To investigate the structure of Alpinia oxyphylla Miq. oligosaccharides (MC) and their impact on human gut microbiota, MC was extracted and purified using ultrasound-assisted high-voltage pulsed electric fields. Its structural characteristics were analyzed using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Its in vitro antioxidant and hypoglycemic activities, as well as its regulatory mechanism on the intestinal flora were investigated. Results showed that the extracted MC was a glucose homopolymer (100% glucose monosaccharide composition) with a molecular weight of 2461 Da. The β-glycosidic bond configuration of MC was confirmed by FT-IR spectroscopy, with characteristic peaks observed at 1656 cm⁻¹ and 1623 cm⁻¹. A hierarchical structure characterized by coexisting crystalline and amorphous domains within the β-glucan backbone was demonstrated through XRD and SEM analyses. These structural features constituted a structural basis for targeting gut microbiota. In vitro activity assays indicated that MC exhibited negligible antioxidant activity, but demonstrated notable hypoglycemic activity. Fecal fermentation experiments demonstrated that MC markedly increased the abundance of Bacillota, reduced Bacteroidetes, and enriched the genera Ligilactobacillus and Weissella, thereby regulating and improving intestinal function. This study provides a theoretical foundation for developing Alpinia oxyphylla Miq. oligosaccharides as prebiotics.

To enhance the bioaccessibility of astaxanthin (ASTA), this study constructed astaxanthin nanoemulsions (ASTA-NEs) using high-pressure microfluidization technology, with methyl linolenate (ML, esterified modification), flaxseed oil (FO, rich in unsaturated fatty acids), and coconut oil (CO, rich in saturated fatty acids) as the oil phases, respectively corresponding to astaxanthin-loaded methyl linolenate nanoemulsions (MLA), flaxseed oil nanoemulsions (FOA), and coconut oil nanoemulsions (COA), with astaxanthin-free methyl linolenate emulsion (ML) serving as the control. By characterizing the emulsion structure, stability, in vitro digestive behavior, and ASTA bioaccessibility, the regulatory mechanism of oil phase composition on the performance of the delivery system was revealed. Results showed that all emulsions exhibited a single narrow-peak distribution, with a polydispersity index (PDI) below 0.2 and negative Zeta potential, indicating stable and homogeneous systems. Among them, MLA had the optimal dispersion uniformity. The stability of emulsions with different oil phases was affected by pH, Na⁺ concentration, and temperature. Within the pH range of 5~9, MLA showed a smaller PDI value (P<0.05). For ionic stability, in the range of 0~300 mmol/L NaCl, the particle size of ML increased significantly with the increase of Na⁺ concentration (P<0.05), while the particle sizes of MLA, FOA, and COA remained stable. In addition, the thermal stability of different samples was evaluated within the temperature range of 30~90 ℃: At 30~60 ℃, MLA showed no significant change in particle size (P>0.05) and exhibited the best thermal stability. At 90 ℃, the particle sizes of all samples increased, but MLA still maintained a relatively small particle size (<195 nm). During in vitro digestion, the emulsion structure remained stable in the oral and gastric phases. In the intestinal phase, the particle size of COA increased significantly (P<0.05) due to the rapid hydrolysis of high saturated fatty acids. After digestion, MLA had the highest ASTA retention rate, with a bioaccessibility of 26.8%, which was significantly higher than that of FOA (24.8%) and COA (22.4%) (P<0.05). This study clarifies the regulatory mechanism of oil phase properties on the performance of astaxanthin nanoemulsions, providing a theoretical basis for the rational design and industrial application of functional lipid delivery systems.

In this study, the aim was to determine the influence of ultrasound-assisted phosphorylation on the physicochemical properties of chickpea protein isolates (CPI). Three aspects of the effects of combined treatment on the properties of CPI were assessed: Physicochemical properties, molecular structure, and functional characteristics. The results showed that with the increase of ultrasound intensity, the physicochemical properties and structure of CPI changed significantly. Among them, ultrasound-assisted phosphorylation at 300 W led to a maximum phosphate content of 10.63 μg/mL in the proteins, while increasing the solubility to 89.02% and turbidity to 1.98. In addition, both sulfhydryl contents and surface hydrophobicity were decreased to 10.48 μmol/g and 80.5, accompanied by changes in the secondary structure of the proteins. These findings indicated that ultrasound promoted effective phosphorylation. Hydrophobic aggregation caused by protein unfolding was mitigated by electrostatic stabilization, thereby enhancing the emulsification and foaming properties of CPI. Multiscale analyses demonstrated that ultrasound-assisted phosphorylation effectively enhanced the physicochemical properties and structural characteristics of CPI molecules. The findings of this study provide a theoretical basis for advancing food protein modification technologies.

