Role of constituents on the network formation of hydrocolloid edible films

摘要

In this work, the influence of pectin surface density (ρ_s), soy flour-to-pectin weight ratio (Y_(SF/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 ρ_s, 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 Hey-mann model. The order of the relaxation function (α) and material elasticity parameter (E_α) resulted to be independent of ρ_s for the pectin-based films. On the contrary, for SF/P-based films, α and E_α values tended to increase and decrease, respectively, as Y_(SF/P) was increased. The film network link density appeared to increase as Y_(SF/P) was increased from 0 to 0.62 g g~(-1); however, any further increase in Y_(SF/P) was found to be ineffective on link density.