Study on the starch granules morphology of local varieties of Dioscorea hispida and Dioscorea alata

Starch is regarded as vital in the food industry, where granule size and shape determine its function and uses. One plant taxon that is widely known as a starch source is Dioscorea (Dioscoreaceae), whose starch and protein content make it as healthy food. As the initial step to identify which varieties possess potential as starch sources, we conducted the study on starch granule morphology of some local varieties of D. hispida and D. alata. The aim of this study was to determine the shape and size variation of the starch granule of each variety of D. hispida and D. alata. The results showed that starch granule morphology does not only vary between species of D. hispida and D. alata, but also among varieties of those species. The method used was a simple preparation of starch granules with 10% iodine staining and transparent polish to prevent the preparations from shifting. The shape of starch granules in D. hispida is dominantly polygonal (polyhedral). It showed similar results as those reported by other authors in their studies, except that – in this study - we found there is also a triangular shape, which has never been reported before. The Starch granule size of D. hispida is found to be “Very small – Small” and only one variety of the species – that is Gadung Jahe (DC9) – is classified as “Small” type. According to previous studies, varieties with small type starch granule are recommended as potential sources for non-food industrial raw materials. The shape of starch granules in D. alata is similar to those reported in other studies, which is dominantly triangular and polygonal; the size is classified as “Medium” type, except for two varieties that are Uwi Ratu (DC4) and Uwi Ulo (DC5), which are classified as “Large”. According to previous studies, varieties with large type starch granule are recommended as potential sources of food. Thus, from this study three potential local varieties are identified, i.e. gadung jahe of D. hispida, and Uwi Ratu (DC4) and Uwi Ulo (DC5) of D. alata.