Effect of Porosity on the Esterification Efficiency and Physicochemical Properties of Corn Starch

Abstract

Native starch (NS) has limited surface area and porosity, which restricts its performance in adsorption, encapsulation, and emulsification systems. We hypothesized that introducing porosity into starch granules would increase hydroxyl accessibility and enhance esterification efficiency, yielding amphiphilic derivatives with improved functional properties compared with NS. To test this hypothesis, native and porous corn starches were esterified with octanoyl chloride under mild alkaline conditions and characterized by 1 H NMR, FTIR, XRD, SEM, DSC, particle‐size analysis, zeta potential, oil absorption capacity (OAC), and enzymatic degradation. Quantitative 1 H NMR confirmed a higher degree of substitution (DS) for porous starch (DS = 0.038) than for NS (DS = 0.030), indicating enhanced reactivity toward esterification. SEM and XRD analyses showed that modification primarily occurred on the granule surface, while the crystalline structure was largely preserved, with a slight decrease in relative crystallinity (RC) after esterification. DSC analysis revealed a reduction in gelatinization enthalpy for all esterified samples, which was more pronounced in porous starch (PS), consistent with partial disruption of hydrogen bonding. Esterified PS (EPS) exhibited a greater decrease in zeta potential, as well as higher hydrophobicity, oil‐binding capacity, and enzymatic degradability than esterified NS (ENS). These findings demonstrate that starch porosity is an effective strategy for enhancing esterification efficiency and tailoring biodegradable starch derivatives with improved physicochemical and functional properties.