Zein films were produced as described in Padgett et al. (1998).
Briefly, 1.4 g corn zein was dissolved with 8.1 ml of ethanol (96%) by
mixing slowly with a magnetic stirrer for 25 min. 0.4 ml glycerol was
then added to the medium and the temperature of the mixture was
increased until it started to boil. The mixing was then ceased and the
film solution was boiled for 5 min