Mechanical properties and water vapor permeability of edible films from whey protein isolate and sodium dodecyl sulfate

The ability of sodium dodecyl sulfate (SDS) to plasticize edible films from whey protein isolate (WPI) was assessed. SDS was not able to plasticize WPI films on its own, but it was an effective coplasticizer in films containing either sorbitol or glycerol as the main plasticizer. In films that contained sorbitol, a mass ratio of SDS to WPI (R_s:w) of 0.2 resulted in films that were more extensible and more soluble but with almost unchanged water vapor permeability (WVP). In films that contained glycerol, the same R_s:w resulted in less extensible and soluble films with slightly higher WVP values. Values of R_{S W} > 0.3 resulted in antiplasticization, although there was a reduction in WVP. At R_S:W > 1 films were so brittle that they could not be handled without breaking. The mechanical properties of WPI films that contained SDS were comparable to published values for other proteinaceous, edible films.