The Study On Producting Of Soybean Peptide And Debittering It With Enzyme

Some bitter components, affecting the flavour of products, will be produced after the hydrolyzation of soy protein. The debittering methods now exist are not only laborious but also high cost, In this paper, Isolated soybean protein was hydrolyzed by alkaline protease to produce soybean peptide, we used laccase and acidic protease to debitter. This thesis focused on the following aspects and the result as follow:(1) In the process of bacillus licheniformis 10006 produces alkaline protease, the optimized conditions were established as follow(w/v): Bran 1.2%, bean cake 1.0%, CaCl2 0.03%, Na2HPO4 0.2%, inoculum ratio 1.5%, The best fermentation conditions of this strain were: incubation temperature 40℃, 48h, agitation speed 150r/min, initial medium pH 7.0, a 250m1 flask containing 30ml medium. Use the alkaline protease to hydrolyzes Isolated soybean protein, the optimization condition: hydrolysis time 2h., enzyme concentration at 100U/ml, pH10 and 50℃. the DH can reach to 31.45%. the molecular weight of soybean polypeptide ranges from 370 to 5,000 daltons.(2) In the all process,the total protein of cross enzyme is reduced from 501.3mg to 1.122mg.and the total activity reduced from 29747.2U to 965.8U. It has been purified 14.5-fold with a yield of 3.24%. The purified enzyme showed one protein band on SDS-PAGE and its molecular weight was estimated to be about 41 kDa.(3) The acidic proteinase reactived with the soybean ploypeptides, after contrasting with the change of dissociate amino acid, it can demonstrate this acidic proteinase had exopepitase activeness and had the ability to debitter. Selects proline to as the standard, exopepitase activity condition: 30℃, pH5.0 was advantageous to leaves the amino acid from the ploypeptides terminal hydrolisis. Along with the reactive time increase, the proline peak area gradually increases, but grows slowly.(4) The preliminary study indicated that the laccase play the good role to degenerate or remove aromatic amino acid which has the ability to cause more bitter than any other amino acid. rective the same time with tyrosine, the more of the enzyme concentration, the smaller of the last tyrosine which can be measured. possibly the tyrosine structure changed by laccase. After the reaction between the laccase and soybean polypeptide, the absorbency become lessene around 280 nm, which also reflect the laccase changes the structure of aromatic amino acid.used immobilized laccase and acidic proteinase to debitter soybean polypeptide, the result showed that each of the enzyme could play the role to debitter...