Effects of Gamma Irradiation on Sprout Suppression, Shelf-Life Extension, and Quality Preservation of Yellow Yam (Dioscorea cayenensis) During Ambient Storage

Abstract

In West Africa, Dioscorea cayenensis (yellow yam), one of the major staple food crops, is vulnerable to ambient storage losses due to sprouting, rotting, moisture loss, and quality deterioration.  The effects of low-dose gamma irradiation on the suppression of sprouts and proximate composition of yellow yam during ambient storage, storage quality, weight loss, and rotting incidence were evaluated in this study.  The 60 healthy tubers were randomly divided among the six treatments (10 tubers/treatment): unirradiated (0 Gy) and irradiation at a cobalt-60 gamma source of 50, 70, 80, 90, and 100 Gy doses.  After irradiation, tubers were placed under ambient conditions and were examined periodically for sprouting, rotting, and loss in weight, and the proximate composition was determined by standard AOAC methods after storage for five months.  Gamma irradiation was found to give dose-dependent improvements in storage performance.  The sprouting dropped to 20% at 50 Gy and 10% at 70 Gy, and was completely suppressed at 80-100 Gy.  Rotting was only observed in the control group (10%), while no rotting was observed in the tubers subjected to irradiation.  Mean weight loss declined from 64.79 ± 13.45% in the control to 17.27 ± 5.45% at 100 Gy. Ash, crude fibre, protein and carbohydrate contents were higher, and moisture and crude fat were lower in the irradiated tubers as compared to the control.  The results of statistical analysis revealed statistically significant differences among the treatments for the sprouting, loss of weight and proximate composition (p<0.05) of the sprouts.  It was concluded that low-dose gamma irradiation, especially 80–100 Gy, was a potential technology to stop the sprouting and enhance the storage quality of yellow yam over five months of ambient storage without compromising its nutritional attributes.  There is a need to conduct more extensive tests with commercial storage before widespread use.