammonium sulfate for nisin Q13 precipitation was 60%. After ultrafiltration, only one fraction, whose molecular mass was greater than 10 kDa, had an antibacterial effect. The fraction was further purified by dextran gel column chromatography, yielding two peaks with antibacterial activity. The polyacrylamide gel electrophoretogram showed only one protein band with a molecular mass of about 17.5 kDa, which may be a polymer of nisin. The antibacterial mechanism of nisin Q13 may be related to the fact that it can cause the formation of holes in the cell membrane of the target cells, increase the permeability of the cell membrane and destroy the integrity of the cell membrane, leading to the leakage of cellular contents, reducing the contents of key enzymes such as Na+/K+-ATPase and alkaline phosphatase (AKP), affecting the normal energy metabolism of cells, and eventually resulting in cell death.

In order to comprehensively understand the genetic background of Paenarthrobacter ilicis CR5301 and dissect the key enzymes of CR5301 for transforming rebaudioside C (RC), the whole genome of CR5301 was sequenced using next-generation Illumina HiSeq and third-generation Nanopore-based DNA sequencing, and the key enzymes for RC convertion were predicted. The results showed that CR5301’s genome was a closed circular chromosomal DNA molecule without plasmids. The genome sequence was 4 748 281 bp in length, with a GC content of 62.92%. The genome encoded a total of 4 458 genes, including 4 gene islands, 1 prophage and 14 CRISPR-Cas coding sequences. CR5301 is the first strain of P. ilicis whose genome has been completely determined, and it is also the strain with the largest known genome of the genus Paenarthrobacter. P. ilicis CR5301 was more closely related to P. aurescens, but more distantly related to P. ureafaciens, according to genome collinearity and 16S rRNA gene-based phylogenetic tree analysis. Comprehensive annotation analysis against seven protein databases showed that P. ilicis CR5301’s genome contained 523 carbohydrate active enzyme genes, of which 18 glycosidase genes may be the key enzyme genes for the transformation of RC by CR5301. Finally, the physicochemical properties and secondary structures of the 18 glycosidases were predicted by the bioinformatics software ProtParam and SOPMA. These results provide clear and complete genetic information for understanding the mechanism of RC transformation by CR5301, and provide a complete and reliable reference genome sequence for extensive biological studies on P. ilicis.

In order to explore whether co-fermentation of garlic and ginseng could affect the microbial diversity, chemical composition and physiological function of black ginseng, fresh garlic and ginseng were used as raw materials to make black garlic, black ginseng and ginseng garlic by liquid-state fermentation. During the fermentation process, their microbial diversity, major components and antioxidant properties were analyzed. The results showed that the dominant bacterial phylum in ginseng garlic was Firmicutes, and the dominant bacterial genera included uncultured_bacterium_f_Muribaculaceae and Lactobacillus. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that there were no obvious differences between the metabolic pathways of ginseng garlic, black garlic and black ginseng, mainly including Global and overview maps, carbohydrate metabolism and amino acid metabolism. The contents of reducing sugars and total phenols in ginseng garlic were significantly increased, the total acid content was decreased, the conversion rate of rare ginsenosides was significantly increased, and the content of the potential harmful substance 5-hydroxymethylfurfural (5-HMF) was significantly reduced. Moreover, ginseng garlic had good free radical scavenging capacity. The above findings provide a theoretical basis for the development of ginseng garlic products and for promoting the development of the black ginseng industry.

The physicochemical properties and microbial community structure of two grades of Nongxiangxing Daqu were analyzed, and the internal relationship between them was investigated. High-throughput sequencing was used to analyze the differences in the microbial community structure between the two grades of Daqu. Meanwhile, we determined their physicochemical properties. Redundancy analysis (RDA) was used to study the relationship between microbes and physicochemical properties. The results showed that the bacterial community structures in the two grades of Daqu were similar, and the dominant bacterial genus were Thermoactinomyces, Weissella, and Lactobacillus, Kroppenstedtia; the domininant fungi were Thermomyces, unclassified_f__Aspergillaceae, and Thermoascus. We found that the relative abundance of Thermoascus in the superior grade was significantly higher than the first grade through differential microbial analysis, while the reverse was observed for unclassified_f__Aspergillaceae. The differential bacteria were all low-abundance species (relative abundance less than 1%). In addition, the moisture content, pH, liquefaction power and saccharification power of the superior grade were significantly lower than the first grade, while the total acid content and esterification power were significantly higher than the first grade. However, there was no significant difference in fermentation power between them. RDA analysis showed that the baterial genera Lactobacillus, Staphylococcus, Weissella and the fungal genus Thermoascus were positively correlated with fermentability and pH, whereas Thermoactinomyces and Kroppenstedtia were negatively correlated with pH. These results may provide a theoretical basis for establishing a more scientific quality evaluation standard for Daqu.

