GB427680A - Process for refining vegetable and animal oils and fats - Google Patents

Abstract

For freeing animal or vegetable oils and fats from fatty acids which have been converted into fatty acid soaps by the addition of caustic or carbonated alkali, or from mucinous substances, phosphatides, bitter principles &c., the separation of the soaps and other impurities is effected by means of concentrated alcoholic solutions of salts such as sodium chloride, nitrate, formate or acetate which do not form insoluble compounds with the substances to be separated. The alcoholic solution may contain 40--80 per cent of water; as a rule it is maintained practically saturated with the salt; and it is preferred to use such solution at 45--70 DEG C. The procedure may be as follows:--the mucins &c., are first precipitated in the oil; sufficient alkali is then added to convert the free fatty acids into soaps; the oil is then actively stirred with the addition of aqueous alcohol and a concentrated salt solution sufficient to dissolve the soap flakes, the mucins &c., being at the same time taken up in the alcoholic salt solution; the soap solution together with the impurities are separated from the oil, and the alcohol distilled off before or after addition of mineral acid in order to obtain eventually free fatty acid. Alternatively, the impurities precipitated in the oil at the pre-refining treatment may be first separated from the oil; or such treatment may be omitted, the crude oil being directly subjected to the treatment. Treatment with alcoholic salt solution may be employed for the purpose of separating the mucins, phosphatides and bitter principles from the crude oil prior to its neutralization, such impurities being coagulated in or extracted from the oil which separates quickly. The addition of the alcoholic salt solution may take place before or during the refining, or before, during or after the neutralization; and the alcohol and the salt in the form of an aqueous or alcoholic solution, may be added separately and if desired at different stages of the process. Soap stocks which have been freed from the bulk of the oil by decantation, may be subjected to the process. Before extraction with alcoholic salt solution, the soap flakes floating in the oil may be dried by the application of a vacuum.