Yufang Li

Mozzarella cheese produced with Moringa oleifera seed rennet (MSR) showed excellent sensory attributes, which possessed a smooth surface, uniform texture, and a delicate, well-rounded taste. Electronic tongue and nose confirmed that MSRC has a unique and distinguishable taste and aroma. Proteolysis by MSR released elevated levels of sweet and umami free amino acids (FAAs), particularly leucine and phenylalanine (VIP >1). MSRC also contained higher amounts of free fatty acids (FFAs), C4:0 and C6:0 provided creamy and cheese-like flavors. MSRC had the highest content of odor-active substances, with esters being the most abundant group (23.9%). Notably, ethyl lactate imparted a distinct fruity character. Flavor formation involved the integrated regulation of proteolysis, lipolysis, and volatile synthesis. Partial least squares regression effectively modeled the relationships between flavor compounds (FAAs, FFAs, volatiles) and sensory properties. The results of this study provide a theoretical basis for the application of MSR in mozzarella cheese.

This study evaluated the potential of Moringa oleifera seed rennet (MSR) as a novel hydrocolloid coagulant for mozzarella cheese production compared with commercial rennets. Mozzarella cheeses were manufactured using MSR and 3 commercial rennets (calf rennet, CR, papain rennet, PR, rice black mold rennet, MR). MSR-treated cheese (MSRC) showed comparable nutritional value to calf rennet cheese (CRC), with no significant differences in protein and fat content (P > 0.05), while exhibiting superior hardness and elasticity compared with PR- and MR-treated cheeses.Mechanistically, MSR specifically hydrolyzed κ-casein, increasing α-helix content and fluorescence intensity while reducing free sulfhydryl content, indicating strengthened protein secondary and tertiary structures. These changes led to a denser, more stable protein gel network with smaller pore sizes and more uniform casein distribution, as confirmed by microstructure analysis. Rheologically, MSRC exhibited higher G' and G" values, indicating enhanced elastic and viscous gel-like behavior. Correlation analysis revealed strong positive correlations between fat content and hardness (r = 0.995) and between protein content and elasticity (r = 0.951), while α-helix structure was negatively correlated with moisture (r = -0.980), resilience (r = -0.915), and meltability (r = -0.880). These findings demonstrate that MSR is a viable plant-based, sustainable alternative to commercial rennets for mozzarella cheese production.

The present study characterized a novel antimicrobial peptide (AMP) identified from the hydrolysates of fermented yak milk proteins. In total, 469 peptide fragments were identified. Enzymatic cleavage site analysis indicated that the AMP were predominantly enriched in α_s1-casein. A novel AMP (FYMp9) was identified, and it exhibited significant antibacterial activity against Staphylococcus aureus (half maximal inhibitory concentration [IC₅₀] value of 0.32 mg/mL) and demonstrated good biosafety. We found that FYMp9 irreversibly damaged S. aureus cells by disrupting the bacterial cell membrane structure. Molecular docking analysis revealed that FYMp9 bound to specific amino acid residues of DnaK and histidine kinase accessory gene regulator C (AgrC), forming stable complexes and exerting synergistic antibacterial effects via a dual mechanism. The present study revealed the release pattern of AMP in fermented milk proteins, providing a theoretical foundation for the molecular design of novel antimicrobial agents and offering new insights into addressing global food safety and antimicrobial resistance challenges.

Diannan small-ear pig (DSP) ham is known for exceptional flavor. However, the composition of flavor components and the mechanisms underlying flavor development remain unclear. In this study, we employed lipidomics, flavoromics, and ultra-high-performance liquid chromatography–tandem mass spectrometry technologies to investigate the composition and formation mechanism of DSP ham flavor compounds. On a 10-point scale, the results demonstrated that DSP ham had good flavor qualities with sensory scores of 8.6 ± 0.52 for flavor, 7.9 ± 0.57 for taste, 8.2 ± 0.79 for texture, 8.8 ± 0.42 for color, and 8.3 ± 0.48 for acceptability. A total of 1534 lipids, 80 volatile flavor compounds, and 25 free amino acids were identified in the ham, including 14 characteristic lipids and 28 characteristic flavor compounds. Triglycerides (TG) and diacylglycerol (DG), two important lipids, are broken down into free fatty acids, which are essential building blocks for flavor formation. Non-volatile sweet amino acid L-alanine and bitter amino acid L-lysine are combined with volatile components, including 1-octene-3-ol, hexanal, benzaldehyde, and octanal, to enhance the development of DSP ham flavor. Correlation analysis indicated that key lipids, including TG, DG, and phosphatidylcholines (PC), facilitate the formation of volatile compounds in DSP ham via the glycerophospholipid metabolic pathway. This study provides a theoretical reference for further research and product development of high-quality DSP ham.

