Study On Soybean Peptides Prepared By Fermentation

Soybean peptides, which can be a kind of potential function food, are applied widely in many areas. Soybean meal contains a great quantity of soybean protein, about 45.0%~55.0%. Soybean protein is a superior protein. It can be hydrolyzed into soybean peptides. However, some bitter components, affecting the flavour of products, will be produced after hydrolyzation of soybean protein. The methods of debittering used now were not only complicated but of high cost. The method cut down production cost, and accelerated the industrialization of functional peptides to produce peptides which combined hydrolyzing soybean protein and debittering in one-step with food-grade Bacillus subtilis1389 and Aspergillus niger3.350. There are no relative at home and abroad reports so far. This thesis focused on the following four aspects: First, studied on effects of soybean peptides preparede by Bacillus subtilis1389,Aspergillus niger3.350,and Bacillus subtilis1389 in combination with Aspergillus niger3.350, and gained the best fermentation conditions of producing soybean peptides optimized by RSA ; Second, studied on the processing viability of protease producted by Bacillus subtilis1389,Aspergillus niger3.350,and Bacillus subtilis1389 in combination with Aspergillus niger3.350, and determined the best fermentation conditions of prepared protease by Response Surface Analysis; Third, soybean meal was hydrolyzed with fermentation liquid proposing the maxium protease and gained the best hydrolyzing conditions of producing soybean peptides by RSA. Forth, the bitterness of different fermentation liquids was evaluated. The results were as follows:First: Under the conditions of fermentation at 30℃for 48h, the best fermentation conditions of producing soybean peptides by Bacillus subtilwas1389, was that the volume of inoculation was 13.0%, the initial pH was 8.0, the soybean concentration was 4.2%, and soybean peptides concentration was 897.6μg/mL; by Aspergillus niger3.350, was that the volume of inoculation was 8.2%, the initial pH was 5.3, the soybean concentration was 1.7%, and soybean peptides concentration was 568.6μg/mL; by Bacillus subtilwas1389 in combination with Aspergillus niger3.350, was that the volume of inoculation was 10.0%, the ratio of inoculation was 1:1.5, the soybean concentration was3.4%, and soybean peptides concentration was 1147.5μg/mL.Second: Under the fermentation conditions at 30℃for 48h, the best fermentation conditions of producing protease by Bacillus subtilwas1389, was that the volume of inoculation was 10.5%, the initial pH was 8.2, the soybean concentration was 5.7%, and protease activity was 449.2u/mL; by Aspergillus niger3.350, the volume of inoculation was 11.5%, the initial pH was 4.9, the soybean concentration was 2.0%, and protease activity was 36.7u/mL; by Bacillus subtilwas1389 in combination with Aspergillus niger3.350, the volume of inoculation was 10.8%, the ratio of inoculation was 1:1.2, the soybean concentration was 5.2%, and protease activity was 646.8u/mL.Third: The best hydrolyzing conditions of producing soybean peptides by Bacillus subtilwas1389 fermentation liquid, the soybean concentration was 8.1%, the initial pH was 8.6, hydrolyzation temperature was 48.4℃, and soybean peptides concentration was 970.5μg/mL; by Aspergillus niger3.350, the soybean concentration was 7.1%, the initial pH was 4.8, hydrolyzation temperature was 47.5℃, and soybean peptides concentration was 468.7μg/mL; by Bacillus subtilwas1389 mixed with Aspergillus niger3.350 , the soybean concentration was 8.8%, the initial pH was 7.9, hydrolyzation temperature was 48.4℃, and soybean peptides concentration was 1340.5μg/mL.Forth: The sensory evaluation of fermentation liquid and hydrolyzation liquid by Bacillus subtilis1389 in combination with Aspergillus niger3.350 were the best. The bitterness and odor were weak, but the method of hydrolyzing soybean meal with fermentation liquid to prepare soybean peptides by Bacillus subtilis1389 in combination with Aspergillus niger3.350 was the best to industrial production, because we can get better production efficiency. During soybean peptides prepared by fermentation, we can fermentate soybean meal by Bacillus subtilis1389 in combination with Aspergillus niger3.350 firstly, and then hydrolyze soybean meal with fermentation liquid in order to get more soybean peptides and better sensory.