Optimizing the chemical refining process parameters on the removal of free fatty acid in distillers corn oil

Distillers corn oil (DCO) has commonly been used for non-edible purposes due to its high levels of free fatty acid (FFA). Food-grade corn oil is usually obtained from oil extracted and refined from corn germs rather than DCO. To enhance the market value and reduce the cost of refining DCO, it is important to optimize the removal of FFA since the chemical refining process conditions for DCO have not yet been studied in-depth. Therefore, a response surface methodology with a Box–Behnken design was utilized to study the effect of various process conditions during the neutralization of DCO using sodium hydroxide solution, a commonly used and effective neutralizing agent in the food industry. The process parameters selected were the excess level of sodium hydroxide (0%–0.4%), time (0.5–2 h), and temperature (60–70°C). The experimental data were fitted into a second-order polynomial equation using regression analysis. A well-fitting model was developed to predict the percent of FFA removed (R² = 0.9963) at different process scenarios. The optimal process parameters of chemical refining removed approximately 90% of FFAs at an excess level of sodium hydroxide of 0.2%, temperature of 70°C, and time of 2 h. The experimental and predicted values for FFA removal showed minimal deviations during the validation of the developed regression model. Soap and FFA contents of neutralized DCO was within the acceptable limit after the process without any significant changes to the fatty acid profile.