Proteolysis in Cheese during Ripening

This chapter discusses proteolysis process in cheese during ripening. Proteolysis contributes to: (1) The development of cheese texture: via hydrolysis of the protein matrix of cheese; via a decrease in aw through changes to water binding by the new carboxylic acid and amino groups liberated on hydrolysis of peptide bonds. These groups are ionized at the pH of cheese and thus bind water; indirectly via an increase in pH caused by the liberation of ammonia from amino acids produced by proteolysis. (2) Flavor and perhaps the off-flavor of cheese, directly by the production of short peptides and amino acids, some of which have flavors; indirectly by the liberation of amino acids, which act as substrates for a range of catabolic reactions, which generate important volatile flavor compounds; by facilitating the release of sapid compounds from the cheese matrix during mastication. Proteolysis in cheese during ripening is catalyzed by proteinases and peptidases from six sources: (1) the coagulant—the enzymes involved depend on the type of coagulant used. (2) the milk—a number of indigenous proteinases are present in milk, the most important of which is plasmin, which is produced from an inactive precursor, plasminogen. (3) starter lactic acid bacteria (LAB) contain a cell envelope-associated proteinase, which contributes to ripening principally by hydrolyzing intermediate-sized and short peptides produced from the caseins by the action of chymosin or plasmin. The other three sources are nonstarter lactic acid bacteria (NSEAB), secondary starter ( Propionibacterium freudenreichii subsp, shermanii in Swiss-type cheese), and exogenous proteinases and peptidases.