The properties of different cultivars of Jinhai sweet potato starches in China.

IR, (13)C NMR, X-ray diffraction and DSC applied to study the physicochemical properties of starches from six different cultivars of Jinhai (I-VI) sweet potato strains in China. Jinhai II showed the highest rate of retrogradation while Jinhai III showed the lowest in all studied cultivars. The hydrolysis rates of those starches by α-amylase were from 98.1% in Jinhai II to 99.9% in Jinhai VI with a mean value of 99.3%. The ratio of R (1158/991cm(-1)) in IR spectra of those six different sweet potato starches could be the feature to identify them. All of the six studied Jinhai sweet potato starches showed strong peak at diffraction angle (2θ) of 17°, 15° and 23°, meanwhile an extremely weak peak at 2θ around 5.5° was also identical. XRD pattern of Jinhai II and IV starch also gave strong diffraction peaks at 26.6°, which could be the characteristics of them. The enthalpy and Tp of Jinhai II were especially lower than other cultivars. Jinhai IV revealed two Tp of 128.0°C and 140°C, respectively. The second Tp was maybe the characteristic of Jinhai IV starch. IR and DSC were the most effective methods to distinguish different cultivars of sweet potato.