Abstract:Food packaging sterilization is an important technical means to avoid the spread of SARS-CoV-2 and the cross-contamination of foodborne viruses. However, the secondary hazards generated after sterilization are complex and have different characteristics, and a wide range of factors affect the formation of these hazards. The studies about the migration behavior of secondary hazards from packaging materials to food remain to be reviewed. Therefore, the author systematically reviewed the correspondence between sterilization technologies and secondary hazards generated after food packaging sterilization, the characteristics of secondary hazards, the factors affecting the formation of secondary hazards, and the detection technologies of secondary hazards. By outlining the classical migration model, the author summarized the migration patterns and harm of secondary hazards generated by different sterilization technologies and the specific measures to prevent the migration, thus providing guidance for guaranteeing the safety of pre-packaged food during transportation and storage after sterilization.

Abstract:Phytosterols esters are a type of compound synthesized through the esterification reaction between phytosterols and fatty acids. To clarify the research and application of phytosterols (esters), the author provided an overview of their structural characteristics, synthesis methods, and physiological functions. Additionally, it was elucidated that phytosterols (esters), as functional food ingredients, play a significant role in reducing cholesterol levels and exhibiting antioxidant properties in the human body. By delving into the bioactivity of phytosterols (esters) and enhancing people’s awareness of their nutritional value, this study makes an outlook on the research and application prospects of phytosterols (esters) in food, thereby providing a crucial theoretical basis for the application of functional foods.

Abstract:[Objective] This study aims to enhanced the conversion efficiency of allitol through biocatalytic methods. [Methods] The ribulose dehydrogenase (RDH) genes rdh from Providencia alcalifaciens, Klebsiella pneumoniae and Klebsiella oxytoca were respectively expressed in Escherichia coli (E. coli) BL21, designated as Pardh, Kprdh and Kordh respectively to identify the target genes with higher transformation rates. Further, the RDH from Klebsiella oxytoca was coupled with the formate dehydrogenase (FDH) from Candida boidinii for co-catalysis, and the catalytic conditions and the addition amounts of co-substrates were optimized to achieve efficient enzymatic catalytic synthesis of allitol. [Results]When using FDH and RDH from Klebsiella pneumoniae with an initial substrate D-piscose of 50 g/L and continuous feeding over 6 h to a total concentration of 100 g/L, in the presence of sodium formate as the auxiliary substrate, the conversion rate of allitol reached 53.3%. [Conclusion] By coupling the RDH and FDH systems, the conversion rate of allitol can be increased.

Abstract:[Objective] The strains with high-yield for active compounds such as cordycepin and cordycepic acid were screened from Cordyceps militaris (C. militaris) collected in Shaanxi Hualongshan National Nature Reserve. [Method] Three strains LH3, LY1, and LY9 of C. militaris were isolated and identified. The yields of the primary active compounds, hydroxyl radical scavenging activity, and cellular oxidative protection activity in the extracts of the mycelial and fermentation broth of each strain were determined. [Result] The yields of cordycepic acid, crude polyphenols, and crude polysaccharides, which were the main active compounds of C. militaris, were the highest in the mycelia extract of strain LY9, with values of 2.94, 28.79, 65.01 mg/g, respectively, while the yield of cordycepin was the highest (0.53 mg/g) in the fermentation broth extract of strain LY1. Both the extracts of mycelia and fermentation broth of strain LY9 exhibited significant hydroxyl radical scavenging (IC₅₀ values of 0.923 mg/mL and 0.619 mg/mL, respectively) and cellular oxidative protection activities, with cell viabilities of 82.65% and 78.46% at a mass concentration of 1.00 mg/mL. When being cultivated for fruiting bodies, only strain LY9 successfully formed fruiting bodies, with higher yields of cordycepic acid, crude polyphenols, and crude polysaccharides than those in its mycelia. [Conclusion] Strain LY9 exhibits high yields of active compounds, outstanding antioxidant and cellular oxidative protection activities, and a stable ability to form fruiting bodies with high mass fractions of active compounds. Therefore, it has the potential to be domesticated for commercialization of C. militaris.

