Enzymatic proteolysis during the conversion of milk into cheese

The transformation of milk into cheese occurs under the influence of many physicochemical, biochemical and microbiological processes, among which proteolysis plays a very important role. Proteolysis belongs to the most complex type of irreversible post-translational modification of proteins. Enzymatic proteolysis catalysts at different stages of cheese production are native milk enzymes, exo- and endopeptidases of starter and non-starter microorganisms, and milk-clotting enzymes. The article presents a brief overview of modern ideas about the properties, mechanism of action and specificity of the main representatives of enzymes that hydrolyze milk proteins at the stages of preparing milk for coagulation, during rennet coagulation and subsequent maturation of cheeses. These include the plasmin system of milk, enzymes of psychrotrophic bacteria and lactic acid microorganisms that enter milk both accidentally (non-starter microflora) and planned in the form of starter cultures from specially selected strains. Milk-clotting enzymes, having fulfilled their main function — milk coagulation — partially pass into cheese and, along with enzymes of starter microorganisms and plasmin, participate in proteolytic processes during cheese ripening. It is generally accepted that proteolysis in ripening cheeses is the most significant biochemical process that affects the formation of taste, aroma and texture along with lipolysis and glycolysis. The combination of proteolysis products (peptides, amino acids, amines, etc.) is individual for different types of cheese and varies depending on the technological parameters of production, including the duration of maturation. Proteolysis in cheeses has been studied by many scientists in various aspects. This review supplements the known information with new information, without claiming to be comprehensive.