Optical, mechanical, and moisture sorption properties of whey protein edible films

The impact of protein and glycerol concentration on the optical, mechanical, and moisture sorption properties of whey protein isolate edible films was determined. The increasing of protein concentration leads to decreasing opacity and moisture adsorption of films but improving its tensile strength and elongation at break. Color parameters for all films remain constant and were not dependent on the film composition. Films with increasing glycerol concentration showed weakened mechanical resistance and higher moisture adsorption rates. Moisture sorption isotherms data were well described by GAB, Peleg, and Lewicki equations. These findings can be used to better design applications of whey protein films containing plasticizers, in order to optimize film formulation in a rational manner considering their practical use as protective coatings or edible packaging. Practical applications The increased interest in the development of edible films for food packaging applications has been raised to minimize the use of synthetic petroleum-based polymers. Moisture sensitivity of films showed the capacity of such materials to modify their physical properties which are influenced by different relative humidity or temperature conditions. The results presented in this study, concerning optical, mechanical, and sorption properties of whey protein-based edible films, would provide the scientific basis for developing functional protein films and their application for food products including nuts, seeds, fruits, or vegetables.