Enzymatic hydrolysis and saccharification optimisation of sago starch in twin-screw extruder

The influence of processing conditions in a combined gelatinisation and liquefaction extrusion system on subsequent saccharification was examined. Extrusion conditions investigated were barrel temperature (70 - 130 degrees C), screw speed (70-190 rpm), enzyme concentration (0-1%) and feed moisture content (28.5-50.5%). Feed moisture, barrel temperature and enzyme concentration had significant effects on saccharification, which ranged from 32 to 98% (dextrose equivalent = 83-98) after 8 h reaction with 0.50 AGU/ml amyloglucosidase (AMG). Die pressure tvas negatively correlated with saccharification (r = -0.75), implying that products formed from a high viscous mass were poorly saccharified. Greater extent of saccharification was achieved with lower SME input. Saccharification in the extruder was initiated by adding AMG during the extrusion processing. Both initial and subsequent saccharification were dependent on the AMG concentration, moisture content and the stage of AMG addition. In this mixed-enzyme system, synergistic effects of both enzymes (alpha-amylase and amyloglucosidase) were evident. High performance size-exclusion chromatography profiles showed that incorporating AMG led to loss of G6 and G2 in the oligosaccharide spectra but with formation of G5. (C) 1997 Elsevier Science Limited.