Studies on Casein. IV. The Sialic Acid Content of Casein

Abstract
A study has been made of conditions of hydrolysis and color reagent (resorcinol, orcinol) on the apparent concentrations of sialic acid in whole casein. Consistently higher values were obtained with hydrolysates prepared by hydrolysis of the protein with Dowex 50 x 12 -hydrochloric acid mixture for 0.5 hr at 95CC, and with use of the resorcinol reagent. The sialic acid content of whole casein, alcohol washed casein, [alpha]-casein, [beta]-casein, gamma-casein, and two fractions prepared from [alpha]-casein (Fraction A and [alpha]-casein - Fraction A) were 3.84, 3.53, 4.10, 1.36, 0.82, 22.2, and 0.64 mg/g, respectively.