The first stage of refining of post-fermentation corn oil with a high content of free fatty acids and phytosterols – Comparison of neutralisation by an ion-exchange resin without solvent and base neutralisation

Abstract

Post-fermentation crude corn oil obtained as a by-product in the production of bioethanol from maize grains is characterized by a very high content of free fatty acids. Refining of post-fermentation corn oil will give a product that will be different from the refined oil obtained by extracting oil from corn germs. From the point of view of refining vegetable oils, the neutralisation of this oil is the most important process. Anionic ion-exchange resin was used in the research in a way to avoid the use of harmful organic solvents and a comparatively standard method of neutralising free fatty acids based on the use of a sodium hydroxide solution. Ion-exchange resin can be used in the processes of neutralising vegetable oil with an average content of free fatty acids, then the oil is neutralised in miscela. In the research, no organic solvent was used, but to reduce the flow resistance, a system based on an adjustable reduced pressure in the range of 300–50 mbar was used, to maintain a constant contact time of the oil with the resin in each cycle. The aim of the research was to obtain neutral oil with a high content of biologically active substances such as phytosterols and carotenoids. Both methods showed a reduction of free fatty acids up to 93–96 % and a similar refining loss of 18–19 %. The use of an ion-exchange resin allowed to obtain an oil in which the phytosterol content increased by 5 % for β-sitosterol, by 6.3 % for ϭ5-avenasterol, and the carotenoid content was reduced by 35 %. An increase in the number of fatty acids, such as 18:1 cis-oleic acid and 18:2 cis-linoleic, was observed.