Barrier and mechanical properties of methyicellulose-whey protein films

Water vapour permeability (WVP) and mechanical properties were assessed in edible films prepared from methylcellulose (MC) and MC-whey protein isolate (WPI) or MC-whey protein concentrate (WPC). Glycerol (Gly) was used as the plasticizer. Two MC-WP films were formulated. For Group I films, the mass ratio of WP: Gly was constant, whereas for Group II films the mass ratio of polymer (MC + WP): Gly was constant. The WVP of MC-Gly film decreased with increasing MC concentration, while the tensile strength (TS) and percent elongation (E) increased. The WVP of Group I and Group H films decreased erratically and TS increased when the MC concentration was increased. Group I films had higher TS values than Group II films at the same MC:WP ratios. E of both groups increased with increasing MC concentration (p < 0.05), excluding the films with the highest MC: WP ratio tested (0.8) in Group I films. Group I films had lower E values than Group II films at the same MC:WP ratios. MC effectively governed WVP, TS and E of the WP films. Generally, MC-WPfilms of this work showed lower WVP than that of MC- and WP-based edible films in the literature. This can potentially make MC-WP films a suitable film material for moisture-sensitive food products. Copyright (c) 2005 John Wiley & Sons, Ltd.