Enzymatic Conversion of Starch in Twin‐Screw HTST‐Extruder

Wheat starch was liquefied to DE 25–30 employing heat stable α‐amylase and twin‐screw Werner & Pfleiderer Continua 58 HTST‐extruder. Most significant reduction in batch saccharification time was obtained when starch was liquefied as a slurry containing 60% water at 120°C mass temperature, feed rate 1 500 g min −1 , screw rotation rate 250 min −1 , and 0.9% (w/w, d.s.) Novo Termamyl 120 L α‐amylase was added immediately after initiation of gelatinization in the extruder. Saccharification was carried out at 60°C employing 0.36% (w/w, d.s.) Novo glucoamylase 150 L to reach a DE 96 in 22 h. Best total conversion was, however, obtained when also saccharification was initiated in the extruder by adding glucoamylase just before the die element, after lowering mass temperature to 60°C, and by allowing the saccharification to continue at 60°C after extrusion processing to reach a DE 94 in 5 h and DE 97 in 21 h.