Improved emulsification behaviour of pea protein-polysaccharide complexes for beverage application

Abstract

Proteins are widely used as emulsifiers in food formulations. However, emulsifying properties of proteins are weak at pH values close to their isoelectric point resulting in destabilization. Protein-polysaccharide interactions have been proposed to improve the emulsification behaviour of proteins in such conditions. In this work, two different polysaccharides (pectin and gum Arabic) with a range of surface charges were chosen to investigate their interactions with pea proteins. The initial aim was to investigate the effect of heat treatment on the complexation of pea protein isolate (PPI) and the polysaccharide with the ultimate purpose of using them as effective emulsifiers at various pH values for beverage application. The emulsions were prepared, and the emulsification ability was determined with the selected protein-polysaccharide complexes at both basic (pH 8.0) and isoelectric pH (pH 4.5) conditions. Turbidity graphs of gum Arabic-PPI and or pectin-PPI complexes at 1:1 mixing ratio revealed an increase in the pH range of the soluble complexes upon heat treatment of the mixture to 75ºC. The soluble complexes of the protein and polysaccharide were able to stabilize oil-in-water beverage emulsions at the isoelectric pH of the protein. The stabilization effect of soluble pectin-PPI complexes was better than gum Arabic-PPI complexes at pH 4.5. At pH 8, although droplet sizes were similar, pectin-PPI complexes caused depletion flocculation leading to a higher accelerated creaming velocity of the emulsion than the gum Arabic-PPI complexes. The emulsions stabilized by pectin-PPI complexes at pH 4.5 had the highest emulsion stability in terms of lower instability index, lower accelerated creaming velocity and the lowest droplet diameter than all other emulsions. The findings of this study will provide beneficial information on the effect of processing conditions on biopolymer interactions and the emulsification ability of protein-polysaccharide complexes for the application in beverage emulsions.