Some properties of taro (ishikawa-wase and takenokoimo) and yam (iseimo and nagaimo) starches.

Abstract

Some chemical and physical properties of taro (ishikawa-wase and takenokoimo) and yam (iseimo and nagaimo) starches were investigated. The results obtained were as follows:1) The mean particle sizes of the taro (ishikawa-wase and takenokoimo) starches were 1.4μm and 2.0μm, respectively, and those of the yam (iseimo and nagaimo) starches were 16.8μm and 18.8μm, respectively.2) The susceptibilities of the taro (ishikawa-wase and takenokoimo) starch granules to hog pancreatin were similar to that of normal maize starch granules. The percent degradation of yam (iseimo and nagaimo) starch granules by hog pancreatin was approximately 20.0% on 24hr's reaction.3) On scanning electron microscopy (SEM), we observed hollows on the surface of taro (ishikawa-wase and takenokoimo) starch granules and scratches on the surface of yam (iseimo and nagaimo) starch granules, after an attack by pancreatin.4) The initiation temperatures for gelatinization, determined by photopastegraphy, were 62.0°C for taro (ishikawa-wase), 73.0°C for taro (takenokoimo), 63.0°C for yam (iseimo) and 65.0°C for yam (nagaimo). The onset temperatures, determined by differential scanning calorimetry (DSC), were 65.0°C for taro (ishikawa-wase), 76.0°C for taro (takenokoimo), 65.0°C for yam (iseimo) and 66.0°C for yam (nagaimo).5) The amylose contents determined by gel filtration of isoamylase-debranched starches, were 13.5% for taro (ishikawa-wase), 10.8% for taro (takenokoimo), 24.2% for yam (iseimo) and 26.1% for yam (nagaimo).6) On X-ray diffractometry the taro (ishikawa-wase and takenokoimo) starches showed A-type patterns, and the yam (iseimo and nagaimo) starches showed C-type and Cb-type patterns, respectively.