Effect of granule size on physicochemical, morphological, thermal and pasting properties of native and 2-octenyl-1-ylsuccinylated potato starch prepared by dry heating under different pH conditions

Abstract

Potato starch was fractionated into small granule fraction (SGF) and large granule fraction (LGF) and both fractions were then modified by octenyl succinylation at pH 4, 6 and 8 followed by dry heating at 130 °C for 2 h. The effects of starch granule size and pH conditions of dry heated octenyl succinic anhydride (OSA) modification on physicochemical, morphological, thermal and pasting properties of both the starch fractions were investigated. Amylose content and swelling power of OSA modified both starch fractions at different pH's were significantly (p < 0.05) lower as compared to their native counterpart starches. OSA modification at different pH's resulted in decrease in light transmittance of both starch pastes. Morphological investigations revealed that the modification caused drastic changes on the surface of starch granules. OSA modification at different pH's resulted in decrease in gelatinization temperatures for both SGF and LGF potato starches as compared to their native counterpart starches. The variations in pH during modification had great effects on the pasting characteristics of both starch fractions. When OSA modified potato starch (both LGF and SGF) was reacted at pH 4 and pH 6, the peak viscosity decreased significantly (p < 0.05) as compared to their native counterpart starches.