Optimization of chemical esterification process of saponificated and acidulated soybean oil deodorizer distillate

Abstract

In this research work, it was optimized the reaction conditions for the chemistry esterification of unsaponifiable matter in soybean oil deodorizer distillate. The process involves (i) alkaline hydrolysis of saponifiable matter; (ii) acidulation of soaps and (iii) acid catalyzed esterification of resulting total fatty acid. To determine the best process conditions to get the higher conversion rates of total fatty acids to ethylic esters, preserving the tocopherols, it was used, to analyze the results, the response surface methodology in a 2nd order factorial planning. In the step (i) saponification of soybean oil deodorizer distillate saponifiable matter using NaOH:total fatty acids molar ratio = 2:1, temperature = 80º C and reaction time of 40 min. In the step (ii) the resulting soaps were rapidly and stoichiometrically converted in free fatty acids with sulfuric acid (23 %), using an acid molar excess of 50 %, at 80º C, for 40 min and under atmospheric pressure. In the step (iii) the optima conditions for the esterification reaction of soybean oil deodorizer distillate were: ethanol:total fatty acids molar ratio from 6.4 to 11.2:1, SO₂H₄ concentration from 0.9 to 1.5 % and reaction time from 1.3 to 2.6 h, with ethyl esters conversion rates up to 98 %. The mathematical model obtained is predictive and statistically significant (p<0,05). The total tocopherol losses during the process were less than 10,5 %.