Plasmin and coagulant activities in a minicurd model system. Study of technological parameters

Abstract

The effect of scalding temperature of the curd, the inclusion of a washing step and the pH at whey drainage on plasmin and coagulant activities were assessed in a minicurd model of young hard cooked cheese. The variables were tested as follows: draining pH was assayed at three levels (4.6, 5.6 and 6.4), curd scalding temperature was tested at 50 and 56ºC, and washing of the curd was examined at two levels (no washing step, and the replacement of the whey by water). Increase in pH at whey drainage and washing of the curd had a positive effect on plasmin activity, which was also evidenced by compatible changes in soluble peptide profiles. No impact of increased cooking temperature was found on plasmin activity. Plasminogen activation was not verified in any treatment. As for coagulant, lower pH values at whey drainage and a decrease in curd cooking temperature increased its activity; washing of the curd showed no influence on coagulant residual activity. These results were consistent with proteolysis described by peptide profiles, electrophoresis and soluble nitrogen fractions.