Abstract:In the production, processing, storage and transport of dairy products, there are two types of proteases, the endogenous proteases of dairy products and the exogenous proteases produced by microbial contamination. These proteases not only cause a number of problems, such as the deterioration of dairy product quality, resulting in a significant reduction in the shelf life of the product and serious damage to taste and flavour, but also add to the cost of dairy companies in the production and processing process, compressing profit margins, limiting the economic efficiency of the industry. Research has shown that the heat-resistant protease secreted by cold-loving bacteria is one of the key elements affecting the quality and safety of dairy products. In the dynamic and complex process of dairy processing, storage and transport, real-time and accurate quantitative monitoring of thermoprotease activity remains a major technical barrier and challenge for the dairy industry. The existing knowledge on heat-resistance proteases in dairy products was comprehensively reviewed, its primary sources, specific heat-resistance mechanisms, and protein hydrolysis patterns were analyzed, while its distinctive biological functions within dairy environments were elucidated. At the same time, the technical advantages and limitations of traditional classical assays for monitoring endogenous and exogenous proteases in dairy products were analyzed, and emerging detection strategies such as peptidomics and biosensors were reviewed. Due to their unique technical principles and detection modes, these emerging detection methods have good application prospects in the field of real-time monitoring of heat-resistance proteases and are expected to overcome existing technological bottlenecks such as interference from complex matrix in samples, difficulty in balancing detection sensitivity and specificity, and high demand for real-time performance.

Abstract:Vitamins are essential organic small molecules that maintain normal physiological functions in living organisms. Most vitamins cannot be synthesized autonomously by the human body and must be supplemented through food or pharmaceuticals to meet physiological demands. Driven by the growing emphasis on healthy diets and the advancement of carbon neutrality strategies, the development of bio-manufacturing technologies for vitamins has become increasingly significant. While China is a global leader in vitamin production, technical bottlenecks persist in the areas of high-end vitamins and critical intermediates. Taking the representative water-soluble vitamin B5(VB5) as an example, the current state of vitamin synthesis technologies were systematically summarized. The evolution of VB5 manufacturing technologies, from first-generation chemical synthesis, second-generation chemo-enzymatic/enzymatic catalysis, to third-generation fully biofermentation-based synthesis were elaborated, highlighting the iterative advancements in vitamin synthesis pathways. The applications of multi-strategy approaches in third-generation fully biofermentation-based synthesis for VB5 production were examined, including the enhancement of sugar uptake systems, redirection of central carbon metabolism flux, cofactor balancing, regulation of competitive pathways, and optimization of transport systems. Additionally, interdisciplinary research directions such as systematic metabolic engineering modification coupled with fermentation process optimization were proposed. These strategies aimed to drive continuous innovation in vitamin bio-manufacturing technologies, providing robust support for the high-quality development and enhancing international competitiveness of China's vitamin industry.

Abstract:Docosahexaenoic acid (DHA) is an important omega-3 long-chain polyunsaturated fatty acid. As a main fatty acid in the brain and retina, DHA is crucial for the neurological health of fetuses, infants, and the elderly. It can help to improve cardiovascular health, prevents cognitive decline, and has anti-inflammatory and antioxidant effects. The structure, functions, and main sources of DHA were reviewed, with a focus on the challenges faced by microbial DHA oil synthesis, particularly the complexity of metabolic pathways and the diversity of oil components. The strategies for enhancing DHA production were also discussed, including the directional selection of lipid-producing microorganisms, regulation of metabolic mechanisms, and the application of fermentation amplification technology. Furthermore, the future development of DHA-rich oil derivatives has been prospected, highlighting products with greater potential. With continuous advancements in biotechnology and metabolic engineering technology, the applications of DHA-rich oils would extend beyond traditional dietary supplements to encompass functional foods, precision nutrition, and medical therapeutics, and ect., promoting the development of DHA products toward higher value-added applications with enhanced bioactivity.