To elucidate the differences in the antioxidant and antidiabetic activities of different phenolic fractions from Rubus chingii Hu, aqueous-soluble, alcohol-soluble, free and bound polyphenols from the fruits of R. chingii Hu were extracted using different solvents and methods. The difference in the contents of total phenolic compounds, total flavonoids, and hydrolyzable tannins in the different extracts were compared, and the radical scavenging, α-glucosidase inhibitory and antiglycation activity of the extracts were determined. The major chemical components in the extract with the highest activity were determined using mass spectrometry (MS). The results indicated that the alcohol-soluble polyphenol-rich extract had the highest contents of total phenols and hydrolysable tannins (414.95 μg/mg and 182.47 μg/mg (expressed as gallic acid equivalent in per milligram of extract), respectively). Meanwhile, it also presented the strongest ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) cation radical and to inhibit α-glucosidase activity with half maximal inhibitory concentration (IC50) values of 40.68, 23.90 μg/mL and 1.65 μg/mL, respectively. But the highest total flavonoid content and antiglycation activity were observed in the bound polyphenol-rich extract. Totally, 31 compounds were tentatively identified from the bound polyphenol-rich extract, and tannins and flavonoids were the major bioactive constituents. Therefore, the R. chingii Hu residues left after the extraction of free polyphenols and aqueous-soluble constituents can be further utilized to develop bioactive constituents with high antioxidant and antidiabetic activities.

Sensory evaluation, gas chromatography-ion mobility spectrometry (GC-IMS) and multivariate statistical methods such as principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to analyze the changes of volatile flavor compounds in sea duck egg white during salting. A total of 43 volatile organic compounds (VOCs) were identified, including esters, ketones, aldehydes, acids and alcohols, ranked in decreasing order of their numbers. A total of 20 characteristic compounds were identified throughout the salting process, including ethyl acetate, 3-hydroxy-2-butanone, n-propanol, isobutyric acid, isopropyl acetate, 2,3-butanedione, propionic acid, 3-methyl-3-butene-1-alcohol, 2-methylbutyraldehyde, propyl acetate, n-butyraldehyde, 2-butanone, isopropanol, isovaleraldehyde, ethyl isobutyrate, tetrahydrofuran, 2-pentanone, n-butanol isoamyl alcohol and trans-2-pentenoaldehyde. Isobutyric acid and propionic acid were the major fishy odor compounds of salted egg white. The content of 2-butanone in fresh duck eggs was the highest. After five days of salting, ethyl acetate became the most abundant volatile compound. After 25 days of salting, the relative proportions of isobutyric acid and propionic acid gradually increased. The relative contents of n-butyraldehyde and isovaleraldehyde increased gradually during salting. The characteristic flavor substances clearly differed among salting stages. GC-IMS identification of flavor substances in sea duck egg white can provide a theoretical basis for identifying the unique flavor and judging the quality change of sea duck eggs during salting.

The differences in the sensory quality of fillets from diploid and triploid rainbow trout from the same parents farmed under the same conditions were analyzed in terms of their color, texture, and flavor substances. Results showed that the yellowness value of diploid rainbow trout fillet was significantly higher than that of triploid rainbow trout fillet (P < 0.05), while no significant difference was found in lightness or redness values. The springiness and chewiness values of triploid rainbow trout were significantly higher than those of diploid rainbow trout (P < 0.05), while no significant difference in water-holding capacity or pH was observed. Triploid rainbow trout muscle had a richer taste than diploid rainbow trout muscle, and both had umami, salty, bitter and sweet tastes. In total, 77 volatile compounds were detected in each sample, and 1-octene-3-ol, hexanal, octanal, nonanal and (E)-2-nonenal were identified as the major characteristic compounds according to their odor activity values (OAV), which could present grassy, fatty and fruity flavors. The OAV of total characteristic odorant compounds in triploid rainbow trout fillet was significantly higher than that of diploid rainbow trout fillet (P < 0.05). This study shows that diploid and triploid rainbow trout have different sensory quality characteristics.

