Abstract:To obtain the sour soybean milk which was higher amino nitrogen and fatty acid, nutritious, absorbable, well stability but without thickeners, the processing order of fermentation were studied. The effects of inoculation amount of lactic acid bacteria, initial pH value, fermentation temperature and fermentation time on amino nitrogen content, sensory evaluation and pH value, were determined by the single factor and orthogonal experiments. The results showed the optimal process orde for fermentation, were inoculated lactic acid bacteria, then inoculated Rhizopus oligosporus Saito. the optimal process was firstly fermented at 42 ℃ for 5h with 4% of lactic acid bacteria with the mass ratio of soybean and water at 1∶10, and adjusted pH to 4.5 and cooled to 31 ℃, then fermented for 18h with 3% of Rhizopus oligosporus saito. Under this condition, the fat content and fatty acid content of the products changed significantly compared with the fermantation of lactic acid bacteria. The results showed that the fat content decreased by 55.8%, whereas the fatty acid content increased by 50.3%. The research provided theoretical basis for the process improvement of sour soybean milk.