Optimization of high voltage electric field as a novel non-thermal method of sunflower oil neutralization

Abstract

Caustic neutralization produces large amounts of soap-stock. Soap-stock is a byproduct of little value, though it is quite costly to dispose. Water consumption in caustic neutralization is also high. In this study, the high voltage electric field (HVEF) method was used for neutralization of sunflower oil to omit drawbacks of caustic neutralization. Response surface methodology was used to determine the optimum conditions for high voltage electric field (HVEF) neutralization of sunflower oil under laboratory conditions. The voltage (5–15 kV), clay (0–1%), electrolyte concentration (0–50 mM), the number of electrodes (1–5 pairs), electrode distance (1–3 cm), temperature (55–75 °C), and reaction time (10–30 min) were the factors investigated with respect to free fatty acids contents. A central composite design (CCD), with seven variables and two response functions, was employed to study the effect of the individual variables on the response functions. For responses, the second-order polynomial models were developed using multiple linear regression analysis. two well-fitting models were successfully generated for the responses of free fatty acids (FFAs) and peroxide value (PV) (R2 = 0.9804 and 0.9958, respectively) with a probability value less than 0.0001: this demonstrated a high significance for the regression models. Applying the desirability function method, laboratory optimum operating conditions were found to be voltage = 15 kV, clay = 1%, electrolyte concentration = 50 mM, number of electrodes = 5 pairs, electrode distance = 1 cm, temperature 65 °C, and reaction time 20 min. At this optimum point, free fatty acids content and peroxide value of neutralized oil were reduced by 39 and 49% respectively. In addition, free fatty acids and peroxide value were reduced by 48 and 57% respectively by HVEF neutralization under N2 atmosphere.