Date of Award:

5-1967

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Department name when degree awarded

Dairy Science

Committee Chair(s)

C. A. Ernstrom

Committee

C. A. Ernstrom

Committee

Paul B. Larsen

Committee

George E. Stoddard

Committee

Harris Van Orden

Abstract

Milk serum proteins have been shown by other workers to be partially protected from heat denaturation by the presence of milk solids (8, 15, 16) and whole caseinate (14). This study revealed that some serum proteins (B-lactoglobulin), as shown by the Harland-Ashworth test (14, 17), were more readily denatured in skimmilk than in rennet whey. A comparison of the heat denaturation rate of serum proteins in whey as opposed to those in whey containing 2.5 percent isoelectric casein was also studied. A striking protection of serum proteins seemed apparent in the presence of isoelectric casein. However, it was learned that isoelectric casein interferes with results of the Harland-Ashworth test, and by taking this interference into account, that isoelectric casein has no affect on the heat denaturation rate of serum proteins. Some proteins are more sensitive to heat in the presence of miceller casein than in the presence of isoelectric casein or no casein at all.

The addition of sulfhydryl-group blocking agents (P-chloromercuribenzoic acid and N-ethylmaleimide) inhibited serum protein denaturization in both skimmilk and rennet whey. Reactions of sulfhydryl groups following their liberation by heat resulted in much of the physical instability measured by the Harland-Ashworth test. The complex between B-lactoglobulin and K-casein, if it had any affect at all, was not one of the significant sulfhydryl-group reactions involved in the heat denaturation of the serum proteins.

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