Effect of enzymatic pretreatment on the extraction yield and physicochemical properties of sago starch

The aim of this research was to investigate the extraction yield and physicochemical properties of sago starch extracted after enzymatic pretreatment. Sago pith was enzymatic-pretreated by varying enzyme (cellulase enzyme complex) concentration, pretreatment time, and sago pith slurry concentration. The extracted sago starch was analyzed for its properties, e.g., extraction yield, pasting and thermal properties, and in vitro starch digestibility. Sago pith contained 82% (db) starch. The extraction yield and reducing sugar released increased with enzyme concentration and pretreatment time. The optimum enzymatic pretreatment conditions were 10% (w/w) sago pith slurry, enzyme concentration of 0.25 mL (618 carboxymethylcellulose unit and 139 p-nitrophenyl-beta-D-glucopyranoside unit)/g substrate, and 24 h pretreatment time, providing the highest extraction yield of 71.36% (w/w sago pith, db), while control method, without enzymatic pretreatment, provided 61.01% extraction yield. Results from pasting and thermal properties confirmed that the granular stability, resistance to shear, and crystalline perfection of sago starch were improved due to hydrothermal effect of annealing during enzymatic pretreatment. The enzymatic-pretreated sago starch also had lower retrogradation but higher starch digestibility than the control sago starch. The enzymatic pretreatment enhanced the extraction yield of sago starch and also improved its quality by the effect of annealing.