High internal phase emulsions and edible films with high methoxyl pectin and pea protein isolate or sodium caseinate

Abstract

Structuring of sunflower oil by forming HIPEs in the presence of high methoxyl pectin (HMP) and pea protein isolate (PPI) or sodium caseinate (SC) was evaluated first. Initially, emulsions with protein: polysaccharide ratios of 2:1 and 6:1 and two different pectin concentrations (0.5 and 1% wt) were formed and compared with emulsions with just protein, with the former exhibiting greater viscosity and stability. All emulsions exhibited pseudoplastic behaviour with the higher biopolymer concentrations leading to increased emulsion viscosity. The type of protein was significant for stability only for the initial pectin concentration of 0.5% wt. Then, SC and PPI emulsions with a protein: polysaccharide ratio of 6:1 for both pectin concentrations were selected for HIPE formation. The formed HIPE for both proteins had a great oil loss (83–95%), showing that the used combination of biopolymers did not lead to the formation of a structured system. Subsequently, edible films formed by drying the aqueous dispersions of the previously selected protein-polysaccharide binary systems were studied. All films had the same density. The greater total biopolymer concentration led to thicker, heavier, stronger and stiffer films with greater water vapour permeability and opacity. SC films were thicker, heavier, stronger, stiffer and brighter than PPI films, with lower moisture content and opacity. Overall, the used protein affected the studied properties of the films, indicating differences in the formed network.