Quantitative contribution of rennet and bacterial proteolytic enzymes to the primary proteolysis in sodium caseinate solution

In this study the contribution of different proteolytic agents to primary p roteolysis in a sodium caseinate solution under cheese-like conditions was quantified, The sodium caseinate solutions were treated with rennet, sonica ted cell suspension of Lactococcus lactis subsp, cremoris SK11 and heat ina ctivated sonicated cell suspension. Proteolysis was assessed after 3, 10 an d 17 days incubation at 8 degrees C by urea-PAGE gels of the pH 4.6-insolub le fraction. Principal component analysis of the gels estimated rennet and incubation time to contribute to > 90% and -3%, respectively, of the total variation in primary proteolysis between the assessed samples. Sonicated ce ll suspension was estimated to contribute to similar to 8% of the total var iation in primary proteolysis between samples incubated for 17 days. Bacter ial proteolytic enzymes showed an interactive effect with rennet by degradi ng beta-I-CN (beta-CN f1-192) in the rennet-treated samples. A heat-inactiv ated sonicated cell suspension had no detectable influence on proteolysis.