Adding value to soapstocks from the vegetal oil refining: Alternative process

Abstract

Soapstock is a major by-product from vegetable oil refining, conventionally recovered by acidification with a strong acid to obtain an acid oil which might be further used. In the present study, acidification with HCl was performed and compared to an alternative process of enzymatic hydrolysis with hexane as organic solvent to enable the direct recovery of soaps and lipids aiming at further integration within a biofuel production process. The best condition achieved in the first case was 10 wt.% of HCl allowing to obtain FFA content of around 60 wt.% and mass yield of 43 wt.%; and, considering the moisture content of the soapstock (47 wt.%), the soaps were converted into FFA efficiently. Regarding the enzymatic hydrolysis using 10 wt.% of enzyme and 1:8 of soapstock: hexane mass ratio, a final FFA content of around 36 wt.% was obtained, showing the hydrolysis of glycerides present in the soapstock.