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Cereal Chem 65:228-232   |  VIEW ARTICLE

A Scanning Electron Microscope Study of Maize Gluten Meal and Soy Coextrudates.

P. L. Harris, S. L. Cuppett, and K. W. Lee. Copyright 1988 by the American Association of Cereal Chemists, Inc. 

The effect of altering extrusion conditions and ingredient levels on the internal structures of maize gluten meal-defatted soy flour coextrudates was studied using scanning electron microscopy. In addition, the relationship of the internal structure to product functionality was examined. Coextrudate water-holding capacity, bulk density, and shear resistance increased as maize protein concentration increased. The dense globular network observed in the low concentration maize gluten meal coextrudates changed to a more organized and striated matrix exhibiting an increased number of aligned, undirectional fibers. The lacy, thin-walled, single-layered interiors observed in the low-moisture coextrudates were transformed into a multilayered, bundle-like network as moisture levels approached the optimum (32%). Coextrudates processed at high moisture levels exhibited significantly lower BDs (P less 0.01) than those processed at lower moistures. As processing temperatures increased, extrudate walls became thinner, increasingly organized, fibrous, and porous. A more straited, organized texture with definite bundle formation was observed in the coextrudates processed at a neutral pH compared with the denser, unorganized interiors observed in coextrudates processed at extreme pH values.

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