Influence of pH and protein thermal treatment on the rheology of pea protein-stabilized oil-in-water emulsions

The influence of emulsion pH and previous thermal treatment of the protein on the rheological behavior of pea protein-stabilized emulsions has been studied. Oil-in-water emulsions with 65% weight oil and 6% weight pea protein isolate were prepared. Emulsion pH was varied between 3.5 and 7.0. In addition to this, the protein aqueous phase was submit ted to different previous thermal treatments by modifying temperature from 25 to 90 degrees C and heating time from 20 to 60 min. To study the influence of the above-mentioned variables, droplet size distribution and steady-state flow curves were determined, and linear viscoelastic measurements were carried out. An increase in the pH of the emulsion initially leads to an increase in emulsion viscosity and viscoelastic functions, as well as to a decrease in the mean droplet size, up to an emulsion pH close to the protein isoelectric point, where a singular rheological behavior is found. An increase in temperature or heating time on the protein aqueous phase yields higher values of steady-state viscosity and linear viscoelasticity functions, up to a complete denaturation of the protein.