Melting properties of vegan cheese : Effect of emulsion and protein addition on the thermal behaviour of starch gels

The aim of this study was to understand the effect of emulsion and protein incorporation on the structural and melting properties of starch gels designed as model systems for specific types of vegan cheese, and to explore the potential of using these ingredients to mimic the melting properties of dairy cheese. To characterise the melting properties of the gels, temperature sweep tests were conducted. In addition, pictures were taken to visualise changes in appearance upon increasing temperature. The microstructure of the gels was investigated with confocal laser scanning microscopy (CLSM). Whereas gels of native maize starch did not melt, those made from oxidised potato starch melted completely at temperatures above 70 °C, resulting in a fluid with a viscosity much lower than that of molten dairy cheese. With the addition of a protein-stabilised sunflower oil emulsion, at oil contents >10%, an oil droplet network was formed in the starch matrix, which partly inhibited the melting of the gel. The addition of pea protein that was subsequently heated together with the starch also resulted in the formation of a network that limited melting. However, due to the high degree of pea protein aggregation, an inhomogeneous appearance was obtained. At low protein contents syneresis occurred. When protein was added without heat treatment, the melting degree was inhibited already at low contents, a more homogeneous appearance was obtained, and syneresis was prevented due to the high-water holding capacity of the protein. When emulsion and protein were added together at high contents, the appearance was also more homogeneous, and the melting degree of the composite gels was further limited. When comparing the relative inhibiting effect of oil and protein content on melting, protein was found to be more effective. By changing both oil and protein content, samples with melting properties similar to those of processed cheese were obtained, which shows that the design of multi-component starch-protein-oil gels is a promising approach in optimising the functional properties of dairy cheese substitutes.