STUDIES ON THE PROPERTIES OF STARCH OF DIPLOID IPOMOEA-TRIFIDA (HBK) DON STRAINS

Starches of six diploid Ipomoea trifida (H. B. K.) DON. clonal strains were examined. Granule size, granule traits obtained by scanning elec tron microscopy (SEM), X-ray diffraction patterns and differential sca nning calorimetry (DSC) parameters of starches of the diploid strains were compared with those of two sweet potato cultivars. The granule si zes of the diploids were definitely smaller than those of cultivars. S EM showed that starches of the diploid strains were composed of predom inantly angular granules having crater-like impressions. Starches of b oth the diploids and the cultivars showed typical X-ray diffraction pa tterns (C type) with diffuse maximum peak around 18.5-degrees 2theta, but in the case of diploid strain ''H3-28'', distinctive sharp peaks s uggesting some differences in crystal structure were observed. DSC par ameters, namely, onset temperature (To), peak temperature (Tp), conclu sion temperature (Tc) and enthalpy of gelatinization (DELTAH) obtained from starch-water mixtures (ratio 1:3) were higher in the diploid sta rches compared to those of the two cultivars. Significant correlation coefficients were found between the gelatinization parameters and mean granule diameter of the starches studied.