Response surface optimization of ultrasound-assisted extraction of sago starch from sago pith waste

Abstract

This present study employs ultrasound-assisted extraction (UAE) to optimize the yield of sago starch (SG) from sago pith waste (SPW) fiber. Slurry concentration, sonication time and sonication temperature are optimized adopting a Box-Behnken design for the maximum extraction yield as main response. The analysis of variance based on 17 runs of experiments reveals that the slurry concentration and sonication temperature has a significant influence, while the sonication time shows no statistically effect on the response. The optimal UAE conditions of SG are obtained at slurry concentration of 14.43 wt%, sonication time of 10 min and sonication temperature of 38.3 °C. At these optimized conditions, 78.68% of extraction yield is obtained. Short-range ordered structure shows that ultrasound influences the degree of order and amylose to amylopectin content of SG. The numerous scratches and fissures on the surface of SG granules are caused by the shear forces generated by the collapsing bubbles during cavitation. The thermal properties of SPW and SG show an average weight loss of more than 90% when a temperature beyond 300 °C is applied. The high onset temperature and reduction on gelatinization enthalpy and final temperature of SG indicate that ultrasonic irradiation highly influences the thermal characteristics of the extracted SG.