Consumer Packaged Cheese. II. Chemical Changes

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Summary A study was conducted of fluorescent light-exposed and light-protected consumer-packaged Cheddar cheese during refrigerated storage to relate chemical changes to flavor changes, and to determine the Eh-flavor stability relationship of Cheddar cheese. Chemical changes were determined by the Thiamine Disulfide (TDS), Thiobarbituric Acid (TBA), and Peroxide tests, and by a copper method for α-amino nitrogen. The TDS results revealed that the -SH group concentrations of consumer-packaged Cheddar cheese decrease during storage. Decrease in -SH groups was retarded by decreasing the surface-mass ratio of the cut cheese, coating the cheese surface with Myvacet-700, and packaging the cheese in aluminum laminated film. For chunk-style light-exposed cheese, the loss of -SH groups levelled off or was reversed after approximately seven days of storage. The persistence of -SH groups of light-protected cheese during storage related directly to the flavor stability of the cheese. The TBA, Peroxide, and α-amino nitrogen results revealed only slight changes in the fat and protein systems of the cheese during storage, and the methods did not differentiate conclusively between oxidized (light-exposed) and nonoxidized (light-protected) cheese. The Eh stability of Cheddar cheese of high flavor quality varied widely when the cheese was exposed to air. There was a direct correlation between Eh stability and flavor stability, persistence of -SH groups, and relatively small increases in pyruvic acid. Cheese lacking Eh stability was characterized by unstable flavor, loss of -SH groups, and relatively large increases in pyruvic acid.