LIQUEFACTION OF STARCH BY A SINGLE-SCREW EXTRUDER AND POST-EXTRUSION STATIC-MIXER REACTOR

The production of ethanol has increased rapidly during the past few ye ars, especially sii-tce enactment of the 1990 Clean Air Act. Productio n costs, however, are high, requiring improved conversion technologies . The gelatinization of starch with conventional jet cookers requires a minimum moisture content of 65% by weight An alternative to jet cook ers is extrusion, which requires significantly less moisture to gelati nize starch. Starch gelatinization and liquefaction was achieved using single-screw extrusion and a post-extrusion static-mixer reactor. The effects of moisture content, reactor temperature, reactor length, and enzyme concentration on liquefaction were evaluated using response su rface methodology The else of a static-mixer reactor tube improved mix ing of the gelatinized slurry and increased residence times, resulting in increased starch degradation and reduced viscosity. Comparison of costs for extrusion and conventional technology indicates extrusion ha s potential as a cost-effective alternative.