Variations in Chemical Composition, Functional Properties and Oil Quality of Groundnut (Arachis Hypogaea) as Influenced by Medium Dose Gamma Irradiation using Cobalt-60 Source

Abstract

Groundnut samples were irradiated at 2.5 and 10 kGy, using cobalt-60 gamma source; non-irradiated nuts served as control. The parameters determined were the proximate and mineral composition, anti-nutritional factors and functional properties, as well as amino and fatty acids profiles, and oil quality of the samples. Irradiation did not have any significant effect on the proximate composition, except that fat content increased from 41.98 ± 0.03% dry wt. at 0 kGy to 42.06 ± 0.03% and 42.08 ± 0.05% at 2.5 and 10 kGy, respectively. The mean protein content of all the samples was 29.77%. Irradiation significantly (P ≤ 0.05) increased the mineral contents of groundnut. Potassium being the most abundant in groundnut (28.56 ± 0.03 mg/100g) at 0 kGy was increased to 37.56 ± 0.01 mg/100g at 2.5 kGy and 36.31 ± 0.01 mg/100g at 10 kGy, respectively. Iron and sodium were low (2.05 ± 0.03 and 2.08 ± 0.03 mg/100g at 0 kGy, respectively; and 2.58 ± 0.02 and 2.82 ± 0.02 mg/100g, respectively). The oil absorption capacity for the groundnut flour samples increased significantly, with increased dose of irradiation (86 ± 0.58, 87 ± 0.58, and 94 ± 0.58% at 0, 2.5 and 10 kGy, respectively); while the foaming and emulsion capacities decreased. Interestingly, the water-holding capacity of groundnut flour was not affected by irradiation. Peroxide and saponification values were not affected significantly (P ≤ 0.05) by irradiation, while the iodine value decreased. Sulphur and aromatic amino acids were reduced significantly (P ≤ 0.05) with increased dose of irradiation. There was reduction or elimination of unsaturated fatty acids at 2.5 and 10 kGy doses, with increase in saturation level due to irradiation. Anti-nutritional factors were reduced with increased dose of irradiation. The findings revealed that irradiation is still suitable as a method of preservation for groundnut, with minimal negative impact on overall nutritional quality.