The production of sterols and tocopherols from a variety of animal and vegetable raw materials, more particularly vegetable oils, such as wheat germ oil, corn oil, soybean oil, safflower oil, peanut oil, cottonseed oil, sunflower oil, rapeseed oil, palm oil and other oils, has already been variously described in the literature, cf. WO 9721697 and EP 0 656 894 where the prior art is extensively acknowledged. Natural vegetable oils contain only small quantities of tocopherol. Accordingly, the described processes always involve a concentration step. The term xe2x80x9ctocopherolxe2x80x9d is intended to encompass the tocopherol derivatives of tocotrienol and tocol.
Accordingly, the most important natural sources of tocopherol are not the vegetable oils themselves, but rather the steam distillatesxe2x80x94also known as deodorizer distillatesxe2x80x94obtained in the deodorization of animal and vegetable oils. Although the tocopherols are obtained in concentrated form in this case, they are mixed with sterol and sterol esters, free fatty acids and triglycerides. According to EP 0 656 894, the free fatty acids present in a mixture containing tocopherol, fats and/or fatty derivatives, more particularly fatty acids, and optionally sterol and/or sterol derivatives are esterified with a lower alcohol. The mixture is then transesterified with a lower alcohol in the presence of a basic catalyst. After the transesterification, the excess lower alcohol is distilled of from the reaction mixture. The transesterification catalyst and the glycerol present, if any, are removed and the fatty acid alkyl ester is distilled off from the mixture. However, the sterol yield is unsatisfactory. It is improved in a process described in DE 199 16 034. These processes may be used for many different starting mixtures and do not involve the use of toxicologically and ecologically unsafe solvents. Nevertheless, the transesterification catalysts used therein frequently contain metals and may also be classified as an environmental hazard.
Accordingly, the problem addressed by the present invention was to provide a process for the simultaneous production of tocopherol and sterol which would be applicable to many different starting mixtures, would not involve the use of toxicologically and ecologically unsafe solvents, would use even low-concentration starting materials sparingly and would still give high yields without the use of metal-containing catalysts. In addition, the process would be economically workable on an industrial scale.
The present invention relates, in general, to the production of sterols and tocopherols and more particularly to a process for isolating sterols and tocopherols from mixtures of fats and fatty derivatives and from residues left after they have been worked up.
The present invention relates to a process for concentrating and isolating sterols and/or tocopherols from sterol- and/or tocopherol-containing mixtures of fats and/or fatty derivatives containing glycerides, characterized in that
(a) a mixture is hydrolyzed to split the glycerides present into free fatty acids and glycerol,
(b) the glycerol-containing hydrolysis water is removed,
(c) the free fatty acids and readily volatile unsaponifiable components are removed by distillation,
(d) one or more additional hydrolyses of the distillation residue is/are carried out to split the sterol esters into free fatty acids and free sterols,
(e) the hydrolysis water is removed and
(f) the fatty acids formed are removed by distillation.
It has been found that, after splitting of the glycerides by hydrolysis and subsequent removal of the free fatty acids by distillation, the sterol esters still present can largely be split into free sterols by another hydrolysis step. This characterizes the process according to the invention for concentrating and isolating sterols and optionally tocopherols from sterol- and/or tocopherol-containing mixtures of fats and/or fatty derivatives which contain hydrolyzable products, such as sterol esters and/or glycerides. The advantage of the process according to the invention is that it does not involve the use of metal-containing catalysts (such as, for example, zinc, tin, sodium) or toxicologically and ecologically unsafe solvents and that even starting materials of low concentration, for example physically refined deodorizer distillates, can be economically used. The required degree of concentration can be controlled through the number of hydrolysis steps.
Deodorizer distillates of the oils such as, for example, rapeseed oil, sunflower oil, palm oil, palm kernel oil, coconut oil, soybean oil, corn oil and cottonseed oil, may be used as the starting material. Mixtures of different oils and deodorizer distillates may be used although the deodorizer distillates of individual oils, more particularly rapeseed oil, sunflower oil or soybean oil deodorizer distillates, are preferred.