To prepare a selenium-enriched probiotic fermented milk, Lacticaseibacillus paracasei SCFF20, a selenium-enriching strain isolated in our laboratory, was employed to ferment milk at 42 ℃ for 12 hours. The physicochemical indexes, selenium content, flavor compounds and some other indicators of the prepared fermented milk were systematically evaluated. Four experimental treatments were conducted as follows: SF group was performed using commercially available L. paracasei. BF group was performed using L. paracasei SCFF20 alone. XF group was performed using L. paracasei SCFF20 and selenium nanoparticles (SeNPs), and YF group was performed using L. paracasei SCFF20 and sodium selenite. Results showed that the XF group exhibited significantly higher Se(0) content (4.05±0.01 mg) and a^* value (1.30±0.02) compared to other groups (P<0.05), demonstrating L. paracasei SCFF20's ability to selenium biotransformation and its synergistic effect with SeNPs during milk fermentation. Furthermore, electronic nose and GC-MS analysis indicated that both L. paracasei SCFF20 and commercial L. paracasei contributed esters, alcohols and aldehydes to the flavor profile of the fermented milk. Notably, the XF group showed enhanced flavor diversity, particularly in esters and acids compared to the SF group. Therefore, the incorporation of L. paracasei SCFF20 with SeNPs markedly improved both the selenium content and flavor complexity in the fermented milk. This study provides a theoretical basis for research on biogenic selenium-enriched fermented milk and its related product development.

Objective: To elucidate the structural basis underlying the diverse extremophilic catalytic properties of β-galactosidases in the GH42 glycoside hydrolase family, enzymes with resolved crystal structures were systematically analyzed to reveal the relationship between structural features and catalytic characteristics. Methods: Correlation analysis between catalytic properties and microbial habitats was performed, combined with amino acid composition, phylogenetic evolution, hydrophobicity distribution, and structural bioinformatics approaches, to investigate the structural determinants responsible for catalytic diversity among GH42 β-galactosidases. Results: GH42 β-galactosidases exhibited a biased amino acid composition characterized by relatively high glutamate (E) content and low lysine (K) content, resulting in generally low isoelectric points (pI). The catalytic properties of these enzymes were adaptively correlated with the growth environments of their host microorganisms. A ''paired'' evolutionary pattern was observed between thermophilic and cold-adapted β-galactosidases within the family. Thermostable enzymes possessed higher internal hydrophobicity, whereas cold-adapted enzymes display stronger surface hydrophilicity. Cold-adapted enzymes exhibited significantly distinct flexible regions at the junction between the TIM-barrel domain and Domain B, as well as at the C-terminus. In contrast, thermostable enzymes enhanced structural rigidity by increasing hydrogen bond numbers and proline (P) content to improve their optimal temperature range. Conclusion: GH42 β-galactosidases shared a conserved molecular scaffold and diverged into cold-adapted and thermostable enzymes via differential internal and surface hydrophobicity. Temperature adaptation of these enzymes arised from the synergistic effects of monomer flexibility, number of hydrogen bonds, and oligomeric state. Based on the evolutionary relationships within the family, this study systematically explored the structural divergence and catalytic differentiation among GH42 enzymes. These findings provide a general reference for further investigations into extremophilic catalysis of GH42 β-galactosidases and the development of engineered enzymes with multi-tolerant properties.

