ANALYSIS OF CASEIN DEGRADATION IN TILSIT CHEESES

Extraction methods for proteins and peptides from cheese have been opt imized for the subsequent analysis of the ripening of Tilsit cheeses. Proteins were extracted with a reducing alkaline buffer containing hig h concentrations of urea. Small peptides (< 10 kDa) were extracted wit h an acidic citrate buffer. Analysis of casein breakdown revealed only a small additional effect of the surface flora. This was only visible in the surface region (0-0.5 cm depth). Most of the casein degradatio n was shown to be caused by plasmin, rennet, and starter or non-starte r proteinases. It was independent of the presence of a surface flora. However, analysis of low molecular weight peptides showed a large numb er of additional peaks in the surface region of smeared Tilsit cheese (0-0.5 cm depth). Results indicate that the very intense aroma of smea r cheeses after only weeks of ripening is due to the accelerated turno ver of peptides and probably amino acids to aromatic compounds.