Abstract:To examine the fermentation characteristics of oat β-glucan (OG) and its impact and mechanism on host circadian rhythms, an in vitro fecal microbial fermentation experiment was performed. 16S rDNA and non-targeted metabolomic analyses were conducted on the fecal flora and culture supernatant of OG fecal fermentation system, and a microbe-metabolite association network was constructed. The influence of altered gut microbiota and metabolites after OG treatment on the expression of rhythmic genes in Caco-2 cells were explored through in vitro cellular experiments. The results of the study demonstrated that OG induced notable alterations in the composition and structure of the gut microbiota. OG supplementation led to an increase in the abundance of Firmicutes, Faecalibacterium, Parabacteroides, and Bifidobacterium longum, along with other gut microbiota. The changed microbiota induced by OG was observed to produce more metabolites with rhythm-regulating potential, such as 5-hydroxytryptophan, L-tryptophan, and glycitein. The metabolic pathway based on differentially present metabolites after OG intervention was significantly enriched in the tryptophan metabolic pathway. The analysis of the microbe-metabolite interaction network revealed a positive correlation between the abundance of Fusicatenibacter and the level of L-tryptophan, while a negative correlation was observed between the abundance of Megamonas and the level of glycitein. Furthermore, the OG-treated fecal microbiota and associated culture supernatant were found to significantly regulate the expression of the majority of tested core clock genes in the in vitro Caco-2 cells. The findings indicated that OG might exert an indirect influence on the expression of rhythm genes in intestinal cells through the regulation of the composition of gut microbiota and associated metabolites, especially the metabolites related to the tryptophan metabolic pathway. The study would provide theoretical guidance for the development and future application of OG in alleviating circadian rhythm-related disorders.

Abstract:The construction of iron loaded hydrogel delivery carrier is an important strategy to solve the gastric digestion stability of peptide-iron chelate. Sodium alginate and potato starch were used as raw materials, and calcium chloride was used as cross-linking agent to prepare hydrogel beads loaded with different iron sources [yolk peptide-iron chelate (EYP-Fe), iron dextran and FeSO₄] by external gel method. The results showed that the hydrogel beads prepared with 1.5g/100mL sodium alginate and 1.0g/100mL potato starch mixed solution had good molding effect and stability, and the encapsulation efficiency for different iron sources could reach more than 84%. The hydrogel beads showed high stability in acid environment, with swelling rate less than 10%. Under neutral to weak alkaline conditions, hydrogel beads showed significant swelling properties. This indicated that iron could prevent precipitation in the stomach and be effectively released and absorbed in the intestine. Infrared spectrum and X-ray diffraction results showed that hydrophilic interaction was the main driving force for the formation of hydrogel beads. The simulated in vitro digestion process indicated that the hydrogel beads contracted in the stomach (29%-31%), and the iron release rate was maintained at 11.0%-19.0%. Among them, the EYP-Fe loaded hydrogel beads exhibited the lowest iron release rate (11.2%±2.9%). During intestinal digestion, hydrogel beads swelled and slowly released encapsulated iron sources, with an iron release rate of more than 79%. Therefore, sodium alginate/potato starch composite hydrogel beads could improve the stability of EYP-Fe in the stomach and had the ability to deliver iron to the intestinal environment. The research aimed to provide theoretical and technical references for the development of new oral iron supplements.

Abstract:Mepiquat (Mep) is a food contaminant produced usually during heat processing. It is formed by Maillard reaction with free lysine, reducing sugar and alkylating agent under typical roasting conditions. It was found that Mep exposure could cause kidney vacuolization, liver and spleen damage, but its metabolic mechanism in vivo was still not clear, which made it difficult to assess its exposure risk. Untargeted metabolomics was used to reveal effects of Mep on the metabolic profile of urine in rats based on gas chromatography-mass spectrometry. Differential metabolites and histopathological changes of rat kidneys were analyzed. The result showed that 24 differential metabolites were screened out from rat urine before and after Mep exposure. Among them, 5 metabolites were upregulated, 19 metabolites were down-regulated. Metabolic pathway analysis of the differential metabolites revealed that 5 major perturbed metabolic pathways were found with response values greater than 0.1 before and after the exposure of Mep, which were glycine, serine and threonine metabolism, glycerolipid metabolism, pentose and glucuronate interconversions, inositol phosphate metabolism, and glyoxylate and dicarboxylic acid metabolism. These pathways were mainly related to amino acid metabolism, energy metabolism, carbohydrate metabolism and lipid metabolism. Glycine, serine and threonine metabolism was the metabolic pathway with the largest response value. It was hoped that this study could provide theoretical reference for elucidating the toxic mechanism of Mep.

