| Soymilk products represent the developmental tendency of soy-bean products, and are of this kind with quality which combined flavor, nutrition and health protective function. The most pressing problem to be solved is how to extend its shelf-life. The paper studied antisepsis effects of natural preservatives in soymilk, and determined the optimum preservatives, corresponding sterilizing techniques. The result was showed as follows:1. The experiment of sole factors showed that: Nisin TP poly-lysine had strongest bacteriostasis, lysyme and Vc take second place, NaAc2 is minimum. Owing to TP's brown color and high price of poly-lysine, Nisin, lysyme and Vc were choosed to do the latter experiment.2. Nisin, lysyme and Vc had significant inhibitory effect on spoilage bacteria in soymilk. To some extent, Nisin and lysyme, lysyme and Vc woked synergis tically to enchance the effect. The optimum formula was 0.0162% Nisin, 0.0364% Vc and 0.059% lysyme.3. High pressure, water bathing and microwave heating were used for sterilizing in present study. High pressure had the best sterilizing effect among them, water bathing takes second place; microwave heating is minimum. High pressure has good sterilizing effect, but harm soymilk color. Sterilizing effects of water bathing such as 85 ~ 90℃, 90 ~ 95℃. 95 ~ 100℃ were magnified gradually. Temperature range from 85 to 90℃had poorer effect than 90~95℃ or 95 ~ 100℃, but the latter two didn't show any significant differences. Therefore 90 ~ 95℃ ,heating 30 min ,immediately rapid cooling should be adopted in practice. As for as effects of microwave, the paper studied initially, the two didn't show any significant differences. Its antisepsis mechanism should be further studied.4. The result of synthetical preservation studies showed that the shelf-life of soymilk could be extended to 6 weeks at for optimum water bathing treatment combined with the application of the optimum formula for preservatives.
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