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Tritium Radioactive-Casein and Cheese Ripening

Department of Dairy Industry, Cornell University, Ithaca, New York

ABSTRACT

Investigations were concerned with the preparation of casein containing radioactive hydrogen, tritium, suitable for cheese-ripening studies, the properties of the radioactive casein, and the appearance of the radioactive hydrogen of the casein in some nonprotein component of ripened cheese. The addition of tritium to casein was accomplished by the gas-exposure technique, producing a concentration of 6 mc. of tritium per gram of casein. The tritium labelling observed was that of random distribution of the isotopic hydrogen in the various amino acids of the casein. Introduction of the tritiated casein into a cheese system did not affect the ripening process. Cheese prepared with labelled casein showed the same changes in the free amino acids, rate of acid formation, and soluble nitrogen as the unlabelled cheese. An appreciable concentration of tritium was observed in two carbonyls of ripened cheese, pointing to protein as a possible source of these compounds. Tritium labelling was shown applicable in casein-degradation studies and, with certain reservations, may be extended to other compounds of cheese ripening.