Nitrite is a major hazardous substance in fermented sausages, and excessive human intake poses health risks. This study aimed to develop a low-nitrite fermented duck sausage. Lactic acid bacteria (LAB) can effectively degrade nitrite; astaxanthin exhibits excellent antioxidant and colorant properties, and nanoencapsulation technology can improve astaxanthin stability. Additionally, milk fat globule membrane-enriched whey protein powder (MFGM-WPI) is a promising food-grade encapsulation wall material. In this study, a selected strain of Lactobacillus sakei was combined with other LAB as the starter culture for duck sausage fermentation. Furthermore, gum arabic and MFGM-WPI were used as raw materials to prepare a novel astaxanthin nanoparticle additive, which aimed to improve the color of the sausage and endow it with antioxidant effects. The results showed that the fermented duck sausages added with astaxanthin-rich nanoparticles and composite LAB exhibited superior color stability and textural properties, characterized by a reddish hue, reduced nitrite content, and enhanced astaxanthin levels. Among all tested fermented duck sausage groups (including the natural fermentation group, single LAB fermentation group, and free astaxanthin-added group), the specific group (astaxanthin-rich nanoparticles + composite LAB) exhibited the highest 1,1-diphenyl-2-picrylhydrazyl radical and hydroxyl radical scavenging activities, alongside the lowest peroxide value. In conclusion, the combination of composite LAB strains and astaxanthin nanoparticles represents a potentially effective strategy for reducing nitrite content and enhancing the antioxidant capacity of fermented duck sausages.

In this work, the probiotic properties of Lacticaseibacillus paracasei K56 were examined by measuring its ability to tolerate gastrointestinal fluids and its adhesion characteristics. Additionally, the role of its surface proteins in mediating intestinal cell adhesion was investigated by laser confocal microscopy (LCM) and liquid chromatography-mass spectrometry (LC-MS). After 3 h of incubation in artificial gastric fluid, the survival rate of L. paracasei K56 was (88.78 ± 3.31)%, but increased to (91.57 ± 2.24)% when it was transferred into intestinal fluid and further cultured for 2 h. It possessed strong bacteriostatic activity, antioxidant capacity, and good gastrointestinal tolerance. The surface hydrophobicity of L. paracasei K56 toward xylene was (26.24 ± 0.53)%, and the self-polymerization capacity after 5 h was (28.47 ± 1.19)%. Removal of surface proteins decreased the adhesion of L. paracasei K56 to mucin, collagen, and Caco-2 cells. LC-MS analysis identified LPXTG-motif proteins and moonlighting proteins as some of the surface proteins of L. paracasei K56. It was hypothesized that L. paracasei K56’s surface proteins were crucial to the adhesion process, mediating specific adhesion to intestinal epithelial cells and extracellular matrix. The findings of this study offer a theoretical foundation for future research on the utilization and development of L. paracasei K56 in dietary supplements and dairy manufacturing.

In vitro simulated colonic fermentation studies have shown the prebiotic potential of exopolysaccharides from Lactiplantibacillus plantarum YY-112 (YEPS). Its immunomodulatory effects and related mechanisms were systematically investigated in this study. We observed that YEPS intervene in immune responses and improve intestinal microbial structure in normal mice, including significantly increasing the relative abundance of Enterorhabdus and norank_f_norank_o_Clostridia UCG-014 as well as decreasing that of unclassified_c_Bacilli (P < 0.05). In the immunocompromised mouse model, YEPS decreased interleukin-6 levels (P < 0.05) and protected the spleen by regulating lymphocyte levels. YEPS preserved the intestinal barrier by improving Mucin 2, Zonula occludens protein 1, and Occludin expression. Moreover, YEPS significantly reduced the relative abundance of Bacillus, unclassified_c_Bacilli, Lachnoclostridium, Eubacterium_xylanophilum_group, and Desulfovibrio (P < 0.05), potentially enhancing mice immunity by improving the intestinal microbiota associated with immune function. In conclusion, YEPS can be used as a natural functional extract with prebiotic effects that may improve host immunity. This provided the basis for the application of YEPS as a novel potential food additive.