Isolation of Sialic Acid from Casein and Reclamation of Residual Casein

Open Access
Publisher Website
Google Scholar
Abstract
[The possible isolation of sialic acid from casein in a practical, economical manner was explored. The properties of sialic acid-free casein for possible use as a casein replacement in food manufacture was also examined.] Crystalline sialic acid was isolated in 50-60% yields from a commercial grade of dry isoelectric casein by Warren''s hydrolysis procedure. One part of casein was heated at 80.degree. C/60 min in 10 parts of .18 N sulfuric acid (pH 1.5). A crude sialic acid preparation (7.8%) was obtained from the hydrolysate after addition of Ca(OH)2 to remove protein at pH 4.6 and sulfate as calcium sulfate at pH 7.0 followed by concentration and lyophilization of the soluble material. Highly purified sialic acid (95%) was obtained by chromatography on Dowex-1 .times. 8 with a gradient of 0-2 M sodium acetate. The sialic acid positive fraction was passed through Duolite C-20H followed by lyophilization. Slow evaporation of a concentrated solution of this material produced typical crystals of N-acetylneuraminic acid. The properties of the residual sialic acid-free casein were also examined. Electrophoretic patterns, solubility properties, rennet sensitivity and viscous character revealed that the residual casein was remarkably similar to intact casein. Ca sensitivity of this modified protein was increased in the presence of .1 M calcium chloride.

This publication has 7 references indexed in Scilit: