Structural, thermal and viscoelastic properties of potato starches

The starches separated from different Indian potato cultivars (Kufri Sindhuri, Kufri Jyoti, Kufri Pukhraj, Kufri Chipsona-1, Kufri Chipsona-2, Kufri Bahar and Kufri Chandermukhi) were evaluated for granule size, amylopectin structure, thermal and pasting properties. The changes in viscoelastic properties of cooked starch pastes during cooling and heating were also evaluated using a dynamic rheometer. Unit chains of amylopectin between DP 6 and 30 were analyzed by fluorophore-assisted capillary electrophoresis. Pearson correlation coefficients between different properties were also determined. Starches from all the cultivars showed peak DP 12–13. DP 6–7 content varied significantly among the starches studied; K. Chandermukhi showed the highest and K. Pukhraj showed the lowest. K. Chandermukhi starch showed significantly lower DP 14–30 content than starches from other potato cultivars. DP 14–30 content was in the order of K. Chipsona-1>K. Jyoti>K. Sindhuri>K. Pukhraj>K. Bahar>K. Chipsona-2>K. Chandermukhi. DP 6 was significantly and negatively correlated to peak gelatinization temperature (Tp) and conclusion temperature (Tc) (r=−0.780 and −0.824, respectively, p⩽0.05). Pasting temperature, hot-paste viscosity and cold-paste viscosity showed significantly negative correlation with DP 6 (r=−0.780, −0.824 and −0.808, respectively, p⩽0.05). However, pasting temperature, hot-paste viscosity and cold-paste viscosity showed positive correlation with DP 15–17. K. Pukhraj with the lowest amount of short-side-chain amylopectin fraction showed the highest moduli. K. Pukhraj starch with G′ much greater than G″ indicates its predominantly more elastic than viscous character. Chipsona-2 and K. Chandermukhi starches with a higher amount of short-chain amylopectin fractions (DP 6–12) showed a greater change in moduli during cooling of cooked paste and had more viscous character than other starches with lower amounts of these fractions.