Structural properties and digestibility of amylopectin-palmitic acid complex formed by amylosucrase treatment on waxy corn starch

Abstract

Structural properties and in vitro digestibility of amylopectin-palmitic acid (AP-PA) complex were studied. Amylosucrase (AS) was treated on waxy corn starch (WC) for 1, 3 and 6 h to have AP chain elongated. AS-treated starch formed AP-PA complex by complexation process including heat treatment such as autoclaving of the starches at 121°C and incubation of starches at 95°C and palmitic acid mixture. AS6-PA showed the much higher ability to form complex with palmitic acid than WC-, AS1- and AS3-PA. It reflected that prolonged AS treatment time could enhance the formation of AP-PA complex. complex samples with AS-treated starches and PA (ASs-PA) had a lower relative crystallinity than their FA controls. Both of FA controls and ASs-PA from AS-treated starches had lower in vitro digestibility and slower hydrolysis rate with increasing AS reaction time. AS treatment on WC reduced rapidly digestible starch (RDS) content while increased slowly digestible starch (SDS) and resistant starch (RS). The formation of complex in ASs-PA did not show significant effect on in vitro digestibility and maintain the low digestibility which was induced by AS treatment on WC. It might be too small amount of complexes formed in ASs-PA to affect the hydrolysis rate of AS-treated starch. In DSC therograms, the complexes from elongated amylopectin displayed the type I peaks inducing higher Tc and ∆H than FA control while the complexes showed higher ∆H in the endothermal peak of long chain double helix. These changes of thermal properties resulted from formation of complexes were more distinct in AS6-PA than others.