Pasteurized milk is highly regarded for its ability to effectively retain nutrients and sensory quality, but its shelf life is limited by the heat-resistant microorganisms and their metabolic products remaining during the mild sterilization process. To solve this problem, the key is to identify the core residual flora and its metabolic network that lead to quality degradation. In this study, pasteurized milk stored at 4 ℃ for 0, 6, 9, and 12 days was examined to explore the changes in physicochemical properties, microbial communities, and functional metabolism during storage. Physicochemical analysis showed a slight decrease in fat, protein, and lactose content and a significant increase in acidity, particle size, and yellowness during storage. Among three pasteurization treatments (65 ℃/30 min, 75 ℃/15 s, and 85 ℃/15 s), the 75 ℃/15 s protocol optimally preserved nutrients and sensory quality, providing critical parameters for process optimization. Metagenomic analysis by Illumina HiSeq sequencing platform showed that Acinetobacter, Pseudomonas and Lactococcus might be the main core microflora leading to the deterioration of pasteurized products during storage. Pasteurized milk processed for 75 ℃/15 s can maintain good quality when stored at 4 ℃ for 0-9 days. Storing at 4℃ for 9 days may be the key storage point for microbial dynamics. Functionally, genes related to carbohydrate metabolism, amino acid metabolism, and energy metabolism increased with storage time. These metabolic pathways are crucial for microbial growth and may affect the nutritional composition and quality of pasteurized milk. Core microbiota primarily impacted milk quality through pyruvate metabolism and valine, leucine, and isoleucine biosynthesis pathways, leading to changes in acidity, bitterness, and texture. This study provides a basis for the monitoring and quality safety management of the main microorganisms and active metabolites during the production, processing and storage of pasteurized milk, and lays a foundation for obtaining high-quality pasteurized milk with long shelf life.

This study was implemented in order to obtain Tetraplococcus halophilus with the ability to produce umami peptides. A total of 83 strains suspected of being T. halophilus were isolated from 96 naturally fermented soybean paste samples from seven different areas of Liaoning province. Through DNA extraction, 16S rDNA sequencing and comparative homology analysis, 47 of these strains were identified as T. halophilus and were screened for their ability to produce polypeptide, γ-glutamyl transpeptidase and protease and their electronic tongue flavor values. Moreover, factor analysis and factor score comprehensive evaluation were carried out, revealing that T. halophilus LY9-1 had the greatest potential to produce umami peptides. The results of electronic tongue also proved that the fermentation broth of T. halophilus LY9-1 had the highest umami value of 15.05 ± 0.02, as well as protease activity of (85.45 ± 0.03) U/mL, γ-glutamyl transpeptidase activity of (44.23 ± 0.03) U/mL, and polypeptide production of (17.55 ± 0.13) mg/mL. It is speculated that the strain has a strong umami-enhancing potential. The findings reported here can motivate further research on the umami-enhancing mechanism and encourage the industrial application of T. halophilus LY9-1 to enhance the umami of fermented foods.

Platycodonis Radix, a well-known edible and medicinal plant, has been used to create functional meals or dietary supplements. The primary bioactive effects constituents in it, known as platycosides, are pentacyclic triterpenoid saponins of the oleanane type. Compared to glycosylated platycosides, deglycosylated platycosides have stronger bioactivities. Herein, Lactobacillus plantarum M3, which was isolated from Platycodonis Radix pickles, was used to ferment the total platycosides and the products' effect on fat accumulation was evaluated in HepG2 cells. We demonstrated this strain can biotansformate glycosylated saponins into platycoside D₃, deapiosylated platycoside D₃ and deapiosylated platycoside D. The products have the ability to significantly reduce the accumulation of intracellular lipids and the contents of cholesterol (TC) and triglyceride (TG) in HepG2 cells. Additionally, deapiosylated platycosides had a stronger anti-inflammatory impact than their precursor glycosylated counterparts. In conclusion, deglycosylated platycosides have a potential lipid-lowering capacity and can be used as functional food additives.

Probiotics exert numerous beneficial effects by regulating gut microbiota composition and are considered a promising nutritional strategy for ameliorating lipid metabolism disorders. This study evaluated the beneficial effects of Lactiplantibacillus plantarum FS5-5 (L. plantarum FS5-5), a candidate probiotic with lipid-lowering ability, on diet-induced lipid metabolism disorders. The results showed that strain FS5-5 significantly decreased weight gain, fat coefficient, and lipid levels while alleviating liver oxidative stress damage in high-fat diet (HFD) mice. Serum metabolomics results showed that L. plantarum FS5-5 modulated lipid metabolism, particularly in linoleic acid metabolism, alpha-linolenic acid metabolism, and primary bile acids (BAs) biosynthesis pathways. Mechanism analysis suggested that L. plantarum FS5-5 promoted fatty acid β-oxidation (FAO) by regulating the expression of key genes in the lipid metabolism pathway, including Fxr, Fgf15, Shp, Pparγ, Pgc1α, etc. This effectively reduced several medium/long-chain acylcarnitines levels in serum and promoted fat breakdown. Further analysis showed that the abundance of gut-beneficial bacteria was increased, and intestinal permeability and barrier damage were alleviated after FS5-5 intervention. Spearman correlation analysis showed that several specific genera were notably associated with HFD-related indicators. These findings demonstrated that L. plantarum FS5-5 was a potential functional food for preventing lipid metabolism disorders.

