Proteolytic and rheological changes during ageing of cheese analogues made from rennet caseins

Abstract

On storage of cheese analogues at 4°C for up to 51 weeks, proteolysis, as measured by pH-4·6-soluble nitrogen, increased, whereas cheese hardness, stress at 15% compression, gumminess, elasticity, and chewiness decreased. Polyacrylamide-gel electrophoretograms of the cheese analogues showed that β-casein was hydrolyzed more extensively than αs1-casein and that the concentration of γ-caseins increased on storage. The pattern of casein proteolysis was similar to that reported for the hydrolysis of caseins by the indigenous alkaline milk proteinase, plasmin. Changes in the rheological properties of the cheese analogues were statistically significantly correlated with cheese age, pH 4·6-soluble nitrogen and αs1- and β-casein contents; it is suggested that plasmin is responsible for proteolysis and rheological changes during cheese-analogue storage.