CONICET | Buscador de Institutos y Recursos Humanos

Edible films are subject to change and deterioration because they are made from food ingredients. Few studies have investigated changes in the properties of whey protein concentrate (WPC) edible films during long-term storage or freezing. Formulation of protein-based films requires incorporation of plasticizer above a minimum threshold. Among these, glycerol (Gly) produces the best effect in whey protein films. Trehalose (Tre) is a naturally occurring, non-reducing, non-toxic, dietary disaccharide, approved to be used as a GRAS additive for foods. Tre can protect proteins from inactivation or denaturation caused by a variety of stress conditions, including desiccation, dehydration, heat, cold, and oxidation. The use of Tre as a drying aid in food for freeze drying has been reported. In this work, we compared the plasticizer ability of Gly and Tre on WPC-based films and studied the effect of the storage temperature on the mechanical and optical properties of the films. WPC/Gly (2:1), WPC/Tre (1:1) and WPC/Gly/Tre (2:1:2) films were obtained by drying and stabilization in an environmental chamber (25°C, 58% RH). Films were stored at 25ºC and 58% relative humidity or at -20ºC for 90 days. Thickness, tensile strength, Young´s modulus, elongation at break and transparency (%T600nm) were measured. In spite of the differences at the % total solids of the formulations all films showed an average thickness of 0.132 ± 0.037 mm. WPC/Tre films were the most rigid but less stable to storage at both conditions resulting more susceptible to rupture and cracking. Incorporation of Tre into WPC/Gly films decreased elongation at break and tensile strength; but improved Young´s modulus as an indicative of an enhanced mechanical resistance of the films. In general, mechanical properties of WPC/Gly and WPC/Gly/Tre films remained unchanged after frozen storage. WPC/Gly and WPC/Tre films were clear enough for use as see-through packaging (%T600nm ~57%) and transparency was maintained during storage at 25ºC. WPC/Gly opacity increased after frozen storage, whereas WPC/Tre did not resist this process. When Tre was included into WPC/Gly formulation films opacity increased because the growth of Tre crystals after storage at both conditions. In conclusion, the use of Tre did not significantly improved films? physicochemical properties during long-term storage neither at 25ºC nor at -20ºC. More research is necessary to better design edible films containing plasticizers like Tre, that crystallize over time, in order to exploit their protein cryoprotective properties towards its potential use at the food packaging industry.