Determination of alginate in dairy products.
Abstract Comprehensive study was made of the precipitability of several hydrocolloids and other related compounds by divalent cations and, specifically, of the optimum conditions for recovering alginate from milk and dairy products by precipitation as calcium, strontium, and manganese salts. In aqueous dispersion, these cations selectively precipitated alginate, pectinic acids, and pectic acid. Alginate was recovered from milk, chocolate milk, ice cream, cheese spreads, cream cheese spreads, and other products by predigesting the mixture with papain, clarifying the digest with Celite 535 and charcoal, filtering and converting any pectin, pectinic acid, and pectic acid to galacturonic acid by pectinmethylesterase (pectinesterase) and polygalacturonase. Then, calcium chloride was added to the filtrate. The calcium alginate precipitate was washed free of sugars, dispersed by sodium hexametaphosphate, and the amount of alginate in the dispersion determined by the phenol-sulfuric acid test. Recoveries obtained were 96-101% for water dispersions, 92-96% for milk, 90-95% for ice cream, and 85-95% for cheese products.
Spectrophotometric determination of carrageenan ester sulfate in milk and milk products with barium chloranilate.
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 m μ . The influence of several variables affecting both the precipitation of the carrageenan and the colorimetric determination was examined.
A Quantitative Test for Carrageenin Ester Sulphate in Milk Products
Summary A method was developed to determine gravimetrically the concentration of carrageenin in some milk products by the sulphate content of a dialyzed milk-carrageenin system after hydrolysis with hydrochloric acid and decolorization with activated carbon. The effects of the variables involved were studied. The method was employed to determine the ester-sulphate content of the carrageenin anions of various salts of κ- and λ-carrageenin. The results obtained for the λ-carrageenin were in agreemnt with those predicted from the commonly accepted structure of this fraction, whereas the value for the κ-fraction suggested a slight alteration in its reported structure. It is suggested that this method could also be used to determine the sulphate content of milk if the dialysis step were omitted.