Rheological Modeling of Corn Starch Doughs At Low to Intermediate Moisture

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Abstract
A generalized model for predicting the extrudate viscosity of starch based products at low to intermediate moisture content is presented. It incorporates the effects of shear rate, temperature, moisture content, time‐temperature history and strain history. The model was tested using corn starch dough at various moisture contents. An Instron capillary rheometer and a Baker Perkins MPF 50 D/25 co‐rotating twin screw extruder were used to collect all data. Viscosity was found to be a function of cook temperature and moisture content but not cook time. Observed versus predicted viscosity gave an R2 of 0.975 after accounting for shear rate, temperature, moisture content and time‐temperature history in the capillary rheometer. Extrusion tests indicated that correction for strain history was important for highly puffed extrudates.