A comparative study of Indian rice starches using different modification model solutions

Starches extracted from rice flour from broken kernels of three rice cultivars (PUSA-44, PR-106 and PR-114) have been selected for modification studies due to their varied amylose content. Model solutions with different types and concentrations of modifying agents were prepared for comparative study of effect of amylose variation among the varieties and also individual and combined effect of modifying agents used. There was an increase in hot paste viscosity at 90 °C in modified starches whereas, cold paste viscosity decreased upon modification. A greater effect was observed with in dual modification of starches. The total set back was significantly lower in modified starches indicating the decreased retro-gradation of starch gels upon modification. The DSC results showed decreases in ΔH, To, Tp, and Tc, indicating that hydroxypropylation cross-linking and acetylation affect the structure of starches granules, requiring less heat for gelatinization. Pasting and thermal properties of PUSA-44 were significantly different from those of PR-106 and PR-114, probably due to relative higher amylose contents in the former. As observed in this study, bi-functional modifying agents can reduce the extent of cross-linking. Acetylation modified the morphology of the starch. However, hydroxypropylation cross-linking and dual modification retained the original structure with little modification.