Abstract:To investigate the effect of Lacticaseibacillus?paracasei (Jlu-CH9) as an auxiliary starter culture on yogurt quality, and to evaluate its ability to alleviate dextran sulfate sodium (DSS)-induced colitis in mice. Yogurt was prepared by combining Jlu-CH9 with a commercial starter culture, and the pH, titratable acidity, water-holding capacity, texture, and rheological properties of the yogurt were measured during storage. An acute colitis model induced by DSS in mice was established, and the intervention effects of the yogurt containing the combined starter culture on colitis were systematically evaluated by monitoring the mice’s body weight, Disease Activity Index(DAI), colon length, histopathological changes, intestinal permeability, expression of tight junction proteins in the intestinal mucosa, and levels of inflammatory factors to systematically evaluate the intervention effects of co-fermented yogurt on colitis. The results showed that, compared with fermentation using commercial starter cultures alone, co-fermentation with Jlu-CH9 significantly improved yogurt quality, as evidenced by increased water-holding capacity, enhanced textural properties such as hardness, cohesiveness, adhesiveness, and viscosity, an increase in the storage modulus, and a more stable gel network structure. Results from animal experiments indicated that co-fermented yogurt significantly alleviated DSS-induced weight loss, elevated DAI scores, and colon shortening in mice; reduced histopathological damage to the colon; lowered intestinal permeability; upregulated the expression of tight junction proteins such as E-cadherin、Occludin and ZO-1, downregulate the expression of pro-inflammatory factors such as TNF-α, IL-1β, IL-6, and IL-17A, and increase the levels of anti-inflammatory factors such as IL-10. Therefore, it can be concluded that Jlu-CH9, as a co-fermentation starter, improves yogurt quality and confers beneficial intestinal protection. Yogurt fermented with this strain alleviates DSS-induced colitis in mice by enhancing intestinal mucosal barrier function and regulating inflammatory responses, thereby providing a theoretical basis for the development of functional probiotic yogurt and its application in the field of intestinal health.