Proteolysis in cheese curd as affected by subcellular fractions from Lactococcus, Lactobacillus and Propionibacterium

Intracellular fraction (IF) and cell wall-associated fraction (CWAF) from l actococci, lactobacilli and propionibacteria were added to cheese curd slur ries according to a mixture design. Response surface and estimation of Sche ffe's polynomial revealed synergistic interaction effects between lactococc i and lactobacilli on secondary proteolysis determined by an o-phthaldialde hyde assay. Ifs from propionibacteria had a lower proteolytic activity than those from lactococci and lactobacilli used. Principal component analysis of capillary electropherograms of the trichloroacetic acid-soluble fraction , discriminated between slurries treated with Ifs and CWAFs, It also showed an effect of proteolytic enzymes from the IF of propionibacteria together with IFs from lactococci and I or lactobacilli, on small changes in overall peptide profile.