Influence of extrusion variables on subsequent saccharification behaviour of sago starch

Abstract

This study reports the effects of substrate concentrations (21.6–38.4 g/100ml), amyloglucosidase (AMG) concentrations (0.66-2.34 U/g) and hydrolysis time (14.8–65.2 h) on the saccharification of sago starch extrudates. Regression analysis established AMG concentration and hydrolysis time as the most significant factors; a generated regression equation adequately predicted the outcome of saccharification. Using 30 g/100 ml solid content, 65.2 h and 2.34 U/g of AMG, syrups of highest glucose content (87.9%) were attained. Effects of extrusion conditions, i.e. feed moisture content (21.6–38.4), enzyme (Termamyl 120L) concentrations (1.48–6.52%) and mass temperatures in the compression and die zones (70.5–97.5 .C) during the combined gelatinisation and liquefaction of sago starch, on the amount of glucose produced were evaluated. Enzyme concentrations and feed moisture contents had the most pronounced effects on saccharification, which ranged from 47.6 to 73.3% (DE = 85–94) and 54.5–93.8% (DE = 90–98) after 24 and 65 h, respectively. Response surface plots suggest that a higher percent saccharification can be achieved when sago starch is extruded at high Termamyl concentrations but low moisture contents.