Gelatinized Cassava Starch Obtained via Low Molar Ratio Hydroxypropylation Reaction

Abstract

Hydroxypropylated starch was successfully synthesized, aiming to address the limitations of native starch, such as poor mechanical properties and water sensitivity, which hinder its application in biodegradable polymers. The modification process, conducted at 115-135 °C with propylene oxide (PO) molar ratios of 0.4-0.8 [PO molecule per OH of starch], effectively disrupted the native starch structure. FTIR and 13C NMR confirmed methyl group incorporation, with lower temperatures and higher PO ratios yielding greater modification. SEM and XRD analyses demonstrated complete gelatinization; although some short-range order structures are present, long-range structures were eliminated, while DSC confirmed the absence of gelatinization peaks. TGA revealed the integration of lower molecular weight molecules, suggesting PPO homopolymerization within the starch granules. These structural transformations enhance the feasibility of producing hydroxypropylated starch films with reduced plasticizer content and energy requirements, offering a novel approach to improving starch-based materials for biodegradable applications.