Lactiplantibacillus plantarum B22 exhibits a high esterase/lipase activity, but the genomic and probiotic potential remains unclear. We employed an integrated approach combining whole-genome sequencing, molecular docking studies, and phenotypic assays to dissect the genomic and functional basis underlying the high lipolytic activity and probiotic traits of L.plantarum B22. This strain exhibited a robust lipase activity (3.45 ± 0.13 U/mL), with whole-genome analysis revealing that the complete genome of this strain spans 2,027,325 bp, encoding 2005 genes with a guanine-cytosine (GC) content of 35.06%. Notably, 13 esterase/lipase genes were identified, 4 of which (gene3060, gene3059, gene2553, gene0798) harbor conserved catalytic triads (Ser-His-Gly/Ala), essential for lipase function. Molecular docking studies confirmed strong binding affinity to tributyrin (ΔG ≤ –5.52 kcal/mol) and elucidated the interaction mechanisms, involving hydrogen bonding and hydrophobic interactions between the esterase/lipase enzymes and tributyrin. Phenotypic and genomic analyses further demonstrated that L. plantarum B22 possesses excellent tolerance to simulated human gastrointestinal tract conditions, along with potent antioxidant and antimicrobial activities, highlighting its strong probiotic potential. Genomic annotation also identified 68 genes associated with lipid metabolism and an intact fatty acid synthesis pathway. Importantly, the analysis of phenotypes and genes involved in virulence factors, and the production of harmful metabolites suggests that L. plantarum B22 is safe. Collectively, this study offers novel insights into the genome-guided functional characterization of L. plantarum B22, providing a robust foundation for its development as a functional probiotic strain.

Chlorogenic acid (CGA), a polyhydroxy phenolic acid, has been extensively studied for its antimicrobial properties. Staphylococcus aureus (S. aureus) threatens food safety by forming biofilms. This study aimed to investigate the mechanism of CGA against S. aureus and its biofilm. The anti-bacterial activity of CGA was assessed using crystal violet staining, TEM, SEM, a CLSM, and using metabolomics and molecular docking to elucidate the mechanism. The results indicated that the minimum inhibitory concentration of CGA against S. aureus was 2.5 mg/mL. CGA disrupts the integrity of bacterial cell membranes, leading to increased hydrophobicity, morphological changes, scattering, and reduced spreading. This disruption decreases biofilm adhesion and bacterial count. Metabolomics and molecular docking analyses revealed that CGA down-regulates key amino acids. It forms hydrogen bonds with penicillin-binding protein 4 (PBP4), Amidase, glutamate synthetase B, and glutamate synthetase A. By inhibiting amino acid metabolism, CGA prevents biofilm formation. CGA interacts with amino acids such as aspartic acid, glutamine, and glutamate through hydroxyl (-OH) and carbonyl (-C=O) groups. This interaction reduces cell viability and biofilm cohesion. The novel findings of this study, particularly the extension of the shelf life of pasteurized milk by inhibiting S. aureus growth, highlight the potential of CGA as a promising anti-biofilm strategy and preservative in the dairy industry.

BCp12 is a novel casein-derived antibacterial peptide with a broad-spectrum antibacterial effect. However, its action mechanism against E. coli is unknown. In this study, the growth curve showed that BCp12 had excellent antibacterial activity against E. coli. Red (propidium iodide staining) and green (fluorescein isothiocyanate staining) fluorescence signals were detected at the edges of the E. coli cells treated with BCp12. scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that E. coli cells became rough and shrunken, and part of the cell contents leaked to form a cavity. Furthermore, the iTRAQ proteome analysis showed that 193 and 174 proteins were significantly up-regulated and down-regulated, respectively, after BCp12 treatment. Four enzymes involved in fatty acid degradation of E. coli were down-regulated, disrupting the synthesis of cell membranes. Molecular docking and gel retardation assays showed that BCp12 could bind to genes encoding four key enzymes involved in the fatty acid degradation pathway through hydrogen bonding and hydrophobic interactions, thus significantly inhibiting their activities. Overall, the results indicate that BCp12 inhibits the growth of E. coli, causing metabolic disorders, thus destroying the structure of cell membranes.