Under the optimal extraction conditions, a method of ultrasound-assisted solvent extraction (USE) combined with gas chromatography-mass spectrometry (GC-MS) was established to determine volatile substances in polypropylene (PP) packaging materials for self-heating foods. The extraction efficiencies of n-hexane, ethanol, ethyl acetate and dichloromethane for the extraction of volatile substances from self-heating food packaging material were examined. The analytes were qualitatively identified by mass spectral deconvolution with the MS-DIAL software, NIST mass spectral library searching, and chromatographic retention indices. The Cramer class for each identified compound was determined by the threshold of toxicological concern to evaluate their safety, and relative odor activity values were calculated to identify potential odorants. The results showed the extraction efficiencies of n-hexane, ethyl acetate and dichloromethane were similar, and they all had higher extraction efficiency for hydrocarbons, while ethanol had higher extraction efficiency for esters. A total of 72 volatile components were detected in 3 samples, among which 12 components such as N-(2-ethylamino)-1,3-propanediamine, nonanal, 2,4-di-tert-butylphenol, butylated hydroxytoluene, and 2-bromotetradecane should be of more concern. In addition, 14 volatile odor substances were identified, among which nonanal, undecane and hexadecane could potentially contribute to the odor of self-heating food polypropylene packaging. This study provides a scientific method for the analysis of volatile components in self-heating food PP packaging, and provides data support for the safety assessment as well as odor analysis of self-heating food PP packaging.

The sensory quality of six brands of strong and light aroma-type Anxi Tieguanyin tea (three batches each) was evaluated by sensory testing, and their chemical quality was analyzed by gas chromatography-mass spectrometry (GC-MS) combined with multivariate statistical analyses including principal component analysis (PCA), partial least square (PLS) and hierarchical cluster analysis (HCA). The results showed that there were differences in sensory quality among the six brands. Moisture, free amino acids and flavonoids were the key components contributing to the differences in taste among tea products. Light aroma-type tea products A and B had high contents of moisture and free amino acids, and tasted clean, fresh and mellow. The moisture content, free amino acids and flavonoids of strong aroma-type tea products C and D were in the middle and they tasted mellow and relatively thick. Strong aroma-type tea products E and F had high content of flavonoids, and tasted thick, heavy and mellow. These differences in flavor components could mainly be affected by the baking process. Indole, jasmine lactone and cis-3-hexenyl caproate were the key components that determined the aroma characteristics of different tea products. The relative contents of indole, jasmine lactone and cis-3-hexenyl caproate in light aroma-type products A and B were higher, and they had a clean and high aroma. Product A had more esters with a green odor than product B. The contents of indole and jasmine lactone in strong aroma-type products C and D were the lowest, and their aroma was relatively strong. The contents of indole, jasmine lactone and cis-3-hexenyl caproate in product D were slightly higher than those in product C, so the aroma was better. The contents of indole and jasmine lactone aroma components in strong aroma-type products E and F were in the middle, and the baking degree was slightly higher, so the aroma was strong and rich with flowery and fruity fragrance, and product F had more aldehydes which may be responsible for the fragrant aroma with fruity and flowery notes of product F. The difference in aroma components could mainly be affected by raw materials and the baking process. This study is expected to provide some theoretical basis for the fine production, quality management and flavor innovation of Anxi Tieguanyin tea products.

The difference in metabolite composition between De’ang sour tea and ripe Pu’er tea both made from the Yunnan Daye tea cultivar was investigated by non-targeted metabolomics based on ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/QTOF-MS). The results showed that there was a big difference in metabolite composition between De’ang sour tea and ripe Pu-erh tea. Principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) could clearly distinguish the two kinds of tea according to their metabolite composition. A total of 268 significantly differential metabolites belonging to 21 classes were detected between them, accounting for all metabolites of 63.81% of the total metabolites, including 49 amino acids, 39 fatty acids, 36 nucleotides, 29 organic acids, and 18 sugars. The differential metabolites ergothiine, 3-dimethoxyphenylacetic acid, 3-hydroxymandelic acid, acetylcholine chloride, 2-hydroxy-4-methylvaleric acid, misoglitol, L-proline, 4-dioxyheptanoic acid, propanediol, proanthocyanidin B2, N-acetylglycine may have important contributions to the formation of the taste quality of the two kinds of tea. Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis showed that there were significant differences in the metabolism levels of amino acids and nucleotides in De’ang sour tea and Pu’er tea, and that the pathways related to amino acid metabolism and nucleotide metabolism had an important impact on the taste and quality of both kinds of tea.

