Rennet activity and proteolysis in Reggianito Argentino hard cooked cheese

It is generally believed that enzymes in rennet are largely denatured by cooking during the manufacture of hard cheese. However, typical products of rennet action on α_s1-casein have been detected in these varieties. The aim of the present work was to relate residual rennet activity with proteolysis in Reggianito Argentino, a hard cooked cheese. For that purpose, we analysed samples of cheese cooked at low (45°C), control (52°C) or high temperature (60°C) for residual rennet activity. We also studied proteolysis in cheese at the end of ripening by means of peptide mapping and electrophoresis. Rennet activity was inversely proportional to cooking temperature, although the activity was quantifiable even in cheeses cooked at high temperature, suggesting renaturation or incomplete denaturation of the enzyme. Indices of proteolysis, especially the levels of the peptide α_s1-CN(f24-199), were consistent with residual rennet activity. Secondary proteolysis was also different for cheeses cooked at different temperatures.