Enzymatic conversion of high moisture shear extruded and gelatinized

Abstract

Methods and apparatus for high-moisture extrusion of starch-bearing grains is disclosed which yield cooked, gelatinized products suitable for short-time enzymatic conversion to sugars, and particularly those subject to fermentation to alcohol; the high production rates afforded through use of extrusion equipment, and the short conversion time of the resultant products, is particularly advantageous for economical alcohol manufacture, both for alcoholic beverages and for use as fuel. Preferably, whole or cracked starch-bearing grain is presoaked in an excess of water to a substantial moisture level, and the resultant slurry is fed to a specialized extruder. In the extruder the water is at least partially separated and carried from the process, and the grain is highly cooked and gelatinized for subsequent conversion. The overall apparatus preferably includes presoak tanks for the grain, a grain-conveying feeder, an extrusion cooker, and enzyme conversion tanks; the apparatus is advantageously sized for batch-continuous operations to produce a continuous flow of sugars. Conversion times for the gelatinized starches are low, less than about 45 minutes, and moisture and extrusion conditions can be altered to further lower sugar conversion time.