Microwave transmittance in gelatin-based films

Abstract

Biopolymers are alternative materials used in the production of edible and/or biodegradable films. A very important restriction factor concerning the films is their sensitivity to environmental conditions, such as temperature and relative humidity. The production of films based on gelatin and polyvinyl alcohol blends can be an alternative solution in order to reduce the sensitivity to the humidity. Thus, the aim of this work was to apply the microwave transmittance technique to measure qualitative effects of the presence of glycerol and polyvinyl alcohol on the moisture content of gelatin-based films. The results show that the films with glycerol, conditioned for one week in NaBr, revealed visible changes between 11 and 13 GHz as the plasticizer concentration increased. For gelatin films containing PVA, the results revealed very low microwave insertion losses. Thus, this behaviour was attributed to the presence of water molecules in gelatin films.