Abstract:[Objective] This study aims to establish a method for determining the residual amount of cethromycin in poultry eggs based on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).[Method] Four representative poultry eggs (chicken eggs, duck eggs, goose eggs, and quail eggs) were selected as the research matrices. Cethromycin was extracted with Mcllvaine-Na2EDTA buffer solution, purified by hydrophilic-lipophilic balanced polymer solid-phase extraction column (HLB), separated by a C18 column with 0.1% (volume fraction) formic acid water and acetonitrile as the mobile phase, and determined by HPLC-MS/MS in the multiple reaction monitoring (MRM) mode combined with an external standard method.[Result] Cethromycin was well separated on the chromatographic column. The standard curve had a good linear relationship (R2≥0.999) in the range of 1~100 μg/kg. The limit of detection (LOD) was 0.3 μg/kg, and the limit of quantification (LOQ) was 1.0 μg/kg. The spiked recovery rates ranged from 76.3% to 102.6%, and the relative standard deviations (RSD) were all less than 15% (n=6).[Conclusion] The established method is simple to operate and accurate in qualitative and quantitative analyses. It can be used for the rapid screening and quantitative analysis of cethromycin in poultry eggs.

Abstract:[Objective] This study aims to verify and screen the Bifidobacterium adolescentis strains with vitamin A (VA) metabolic capacity, and investigate their effects on colitis symptoms and gut microbiota in mice. [Method] The VA metabolic capacity of a panel of Bifidobacterium adolescentis strains was evaluated through in vitro fermentation, and the strain with the highest VA metabolic capacity was ultimately selected. This strain was administered orally to mice with dextran sulfate sodium (DSS)-induced colitis for 6 consecutive days. After the intervention, histopathological changes in the colonic tissue were assessed, and the levels of intestinal injury markers in the serum and cytokines, antioxidant enzymes, and retinoic acid (RA) in the colonic tissue were measured. Additionally, gut microbiota composition was analyzed by metagenomic sequencing. [Result] Bifidobacterium adolescentis FHNFQ5M4 which possessed the highest VA metabolic capacity significantly alleviated the damage induced by DSS, modulated the cytokine and RA levels, and mitigated the oxidative stress in mouse colonic tissue. Moreover, Bifidobacterium adolescentis FHNFQ5M4 markedly altered the gut microbiota composition in colitis mice, leading to enrichment of Butyricimonas and reduced relative abundance of Staphylococcus. [Conclusion] Bifidobacterium adolescentis FHNFQ5M4 can effectively modulate the gut microbiota and alleviate DSS-induced colitis symptoms in mice, demonstrating the potential as a probiotic candidate for the treatment of ulcerative colitis (UC).

Abstract:[Objective] This study aims to develop a lipase-mediated furfural oxidation system in ionic liquid for the green synthesis of furoic acid, 5-hydroxymethyl-2-furancarboxylic acid, and 2,5-furandicarboxylic acid under mild reaction conditions. [Method] Using furfural as the substrate, Novozym 435 lipase as the catalyst, hydrogen peroxide as the oxidant, and 1-butyl-3-methylimidazolium acetate ionic liquid as the solvent, the conditions including reaction temperature, reaction time, initial furfural concentration, and initial hydrogen peroxide concentration were optimized. The system was further extended to the oxidation of 5-hydroxymethylfurfural, and coupled with a chemical oxidation process using an imidazolium-based ionic liquid and tert-butyl hydroperoxide to achieve one-pot synthesis of 2,5-furandicarboxylic acid. [Result] Under the optimized conditions, the yield of furoic acid exceeded 99%. The oxidation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furancarboxylic acid achieved yield of 94%. 2,5-furandicarboxylic acid was synthesized via the one-pot coupled reaction with a yield of 90%. [Conclusion] This study provides a novel strategy and methodology for the green synthesis of bio-based chemicals such as furoic acid and 2,5-furandicarboxylic acid.

