Comparison of oil quality extracted from selected conventional and non conventional sources of vegetable oil from Malawi

In this study, oil quality with respect to physicochemical and phytochemical characteristics extracted from nonconventional seed oil namely Moringa oleifera, Adansonia digitata, Parinari curatellifolia and Cajanus cajan and conventional seed oil namely soybean (Glycine max) and groundnut (Arachis hypogaea) was assessed and compared. Results showed that there were significant differences in various quality parameters such as saponification number, peroxide value, free fatty acids in oils extracted from non-conventional and conventional sources. Oil yield ranged from 4.71  to 46.05% with pigeon peas registering the lowest yield and P. curatelifolia registering the highest yield. The following range of values in quality parameters were obtained: values in saponification number ranged from 55.91 mg KOH/g (C. cajan) to 220.54 mg KOH/g (groundnut): Peroxide value ranged from 2.79 meq O2/kg (M. oleifera) to 10.47 meq O2/kg (C. cajan): Free fatty acids ranged from 1.11 mg/100 g (P. curatelifolia) to 4.80 mg/100 g (pigeon peas): Specific gravity ranged from 0.87 (P. curatelifolia) to 0.91 (groundnuts): Oxalate ranged from 75.41 mg/100 g (groundnuts) to 632.56 mg / 100 g (pigeon peas): Acid value ranged from 2.21 mg KOH/g (P. curatelifolia) to 9.53 mg KOH/g (Pigeon pea): Iodine value ranged from 35.53 g/100 g (P. curatelifolia) and alkaloids ranged from 58.28 mg/g (M. oleifera) to 123.60 mg/g (groundnuts). Irrespective of the source of the oils, it was observed that the values in most of the oil quality parameters were within the acceptable levels. The findings in this study have demonstrated that nonconventional sources of oil have the potential to adequately supplement oils used for domestic consumption as well as industrial use in Malawi and therefore reduces the volumes of imported oils hence safeguarding foreign reserves.   Key words: Phytochemical, physicochemical, oil quality, Moringa oleifera, Parinari curatellifolia, Adansonia digitata.