PROXIMATE COMPOSITION OF REGIONS OF Dioscorea bulbifera (L.) and Dioscorea rotundata (L.) TUBER DURING STORAGE

There has been so much speculations about the nutritional quality of yams at different stages of storage. Sometimes tubers at post sprouting stages are crudely rejected for food without scientific evidence. This study was therefore designed to ascertain the proximate composition of two species of yam; Dioscorea bulbifera L. and Dioscorea rotundata L. during storage. The objectives of the study included to ascertain the composition of the proximate in white and aerial yams. There was also the objective of finding out the value and mobilization of the nutrients within the three regions of both yam species. Yams used for the study were harvested the same day under special arrangement with a farmer. The tubers selected were closely of the same size, healthy looking and unbruised. Each tuber for analysis was divided into three regions as the head, the middle and the tail parts. The tubers were analyzed at three stages of storage as: initial stage (immediately after harvest); pre-sprouting stage (midway through storage before sprouting), and post-sprouting stage (after sprouting). Proximate assay was carried out using standard methods. At each stage of storage, three tubers of each species were used for each assay and the analysis was replicated three times. A completely randomized design was used for the experiments. Results showed that at harvest the moisture content was highest at the tail region (66.19% and 64.83% respectively for white yam and aerial yam). At harvest, the carbohydrate composition of both white yam and aerial yam were highest (82.96% and 78.91% respectively) at the tail region. At post-sprouting stage, protein content of the head region of aerial yam was significantly highest as 7.44%. In all, the nutritional value of yam during storage is species dependent. White yam remains satisfactorily nutritious even at post-sprouting stage and the head region proved to be the most valued part. In the aerial yam, the nutritional value reduced substantially at post-sprouting although the differences were not significant.