Water vapor barrier and mechanical properties of konjac glucomannan–chitosan–soy protein isolate edible films

The effects of polymer composition, glycerol concentration and pH of film-forming solution on water vapor permeability (WVP), tensile strength (TS) and percentage elongation at break (%E) of composite edible film based on konjac glucomannan (KGM), chitosan and soy protein isolate (SPI) were investigated. Of the plasticizers tested, glycerol was found to be a suitable plasticizer regarding mechanical properties and WVP. The WVPs of the films were determined to be (3.29–9.63) × 10^?11 g m^?1 s^?1 Pa^?1, TS between 16.77 and 51.07 MPa, and %E between 1.29% and 10.73%, depending on film composition. Incorporation of SPI to the polymer matrix decreased both WVP and mechanical properties. Increase in both glycerol concentration and the pH of film-forming solution decreased WVP and TS but increased %E. The results suggest that film composition and the pH of film-forming solution are the major factors influencing the film properties.