Effect of heat treatment on plasmin activity and bio-functional attributes of Cheddar cheese.

Abstract

Plasmin is one of the most important proteolytic enzymes present in cheese. This study envisaged evaluation of the effect of change in heat treatment on plasmin system and consequent effect on formation of antioxidative and ACE-inhibitory peptides. Cheddar cheese of different heating temperature (72, 75 and 78 ?C for 15 s) were studied for plasmin activity, plasminogen activity, antioxidant activity (ABTS, DPPH), ACE-inhibitory activity during ripening period of four months. Plasmin and plasminogen activities were non-significantly affected by heating temperature. Antioxidant activity & ACE-inhibitory activity were significantly affected by heat treatment. Anti-oxidant activity was observed to be highest (22% DPPH scavenging activity & 85.95% ABTS inhibition) for combination of 72 ?C & 60 days of ripening. ACE-inhibitory activity was highest (92.49% ACE-inhibition) in Cheddar cheese of 72 ?C heated milk at 30th day of ripening. It was concluded that 72 ?C heat treated Cheddar cheese had comparably higher increase in plasmin activity during ripening. Faster proteolysis was observed in Cheddar cheese prepared by 72 ?C heated milk with highest anti-oxidant activity (at 60th day) and ACE-inhibitory activity (at 30th day) during ripening. The study returned a possible set of heating temperature and ripening length for achieving the highest bio-functional properties in Cheddar cheese.