Abstract:[Objective] The research on the synergistic use of lactic acid bacteria and yeast in sourdough is beneficial for meeting the industrial production demand of fermentation agents for baking food.[Method] This study investigated the acid tolerance, acid production, enzyme production, gas production, and alcohol production abilities of various strains during the fermentation process by measuring the microbial count, pH, stretching area, elongation, hardness, viscosity, storage modulus (G′), loss modulus (G″), etc. of bread dough. The effects of different fermentation agents on the total titratable acidity (TTA), stretching characteristics, texture characteristics, and rheological properties of bread dough were investigated. [Result] Lacticaseibacillus paracasei LG0260, Lactiplantibacillus plantarum LG1034, Lactococcus lactis LG0827, as well as Saccharomyces cerevisiae J2808 and S. cerevisiae J2815, maintained good acid production rates and abilities throughout the fermentation process. Especially, L. paracasei LG0260, Kluyveromyces marxianus J2828, and L. lactis LG0827 exhibited the highest phytase enzyme activity (23.21 mU/mL), amylase enzyme activity (0.82 U/mL), and protease enzyme activity (2.51 U/mL), respectively. In addition, the fermentation agent MY2L1 prepared by co-culture fermentation of S. cerevisiae J2808 and L. paracasei LG0260 effectively improved the stretching area and elongation of bread dough, with the highest values of 242 cm² and 181 mm, respectively. [Conclusion] Liquid strains have greater impacts on the hardness and viscosity of sourdough than commercial Angel yeast. The mixed fermentation with liquid strains enhances the fluid properties of the dough. This study can provide technical reference for mining type Ⅱ sourdough fermentation agents and improving sourdough quality.

Abstract:[Objective] This study aimed to develop high-quality fermented Rosa roxburghii (R. roxburghii) products by screening yeast strains suitable for R. roxburghii fermentation. [Method] The naturally fermented R. roxburghi pomace was used as the material for preliminary screening through the TTC colorimetric method and secondary screening based on fermentation capacity. The tolerance of strains to SO₂, ethanol, low pH, and glucose was examined. The strains were identified via morphological characterization and molecular biological techniques. [Result] Three high-performing strains (B17, B19, and B29) were obtained. These strains exhibited tolerance to 250 mg/L SO₂, mass fraction 60% glucose, volume fraction 8% ethanol, and pH 3.5 environment. B17 and B29 were identified as Pichia kudriavzevii, while B19 was characterized as Kluyveromyces marxianus, showing ester production of 4.11, 4.31, and 3.93 g/L, respectively. [Conclusion] The screened strains exhibit the potential for industrial production of fermented R. roxburghii products, particularly suitable for crafting low-alcohol, high-flavor fruit wine.

Abstract:[Objective] This study aims to develop functional microbial strain resources from the pit mud of Jiangxiangxing Baijiu and explore their potential in optimizing the fermentation process and improving Baijiu quality.[Method] Lactic acid bacteria were screened from the pit mud of Jiangxiangxing Baijiu by the spread plate method and then identified by morphological and molecular biological methods. The metabolites of the strains were detected by high performance liquid chromatography and gas chromatography, and the whole genomes of the strains were sequenced via the Illumina sequencing technology. [Result] Eleven strains of lactic acid bacteria were isolated and screened from the pit mud of Jiangxiangxing Baijiu. Among them, Lactobacillus plantarum r-JN-1 had the faster growth and the strongest acid production capacity. Lactobacillus plantarum r-JN-1 tolerated pH 4.0~10.0, temperatures of 25~40 ℃, and NaCl solutions with the concentrations of 0~7 g/dL. Meanwhile, it could use a variety of sugars for fermentation. The determination of volatile components in the culture liquid of Lactobacillus plantarum r-JN-1 showed that fermentation with this strain could produce various key aroma components of Jiangxiangxing Baijiu, such as 3-hydroxy-2-butanone and ethyl lactate. The whole genome sequencing results showed that the genome sequence of Lactobacillus plantarum r-JN-1 was 3 330 678 bp, with the GC content of 44.32% and 3 301 protein-encoding genes. The gene annotation results in COG, GO, KEGG, and CAZy databases showed that Lactobacillus plantarum r-JN-1 carried extensive genes associated with the metabolism of carbohydrates. [Conclusion] This study provided a theoretical basis for further exploring functional microorganisms in the brewing of Baijiu and expanding the application of lactic acid bacteria.

