Stability and rheology properties of oil-in-water emulsions prepared with mucilage extracted from Opuntia ficus-indica (L). Miller

The droplet size distributions, microstructure, rheological properties, and stability of oil-in-water emulsions prepared with mucilage (PM) were studied in comparison to guar gum (GG), xanthan gum (XG), and carboxymethyl cellulose (CMC). The results showed that the emulsions with PM had a particle size distribution and droplet diameters on the same order as the emulsions stabilized with GG and XG, and a lower polydispersity index. All emulsions exhibited shear-thinning behavior in the range of the shear rates applied and the concentrations evaluated. Emulsions prepared with PM at 4.5% (w/v) exhibited a k value on the same order as for the emulsion with GG at 1% (w/v). The mechanical spectra of the emulsions with PM showed a viscoelastic behavior similar to that of the emulsions prepared with GG. The emulsion containing mucilage at 4.5% (w/v) presented the highest relaxation time (lambda). This means that this emulsion had a more elastic behavior and greater resistance of its structure. The stability of the emulsions prepared with PM depends on the test conditions. Under static conditions, the emulsion prepared with 4.5% (w/v) mucilage showed similar stability to the emulsion prepared with GX and GG. On the other hand, the PM emulsion stability was higher than that of GX when it was evaluated under stress conditions.