Evaluation of the effects of processing on physicochemical properties of the freshly extracted crude groundnut oil

Abstract

The industrial processing of groundnut oil involves hydrothermal and chemical treatments that could affect its lipid constituents. The effect of this processing on physicochemical properties of freshly extracted crude groundnut oil was determined. Crude groundnut oil was extracted following the traditional method and half of it was processed as done industrially. Chemical properties [acid value, free fatty acid, peroxide value, saponification value, ester value, iodine value, total phenolic content (TPC), p-Anisidine value, total tocopherol (TT), total antioxidant capacity (TAC) and thiobarbituric acid reactive species (TBARS)] and physical properties (refractive index, surface tension, smoke point, flash point, viscosity and specific gravity) were determined following the AOAC and other standard methods. The results indicated that the processing of the crude groundnut oil, although improved the physical appearance and reduced free fatty acid by 56% consequently, could improve its stability but it also compromised the levels of antioxidant compounds such as tocopherols in the oil that reduced by 16.4%. TAC, an antioxidant parameter also reduced by 92% while TBARS increased by 15.1%.   It can be concluded that processing of groundnut oil could either improve its stability or compromise it, therefore, there is a need for the stability study of processed groundnut oil.