COMPARATIVE-STUDY OF PEPTIDOLYSIS IN SOME SEMIHARD ROUND-EYED CHEESE VARIETIES WITH DIFFERENT FAT CONTENTS

Earlier investigations have shown that fat has no direct influence on proteolysis in cheese (Rank, 1985; Banks et al. 1989; Ardo, 1993). The small differences found could be explained instead by the adjustments in the manufacturing procedure necessary because of variations in fat content. In earlier work, we studied the ripening of four semi-hard, round-eyed cheese varieties with different fat contents and the proteo lysis was characterized by crude fractionation methods and Kjeldahl an alysis of N content (Ardo, 1993). The casein was found to be hydrolyse d to a rather greater extent in the normal fat cheeses (280 g fat/kg) compared with reduced-fat cheeses (170 or 100 g fat/kg) during the fir st 3 weeks. In the ripened cheeses, significant differences in the tot al amounts of very small peptides and amino acids were found between c heese varieties with different contents of moisture in non-fat solids (MNFS). The three cheese varieties with reduced fat content contained ten times as many viable lactococci after 24 and 48 h as the normal fa t cheese. The present paper describes further characterization of the peptidolysis in the cheeses studied earlier (Ardo, 1993), using revers ed-phase HPLC profiles of peptides and ion-exchange chromatography of amino acids.