Optimization of ohmic heating parameters for enhancement of oil yield from enzymatically hydrolyzed rapeseeds (Brassica rapa)
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Date
2019-01
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
India is the third largest producer of rapeseeds in the world followed by China and Canada produced 2.35 MT of rapeseeds during 2016-17. In spite of being one of the largest producers of rapeseeds as well as rapeseed oil, India still needs to import the oil from the countries like United States and China to meet the daily requirements of large population. Mechanical expression and solvent extraction are currently used commercial methods of oil extraction. The mechanical expression possesses the limitations like low oil recovery, high energy consumption, higher initial equipment cost etc. while solvent extraction which is the most common used method of oil extraction uses highly flammable solvents therefore, the danger of fire and explosion always exists in the plant and its residual chemical solvents is also very harmful to the human health and for environment as well. The enzyme assisted oil extraction is eco-friendly approach of simultaneous isolation of oil and protein from oilseeds but the oil recovery from this method is low. Therefore, to enhance the oil yield and to fulfill per capita demand of edible oil for large population of the country, the development of modern oil extraction process is necessary which can effectively eliminate the issues related to human health, environmental pollution with producing good quality edible oil. Therefore, the present investigation has been undertaken to standardize and optimize the enzyme assisted aqueous extraction process coupled with ohmic heating for enhancement of oil yield from rapeseeds. Enzyme (Pectinase), enzyme concentration (1.0 %) and slurry ratio (1:3) were selected as constant parameters for final experiments on the basis of results obtained in preliminary trials. Experiments were planned using full factorial design considering three independent variables viz. Voltage gradient (9, 11, 13 and 15 V/cm), end point temperature (70, 80, 90 and 100 ˚C) and holding time (0, 5 and 10 min). The quality of extracted rapeseed oil was evaluated in terms of oil yield, specific gravity, refractive index, colour, free fatty acids, saponification value, peroxide value and iodine value. Statistical analysis and optimization of independent variables was done using Design Expert 11.0 software. Study revealed that the oil yield increased with increasing voltage gradient, end point temperature and holding time. The physicochemical properties of rapeseed oil were found to be 63.69-89.54% of oil yield, 0.796-0.941 of specific gravity, 1.464-1.566 of refractive index, 49.08-61.67 of colour values, 0.447-1.410% of free fatty acid, 169.43-195.32 mgKOH/g of saponification value, 1.28-2.58 meqO2/kg of peroxide value and 96-118 meq I/g of iodine value. Voltage gradient of 13.98 V/cm, end point temperature 90.37˚C and holding time of 9.90 min were the optimized ohmic heating parameters which gave maximum oil yield of 85.96% with maximum retention of oil quality like 0.96% of free fatty acids, 179.96 mgKOH/g of saponification value, 2.34 meqO2/kg of peroxide value and 113.77meq I/g of iodine value. The quantity of oil extracted at optimized conditions of process variables was higher than enzyme assisted aqueous extraction alone. The properties of extracted oil at optimized condition of ohmic heating parameters were much below the acceptable limit prescribed by “FSSAI standards, 2009” and vegetable oil products order (Regulation), 1998.
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