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Journal of Dairy Science Vol. 47 No. 1 1-7
© 1964 by American Dairy Science Association ®
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Comparison of the Proteolysis Produced by Rennet Extract and the Pepsin Preparation Metroclot during Ripening of Cheddar Cheese1

N. P. Melachouris and S. L. Tuckey

Department of Food Science, University of Illinois, Urbana

ABSTRACT

This investigation determined the differences in proteolysis produced by commercial rennet extract and a pepsin preparation during the ripening of Cheddar cheese. Preliminary experiments with the two enzymatic agents were made in fresh pasteurized milk. The bacterial factor was eliminated by the addition of toluene. The general course of protein degradation, as measured by nonprotein nitrogen production, was found to be higher when rennet extract was used. When the pH of milk was adjusted to four different levels from pH 6.5 to 5.3, both rennet extract and pepsin had maximum proteolysis at pH. 6.3, with rennet extract liberating more nonprotein nitrogen than pepsin.

The proteolysis produced by rennet extract in Cheddar cheese during ripening was higher than that produced by pepsin as measured by the nonprotein nitrogen. However, there was almost no variation in the amino acid pattern of Cheddar cheese of the same age, regardless of clotting agent used. The concentrations of the amino acids were measurably different, but no qualitative differences were observed.

Organoleptic evaluation of the cheese revealed that both cheeses were of good quality. However, the texture and body of the cheese made with pepsin was slightly curdy for a longer period during ripening. Bitter flavor did not develop during the ripening period in any lots of cheese.

FOOTNOTES

1 The preparation Metroclot will be referred to as pepsin, although it is known that this material is a commercial pepsin preparation.






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Copyright © 1964 by the American Dairy Science Association ®.