Characterization of chemical composition and anti-nutritional factors in seven species within the Ghanaian yam (Dioscorea) germplasm

This study characterized the most cultivated and consumed yam (Dioscorea) cultivars within the Ghanaian yam germplasm based on their chemical composition and anti-nutritional factors. Matured yam cultivars grown under the same climatic and edaphic factors were harvested from the Roots and Tuber Conservatory Division of the Council for Scientific and Industrial Research-Plant Genetic Resources Research Institute, Bunso Ghana. Samples were analyzed for proximate composition, mineral content and levels of tannins, phytates and oxalates using standard analytical methods. Significant differences (p<0.05) existed between the means of the yam varieties based on their chemical characteristics. The moisture content of the fresh tubers ranged between 58.18 to 77.79%. The varieties had low fat (<1.0%), protein (4.0-6.5%) and fibre (1.25-3.47%) with high carbohydrate (77.5-87.3%) and energy (1451.2-1574.7 kJ/100g). The most predominant minerals were potassium (475-1475 mg/100g), phosphorus (158-294.5 mg/100g) and sodium (62.5-102.5 mg/100g). All the studied varieties had low levels of oxalates, tannins and phytates (<15 mg/100g) and could all be safely recommended for food processing applications. D. rotundata, D. praehensalis, D. cayenensis and D. bulbifera differed from the rest by having higher levels of carbohydrate and energy with appreciable levels of minerals that make them nutritious and can be used as reliable food and energy security crops. D. rotundata (Pona) variety distinguishes itself because of low moisture content (high dry matter) that makes it suitable for high yield flour production.