Physicochemical, crystalline, morphological, pasting and thermal properties of modified lotus rhizome (Nelumbo nucifera) starch

• Carbonyl content ranges 0.03–0.06% where as carboxyl content 0.08–0.19%.
• FTIR and XRD confirmed modification, cross-linking was up to (18.08% & 68.20%).
• Modification improves water binding capacity & color value (whiteness) of starches.
• Diffractogram illustrated the increase in crystallinity of starch upon modification.
• Lower enthalpy (ΔHgel) for obtained modified starches as compared to native starch.

Chemical modification of lotus rhizome starch was carried out for the development of oxidized (OLS), cross-linked (CLS) and dual modified i.e. oxidized cross-linked (OCLS) and cross-linked oxidized (COLS) starches. Carbonyl (0.03–0.06%), carboxyl content (0.08–0.19%), degree of cross-linking, physicochemical, pasting, morphological, thermal, FTIR and XRD analyses of modified starches confirmed the successful modification of native starch. Amylose content of modified starches significantly decreased as a consequence of starch modification, however, water binding capacity and color value increased. Swelling power and solubility of both native and modified starches increased with temperature range (50˚–90 °C). The light transmittance of modified starches was highly improved compared to the native starch, except for cross-linked starch. X-ray diffractogram illustrated an increase in degree of crystallinity of modified starches. The morphology of the starch granules as observed by scanning electron microscope (SEM) presented surface roughness in case of oxidized and dual modified starches, whereas smooth surface of native and cross-linked starches was observed. Pasting profile of modified starches analyzed using rapid visco analyzer (RVA) presented a decrease in viscosity compared to its native counterpart. Differential scanning calorimeter (DSC) was used to study the phase transitions associated with gelatinization, and exhibited lower enthalpy values (ΔHgel) for modified starches as compared to native starch.

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