Abstract:In order to explore the effects of chestnut skin and inner skin bound polyphenols on the intestinal microbiota of SD rats, an in vitro colonic fermentation model was constructed, which was divided into chestnut skin bound polyphenols (CSBP) group, chestnut inner skin bound polyphenols (CISBP) group and control (CK) group, and the microbial diversity analysis of the three groups was determined by 16S rRNA high-throughput sequencing technology. The results showed that compared with the CK group, the relative abundance of intestinal microbiota in the CSBP group and CISBP group increased overall, the ratio of Bacteroidetes to Firmicutes increased, and the relative abundance of beneficial bacteria such as Lactobacillus and Intestinimonas significantly increased. However, the relative abundance of harmful bacteria such as Dorea and Clostridiales significantly decreased. In addition, the function prediction showed that CSBP had the effects of promoting cell growth and reconstruction, maintaining the normal function of tissues and organs, scavenging free radicals and toxic substances, and reducing cell damage and inflammation. CISBP could promote fat metabolism, blood sugar regulation, neurotransmitter synthesis, and protein construction. It could be concluded that CSBP and CISBP had an effect on the intestinal microbiota, promoting beneficial bacteria and inhibiting harmful bacteria by increasing the abundance of intestinal microbiota, and the intestinal microbiota of SD rats developed towards a healthier composition. This study aimed to provide a reference for further development of chestnut resources and the research and development of functional foods that could regulate intestinal microbiota.

Abstract:Zearalenone (ZEN) is one of the most widely distributed Fusarium toxins that can contaminate a variety of agricultural products, such as maize. A strain with high degradation efficiency of ZEN was isolated from wheat inter-root humus soil with ZEN as the sole carbon source. Through morphological observation, 16S rDNA sequencing and whole genome sequencing, it was identified as Acinetobacter pittii M-1. Through degradation activity verification, it was found that the detoxifying enzymes with degradation activity to ZEN were mainly concentrated in the fermentation supernatant. It was found that the optimal degradation temperature and pH for M-1 were 60℃ and 9, respectively. Under these conditions, the degradation rate for 10μg/mL of ZEN reached as high as 90.85% within 48h. Mn²⁺ could significantly enhance the detoxification activity of the fermentation supernatant. Under the optimal conditions, M-1 achieved a degradation of 89.92% for 2μg/mL of ZEN. Based on the Q exactive focus quadrupole orbitrap mass spectrometry, the structure identification of ZEN degradation products was preliminarily completed, and the ZEN degradation product was identified as zearalenone 4-sulfate, which had significantly lower toxicity than ZEN. Based on the M-1 whole genome sequence, screening of genes encoding ZEN detoxification enzyme was carried out, and the coding gene in M-1 was preliminarily identified as ahpC, and the detoxification enzyme was NADH-dependent peroxiredoxin. In addition, it was found that H₂O₂ intervention could significantly improve the degradation efficiency of ZEN in M-1, and further increased the possibility of detoxification enzyme as NADH-dependent peroxiredoxin. This research indicated the ability of Acinetobacter pittii to degrade ZEN, which provided novel microbial resources for ZEN detoxification in grains. Furthermore, it established a foundational framework for high-efficiency expression and industrial application of ZEN-detoxifying enzymes derived from Acinetobacter pittii.

