Clotting of Casein with Pepsin : Amount and Nature of the Soluble Products

Abstract

The amounts of soluble products resulting from the action of pepsin on whole casein at pH 6.5 were determined by precipitating the solutions with CaCl2, (clot formation) and with 12% trichloracetic acid and by adjusting the pH to 4.7 with HC1. [alpha]- and [beta]-Caseins were studied in the same . manner; with the latter, however, no clot was obtained. In general, 2 to 5% of the whole casein and [alpha]-casein N became soluble by the action of pepsin, with lower values obtained with trichloracetic acid as the precipitant. Parallel increases in soluble P were obtained. Increases in the soluble fraction of [beta]- casein indicated that considerable proteolysis had occurred. Most of the soluble fractions did not pass through a cellophane membrane.