Ascorbic acid levels in Ghanaian yams

The ascorbic acid (vitamin C) levels of several Ghanaian varieties of yam (Dioscorea spp.) have been investigated. The distribution of the vitamin within the tuber and the effects of different conditions of growth, of length of post‐harvest storage and of different cooking methods have also been studied. Natural vitamin C levels in fresh material are found to vary greatly between varieties, but little with the district where the crop was grown. Most varieties studied contained between 6.5 and 11 mg of ascorbic acid/100g, but some contain as little as 4.5 or as much as 21.5 mg/100g. Losses during storage up to 4 months are comparatively slight in sound tubers, but severe if the tubers are damaged or bruised before storage. The retention of the vitamin during cooking varies from 65 to 95%, with different cooking techniques. Even allowing for these losses in storage and on cooking, the quantities of yam consumed in West African diets should normally be adequate to supply the entire vitamin C requirements of the consumer.