ACETYLATION OF OZONATED SAGO (Metroxylon sagu Rottb.) STARCH: IMPLICATIONS FOR ITS PROPERTIES ON STARCH NOODLES

Abstract

This study aimed to enhance the physicochemical and functional properties of sago starch for noodle production using sequential ozonation and acetylation. Native sago starch was first ozonated to disrupt its crystalline structure, followed by acetylation with varying acetic anhydride ratios (4–8 g per 100 g starch) and reaction times (5–25 min). The acetyl content (%) and degree of substitution (DS) increased with higher acetylation agent ratios and longer reaction times, peaking at 6.644% acetyl content and 0.268 DS for the highest ratio (A-OS 8) at 25 min. Functional properties were significantly altered, with acetylated-ozonated starches showing increased moisture content (up to 15.168%), a higher water solubility index (WSI: 16.835%), and a reduced water absorption index (WAI: 30.419–33.692%) compared to native starch. Rheological analysis revealed that ozonation reduced the peak viscosity of native starch (5344 cP) to 4474 cP, while acetylation partially restored the viscosity (up to 5214 cP for A-OS 4). Structural characterization via SEM confirmed surface roughness and fissures in modified starches, whereas XRD and FTIR demonstrated retained A-type crystallinity with reduced order and successful acetyl group incorporation (evidenced by C=O peaks at 1740 cm⁻¹). In noodle applications, dual-modified starch improved texture, with reduced hardness (302.37 g for A-OS 8 vs. 593.46 g for native starch) and lower cooking loss (12.85% vs. 19.39%), alongside enhanced brightness (L* = 73.3) and shorter cooking times (5 min for A-OS 8). These results demonstrate that ozonation-acetylation synergistically modifies sago starch, optimizing its properties for noodle production by balancing its solubility, viscosity, and structural stability.