Soybean oil deacidification by liquid–liquid extraction using hydrous ethanol

Abstract

Soybean oil (SO) was deacidified by liquid-liquid extraction (LLE) in a perforated rotating disc column using ethanol as solvent. The extraction assays were performed using two approaches: in the first, response surface methodology (RSM) was used to evaluate the effect of perforated discs' rotation speed and solvent hydration on the transfer of free fatty acids (T FFA ), loss of neutral oil (L NO ), and overall volumetric mass transfer coefficient (K R Áa) in assays using refined SO. In second, the best conditions from RSM were used in the degummed SO deacidification; in this case, the influence of phospholipids on the L NO was observed. The maximization of the values of T FFA and L NO occurs for low water contents in the solvent, regardless of discs' rotation speed. Regarding K R Áa, both independent variables influence this response. An increase in hydration of the solvent decreases the K R Áa by decreasing the free fatty acid (FFA) diffusivity. The total deacidification of degummed SO by LLE is feasible using ethanol with 10 mass% water and a rotation speed of 150 rpm. These process conditions provided reduction on phosphorus, peroxide value, and FFA, along with a low loss of neutral oil, which was significantly lower than the values reported for the traditional process, alkali refining. Practical applicationsThis study is useful to vegetable oil processors and researchers because it is addressed the issue of using a softer deacidification process than traditional methods, which permits to remove free fatty acids, avoiding excessive losses of neutral oil and minimizing the effluent generation when compared to chemical refining. Besides, this process can be accomplished at a temperature below the normal boiling point of the solvent and atmospheric pressure, softer conditions of pressure and temperature than physical method that uses desorption with water vapor, reducing the energy consumption of oil refining. This alternative deacidification process by liquid-liquid extraction uses ethanol, a generally recognized as safe (GRAS) solvent, which allows minimizing the losses of nutraceutical compounds present in the oil. In fact, this study provides data that can be used to design a renewable solvent-based soybean oil deacidification process.