Proteolysis
The slow breakdown of cheese protein during ageing, which softens texture and creates savoury flavour.
Also: protein breakdown
Proteolysis is the breaking of proteins into smaller pieces. In cheese it begins with rennet left in the curd, continues with enzymes from the milk and from lactic bacteria, and on surface-ripened cheeses is driven by moulds and bacteria on the rind. As casein is broken down, a firm, rubbery young curd becomes soft and supple in a Camembert or brittle and flaky in a Parmigiano. Smaller fragments, peptides and amino acids, give savoury, brothy, sweet and sometimes bitter tastes, and in old cheeses some amino acids gather into tyrosine crystals. Too much proteolysis, or the wrong kind, gives bitterness and ammonia, so it must be balanced.