Isolation of starches from different tubers and study of their physicochemical, thermal, rheological and morphological characteristics

Abstract

Isolation of starches from various tubers such as elephant foot yam (NYS), taro (NTS), ginger (NGS), green banana (NBS) and lotus stem (NLS) was carried out for studying various characteristics viz. physicochemical, differential scanning calorimeter (DSC), rapid visco analyzer (RVA), rheological, morphological and colour in order to explore their end use potential. A significant variation was observed in pasting properties of isolated starches. X-ray diffractometery (XRD) showed a B-type crystal pattern of banana starch, while yam, taro, ginger and lotus starches had A-type crystal pattern. Scanning electron microscope (SEM) revealed that taro starch possessed the smallest granule size having cluster pattern while lotus starches have the largest granular size with hemispherical facets having dents or hollows at one end. Thermal properties of isolated starches revealed that NLS had lowest To, Tp, Tc values i.e. 68.3, 72.0 and 76.8C, respectively. Similarly the lowest gel characteristics such as hardness, gumminess, chewiness and adhesiveness 3.09 g, 1.45, 1.27, 8.42 gs, respectively, were also found in NLS. L∗ values of NTS and NYS starches were the highest i.e. 93.36, 93.29 with no significant difference whereas the lowest i.e. 89.917 in NGS.