Influence of pH on linear viscoelasticity and droplet size distribution of highly concentrated O/W crayfish flour-based emulsions

In the present work, the influence of pH on stability of oil-in-water (O/W; 75 wt%/25 wt%) emulsions stabilized by crayfish flour (CF) has been studied. CF (containing ca. 65 wt%) showed poor functionality in a wade range of pH, which inhibits formation of stable emulsions. An indirect procedure has been developed in order to obtain emulsion at a broad pH range, including isoelectric point (pI) value. The emulsions have been characterized by means of linear dynamic viscoelasticity and droplet size distribution (DSD) analysis. These emulsions present a behaviour characteristic of highly concentrated emulsions with a well-developed plateau region. The most unfavourable DSD and linear viscoelastic results correspond to the pI. A significant improvement takes place as the pH value departs from the pI. An exception for linear viscoelasticity results have been found at pH 10, which is close to the pI for rod segments of myofibrillar proteins. Stability of these emulsions has been studied by following the evolution of DSD and linear viscoelastic parameters along time. The poorer results in emulsion stability correspond to pH values close to the pI, at which the increase in droplet size or uniformity parameter as well as the decrease in the plateau modulus become more pronounced. Conversely, the stability significantly improves as the pH departs from pI.