Blends of starch and zein plasticized with glycerol were prepared by melting in a batch mixer at 160 degrees C. Glycerol was used as plasticizer in contents ranging from 20 to 40 wt % with respect to the starch/zein matrix. These blends were characterized by mechanical tests, dynamic mechanical analysis, and optical microscopy. In tensile tests, the Young's modulus and ultimate tensile strength increased with increasing zein content for all compositions, whereas elongation at break decreased sharply with increasing zein content up to 20%, and it remained nearly constant at higher contents of zein, which increased the stiffness of the blends. On the other hand, increase in the glycerol content caused a decrease in mechanical resistance of the blends. Storage modulus increased with increasing zein content and the tan 6 curves showed that the blends exhibited two distinct glass transitions, one for each component, indicating a two-phase system, confirming the morphological evidence of micrographs that displayed two separate phases. (c) 2006 Wiley Periodicals, Inc.