Studies on Potentials And Fungal Spoilage of Two Species of Yam (Dioscorea dumetorum and Dioscorea cayenensis) Seeds Stored at Room Temperature in Jos, Nigeria

Abstract

Food security is an issue of concern globally, especially in developing countries with dense populations, hence the need for this research. Studies were carried out on two species of yam seeds (Dioscorea dumentorum and Dioscorea cayenensis) in Jos, Nigeria to determine the bioactive ingredients, nutritional composition and spoilage fungi associated with them under room temperature (250C) for 4 months. Proximate analysis revealed that D. cayenensis (yellow yam) is richer in dry matter, fat and carbohydrates compared to D.dumentorum (bitter yam) which was richer in moisture, protein, fibre and ash content. Spoilage fungi associated with yellow yam seeds include Aspergillus niger, Rhizopus stolonifer, Penicillium oxilicum, Fusarium oxysporum and Candida spp. while none were isolated from bitter yam. Pathogenicity test revealed Aspergillus niger, R. stolonifer and P. oxilicum as the actual fungi associated with rot of yellow yam, while none is associated with bitter yam. Dioscorea dumentorum peels had abnormal alkaloids and were resistant to fungal attacks compared to D. cayenensis peels which were susceptible to fungal attacks at room temperature hence, the need for an alternative temperature. Yam peels are rich in nutrients and should be included in the daily dietary pattern of humans to help reduce the risks of nutrient deficiency in consumers. The by-products also contain important phytochemicals needed to combat various kinds of infections in humans, thus efforts should be directed towards harnessing their potentials in drug formulation.