Proteolysis and Curd Tension in Milk Associated with Accelerated Starter Culture Growth

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Abstract
Growth rate of mixed strain streptococcus starter cultures in milk were comparable although the cultures showed a 2-fold difference in proteolytic activities. The strength of the curd formed in milk varied as much as 60 g between cultures at the same titratable acidity and also it was not related directly to proteolytic activity of cultures. The addition of up to 1.2 mg pancreas extract/ml of milk caused a 2-fold reduction in proteolysis by the cultures and a concomitant increase in the curd strength at least twice that of the control culture. The proteinase system of the streptococci appeared to be adaptive since cells grown in a medium containing only casein as a N source possessed greater proteolytic activity than when grown in the medium fortified with simpler N compounds contained in pancreas extract. The natural or induced variations in proteolysis and curd tension of starter cultures may be important in determining characteristics and yield of cheese curd.