In order to explore the effects of high-energy electron beam irradiation on the volatile components of Angelicae Dahuricae Radix, changes in its major volatile components after irradiation at different doses were analyzed by using electronic nose combined with headspace solid phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that 54, 64, 59, 53 and 58 compounds were identified in the samples irradiated at doses of 1, 3, 5, 7 and 10 kGy, respectively. In addition, 17 compounds were detected in the untreated control group. The irradiation treatment increased the number of volatile components of Angelicae Dahuricae Radix, and aldehydes and ester hydrocarbons were identified as the major flavor compounds. Besides, ketones were produced after irradiation. Using principal component analysis (PCA), linear discriminant analysis (LDA), cluster analysis and partial least square-discriminant analysis (PLS-DA), all the samples were divided into two groups: 0–3 and 5–10 kGy, indicating that irradiation at a dose of no more than 3 kGy had no significant effect on the odor of Angelicae Dahuricae Radix, and different doses of high-energy electron beam irradiation had different effects on the volatile components of Angelicae Dahuricae Radix.

In this study, Cabernet Sauvignon and Marselan dry red wines were supplemented with grape seed tannins (200 mg/L) before barrel aging. After aging for 12 months, the volatile compounds and aroma characteristics of wine samples were analyzed by gas chromatography-mass spectrometry (GC-MS) and sensory ranking analysis. Results showed that there were different effects of grape seed tannin addition on the aroma of Cabernet Sauvignon and Marselan wine. Grape seed tannin addition promoted the release of vanillic acid, vanillin, ethyl vanillate, furfural, acetylfuran and furfuralcohol from oak wood into Cabernet Sauvignon wine, but inhibited the release of furfural, acetylfuran, furfuralcohol, 5-methylfurfural and 5-hydroxymethylfurfural from oak wood into Marselan wine. Grape seed tannin addition weakened the herbaceous and berry-like aroma notes of Cabernet Sauvignon wine but enhanced the baked aroma note. As for Marselan wine, the herbaceous and floral notes were slightly enhanced. This study is very meaningful for guiding the production of aged dry red wine.

Headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) and similarity analysis were used to evaluate the differences in the volatile flavor compounds of five different colored unpolished rices (red, yellow, green, purple and black) from Yangxian county, Hanzhong city after cooking. The results showed that a total of 61 volatile flavor compounds were identified, including 35 aldehydes ( 49.83%–57.06%), 13 ketones (accounting for 34.40%–41.45%), 5 alcohols (accounting for 1.42%–1.96%), 2 pyrazines (accounting for 0.02%–0.07%), 2 acids (accounting for 0.19%–0.49%), 1 ester (accounting for 0.08%–0.67%), 1 furan (accounting for 5.61%–8.23%), 1 ether (accounting for 0.02%–0.10%), and 1 phenol (accounting for 0.04%–0.22%). The content of aldehydes in cooked unpolished red rice was relatively higher, the content of acids in cooked unpolished yellow rice was relatively higher; the contents of alcohols and ethers in cooked unpolished green rice were relatively higher; the content of furans in cooked unpolished purple rice was relatively higher; and the contents of ketones, esters, pyrazines and phenols in cooked unpolished black rice were relatively higher. Principal component analysis (PCA) showed that the cumulative contribution rate of the first two principal components was 74.1%, which could better explain the characteristics of the original sample data. HS-GC-IMS spectral data could be used to distinguish the volatile flavor components of cooked unpolished rices of different colors. A volatile component fingerprint of cooked unpolished rice of different colors from Yangxian county was established in this study, which can visually presents the contour information of volatile flavor components and enrich the information about the eating quality of the five colored rices from Yangxian.

