Bioethanol cooking and fermentation

After the corn is ground to the correct size, water and the first enzyme (alpha-amylase) are added to breakdown the starch.

During the first step, called gelatinization, hot water (85 °C or 185 °F) is mixed with the flour for 20-60 min, followed by the addition of superheated water at 105 °C (221 °F). During this step the starch absorbs water, swells up and loses its compact crystalline structure. This enables the first enzyme, Alpha-amylase, to break the long starch chains into smaller variable length chains called dextrins via hydrolysis.

The second enzyme, glucoamylase, is added during the passage to the fermentation tank. This enzyme breaks the dextrins into individual glucose molecules. During fermentation the yeasts convert the simple sugar into ethanol.

The dissolved sugar is monitored in the liquefaction tanks by Vaisala K-PATENTS® Process Refractometer PR-43-GP to ascertain the required hold time. Also, a refractometer can be used to monitor and control the quantity of the required Alpha-amylase enzyme.

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