Effect of Asynchronous Fermentation on Quality of Mixed Plant Protein

In this study, soybean meal, rapeseed meal and pea were used as mixed raw materials to improve their protein quality by asynchronous fermentation process. Single factor conditions such as different fermentation strains, raw material ratio, fermentation and enzymatic hydrolysis conditions were investigated, and the best asynchronous fermentation process was determined by response surface test and orthogonal test. The quality of mixed protein was evaluated by crude protein, acid-soluble protein, protein solubility and protease activity. The results showed that Aspergillus oryzae was the best fermentation strain in a single-factor experiment, the activity of neutral protease was reached 676.56 U/g, the solid-state fermentation time was 49 h, the fermentation temperature was 29.9 ℃, and the initial moisture was 39.7%. Under this condition, the crude protein, acid-soluble protein and protein solubility in mixed plant raw materials were increased by 15.5%, 344% and 132%, respectively. The optimum conditions of liquid enzymatic hydrolysis were as follows: The ratio of solid to water was 1:4 (m/m), the time of enzymatic hydrolysis was 18 h, and the temperature of enzymatic hydrolysis was 50 ℃. After enzymatic hydrolysis, the crude protein, acid-soluble protein and protein solubility of mixed plant protein were enhanced by 2%, 101% and 244%, respectively. The results showed that after optimizing the asynchronous process of solid-state fermentation and then liquid enzymatic hydrolysis by fermented protease, the crude protein, acid-soluble protein and protein solubility in the mixed protein raw materials were obviously improved, and the protein products were significantly improved, which would provide a basis for the development and utilization of protein.