Abstract:Liquid nitrogen ultra-low temperature treatment is an efficient and safe method for extending the shelf life of food. Rapid freezing and repeated freeze-thaw treatments on both green and roasted coffee beans were carried out by liquid nitrogen. Sensory evaluation of flavor, analysis of physicochemical components, determination of non-volatile compounds such as chlorogenic acid derivatives, alkaloids, andminerals, and scanning electron microscopy, were used to study the effects of ultra-low temperatures on the non-volatile flavor quality and ultra-microstructure of coffee beans. The results indicated that roasting combined with ultra-low temperature treatment significantly reduced the content of most chlorogenic acid derivatives and γ-aminobutyric acid in coffee beans, while significantly increased the levels of citric acid, malic acid, lactic acid, and alkaloids. Ultra-low temperature treatment had no significant impact on the sensory flavor of roasted coffee beans. Pre-roasting rapid freezing of green coffee beans using liquid nitrogen significantly increased the acrylamide content. Scanning electron microscopy observations revealed that ultra-low temperature treatment did not cause significant changes in the gap width of green coffee beans, whereas internal filamentous connections formed in roasted coffee beans, and the gap width of repeatedly freeze-thawed roasted coffee beans decreased significantly. Mantel tests and Pearson correlation analyses showed that the richness of roasted coffee beans sensory indicators was significantly correlated with chlorogenic acid and other compounds, and balance was extremely significantly correlated with mineral elements Fe and Cu. It was concluded that liquid nitrogen ultra-low temperature treatment could extend the flavor preservation period of coffee beans, but also caused changes in the content of non-volatile flavor components and microstructure. These findings aimed to provide a theoretical basis and data support for the storage and preservation of coffee beans and the control of flavor quality.

Abstract:To investigate taste characteristics of the umami properties and their interaction mechanisms with umami receptors, five Stropharia rugosoannulata umami peptides (EP-6, SG-7, PH-5, SE-6, ES-7) were taken as the research objects, and the combined technology of sensory evaluation, electronic tongue analysis, surface plasmon resonance (SPR) molecular interaction technology, and molecular docking were used to systematically evaluate the umami intensity of the five umami peptides and analyze the molecular action mechanism with umami receptors. Sensory scoring (0-10) and taste dilution analysis revealed that EP-6 and ES-7 exhibited the highest umami intensity (6.90±0.88 and 6.70±0.95, respectively), with detection thresholds of 0.178mmol/L and 0.167mmol/L, significantly lower than the threshold (1.774mmol/L) of 0.3mg/mL monosodium glutamate (MSG). Principal component analysis of electronic tongue data (cumulative contribution rate reached 91.8% for first two components) demonstrated that the umami strength of EP-6 and ES-7 was comparable to 0.1% MSG, consistent with sensory evaluation. SPR kinetic analysis indicated that ES-7 showed the strongest binding affinity with T1R3-VFD receptor (KD=1.471×10-6mol/L), characterized by binding and dissociation rates of fast on and fast off. Molecular docking revealed that EP-6 and SG-7 achieved the lowest docking energies (-436.52kJ/mol and -397.81kJ/mol, respectively), stabilized by hydrogen bonds and hydrophobic interactions with key residues (ASN68, GLU45, HIS278). Notably, sulfur-containing amino acids Cys prolonged umami perception through thiol-mediated interactions, corroborating the kokumi features observed in sensory evaluation. This study established a comprehensive and rapid evaluation system for umami peptides through combination of electronic tongue-molecular interaction-molecular docking technology, overcoming the subjective limitations of traditional sensory methods. The identification of core binding sites in umami receptor domains and elucidation of sulfur-containing amino acids' regulatory role in taste persistence provided molecular insights for rational design and high-value application of natural umami enhancers. These findings advanced the development of precision flavor modulation technologies with significant implications for food science applications.

Abstract:Aiming at the problems of quality deterioration and flavor loss of fresh tomatoes after harvest, the effects of 4kJ/m² short-wave ultraviolet (UV-C) treatment on storage quality of fresh tomatoes was studied by using “original No. 1” fresh tomatoes as experimental materials. The results showed that compared with the control group, UV-C treatment effectively maintained the sensory quality of fresh tomatoes, delayed the decrease of firmness and total pectin content at the end of storage, decreased the content of malondialdehyde, and inhibited the activity of polygalacturonase at the early storage stage and pectin lyase at the late storage stage, consequently maintained the fruit texture. UV-C treatment slowed down the increase of weight loss rate, inhibited the decline of soluble solids, and increased the contents of total phenol and ascorbic acid at the late storage stage, thereby preserving the nutritional quality of fruit. A total of 44 volatile compounds were detected in two groups of fresh tomatoes during storage. UV-C treatment promoted the production of aroma substances, such as linalsol, cyclopentanone, (Z)-6-noneol and phenylacetaldehyde, while inhibited the decrease of characteristic aroma substances, such as 2-methyl-1-butanol, 2-methyltetrahydrofuran-3-one, phenylethanol and isobutyl isobutyrate, and the production of undesirable flavor substances such as propionic acid, 2-methyl-2-propanol, ethanol, 2-methylthiophene and 2-methylbutyrate. UV-C treatment could effectively maintain the quality of fresh tomatoes during storage, preserve their good flavor, and prolong the storage period. The research results aimed to provide theoretical reference for the application of UV-C irradiation technology in the preservation of fresh fruits and vegetables such as tomatoes.

