GB645461A - Improvements in and relating to casein products - Google Patents

Abstract

Raw casein is dissolved in an aqueous solution of one or more water-soluble bases and treated with a solution of one or more salts of aluminium, cadmium or zinc to precipitate a casein product containing the said metal or metals. Raw casein is defined as the protein precipitated from skimmed milk by the addition of organic or inorganic acids, by the acid produced by fermentation, by rennin or any combination of these reagents and includes unhardened casein. Acetates and chlorides are the preferred salts. Sodium hydroxide and borate, ammonia, triethanolamine and methylamine are specified bases. The precipitated product is separated, washed and dried, when it may be hardened with formaldehyde. The nature of the precipitate may be controlled by means of temperature, addition of rennin in the case of an acid casein, or pH adjustment. In examples (1) lactic casein is dissolved in aqueous triethanolamine solution to give a pH of 7.95, a solution of zinc acetate slowly stirred in to form a precipitate, the pH changing to 7.18, acetic acid added to coagulate the precipitate at 40 DEG C., the pH of the clear solution being 6.92 and the precipitate removed and washed four times with water to remove excess metal salts, pressed and dried; (2) a similar solution is prepared of pH 8.2, a solution of basic aluminium acetate in acetic acid added to give a coagulated precipitate and a pH of 4.52 for the clear solution; the precipitate is collected and washed three times to remove excess salts, pressed and dried; and in (3) rennet casein is dissolved in aqueous sodium hydroxide to give a solution of pH greater than 10.0 at 25 DEG C., zinc chloride solution stirred in and the precipitate which forms is collected, washed, pressed and dried, the pH of the clear solution being 5.9.