Volume 1

Chemical technology and analysis of oils, fats, and waxes / by J. Lewkowitsch.

  • Julius Lewkowitsch
Date:
1904
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Chemical technology and analysis of oils, fats, and waxes / by J. Lewkowitsch. Source: Wellcome Collection.

    43/454 (page 23)
    1 in the commercial oils and fats being very small, the amount of hydrolysis so effected will be restricted, hence the proportion of fatty acids in commercial oils and fats, as a rule, does not exceed a few per cent. If, however, the oils and fats be allowed to stand in contact with the organic matter from which they have been obtained, such as the marc of fruits (as in the case of olive oil and palm oil), or animal tissues (as in the case of rough fat), or casein, etc. (as in the case of butter), then the hydrolysis of glycerides increases somewhat rapidly, and may reach very high proportions. Thus the so-called Bagasse olive oils, i.e. oils expressed from exposed olive marc, con- tain as much as 70 per cent free fatty acids. Palm oil may even undergo complete hydrolysis, and hence consist almost exclusively of fatty acids.1 Also in these cases, we can explain satisfactorily the formation of so high a proportion of fatty acids by the conjoint action of enzymes and water, since both are present in considerable quantities. It appears, therefore, unnecessary to invoke the action of air and light in order to explain the presence of free fatty acids. For it has been frequently observed that the hydrolysis of palm oil con- tinues in the closed barrels in which it is shipped, i.e. in the absence of light and also of air, the liberated glycerol separating out (Geitel 2). Further, Dietericli3 has shown in a very instructive series of experi- ments that free fatty acids are formed very much more rapidly in rough beef fat and pig’s fat—containing animal tissues—than in the freshly rendered fat, and that on the addition of 10 per cent of water to both the rough fats and the freshly rendered fats hydrolysis was considerably increased. I therefore ascribe the primary cause of rancidity, namely, the formation of free fatty acids, to the action of moisture in the presence of enzymes, i.e. soluble ferments. It is quite true that both Ritsert4 and Reinemann 5 distinctly state that ferments have no share in causing rancidity, but their experiments with regard to this point are not exhaustive enough to prove their case. The occurrence of small quantities of free fatty acids, even in refined oils and fats (edible oils and fats) would then be explained. Yet these oils and fats are by no means rancid. HeyerdahlG has shown in the case of cod liver oil that addition of its free fatty acids (from 2 per cent downwards) to samples of oils free from rancidity did not impart to the oil a rancid character, although it certainly produced a sharp taste. Further, Ballantyne7 has demon- strated that in many instances free acid is liberated long before the oils have turned rancid (cotton seed oil, linseed oil), whilst in other 1 Adipocere (cp. chap. xiv. “Human Fat”) is another illustration of what maybe termed “ auto-hydrolysis.” Journ. f. praktische Chemie, 1897 [55], 417. “ Chan. Rev. 1899, 168, 181, 201. Cp. Lewkowitsch, Jahrbuchd. Chevi. 9 (1899) 351. ” * Untersuchungen Other d. Raimgwerden d. Fette. Inaug. Dissert. Berlin 1890. * Gentralb. ,f. Bakteriologie, Parasitenkunde, und Ivfektionskrankheitcn, 1900, i31. Jouvn. Hoc. Chevi. Ind. 1889, 54. Cp. also Besana, Chem. Zeit. 1891 410 and v. Klecki, ZeU. f. analyt. Chemie, 1895, 633.