Nutritional assessment of yam (Dioscorea alata) tubers

The nutrient and antinutrient components of tubers from seven cultivars of Dioscorea alata were determined. The average crude protein content of D. alata tubers was 7.4%. Starch (75.6-84.3%) was the predominant fraction of the tuber dry matter. Significant differences in crude protein and starch contents were observed among cultivars. Vitamin C content of the yam tubers ranged from 13.0 to 24.7 mg/100 g fresh weight. The results showed yams to be reasonably good sources of minerals. Phytic acid contents of the yams were low, with values ranging from 58.6 to 198.0 mg/100 g dry matter. Total oxalate levels in yam tubers were found to be in the range of 486-781 mg/100 g dry matter, but may not constitute a nutritional concern since 50-75% of the oxalates were in the water-soluble form. The overall results are suggestive of the nutritional superiority of yams compared to other tropical root crops.