Citrate esterification of debranched waxy maize starch: Structural, physicochemical and amylolysis properties

Abstract Considering that the content of resistant starch (RS) in original starch is very low, chemical modification is one of choices to increase RS level for enhancing its application. The current study applied debranched waxy maize starch (DBS) to produce a citrate-esterified debranched starch (CADS) and investigated impact of the modification on RS formation. Native starch was also citrate esterified without debranching treatment as the control (CANS). Physicochemical and digestion properties of each sample were characterized, and the results indicated an absorption at 1724 cm −1 in FTIR spectrum was determined in either CADS or CANS, indicating the occurrence of the esterification. Debranching of starch molecules led to a higher degree of substitution (DS) of 0.793 for CADS than CANS. Furthermore, re-association of debranched starch achieved a B type crystalline pattern rather than an A type from its native starch granules. Esterification greatly destroyed crystalline regions until completely disappeared in CADS. The loss of crystalline region was highly consistent with the absence of endothermic peak both in CADS and CANS as revealed by DSC. Hydrolysis rate and digestibility of each sample followed the order: native starch > DBS > CANS > CADS, which may indicate that the introduction of the citric anhydride onto the starch molecules led to an increased space steric hindrance that delayed the enzyme contacting within glucosidic bonds. It could be the first report to prepare a citrate-esterified debranched starch with a higher resistance to amylolysis, and the current investigation may highlight a potent to produce a starch derivative with a higher RS content.