Physical, Proximate and Functional Properties of Flour and Protein Isolate from Four γ-Irradiated Groundnut Cultivars

Abstract

Contamination of groundnut seeds with microorganisms and insect’s results in high post-harvest losses of groundnut cultivars. γ-irradiation of groundnut could be a better alternative to chemical preservatives which have been implicated for their residual effect, environmental hazards and carcinogenicity. However, the effect of γ-irradiation at low to high doses on groundnut cultivars and their constituents has not been fully investigated. Four cultivars of groundnut (Arachis hypogeae) namely bororo-white, bororo-red, bororo-hausa and campala were γ-irradiated (2-10 kGy) using 60Co source. Non-and γ-irradiated groundnuts were defatted using solvent extraction method to oil obtain oil and flour. Protein was isolated by isoelectric precipitation method, and freeze-dried. Physical (colour (L*a*b*), chemical composition, physicochemical and functional properties of the sample were determined. Generally, the colour of the protein isolates of bororo-white (L*=39.16-56.00, a*=16.45-33.58, b*=14.20-22.69) were significantly lighter than bororo-red (L*=25.29-32.29, a*=24.29-33.42, b*=9.11-10.66), bororo-hausa (L*=34.60-46.28, a*=15.70- 24.58, b*=11.36-17.97) and campala (L*=37.44-51.52, a*=9.27-16.95, b*=8.21-12.59) varied with γ-irradiation doses. Protein and moisture contents of seeds, flours and isolates varied significantly with cultivars and γ-irradiation from 24.69% to 27.55% and 7.41% to 7.82%, and 38.22% to 56.47% and 9.31% to 12.65%, and 83.46% to 87.79% and 3.77% to 6.75%, respectively. Swelling power and solubility index of flours and isolates increased significantly with increased temperature, varied with γ-irradiation and cultivars. γ-irradiation had no apparent effect on WAC and OAC; however, WAC and OAC of the protein isolates were significantly lower than flours. γ-irradiation, up to 10 kGy, had no deleterious effect on physico-chemical and functional properties of the groundnuts cultivars and their constituents.