Alpha Amylase Activity and Sprouting During Short T erm Storage of Taro Corms

Abstract

The objective of this study was to investigate taro [C olocasia esculenta (L.) Schott] corm quality as determined by changes in starch mor phology and degradation during storage after harvest. Starch is the major nutrient component of taro corms and its quality in corms that are stored as planting materi al or consumption has not been fully explained. Scanning electron microscopy was used to examine the changes that occur to the surface morphology of starch granules in corms of taro landraces, Dumbe-dumbe , Mgingqeni and Pitshi, stored at cool (12ºC) and ambient (20ºC) temperatu res. Alpha- amylase activity and sprouting were used as indicat ors of changes in the starch granules, and hence corm quality, during storage in polyethylene bags, card boxes, and mesh bags. The degradation of starch granules, alph a amylase activity, and sprouting increased over storage time and varied with landrac es, storage material, and temperature. Overall, there was 23% more alpha-amyl ase activity and 67% more sprouting at 20ºC compared with 12ºC. With respect t o storage material, polyethylene bags showed the highest alpha-amylase activity (0.1 8 EU 0.1 g -1 ) followed by card boxes (0.15 EU mg -1 0.1 g -1 ) and mesh bags (0.14 EU mg -1 0.1 g -1 ). A similar, but more pronounced, trend was observed for sprouting. The f indings have implications for selection of storage material for food and propagul e storage. Keywords : Colocasia esculenta, Electron microscopy, Landrace, Starch granules