Development and optimization of ohmic heating device for extraction of oil from enzymatically hydrolyzed rapeseedslurry using multilevel factorial design

Preferred technique of oil extraction such as mechanical expression has lower extraction efficiencies, it is labour-intensive, consumes higher energy and higher initial setup cost. Also, solvent extraction method uses flammable solvents, has higher initial equipment cost, high operating costs and high energy requirements. To address aforesaid issues the novel process for extraction of oil using ohmic heating was developed for the enhancement of oil yield from enzymatically hydrolyzed rapeseed slurry and the process parameters were optimized using multilevel general factorial design. Pectinase enzyme was used for enzymatic hydrolysis. The effect of ohmic heating parameters like voltage gradient (9-15 V/cm), endpoint temperature (70- 100 ºC) and holding time (0-10 min) on oil yield, free fatty acids (FFA) and color of the extracted oil were investigated. The oil yield, FFA and color value varied from 63.69 to 89.54 %, 0.447 to 1.410 % and 49.08 to 61.67 respectively. The optimum conditions were obtained at 13.65 V/cm voltage gradient, 91.12˚C end point temperature and 10 min holding time which resulted in the oil yield of 86.22 %, 1.62 % FFA and color value of 59.89.The FFA of the extracted oil was below the acceptable limit prescribed by BIS and PFA standards.