Proteomic Aspects of Hard and Soft Cheese Ripening

The article presents the results of a comparative study of proteolytic processes in hard (Parmesan, Calvet) and soft (Slavyanskiy, Brynza) cheeses. The size-exclusion chromatography method has made it possible to determine the molecular weight distribution of peptide fractions of water-soluble cheese extracts providing an objective assessment of the depth and direction of proteolysis. The authors have revealed fundamental differences in proteolysis dynamics between the cheese groups under study. In hard cheeses, the process is prolonged and nonlinear. In Parmesan, by the 12th month of ripening, the proportion of low-molecular peptides and amino acids (<2 kDa) have reached 80% of the total pool with a complete absence of peptides in the molecular weight range of 3.5–15 kDa, indicating the dominance of secondary proteolysis catalyzed by enzymes of the starter microflora. In Calvet cheese, there has been a dynamic equilibrium of primary and secondary proteolysis during the first 3 months of ripening, followed by a predominance of the breakdown of medium-molecular peptides. In Slavyanskiy soft cheese, (its manufacturing technology does not involve ripening) there has been an active proteolysis during short-term storage. Over a 6-day period, a redistribution of fractions has been observed, with primary proteolysis predominating. In Brynza cheese, a two-phase process has been observed: during the 5-day salting period, primary proteolysis has been accompanied by temporary peptide aggregation under the effect of sodium chloride; after storage for over 10 days, secondary proteolysis has activated, with a twofold increase in the low-molecular fraction (<2 kDa). It has been established that the background distribution of peptide fractions in both types of fresh cheeses is identical, allowing it to be considered as the initial level from which technologically conditioned changes begin. The study results have practical significance for predicting shelf life, optimizing technological ripening modes, and developing objective criteria for assessing the quality of cheeses of various species groups.