Gamma irradiation and drying method: The effects on kola nut powder

Abstract

Kola nut is a fruit produced by the kola tree which is mostly found in West Africa. Kola nut contains a high amount of caffeine and it is used as a flavoring agent in many drinks. At storage, kola nut may become mold-infested resulting in rotting and rendering it unusable. However, well-dried kola nut coupled with gamma (ƴ) irradiation treatment can prevent fungi infestation at storage. This study sought to determine the effects of ƴ-irradiation and drying method on proximate, phytochemical, and free scavenging properties of kola nuts. The kola nuts were dried in shade and solar tent. The milled samples packaged in polyethylene bags were irradiated with cobalt-60 source at 2 kGy/h dose rate, and the delivered dose determined with ethanolchlorobenzene dosimeter. The ƴ-irradiated and un-irradiated flours were quantitatively analyzed to determine proximate, phytochemical, and free radical scavenging activities. The fat, ash, protein, carbohydrate, and caffeine contents were slightly altered by the ƴ-irradiation, while moisture content remained stable. Total phenolic content in the aqueous extract of the irradiated kola nut increased at irradiation dose above 5 kGy. The changed in total flavonoid content was inconsistent with increasing irradiation dose while 2,2-diphenyl-1-picrylhydrazyl decreased at irradiation dose higher than 5 kGy. Importantly, the health and nutritional qualities of kola nut were not sufficiently affected by ƴ-irradiation. The kola nut type, irradiation dose, and drying method, and the respective interactions differed in effects with respect to proximate, phytochemical and free scavenging properties of kola nuts. Generally, the observed irradiation-induced impacts were not deleterious on the studied properties of kola nut.