Ultrasonic-Assisted Alkaline Extraction of Starch from Solid Sago Pith Waste

Background: Efficient extraction of starch from solid sago pith waste (SPW) presents a valuable opportunity to transform the waste into valuable resources, as it still contains 40-70% of starch. Some conventional extraction methods may alter starch characteristics, impacting yield and functionality. Method: This study evaluates the effectiveness of Ultrasound-Assisted Alkali Extraction (UAAE) in starch recovery from SPW under varying alkali concentrations, solid loading, steeping duration, and SPW particle size, as well as the characterization of the extracted starch. Results: S6 (UAAE with 0.5% NaOH, a 7-hour steeping duration, and 8% solid loading) achieved the highest extraction yield at 50.9%. Using a smaller SPW particle size (<250 μm), S12, under similar conditions, reduced the yield to 45.4%. Characterization showed no significant changes in functional groups, as confirmed by FTIR analysis. TGA and DSC revealed higher gelatination and degradation temperatures in S6 compared to S1 (control). XRD analysis confirmed that the crystalline structure was preserved as C-type starch. FESEM images showed minimal surface disruption, indicating largely intact granular morphology. Discussions: UAAE enhances starch extraction while preserving the physicochemical and structural integrity of starch. However, mechanical actions such as grinding reduce yield, possibly due to solubility effects from starch damage induced by mechanical disruption. The observed thermal properties were consistent with increased amylose content, while structural analysis confirmed retention of native starch characteristics. Conclusion: These findings support UAAE as a viable method for starch extraction from SPW, particularly under conditions that minimize mechanical disruption, with minimal changes observed in starch properties.