This study aimed to investigate the antibacterial effects of Nisin combined with chive seed extract (CSE) against Staphylococcus aureus and their effect on the quality attributes of strawberries and pasteurized milk during storage. The agar well diffusion assay was employed to assess the antibacterial activity of Nisin and CSE against Staphylococcus aureus ATCC 29213. Additionally, the antibacterial efficacy of Nisin and CSE against S. aureus was further investigated by measuring reactive oxygen species (ROS) levels and extracellular polymeric substance (EPS) content. Meanwhile, the effects of Nisin and CSE on the quality of the two food products were further investigated by determining the titratable acidity of pasteurized milk and strawberries during storage, as well as the weight loss and DPPH radical scavenging activity of strawberries and the protein content of pasteurized milk. The results demonstrated that the combination of Nisin and CSE exhibited synergistic antibacterial effect against S. aureus. The ROS levels of S. aureus were significantly reduced by 18.64% and 39.70% in Nisin+CSE group compared to Nisin and CSE groups, respectively (P<0.05). EPS content in S. aureus was remarkably decreased by 17.87% and 32.57% in Nisin+CSE group compared to Nisin and CSE groups, respectively (P<0.05). Furthermore, Nisin combined with CSE effectively delayed spoilage in both pasteurized milk and strawberries during 8-day storage at 25 ℃ and 4 ℃. The combination of Nisin and CSE exhibits a strong inhibitory effect against Staphylococcus aureus, offering a new strategy for the development of natural compound antibacterial agents.

Bacterial spores are common microbes in foods. They are difficult to be inactivated because of their extreme resistances. The synergistic inactivation effects and mechanism of Nisin combined with ε-polylysine treatment on Bacillus subtilis spores in thermal physical field (80, 90 ℃) were studied, and a more effective method for food preservation was provided. The changes of OD_{600 nm}, OD_{260 nm}, OD_{280 nm} values were used for characterizing the inner membrane damage and intracellular components release. Scanning electron microscope (SEM) was used for observing the changes in spore morphology and structure. Fourier transform infrared (FTIR) spectroscopy was used for analyzing the changes in lipids phase of spore inner membrane, the secondary structure of spore proteins, and nucleic acid backbone. The activity of Na⁺/K⁺-ATPase was determined to evaluate spore's metabolic condition. The results are as follows: Under 90 ℃ treatment, 1.59 lg CFU/mL or 1.22 lg CFU/mL Bacillus subtilis spores were inactivated respectively with addition of 0.5 g/L Nisin or 0.25 g/L ε-polylysine, while 4.28 lg CFU/mL spores were inactivated with combined usage of 0.5 g/L Nisin and 0.25 g/L ε-polylysine. After the combined treatment, SEM images indicated that the aggregation of spores significantly intensified. The 2,6-dipicolinic acid (DPA) release raised up to 76.03%, indicating serious inner membrane damage. FTIR spectroscopy indicated that the lipids in the spore inner membrane changed from a gel state to a liquid crystal state, nucleic acid backbone was damaged, and the content of secondary structures in proteins changed (P<0.05), the α-helix and β-folding content decreased, while the β-turn and random coil content increased respectively to 43.81% and 35.37%. In addition, the activity of Na⁺/K⁺-ATPase significantly decreased to lowest value 6.53 μmol/h/mg (P<0.05), and the energy metabolism of spores was severely inhibited. The main mechanism of synergistic spore inactivation by Nisin and ε-polylysine was as follows: Nisin destroyed the inner membrane structure of spores, which resulted in core hydration and release of key components such as DPA. ε-Polylysine penetrated the damaged inner membrane, entered the spore core, destroyed DNA structure, and finally caused spore inactivation.

In this study, we focused on the preparation of hydrogels with good biocompatibility of sodium alginate (SA), chitosan (CS), and calcium carbonate (CaCO₃) by physical cross-linking. We aimed to optimize the hydrogel formulations and systematically explore their structure, physical properties, and freeze-thaw stability. The optimal formula was determined using a single factor experiment and response surface method: SA concentration was 2.14%, CS concentration was 1.7%, Ca²⁺ concentration was 0.31 mol/L, and the hydrogel swelling rate was 17.20%. The freeze-thaw experiment showed that the performance of the hydrogel was significantly improved while freezing at −80 ℃ and thawing at 4 ℃, and the best effect of one freeze-thaw cycle was achieved: The hardness increased from 125.3 g to 189.6 g, the elasticity increased from 0.72 to 0.85, and the storage modulus increased from 2100 Pa to 3500 Pa. There was a minimal decrease in performance after the second cycle. Nuclear magnetic resonance analysis showed that the hydrogel was more water-bound and more stable in structure under these conditions, and Fourier transform infrared spectroscopy confirmed that the hydrogel was physically cross-linked. The dual-network hydrogels prepared in this study had excellent mechanical properties and freeze-thaw stability, which would provide an important theoretical basis and practical reference for their application in frozen food preservation and as biomedical carriers.

