Cinnamaldehyde treatment of gliadin films provided a means of decreasing their solubility, increasing their molecular weight profile, and reducing their overall migration into food simulants as a consequence of the high degree of polymerization achieved. Despite losses incurred in the film manufacturing process, and the amount that remained covalently bonded with protein because of cross-linking, the addition of 1.5, 3, and 5% of cinnamaldehyde (g/100 g protein) to gliadins at pH 2 rendered 1.8, 4.8, and 11.0 mg cinnamaldehyde/g film, respectively, available to be released, and therefore to exert antimicrobial activity. Cinnamaldehyde diffusivity was largely dependent on environmental conditions, increasing from 0.49 x 10(-15) m(2)/s at 30% relative humidity (RH) to 13.1 X 10(-15) m(2)/s at 90% RH and 23 degrees C. This water sensitivity of films provides a mechanism with a noteworthy potential to retain the compound before its use, to trigger its release when needed, and to modulate the release rate according to the product humidity.