The Effects of Compound Starter Culture, Sugar, and Soy Milk on the Quality and Probiotic Activity of Milk–Soy Mixed Yogurt.

This article investigates the development and optimization of milk–soy mixed yogurt, focusing on the effects of fermentation starter cultures, soy milk proportion, and sugar addition on product quality and probiotic activity. The study found that the Lactobacillus paracasei compound starter culture is particularly effective for fermenting soy milk, with an optimal formulation comprising 0.3% L. paracasei, 6% sucrose, and 40% soy milk yielding improved acidity (76°T), sensory scores (92 points), and probiotic survival index (1.25). Mixed yogurt with 50% soy milk and 4–6% sucrose demonstrated enhanced sensory qualities and moderate acidity, while higher milk content increased post-acidification during refrigeration. Additionally, the milk–soy mixed yogurt exhibited superior probiotic tolerance to simulated gastrointestinal digestion compared to pure milk yogurt, suggesting potential for industrial production of high-probiotic dairy-plant blended products.