Properties of transglutaminase crosslinked whey protein isolate coatings and cast films

Whey protein is an excellent barrier material, potentially providing the low oxygen permeability and water vapour transmission rate required for packaging materials for sensitive foods. A topical issue is how to reduce the permeability of the whey protein-based layers. One possible strategy is to apply crosslinking agents. In the present study, the enzyme transglutaminase (TG) was used for this purpose, and the following properties have been measured: oxygen permeability, water vapour transmission rate, effective water vapour diffusion, sorption and permeation coefficients, swellability, light transmission and surface energy. The use of TG was found to reduce the oxygen permeability, reduce the water vapour transmission rate and reduce the effective water vapour diffusion coefficient of the whey protein layers. This study also showed that it was possible to use sorption experiments to approximate the water vapour transmission rates. This work is novel because it deals with the packaging-related properties of whey films crosslinked with TG. Previous studies have focused on the influence of TG on protein formulations or on the measurement of film properties, which is of little relevance for packaging applications.