Emulsions stabilised with cellulose microfibrils and potato protein

Abstract

We investigate oil-in-water emulsions prepared using potato protein and cellulose microfibrils (CMF) in the continuous phase. The ratio of potato protein and CMF is varied, along with the pH of the emulsion, and the volume fraction of the dispersed oil phase. We study how these factors affect the microstructure and flow properties of the emulsion, and link oscillatory rheology data to the microstructure via confocal laser scanning microscopy, cryo-scanning electron microscopy, and droplet size measurements. We find that the concentration of CMF is the key contributor to the flow properties of the continuous phase. While the protein has little effect on the rheology of the continuous phase, it plays a significant role in the flow properties of the emulsion. At low concentrations of protein, the CMF stabilises the emulsion droplets, and as the concentration of potato protein increases,this results in a decrease in droplet size, and an increase in emulsion elasticity. We find that it is also possible to drastically tune the elasticity of the emulsion via acidification. This is due to a combination of several different mechanisms, including altering the degree of attachment between droplets and the gel matrix. We finally investigate the dependence of elasticity on the oil fraction, and find that storage modulus increases for emulsions at pH 4, and decreases at neutral pH. Emulsions with adjustable elasticity offer a highly versatile system, enabling their use in the reformulation of various food emulsions.