Isomalt-Plasticized Methylcellulose-Based Films as Carriers of Ascorbic Acid

In the present study, isomalt-plasticized methylcellulose-based films with and without ascorbic acid (AA) addition were developed. The aims of our research were to analyze the effect of the isomalt concentration and the drying temperature upon the physicochemical properties of films, also the stability of AA during film storage. Films prepared by 1.5% w/v methylcellulose (MC) using isomalt (0.25-1.5 w/v) showed improved properties when compared to those without isomalt. Unplasticized films exhibited higher elastic modulus and lower elongation at break than films with isomalt. The AA addition increased film elongation and decreased elastic modulus. FTIR spectra indicated that addition of AA produces structural changes in films and showed the presence of AA during storage. Two drying temperatures were tested, 37 degrees C and 45 degrees C. The change of drying temperature to a higher temperature significantly increased film water vapor permeability (WVP) and decreased the concentration of AA present in the films compared to those dried at a lower temperature. Thus, based on the WVP and AA retention results, the selected drying temperature was 37 degrees C. Films obtained by methylcellulose (1.5%) with 0.75% of isomalt, 0.4% of ascorbic acid, and dried at 37 degrees C can result in a good carrier of ascorbic acid. These films can be consumed through foods such as fresh or dehydrated fruits coated.