Abstract:[Objective] This study optimized the extraction process of polyphenols from Camellia japonica (C. japonica) flowers and preliminarily explored the antioxidant and blood glucose-lowering effects of the extracted polyphenols, aiming to improve the utilization of C. japonica flowers. [Method] With the flowers of Xinyang Maojian as raw materials, the ultrasonic-assisted method was adopted to extract polyphenols from C. japonica flowers, and the antioxidant and blood glucose-lowering activities of the extracted polyphenols were analyzed. With the extraction rate of polyphenols from C. japonica flowers as the evaluation index, the response surface methodology was adopted to explore the effects of ethanol volume fraction, solid-liquid ratio, extraction time, and ultrasonic power on the extraction rate of polyphenols from C. japonica flowers. [Result] Under the conditions of the ethanol volume fraction of 54%, the solid-liquid ratio of 1 g∶33 mL, the extraction time of 49.5 min, and the ultrasonic power of 210 W, the actual extraction rate obtained from verification experiment was 12.60%, with a relative standard deviation (RSD) of 2.28%, which indicated that the optimization results were reliable. In addition, the polyphenols from C. japonica flowers had strong scavenging abilities against DPPH, hydroxyl, and ABTS⁺ free radicals. The scavenging abilities were positive correlated with the mass concentration of the extracted polyphenols, and the half-inhibitory mass concentrations (IC₅₀) were 0.044, 0.065, and 0.068 mg/mL, respectively. The extracted polyphenols had good inhibitory effects on the activities of α-glucosidase and α-amylase, with the IC₅₀ of 0.054 and 0.057 mg/mL, respectively. [Conclusion] The polyphenols from C. japonica flowers can be used as a good natural antioxidant and blood glucose-lowering agent, demonstrating potential application value. This study provides a theoretical foundation for the refined processing of C. japonica flowers.

Abstract:[Objective] The aim of this study is to investigate the structural characteristics, antibacterial activity, and antioxidant capacity of silver nanoparticles (AgNPs) prepared from Phyllanthus emblica extract. [Method] AgNPs were prepared with Phyllanthus emblica extract as a reducing agent. The structure of the AgNPs was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photon correlation spectroscopy (PCS), and transmission electron microscopy (TEM). Furthermore, the inhibitory effects of AgNPs at different mass concentrations on Escherichia coli ATCC25922, Staphylococcus aureus ATCC25933, and Pseudomonas aeruginosa PAO1 were assessed, with the minimum inhibitory concentrations (MIC) being determined. In addition, the superoxide anion and ABTS⁺ free radical scavenging abilities and the reducing capacity of AgNPs were determined. [Result] The AgNPs prepared with Phyllanthus emblica extract presented a face-centered cubic structure with a particle size range from 10 to 30 nm and good dispersion. Their antibacterial properties gradually increased with the rising mass concentration of AgNPs. AgNPs had strong, moderate, and weak inhibitory effects on Escherichia coli ATCC25922, Pseudomonas aeruginosa PAO1, and Staphylococcus aureus ATCC25933, with the MICs of 0.031, 0.063, and 0.125 mg/mL, respectively. AgNPs at high mass concentrations exhibited strong antioxidant properties. At 1.000 to 2.000 mg/mL, AgNPs showed high superoxide anion and ABTS⁺ free radical scavenging abilities but weak reducing capacity. [Conclusion] The AgNPs prepared by the green method from Pseudomonas emblica extract has good dispersion, strong antibacterial activity, and strong antioxidant capacity. The results provide scientific guidance for the research and development of AgNPs as a preservative and offer a reference for their future application in food preservation.

