The purpose of this study was to compare the effects of denaturation by microwave irradiation on release properties of 2 physically different proteins. Matrices were prepared from water-soluble bovine serum albumin loaded with metoclopramide and sorbed with adequate amount of moisture were thermally denatured in a microwave oven. The release profile of the rather insoluble denatured albumin matrices followed the classical Fickian diffusion profile. The release rate was dependent on the degree of denaturation, which was highly dependent on the level of moisture originally absorbed by the albuminoidal matrices and the period of exposure to microwave energy. Consersely, attempts to reduce the rate of drug release through microwave irradiation of metoclopramide-loaded matrices prepared from water-insoluble gluten were futile. The denaturation process was shown to be limited to the relatively water-soluble protein core fraction, while aggregation between neighboring gluten proteins in the matrix was not achieved even in the presence of considerable amounts of sorbed water.