A pre-column derivatization high performance liquid chromatography (PCD-HPLC) method was developed for simultaneous analysis of short-chain fatty acids (SCFAs) and lactic acid in complex biological samples including intestinal contents and serum. The contents of SCFAs and lactate in mouse feces were determined by PCD-HPLC and compared with those determined by gas chromatography (GC) and high performance liquid chromatography (HPLC). Then, methodological evaluation was performed on PCD-HPLC. PCD-HPLC was applied to analyze intestinal contents and blood. Results showed that GC could rapidly detect acetate, propionate, butyrate and valerate, but not lactic acid. HPLC yielded many impurity peaks and inaccurate results for lactic acid. The PCD-HPLC method was applicable to a wide range of samples and allowed for simultaneous analysis of lactate and five SCFAs in intestinal contents and serum. Only a few impurity peaks appeared in the chromatogram, and a good separation of all analytes was achieved. PCD-HPLC was accurate, giving a coefficient of variation (CV) less than or equal to 8.87% for each analyte. In conclusion, this method is superior to GC and HPLC in determining SCFAs and lactic acid in complicated biological samples such as intestinal contents and serum, and can meet the demand for accurate analysis of SCFAs and lactic acid in complicated biological samples in response to the rapid development of microbial metabolomics.

This study investigated protein oxidation and the changes of free amino acids during the dry salting and ripening of Trachinotus ovatus. For this purpose, the moisture content, salt content and textural characteristics of dry-salted fish, and the carbonyl content, sulfhydryl content, proteolysis index, free amino acids (FFA), secondary structure and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profile of myofibrillar protein from dry-salted fish were analyzed. The results showed that the salt content of cured fish samples increased, and the water content decreased; the hardness increased, and the springiness increased at first and then decreased during curing and air-drying. Protein oxidation occurred during the processing of dry-cured fish. The carbonyl content of myofibrillar protein significantly increased, while the sulfhydryl content decreased. Meanwhile, the α-helix content decreased, while the random coil content increased. The results of SDS-PAGE showed that the myosin heavy chain (MHC) and actin significantly changed and the myosin heavy chain band became lighter and even disappeared after air-drying, indicating that myofibrillar protein degradation occurred. The proteolysis index increased during the whole process. The non-protein nitrogen content decreased after curing but increased during air-drying and the content of total free amino acids reached the highest after one day of air-drying. The contents of umami amino acids and sweet amino acids increased during the whole process. This study can provide a theoretical basis for quality control in the processing of salted aquatic products.

Gas chromatography (GC) and gas chromatography-mass spectrography (GC-MS) were used to identify and quantitate the volatile substances in Maotai-flavoured baijiu produced by two different processes. A discriminant model was established based on odor activity value (OAV) by chemometrics and the key differential substances were identified. The results showed that the contents of volatile compounds in baijiu made from ground sorghum were lower than those in baijiu made from whole sorghum, but the proportions of esters, acids and aromatic compounds were higher, indicating that baijiu quality may be related to the proportion of each compound. Baijiu blends at different ratios were prepared to validate the applicability of the proposed model, four-fifths of which were used as training set, and the remaining one-fifth were used as testing set. The overall accuracy rate was 93.33%, indicating that the model could discriminate the two baijiu samples. The distribution of 9 different proportions of mixed samples in the model showed that it could also be used for preliminary identification of mixed samples, which verified the applicability of the model. In addition, 14 potential differential compounds were identified, and their effectiveness in discriminating the two processes was confirmed by the clustering heatmap. Among these compounds, the variable importance in the projection (VIP) value of furfural was the highest, and the OAV of furfural differed greatly between the two baijiu samples, indicating that furfural may be an important substance causing the difference between the baijiu samples.

The allergen protein Ber e 1 was purified from Brazil nuts by crushing, defatting, extraction, and anion exchange chromatography, and identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), liquid chromatography-tandem mass spectrometry (LC-MS/MS) and Western blot, and its secondary and tertiary structures were characterized by circular dichroism (CD) and UV spectroscopy. The results showed that the purified target protein was identified as Ber e 1, and the yield of Ber e 1 was more than 20 mg per round, and its purity was higher than 95%. The purified allergen showed undamaged secondary or tertiary structures, and could be recognized by the serum of allergic patients. This purification method is simple and efficient with low instrument requirements, which can provide a basis for Ber e 1 research.

