Effect of chemical modification with citric acid on the physicochemical properties and resistant starch formation in different starches

Potato, cassava, sweet potato, banana and lentil starches were modified with citric acid (CA) with the main objective of enhancing the resistant starch (RS) and slowly digestible starch (SDS) fractions and to compare starches of diverse botanical origins. The percentage CA substitution of modified starches ranged from 3.84 to 15.06 and showed similar type of XRD patterns, but with variation in intensity and percentage crystallinity. The peaks around 1705 cm-1 and 1150 cm-1 in FT-IR spectra of modified starches confirmed the presence of CA group. Scanning electron microscopy confirmed that there were no noticeable changes in granular structure and morphology. No peaks could be observed in RVA pasting profiles of modified starches, confirming cross-linking reaction. The SDS and RS were significantly higher in modified starches of all origins and consequently there was a lower estimated glyceamic index (EGI). Modified starches were associated with lower setback viscosity indicating their lower temperature stability.