Water adsorption characteristics of extruded blends of corn gluten meal and distillers dried grains with solubles

Corn-based ethanol has experienced exponential growth during the last decade. As a consequence, the production of byproduct corn protein meals, in the form of DDGS (distillers dried grains with solubles) and CGM (corn gluten meal) has grown as well. These materials are used as livestock feed. Extrusion processing is one method of converting these materials into other value-added materials, bioplastics, or other industrial precursors. The objectives of this study were to extrude blends of these materials, then examine dynamic and equilibrium relationships of extruded products with water. Blends consisted of DDGS:CGM ratios of 0, 33, 50, 66, and 100%. After processing, extrudates were placed in sealed chambers with headspace relative humidities ranging from 10% to 90%. Moisture contents were monitored over time. All samples achieved moisture equilibrium in less than three weeks. As with all biological materials, the extruded corn protein blends exhibited sorption behavior, the magnitude of which varied according to blend ratio. EMC values ranged from approximately 0% to nearly 50%, depending upon the humidity level and fiber:protein ratio. Nonlinear regression was successfully used to model the effects of relative humidity and blend ratio on the equilibrium moisture contents, with a coefficient of determination of similar to 99%. Future work should aim to characterize the mechanical properties of these blends to assess their suitability as either bioplastic feedstocks or pelletized animal feeds. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.