An aptamer sensor (aptasensor) based on gold nanoparticles (AuNPs) was developed for the rapid visual detection of Salmonella typhimurium in foods. The aptamer specifically bound to S. typhimurium in samples to be analyzed, and a capturing probe that could adsorb onto the surface of AuNPs was released, avoiding subsequent aggregation of AuNPs induced by salts. In the absence of S. typhimurium, salts induced the aggregation of AuNPs, leading to color changes visible to the naked eye in the solution, thus allowing for the rapid and simple detection of S. typhimurium. The feasibility, detection performance, and specificity of the developed aptasensor were characterized. The aptasensor had a good response performance to S. typhimurium in the range of 10–109 CFU/mL. A linear regression model equation was fitted as follows: y = ?0.129 98x + 1.244 11 (R2 = 0.992 62), and the detection limit was as low as 124 CFU/mL. Four kinds of non-target bacteria were detected by this aptasensor with good specificity. Because of its high sensitivity, simple operation, rapidity and low cost, it holds great promise for rapid and in situ food safety detection.

The migration of the antioxidant Irgafos168 and its degradation products from poly(butyleneadipate-co-terephthalate)/polylactic acid (PBAT/PLA) composite films into the fatty food simulant isooctane under different working conditions (ultraviolet (UV), high humidity and salt atmosphere) was studied by gas chromatography-mass spectroscopy (GC-MS), and the aging degree of composite films under each condition was investigated in terms of their mechanical properties and infrared characteristics. The results showed that the degradation of PBAT/PLA composite films was greatly affected by UV and high humidity conditions. After two days of UV exposure, 60 days of high humidity exposure and 40 days of salt spray exposure, the tensile strength of the composite films decreased by 61.1%, 41.6% and 35.9% to 10, 15 and 17 MPa, respectively, and the elongation at break decreased by 93.5%, 34.1% and 21.5%, respectively. The antioxidant’s concentration had no significant effect on the properties of the composite films (P > 0.05). The migration of Irgafos168 and its degradation products was positively correlated with their initial levels in the composite films. The migration of Irgafos168 from the untreated composite film was the highest (85.39 mg/kg). The content of Irgafos168’s degradation products in the composite films increased with aging, the major one being tri(2,4-di-tert-butylphenyl) phosphate, which was produced in the largest amounts under UV conditions, and the migration of tri(2,4-di-tert-butylphenyl) phosphate was 3.04-99.50 mg/kg. The migration of the substances could be affected by temperature, their initial contents and the aging degree of the composite films.

This study aimed to develop an immunochromatographic test strip model based on magnetic fluorescence nanomaterials in order to make up for the shortcoming of lateral flow immunoassay and provide technical support for the development of more sensitive rapid immunological assays. Using deoxynivalenol (DON) as the target, carboxyl-modified superparamagnetic particles were prepared by the solvothermal method. The magnetic particles, green fluorescent protein and anti-DON monoclonal antibody were coupled by the carbodiimide method to prepare magnetic fluorescent antibody probe. A magnetic fluorescence immunochromatographic test strip was established with DON-bovine serum albumin (BSA) as the test line. Meanwhile, a colloidal gold immunochromatographic test strip was established with colloidal gold-labeled anti-DON monoclonal antibody as the probe and DON-BSA as the test line. The magnetic fluorescence antibody probe exhibited good magnetic and fluorescent properties and antibody reactivity. The regression equation of the magnetic fluorescence immunochromatographic test strip was y = ?0.562x + 0.921, R2 = 0.990. The half maximal inhibitory concentration (IC50) was 5.611 ng/mL, and the detection limit was 1.089 ng/mL. The sensitivity of the colloidal gold immunochromatographic test strip was 500 ng/mL with naked eyes, the regression equation was y = ?0.543x + 1.485, R2 = 0.991, the IC50 was 65.16 ng/mL, and the detection limit was 11.94 ng/mL. The sensitivity of the magnetic fluorescence immunochromatographic test strip was 10.96 folds higher than that of the colloidal gold immunochromatographic test strip. The magnetic fluorescence immunochromatographic test strip allowed simultaneous sample enrichment and fluorescence signal detection and was successfully used in the detection of DON with high sensitivity. This study may lay the foundation for the application of magnetic fluorescence nanoparticles in the field of immunochromatographic assay.

