This research aimed to prepare soy yogurt using soybeans and milk as raw materials through fermentation technology. It systematically explored the effects of process parameters such as the ratio of soy milk to milk, the amount of sucrose added, the inoculation amount of bacteri, and the fermentation time on the product quality, in order to determine the optimal production formula.

A four-factor three-level orthogonal experimental design was adopted. By adjusting parameters such as the ratio of soy milk to cow milk, the amount of sucrose added, the inoculation amount of the bacteria, and the fermentation time, the prepared samples were evaluated for pH value, acidity, and sensory characteristics. The specific operations included: mixing the raw materials, sterilizing at 70 ℃ for 30 minutes, cooling to 43 ℃, inoculating the starter culture, and then fermenting at a constant temperature of 37 ℃.

The experiment results showed that when soy milk and cow milk are mixed in a 20∶80 ratio, 6% sucrose was added, the inoculation amount was 2%, after being sterilized at 70 ℃ for 30 minutes and then cooled to 43 ℃, the starter culture was inoculated and fermented at 37 ℃ for 9 hours, a high-quality soy yogurt with an appropriate acid and sweetness, uniform and delicate texture, good curd state, harmonious flavor and color consistent with the product characteristics could be prepared.

Through orthogonal experiments, the optimal combination of process parameters for soy yogurt was determined, namely a ratio of 20∶80 of soy milk to cow milk, a sugar addition of 6%, a bacterial inoculation amount of 2% and a fermentation time of 9 hours. This ratio scheme significantly improved the sensory quality and physicochemical properties of the yogurt, providing a scientifically feasible reference basis for home or small-scale production scenarios.