Development of a Quantitative Model for Enzyme-Catalyzed, Time-Dependent Changes in Protein Composition of Cheddar Cheese During Storage

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Abstract
To determine changes in protein composition in long-term stoarge of cheese, two types of cheese, traditional Cheddar and stirred curd Cheddar, were studied. The degradation of caseins in both cheeses during the process of ripening was evaluated by SDS-PAGE and densitometry. Relationships between the method of cheese manufacture and the effects of freezing and thawing of cheese at selected ages were studied. During the storage of cheese in the coolers, the ripening process continued, and as the age of the cheese increased, there were partial breakdowns of caseins into fragmentary products and peptides. Nonlinear regression analysis was used to model the time-dependent changes in casein components. From these analyses, "half-lives" for casein changes could be calculated. Notably, .alpha.s1-casein disappears with a half-life of 2 wk; half-life of .beta.-casein is 37 wk. Neither young nor aged Chedder cheese was affected by differences in freezing temperatures, nor were there differences between samples collected before and after freezing, nor were there significant differences between the stirred curd and traditional Cheddars.