To promote the development and application of Sibiraea angustata polysaccharides (SAPs), this study optimized the cellulase-ultrasonic synergistic extraction process of SAPs using response surface methodology (RSM), and further analyzed their structural characteristics and lipid-lowering activity. The results of process optimization indicated that the order of factors influencing the yield of SAPs was: solid-to-liquid ratio>enzyme addition amount >ultrasonic time. The optimal parameters for SAPs extraction were determined as follows: Liquid-to-solid ratio of 20 mL/g, enzyme addition of 3.5%, and ultrasonic time of 70 min, achieving a yield of 6.98% with extract rate of 65.23%. SAPs was an acidic heteropolysaccharide composed of 9 monosaccharide residues (Mw = 87.72 kDa), with highest galactose (32.9%), followed by rhamnose (25.7%), glucose (15%), and arabinose (12.6%). In addition, the IC₅₀ values of SAPs for scavenging ability DPPH and ABTS⁺ radicals were 99.53 mg/L and 94.75 mg/L respectively, indicating their potential antioxidant activity. In terms of the lipid-lowering mechanism, SAPs exhibit a positive linear dependence on bile salt binding capacity. The binding rate of bile salt exceeds 60% at 5.0 mg/mL SAPs, with the strongest binding ability observed with taurocholate. With increasing concentrations of SAPs, the levels of triglycerides (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) in zebrafish exhibited a dose-dependent decrease. Oil Red O staining further confirmed that SAPs significantly reduced lipid droplet deposition in the zebrafish tail, with the effect demonstrating a concentration-dependent manner. The lipid-lowering effect of SAPs was significantly concentration-dependent (P<0.05). The lipid-lowering rate reached 9.85% at 5.0 mg/mL SAPs, demonstrating that SAPs could effectively ameliorate hyperlipidemia through dose regulation. These results will lay a theoretical and technical foundation for the development of functional lipid-lowering products using SAPs.

To optimize the enzymatic hydrolysis process of Tibetan sheep meat and to characterize the flavor profile of the resulting hydrolysates, using Tibetan sheep meat as the raw material, single-factor experiments combined with response surface methodology were employed to refine the hydrolysis conditions. Flavor compounds and taste characteristics of the hydrolysates were comprehensively analyzed. The optimal enzymatic hydrolysis conditions were determined to be: A solid-to-liquid ratio of 1:2, an enzyme ratio of 3:1, a hydrolysis time of 3.5 hours, an enzyme concentration of 0.9%, pH8.2, and a temperature of 56 °C. Under these conditions, the degree of hydrolysis, peptide yield, and sensory evaluation score reached 28.08%, 81.14%, and 18.00, respectively. Gas chromatography–ion mobility spectrometry (GC-IMS) identified 58 volatile compounds, with multivariate statistical analysis highlighting hexanal monomer, hexanal dimer, 1-octen-3-ol monomer, n-pentanal monomer, and n-octanal dimer as key contributors to the flavor profile. Umami and sweet amino acids accounted for 34.99% of total taste-active amino acids in the hydrolysate. Levels of umami nucleotides (5'-UMP, 5'-GMP, and 5'-IMP) were significantly higher than in the control group (P<0.05), resulting in a markedly increased equivalent umami concentration (EUC), indicating enhanced umami taste. In contrast, the control group exhibited a significantly higher fatty acid content (63.74%) than the enzymatic hydrolysate group (P<0.05). Overall, the enzymatic hydrolysate showed a prominent umami and sweet flavor profile, complex aroma composition, and superior sensory characteristics, indicating its potential application in the development of meat-based seasonings.