GB687843A - Methods of treating and processing animal and vegetable oils - Google Patents

Abstract

Animal or vegetable oils are treated with an aqueous solution of an alkali salt of ethylenediamine tetra-acetic acid, with or without additional alkali hydroxide, whereby, according to the conditions: (1) the oil is freed from metallic or inorganic impurities, or (2) free fatty acids are eliminated, as well as the metallic or inorganic impurities, or (3) the oil is saponified. In treatment (1), the oil is agitated with an aqueous solution of ethylenediamine tetra-acetic acid having at least two but not more than three neutralized carboxy groups, but if the metallic or inorganic impurities in the oil are non-basic compounds, a small proportion of a basic compound, e.g. an alkaline-earth oxide, hydroxide or carbonate, may also be added. The aqueous phase is separated from the purified oil, concentrated, and acidified to about pH 1-2 to precipitate the aminoacid for re-use. In treatment (2), the oil may be agitated with an aqueous solution of the aminoacid containing sufficient alkali hydroxide to neutralize the free fatty acids in the oil and two carboxy groups of the aminoacid. Alternatively, sufficient alkali hydroxide solution to neutralize the free fatty acids may be added first, followed by a solution of the dialkali salt of the aminoacid or, as a further alternative, the oil may be treated with a solution of the trialkali salt of the aminoacid. The aqueous soap solution obtained may be acidified to about pH 4.5 to precipitate the free fatty acids, and the mother liquor may then be acidified to about pH 1.2 to precipitate the aminoacid In treatment (3), the oil may be treated with a solution containing the aminoacid and sufficient caustic alkali to react with the free and combined fatty acids in the oil and with not less than two or more than three carboxy groups of the aminoacid, or alternatively the oil may be treated with a solution of the tri- or tetra-alkali salt of the aminoacid. The aqueous soap and glycerine solution obtained may be treated with brine to precipitate the soap, and the mother-liquor then concentrated until most of the sodium chloride has precipitated. The residual solution may then be acidified to about pH 1.2 to precipitate the aminoacid, whereafter glycerine is finally recovered by neutralization and distillation. In all three treatments, the proportion of aminoacid salt may be 2-10 per cent, preferably 5 per cent, of the weight of the oil, and the volume of the aqueous phase may be 50-100 per cent of that of the oil. The treatments may be effected at atmospheric or raised temperature. The alkali salt of the amino acid is preferably the sodium salt, but the potassium, lithium or caesium salt may also be used.