Development of gelled emulsions with improved oxidative and pH stability

Olive oil emulsions were produced at high pressure homogenization (0–60 MPa), stabilized and gelled with gelatin, alginate or their mixture. Right after homogenization, these systems were evaluated according to their droplet size distribution and after gelation, uniaxial compression properties were assessed. Pure alginate emulsions showed larger mean droplet size and lower values of mechanical properties than emulsions with gelatin. Increasing homogenizing pressure led to monomodal droplets size distribution, although a weakening on gel structure was observed. For oxidative and pH stability assays, emulsions with smaller droplet sizes and polydispersity were chosen (40 MPa). Results of oxidative stability showed lower amount of primary and secondary oxidation products within the 30-day storage for the gelled emulsions as compared to a control sample (non-gelled). Considering the pH stability assays, results indicated that gelatin emulsions were not stable to any incubation condition at 37 °C. Alginate emulsions, on the other hand, showed to be relatively stable at the pH conditions evaluated, although a visible separated oil layer was observed at neutral pH. Generally, alginate–gelatin mixed emulsions showed enhanced oxidation and pH stability as compared to systems produced with only one biopolymer. Such improved stability of mixed gelled systems was associated to the emulsifying properties of gelatin with the high pH resistance of alginate as a delivery system.

Figure optionsDownload as PowerPoint slideHighlights
► Association of emulsifying properties of gelatin with high pH resistance of alginate.
► Development of improved oxidative and pH stability gelled emulsions.
► Reduction of oxidation of olive oil using biopolymers as emulsifyers.