Role of constituents on the network formation of hydrocolloid edible films Original Research Article

In this work, the influence of pectin surface density (ρs), soy flour-to-pectin weight ratio (YSF/P) and cross-linking agent (i.e., transglutaminase, TGase) on the three-dimensional film structural network was studied by dynamic mechanical and microscopy analyses. Small amplitude oscillatory measurements proved that all films behaved as solid-like materials. Storage (E′) and loss (E′′) tensile moduli of pectin-based films were not affected by ρs, whereas the mechanical properties of soy flour/pectin (SF/P) based films declined as the soy flour content was increased. This trend was also confirmed when using TGase to cross-link SF/P-based films, even if the complex dynamic tensile modulus E∗ was found to be more dependent on the angular frequency (ω). The three-dimensional structure of all films examined was well described by using Friedrich and Heymann model. The order of the relaxation function (α) and material elasticity parameter (Eα) resulted to be independent of ρs for the pectin-based films. On the contrary, for SF/P-based films, α and Eα values tended to increase and decrease, respectively, as YSF/P was increased. The film network link density appeared to increase as YSF/P was increased from 0 to 0.62 g g−1; however, any further increase in YP/SF was found to be ineffective on link density.