Morphological, structural and digestibility properties of RS4 enriched octenyl succinylated sweet potato, banana and lentil starches

Resistant starch (RS), RS4 type, has been synthesized by octenyl succinylation of sweet potato, lentil and banana starches and comparatively evaluated for their physicochemical and digestibility properties. The effect of substitution level and physicochemical properties of the modified starches were correlated with their in vitro starch digestibility, rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) contents. The modified starches were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) analyses. The three starches showed distinctly different digestibility and functional properties along with different crystalline pattern, granule shape and sizes. The octenyl succinylated starches showed a significant increase in RS and SDS when compared to the corresponding native starches. Correlation analysis showed that degree of substitution, swelling power and gelatinization temperatures of the modified starches were positively correlated to RS whereas negative correlation was observed for syneresis, setback viscosity and loss modulus with RS. (c) 2018 Published by Elsevier Ltd.