Structure–Function Engineering of Arenga pinnata Starch via Dual Acylation and Phosphate Cross-Linking for Functional Food Systems
Jusman1*, M. Mirzan2, Nurakhirawati3
Abstract
Arenga pinnata is an abundant Indonesian starch resource with considerable potential for functional food applications; however, its utilization is limited by poor processing stability and pronounced retrogradation during storage. This study investigates an integrated chemical modification strategy combining sequential dual acylation (acetylation and butyrylation) with phosphate cross-linking to elucidate structure–function relationships in modified starch from Arenga pinnata. Native starch was dispersed in aqueous media and acetylated using acetic anhydride at varying concentrations (3–12%, w/w), followed by butyrylation with butyric anhydride under controlled alkaline conditions. The acylated starch was subsequently cross-linked using a sodium trimetaphosphate/sodium tripolyphosphate (STMP/STPP, 99:1) system at different levels. Chemical incorporation was quantified by acetyl content and degree of substitution (DS). At the same time, functional performance was evaluated by water- and oil-holding capacities, swelling power, solubility, and digestion–resistance–related parameters. Increasing acetylation levels resulted in a systematic increase in acetyl content and DS, demonstrating that substitution could be effectively tuned by reagent concentration. Higher substitution levels enhanced hydration capacity and swelling behavior, accompanied by reduced solubility, indicating modified intermolecular associations and increased hydrophobicity within the starch matrix. Phosphate cross-linking further contributed to structural stabilization and increased the proportion of digestion-resistant starch fractions compared with native starch. An optimal modification condition was identified at 12% STMP/STPP combined with acetylation within the studied range, yielding an acetyl content of 2.740% and an acetyl DS of 0.112, which provided a balanced combination of functional stability and hydration performance. These results demonstrate that dual acylation coupled with phosphate cross-linking is an effective strategy for engineering the functional properties of Arenga pinnata starch for functional food systems. Nevertheless, the nutritional relevance of digestion-resistant fractions should be further validated using standardized resistant starch assays in formulated food matrices.
Keywords:
Arenga pinnata, acetylation, butyrylation, phosphate cross-linking, degree of substitution (DS), functional food