Abstract:[Objective] To enhance the stability of serine carboxypeptidase during enzymatic hydrolysis and expand its industrial applicability, the author employed rational design and immobilization technology to develop efficient and stable enzymatic catalysts in view of the easy deactivation of this enzyme. [Method] On the basis of the serine carboxypeptidase Y (CPY) derived from Aspergillus oryzae M30011, single mutant enzymes M517R, I464R, and Y271R and the triple mutant enzyme M517R/I464R/Y271R were designed. These mutant enzymes were then prokaryotically expressed in Escherichia coli and subjected to enzyme activity assays. Subsequently, the mutant enzyme with the highest activity was immobilized with covalent organic framework materials (COFs), yielding the composite designated as COFs@mutant enzyme. The free mutant enzyme and the COFs@mutant enzyme were systematically evaluated in terms of the pH stability, thermal stability, half-life, and reusability. In addition, with rice bran protein as the substrate, the hydrolysis effect of the COFs@mutant enzyme combined with alkaline protease (AP) was investigated. [Result] The four mutant enzymes were successfully expressed and purified, with the triple mutant M517R/I464R/Y271R exhibiting the highest enzyme activity (1 069.54 U/mg). Therefore, the triple mutant enzyme M517R/I464R/Y271R was immobilized with COFs (COFs@triple mutant enzyme).Compared with the free triple mutant enzyme, COFs@triple mutant enzyme demonstrated strong stability across wide ranges of pH and temperature, with a half-life extended to 498 min and the relative enzyme activity of approximately 50% after 6 reuse cycles. The results of the enzymatic hydrolysis experiment showed that the Fischer ratio (F-value) of the oligopeptides prepared from rice bran protein by AP combined with COFs@triple mutant enzyme was 34.01, far exceeding the preparation threshold (>20), indicating the good application potential of this combination in the preparation of oligopeptides. [Conclusion] The synergistic strategy of mutant enzyme design and immobilization technology significantly enhanced the industrial applicability of serine carboxypeptidase, providing a new direction for the production of functional oligopeptides and the optimization of industrial enzyme catalysis efficiency, and demonstrating broad application prospects.

Abstract:[Objective] This study clarifies the key roles of naringenin and epigallocatechin gallate (EGCG) in inhibiting 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhlP) formation in roasted meat and reveals the molecular mechanisms by which naringenin and EGCG regulate precursor consumption and intermediate accumulation, aiming to provide a scientific basis for reducing the risk of heterocyclic amines in food processing. [Method] The changes in precursors of PhIP in roasted chicken breast were determined, and a model reaction system of flavonoids, methylglyoxal (MGO), and phenylalanine (Phe) was established. The reaction kinetics curves of key substances were studied to decipher the inhibition mechanisms of naringenin and EGCG against the formation of PhlP. [Result] Naringenin and EGCG inhibited the consumption of creatine and amino acids, precursors of PhlP formation, thereby inhibiting the formation of PhlP in chicken breast during roasting. Replacing glucose (Glc) with MGO in the model reaction system helped to reduce the interference from complex reaction products, which facilitated the identification of the critical point at which naringenin and EGCG intervened in PhlP formation. Naringenin and EGCG reduced the production of the PhlP precursor phenylacetaldehyde and the Maillard reaction intermediate MGO. The reaction kinetic model data revealed that the elimination reaction rates of EGCG and naringenin with phenylacetaldehyde were the highest, indicating that the elimination reaction was a key for the two compounds in inhibiting PhlP formation. [Conclusion] EGCG and naringenin inhibited the formation of PhlP by reducing the amount of phenylacetaldehyde in the reaction system through the elimination reaction.

Abstract:[Objective] This study aims to reduce the cost and simplify the production process of β-nicotinamide mononucleotide (β-NMN) by the enzyme catalytic method. [Method] On the basis of the previously established β-NMN synthesis system with six enzymes, the six enzyme genes were combined in pairs to construct double-enzyme co-expression recombinant strains. Each crude enzyme solution obtained by co-expression was used for multi-enzyme catalytic cascade reaction to synthesize β-NMN. [Result] The yield of β-NMN was as high as 72.90% when the concentration of the substrate D-ribose was 10 mmol/L. The optimal temperature and IPTG induction concentration for inducing the enzyme expression of the recombinant strains were 25 ℃ and 0 mmol/L, respectively. Finally, the salt ions and polyhydroxy compounds that significantly improved the storage stability of 5-phosphate ribose-1-pyrophosphate synthase (EcPrs) were identified. Mn²⁺, lactose, and sorbitol basically had no effect on the yield of β-NMN. [Conclusion] The multi-enzyme catalytic cascade reaction for the preparation of β-NMN under dual-enzyme co-expression system and the optimization for EcPrs storage stability provide a new idea for the enzyme catalytic synthesis of β-NMN.