In order to further analyze the taste characteristics and processing stability of umami peptides from Tetragenococcus halophilus, 41 suspected umami peptides from T. halophilus were tested in this study, and three synthetic peptides (EEEEEE, HAAGMVE, and ESVYAST) with the highest umami values were selected using an electronic tongue. Their taste characteristics were analyzed by sensory evaluation, and the effects of temperature and pH on the stability of the umami peptides were analyzed. The results showed that all three peptides showed umami taste, with perceptual threshold ranging from 0.108 to 0.362 mmol/L. Among them, HAAGMVE demonstrated a particularly potent umami-enhancing effect. The stability analysis results showed that the umami values of EEEEEE, HAAGMVE and ESVYAST increased with increasing pH from 4.0 to 8.0, but remained stable in the temperature range of 25–100 ℃. EEEEEE exhibited the best stability. The results of this study provide a theoretical basis for the development and utilization of umami peptides derived from T. halophilus, and lay a foundation for improving the flavor quality of fermented products and promoting their industrial production.

Ulcerative colitis is a chronic inflammatory bowel disease, and its incidence is increasing year by year in China. Current drug treatments have side effects, so the use of probiotics to regulate intestinal microbiota is emerging as an intervention method. Numerous studies have shown that bifidobacteria have a good clinical effect in alleviating symptoms of ulcerative colitis. However, the underlying mechanism has not been systematically elucidated. In recent years, with continuous breakthroughs in research on multi-omics, the gut microbiota, the gut-brain axis, and the gut-liver axis, significant progress has been made in understanding the action mechanism of bifidobacteria in alleviating ulcerative colitis. This article reviews the latest progress that has been made in the research and application of bifidobacteria in alleviating ulcerative colitis in the past decade, and introduces bifidobacteria alleviating ulcerative colitis, with a focus on the underlying mechanism. This review reports that bifidobacteria alleviates ulcerative colitis mainly by regulating the structure of the intestinal microbiota, restoring intestinal barrier function, improving intestinal immune response, regulating intestinal purine metabolism, inhibiting oxidative stress, and providing energy for the intestinal epithelium. It is our hope that this review will provide a reference for further elucidating the regulatory mechanism of bifidobacteria on life and health as well as for furthering the application and promotion of probiotic preparation.

Docosahexaenoic acid (DHA; 22n-6) possesses multiple biological functions, including antioxidant activity and ameliorating hypertriglyceridemia. However, the application of DHA has been limited due to poor aqueous solubility and susceptible to oxidation. Here, ovalbumin (O), myosin (M), 7S soy globulin (S), and β-lactoglobulin (β), hydrolyzed by chymotrypsin, self-assembled into micelles, respectively. Adding incremental DHA to micelles caused endogenous fluorescence quenching of O, M, S, and β micelles, implying successful incorporation of DHA into hydrophobic cores of micelles (O (DHA), M (DHA), S (DHA), and β (DHA)). The results showed that micelles provided spatial stability and improved solubility, and stability against thermal and ultraviolet (UV) light for DHA. The uptake of DHA from M (DHA), β (DHA), O (DHA), and S (DHA) was 3.27-, 3.91-, 2.7-, and 3.95-fold higher, respectively, than that of DHA by Caco-2 cells. Encapsulation in micelles increased DHA aqueous solubility and uptake, which enhanced cellular endogenous antioxidant defense. Meanwhile, increased uptake of DHA was verified by HepG2 cells, and O, M, S, and β micelles were proven to increase DHA uptake to reduce lipid deposition. Our findings strongly support the possibility that O, M, S, and β micelles can be regarded as a carrier for loading DHA.

Pasteurized milk contains complex microbial communities affected by sterilization and storage conditions. This complex microflora may be the possible reason that pasteurized dairy products are highly prone to spoilage. In this study, packaged pasteurized milk products collected from dairy processing factories in China were stored at 0, 4, 10, 15, and 25 ℃ for 0−15 days and subjected to microbial identification using high-throughput sequencing. Accordingly, 6 phyla and 44 genera were identified as the dominant microbiota. Moreover, the changes in nutritional composition of the pasteurized milk, including in 16 free amino acids, 7 taste values, and 8 chemical constituents, were analyzed using principal component and multi-factor analyses. The Pearson correlation analysis identified Pseudomonas, Aeromonas, Paenibacillus, and Serratia genera as the core functional microbiota that significantly affects the nutritional composition of pasteurized milk. Hence, the results provide a comprehensive understanding of the safety and shelf-life of stored pasteurized milk.