Carbohydrate content of sample was determined by the Clegg-anthrone method (Nollet, 2004). Sample (1 g) was digested with 13 mL of 52 vol% perchloric acid to hydrolyze disaccharides, trisaccharides and higher oligomers to their reducing sugar components and then reacted with anthrone reagent under acidic condition to produce a blue/green color. Anthrone reagent was prepared by dissolving 0.1 wt% anthrone in diluted sulphuric acid (a ratio of sulphuric acid:water = 2.3:1 vol/vol). An aliquot (1 mL) of appropriately diluted hydrolysate was mixed with 5 mL of anthrone reagent. After incubated in boiling water for 12 min and cooled down, the absorbance of the reaction mixture was measured at 630 nm.