In this study, amine-functionalized magnetic mesoporous silica@gold nanoparticles-aptamer-complementary DNA-ferrocene complex (NH2-MMS@Au NPs-Apt-cDNA-Fc) was prepared by using aminated magnetic mesoporous SiO2 supported acetamiprid aptamer and ferrocene-labeled complementary DNA (Fc-cDNA) as probes, and used to construct a highly sensitive electrochemical aptasensor with modification-free electrode for rapid detection of acetamiprid. In 0.1 mol/L phosphate buffered saline (PBS) solution (pH 7.4), using a bare glassy carbon electrode as working electrode, the linear range for acetamiprid detection by square wave voltammetry was 0.055 pmol/L–5.5 nmol/L at the optimal incubation time. The limit of detection was 3.2 fmol/L (RSN = 3). Satisfactory results were obtained for the detection of acetamiprid in vegetables. This method effectively avoids the systematic errors caused by the tedious electrode modification and probe fixation processes, is easy to operate, and has high accuracy. It provides a new and simply sensing technology for highly sensitive detection of pesticide residues in foods, and has a good application prospect.

A novel nanocomposite composed of 1T-phase tungsten disulfide nanosheets (1T-WS2) and gold nanoparticles (AuNPs) was prepared by a simple self-assembly method and was used to construct a white kidney bean esterase-based electrochemical biosensor for the low-cost and highly sensitive detection of fenitrothion, which could enhance the sensor’s sensitivity by virtue of its excellent physicochemical properties. The morphology and composition of the prepared material were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Working parameters such as pH, composite loading and enzyme loading were investigated. Under the optimum conditions, the linear range was 0.1–2 000 mg/L, the correlation coefficient of the standard curve was 0.992 and the limit of detection (LOD) was 0.04 mg/L. In addition, the proposed biosensor showed satisfactory repeatability, stability and selectivity. The biosensor has been applied to the analysis of fenitrothion in real agriculture samples with recoveries of 96.16%–109.60%, indicating that the biosensor has potential application in the detection of organophosphorus pesticides.

Carboxy carbon nanotubes and dialyzed graphene oxide were bound via amio and carboxyl groups using polydopamine as a cross-linking agent to form a three-dimensional mixed aerogel (MA) with a hierarchical porous structure. Silver nanoparticles were loaded in situ onto MA to develop an efficient electrochemical method for the detection of hydrogen peroxide in foods. The response current to hydrogen peroxide of AgNPs-MA modified electrode was 24.5 times higher than that of bare glassy carbon electrode under the optimal conditions (pH 7.4, working bias of ?0.4 V and 5 μL of modified electrode solution). Chronoamperometry was used to detect hydrogen peroxide rapidly and sensitively. The peak current of the modified electrode had a good linear relationship with the concentration of hydrogen peroxide, which was fitted the following equation: I = 0.32c + 1.66 (R2 = 0.999 3), and the limit of detection (LOD) was 0.02 μmol/L (signal-to-noise ratio, RSN = 3). In addition, the electrochemical sensor had high accuracy, stability and anti-interference performance, and could be reused. The sensor was applied to the monitoring of hydrogen peroxide in milk, with a recovery rate of 98.1%–98.8% and a relative standard deviation (RSD) of 0.58%–2.28%. It is expected to be applied to the rapid trace detection of hydrogen peroxide in foods.

An analytical method was established for the determination of 14 phenolic compounds in cream by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and the migration of phenolic compounds from plastic contact materials into cream was studied. The samples were soaked in cream, extracted with acetonitrile/methanol, and separated on a T3 column. The analytes were detected in negative electrospray ionization (ESI) mode with multiple reaction monitoring (MRM), and quantified by the matrix-matched external standard method. The migration of bisphenol A (BPA) and 4-nonylphenol (4-NP) from plastic contact materials into cream was analyzed. The results showed that the limits of detection of the 14 phenolic compounds were 0.15–0.75 μg/kg and the limits of quantification were 0.5–2.5 μg/kg. A good linear relationship was observed for all analytes with correlation coefficients greater than 0.99. The recoveries for spiked whipping cream and non-dairy cream were 78.2%–117.1% and 79.4%–114.6% with relative standard deviations (RSDs) of 1.07%–12.1% and 1.12%–12.5%, respectively. The migration of BPA and 4-NP into cream increased with increasing temperature and contact time. The highest levels of migration of BPA, BPS and 4-NP from plastic cake decorations into cream w were determined to be 4.61, 0.94 and 125.1 μg/kg, respectively. The number of samples that tested positive for 4-NP was the largest. Much attention should be paid to the risk of migration of phenolic compounds into foods.