Abstract:[Objective] This study aims to investigate the effect of exogenous enzyme treatment on the quality of summer green tea and optimize the enzyme treatment conditions. [Method] Sensory evaluation was employed to evaluate and screen the tea samples treated with six exogenous enzymes. The effects of cellulase, tannase, and treatment conditions on the sensory quality, bitter/astringent taste attributes, and main biochemical components of summer green tea were studied by electronic tongue and chemometrics methods. The optimal treatment conditions of cellulase and tannase were comprehensively evaluated by hierarchical cluster analysis, correlation analysis, and principal component analysis (PCA). [Result] Sensory evaluation revealed that cellulase and tannase significantly improved the flavor quality of tea samples. Electronic tongue and biochemical component analysis indicated that both enzyme treatments significantly reduced the predicted mass concentrations of bitterness/astringency as well as the mass fractions of tea polyphenols and ester-type catechins (ETC) while increasing the levels of soluble sugars, non-ester-type catechins (NEC), and gallic acid (GA). Moreover, tannase demonstrated a superior effect compared with cellulase. Hierarchical cluster analysis and PCA showed significant difference between exogenous enzyme-treated tea samples and control tea samples. Predicted mass concentrations of astringency and sensory score were identified as key factors affecting the overall quality of tea samples. The optimal treatment conditions of cellulase and tannase were enzyme concentration of 30 U/mL, solid-to-liquid ratio of 1 kg:20 mL, and treatment time of 40 min. [Conclusion] The results of this study can provide theoretical support for improving the taste quality of summer green tea with exogenous enzymes and the utilization of fresh summer tea leaves.

Abstract:[Objective] This study aims to explore the role of Lactobacillus in enhancing host immunocompetence and preventing vaginal infections with Candida albicans. [Method] A human vaginal epithelial cell (VK2/E6E7 cell) model was employed to screen the most potent strain among ten vaginal Lactobacillus isolates in inducing the antimicrobial peptide LL-37. A mouse model of vaginal infection with Candida albicans was established. The effects of oral administration of the selected Lactobacillus strain on vaginal mucosal immunity, systemic inflammatory balance, and vaginal microbiota homeostasis were systematically evaluated using hematoxylin-eosin (HE) staining, ELISA, qPCR, and 16S rRNA sequencing. [Result] Both the cell lysate and fermentation supernatant of Lacticaseibacillus paracasei CCFM1433 upregulated antimicrobial peptide LL-37 secretion in VK2/E6E7 cells by 22.5% and 12.3%, respectively, compared with the control group, exhibiting superior activity over those of other strains. Live Lacticaseibacillus paracasei CCFM1433 increased the level of cathelicidin-related antimicrobial peptide (CRAMP) in the vaginal tissue to 1.82 times that of the model group, increased the level of secretory immunoglobulin A (sIgA) by 52.9%, and the level of immunoglobulin G (IgG) in the serum by 16.9% compared with the model group. It also increased the level of IL-10 in the spleen by 23.9%, while reducing the TNF-α level by 20.3%. In addition, both live Lacticaseibacillus paracasei CCFM1433 and its postbiotics inhibited the TLR4/MyD88 signaling pathway, preventing overactivation of inflammatory pathways. The 16S rRNA sequencing results indicated that the live bacteria of this strain effectively maintained the vaginal homeostasis of Lactobacillus communities and its intervention effect was closely associated with a significant enrichment of functional genes in the signaling molecules and interaction pathway in the mouse vaginal microbiome. [Conclusion] Lacticaseibacillus paracasei CCFM1433 exerts an anti-infection effect and effectively prevents Candida albicans infections by directly activating host mucosal immunity, modulating inflammatory responses, and restoring the Lactobacillus-dominant vaginal microbiota. These findings provide theoretical support for the application of probiotics in preventing vaginal infections.