The objectives of this study were to understand how intrinsic and extrinsic factors of o2 and QPM starches affected the enzyme digestibility of their starches, to develop novel and economical technologies to produce RS for health benefits. Enzyme digestibilities of starch present in opaque-2 maize (o2) and quality protein maize (QPM) were analyzed to evaluate the uses of the two maize mutants for food, feed, and ethanol production. The starch granules of the dry-ground o2 maize and QPM were hydrolyzed faster than those of the dryground wild-type (WT) maize using porcine-pancreatic alpha-amylase (PPA).