Preventing the loss of tensile, barrier and appearance properties caused by plasticiser crystallisation in whey protein films

Summary Whey protein films plasticised with sucrose have excellent oxygen barrier properties and high gloss that are reduced with time as sucrose crystallises. Whey protein isolate (WPI) films plasticised with sucrose were stored in 53% relative humidity for up to 60 days. The oxygen permeability, tensile properties and gloss of the films were measured periodically following ASTM (American Society for Testing Materials) methodology. Changes in properties were compared with changes in WPI films plasticised with glycerol (no crystallisation) or plasticised with sucrose (crystallisation) plus a crystallisation inhibitor. The two inhibitors studied were lactose and raffinose. Crystallisation in WPI/sucrose films decreased tensile strength and elongation at break. However, the inhibitors hindered sucrose crystallisation, and the desired film properties were maintained for a longer period of time. Raffinose was the more effective inhibitor, maintaining the film flexibility and barrier properties for over 28 days and maintaining gloss at almost 90% of the initial value for 60 days of storage.