Physicochemical and structural characterization of sodium caseinate based film-forming solutions and edible films as affected by high methoxyl pectin.

Present work focused on the role of high methoxyl pectin (HMP) in rheology and physical stability of sodium caseinate (CAS) film-forming solution as well as mechanical and structural characteristics of its edible film. CAS-HMP films were fabricated at different blend ratio. Incorporation of HMP into CAS solution decreased pH value of the solution, acting as a natural acidifier. Turbidity and particle size distribution measurements indicated that some level of protein-polysaccharide interactions developed in 50CAS:50HMP and 25CAS:75HMP. Analysis of steady-state shear viscosity of film solutions showed a transition from Newtonian to shear-thinning flow behaviour by addition of HMP. Dynamic viscoelasticity evaluations revealed that the elasticity of solutions decreased by increasing HMP ratio. Physical stability of solutions was assessed over time using a Turbiscanner. All solutions showed distinct mechanisms of destabilization. 50CAS:50HMP and 25CAS:75HMP samples appeared to be the most stable solutions. Increasing CAS:HMP ratio from 100:0 to 25:75 increased the water solubility and elongation at break of edible films from 27.16 to 63.70% and 2.36 to 16.53%, respectively. SEM analysis exhibited a homogenous microstructure in 50CAS:50HMP and 25CAS:75HMP. DSC thermograms displayed lower glass transition temperatures in HMP-incorporated films. Presence of the interactions among biopolymers in biocomposites was confirmed by FTIR spectra.