Abstract:Newhall navel oranges exhibiting various degrees of maturities were selected as the research object. A sophisticated technique, involving headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry, was employed to meticulously analyze the key flavor-active substances in the pulp and to track the evolving trends of these compounds at different maturities. This research revealed that the a total of 19 aroma compounds were detected in the pulp of Newhall navel oranges at 3 different maturities, including pre-mature, mature, and post-mature. The types of aroma compounds in the pulp of Newhall navel oranges showed no significant differences across various maturities. However, their concentrations exhibited notable fluctuations with changes in maturity. The terpenoids were the main aroma compounds in the pulp of Newhall navel oranges. Specifically, the concentrations of hexan-1-ol, octan-1-ol, geranial, and damascenone displayed an ascending trend from the pre-mature to the mature stage, followed by a decline from the mature to the post-mature stage, peaking during the mature stage. The contents of remaining compounds exhibited a gradual increase across three distinct maturity levels, with their concentrations peaking in the post-mature stage. The odor activity value (OAV) method was used to analyze the flavor-active substances in Newhall navel oranges. It was found that among the compounds with OAV>1, the OAV values ranked in descending order as follows, D-limonene, hexan-1-ol, damascenone, octanal-1-ol, linalool, carvone, neral, geranial, citronellol, and L-perilla aldehyde. Through aroma profile radar chart analysis, it was determined that the pulp of Newhall navel oranges was primarily characterized by citrus and fruity aromas, accompanied by prominent grassy, floral, and sweet aromas, along with minimal woody and unpleasant odors. The citrus and fruity aromas were most pronounced at the post-mature stage. This research was expected to provide an experimental foundation for further studies and development of Newhall navel orange pulp.

Abstract:High-temperature Daqu is the main aroma source of sauce-flavor Baijiu, which has an important impact on the style and quality of sauce-flavor Baijiu. Sauce-flavor Baijiu produced in Beijing and Guizhou has local characteristics, but the differences in flavor compounds and their causes are still unclear. Correlation analysis was conducted on the quality differences between the physicochemical indicators, microbial community composition, and volatile flavor compounds of high-temperature Daqu from Beijing and Guizhou regions. The results showed that the starch content, liquefaction power, and esterification power in the high-temperature Daqu samples from Beijing were significantly higher than those from Guizhou. However, high-temperature Daqu samples from Guizhou region had higher acidity and saccharification power (P<0.001). In addition, the core bacterial communities in high-temperature Daqu samples from Beijing and Guizhou regions were Virgibacillus, Kroppenstedtia, while the core fungal communities were Thermoascus and Thermomyces. There were significant differences in the volatile flavor components of high-temperature Daqu between Beijing and Guizhou regions, with Guizhou sample containing more types of volatile substances (27) than Beijing sample (23). Spearman correlation analysis showed that the bacteria with the highest correlation of flavor compounds in high-temperature Daqu from Beijing and Guizhou were different, which led to different flavors of Baijiu in the two regions. The quality differences of physicochemical indicators, microbial community composition and flavor composition of different high-temperature Daqu in Beijing and Guizhou were compared and analyzed in order to further understand the microbial and functional characteristics of high-temperature Daqu in Beijing and Guizhou, and further clarify the reasons for the differences in flavor of Baijiu in the two regions.

