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Spectrophotometric Determination of Carrageenan Ester Sulfate in Milk and Milk Products with Barium Chloranilate

Biology Department, University of Puerto Rico, Mayaguez

ABSTRACT

Carrageenan in milk and milk products was precipitated by adding Rivanol to the system at pH 4–6. Under these conditions, the milk proteins were precipitated simultaneously. The combined carrageenan-Rivanol and milk proteins-Rivanol precipitates were separated by centrifugation and washed with 0.2% Rivanol in 0.05 N acetic acid, to remove inorganic sulfate. The washed precipitate was hydrolyzed with HCl, decolorized with carbon and interfering cations in the hydrolyate removed with Dowex 50W-X8 resin (H⁺ form, 50–100 mesh). The sulfate content of the deionized hydrolyate, after adjustment to pH 4.0, was determined in a buffered system (pH 4.0) with barium chloranilate. The red color developed was measured at 530 mµ. The influence of several variables affecting both the precipitation of the carrageenan and the colorimetric determination was examined.