Factors affecting proteolytic action of Lactococcus lactis in cheese

Abstract

Model cheeses were developed to study the behaviour of proteolytic agents involved in cheese maturation under conditions that closely resemble those in normal cheese. The models were applied to study protein breakdown by Lactococcus lactis ssp. cremoris HP , as a function of various ripening variables. Proteolysis was monitored by several methods; amino acid-N determinations and amino acid analyses were best suited for quantitatively following protein breakdown. Amino acid production was enhanced at a higher pH, at a lower NaCl content and at a higher ripening temperature of cheese; much larger quantities of amino acids were produced from paracasein being predigested by rennet than from untreated paracasein. Ratios of paracasein to water of 1:2.5 or 1:3.5 did not significantly affect amino acid formation by the starter strain. Compared to intact cells, lysed cells drastically enhanced amino acid production; the results pointed to lysis of a (minor) part of the starter population. It is argued that the use of these model systems can produce unequivocal results