Abstract:Reducing the salinity is an important direction in the development of surimi products, but the low salt addition significantly affected the gel properties of surimi. To investigate the effect of various levels of bamboo salt on the gel properties of reduced-salt surimi, the effects of different contents of bamboo salt on the gelation properties of surimi and its substitution effects of the table salt were systematically investigated, based on the analysis of the elemental composition and physicochemical properties of bamboo salt. The results demonstrated that bamboo salt contained significantly higher mineral element compared to table salt, with the mass fractions of Mg, Ca, and K being elevated by 25.6%, 183.3%, and 18.5%, respectively. The presence of these basic elements significantly improved the pH and conductivity of bamboo salt, and further improved the gel properties of surimi gels. The springiness, strength, and hardness of surimi gels increased with the increase of bamboo salt concentration of 1.0%-2.5%, which was more conducive to the formation of a denser three-dimensional network structure of surimi gels. Meanwhile, the thermal stability, protein intermolecular forces, dynamic rheological properties (energy dissipation density), fracture stress, and fracture strain of surimi gels were gradually increased, resulting in a more stable and mechanically tough surimi gel. Among all studied groups with bamboo salt concentrations ranging from 1.0% to 3.0%, the surimi gel properties of 2.5% bamboo salt group were the best, which significantly increased the gel strength and resilience of surimi gels by 21.4% and 6.0%, respectively, compared with the 2.5% table salt group. Based on the comprehensive analysis of the physicochemical properties, gel properties and sensory evaluation of surimi gels, the concentration of 2.0% bamboo salt showed the same gelation effect with the concentration of 3.0% table salt, reaching a 33% reduction in salt content. The findings could provide technical support for the development of high-quality low-salt surimi products and provide theoretical references for the broadening of the application of bamboo salt in the meat processing.

Abstract:To investigate the effect of selenomethionine on the changes of biochemical properties of pearl gentian grouper under anhydrous preservation conditions, the changes of blood biochemical indexes, selenium content, glycogen content and lactate content of grouper in fresh sample group, control group and selenomethionine fed group (Se-Met group) at different preservation time were determined. The findings indicated that the selenium concentration in the muscle and liver tissues of the Se-Met group peaked at 12h, displaying a notable increase compared to the control group(P<0.05). Moreover, both the overall antioxidant capability and the activity of superoxide dismutase remained consistently superior to those observed in the control group, culminating in peak levels after 6h of anhydrous preservation. The efflux rate of aspartate aminotransferase and alanine aminotransferase in the serum increased initialy and then gradually slowed down due to the effect of the defense system, and were always lower than that of the control group, indicating that the grouper tissue cells were more complete after selenomethionine action. In contrast to the fresh sample group, the levels of glycogen in control group and Se-Met group were notably diminished after anhydrous preservation(P<0.05), with the Se-Met group exhibiting the minimum level of 10.38mg/100g at the 12h. The lactate levels escalated over time, with the Se-Met group achieving the highest concentration of 1.91mmol/L at 6h, and the control group peaking at 1.84mmol/L at 12h. It is noteworthy that the Se-Met group consistently displayed a more elevated lactate concentration than the control group. The orthogonal partial least square analysis indicated that the alanine aminotransferase and glycogen content in the Se-Met group showed significantly influences on the changes of selenium levels. This research aimed to provided a reference for the utilization of selenomethionine in anhydrous preservation.

Abstract:In order to address the issues of high energy consumption and quality deterioration in the traditional Lycium barbarum drying process, the design of Lycium barbarum drying equipment and the optimisation of process parameters were conducted based on high-voltage electric field drying technology, revealing the correlation between electric field characteristics and drying efficiency. Based on research into the principle and structure of the equipment, the shape of the electrode, the form of the needle plate electrode, and the optimisation of process parameters, the influence of voltage, needle-to-plate spacing, and needle spacing on the electric field characteristics were explored. Through the self-developed high-voltage electric field drying experimental platform, the mechanisms of key parameters such as voltage intensity (0-50kV), needle-to-plate spacing (2-6cm), and needle spacing (4-10cm) on the electric field characteristics were systematically analysed. Single factor experiment and a quadratic orthogonal rotation combination design response surface analysis were used to establish a mathematical model correlating the drying rate with the electric field parameters. The electric field distribution characteristics were simulated using COMSOL Multiphysics simulation software. The results indicated that the optimal drying effect was achieved at a voltage of 35kV, a needle-to-plate spacing of 4cm, and a needle spacing of 4cm, with an average drying rate of 0.0549g/(g·h). The results aligned well with the electric field simulation, and the established high-voltage electric field model could be utilised to simulate the change trend of drying rate in the actual drying process. The objective of this study was to establish low-energy-consumption and high-quality Lycium barbarum drying equipment, thereby providing a new approach and technical support for the production of dried Lycium barbarum.