Influence of Free and Encapsulated Olive Leaf Phenolic Extract on the Storage Stability of Single and Double Emulsion Salad Dressings

Valorization of wastes has become an unavoidable goal in the olive oil industry. A possible approach is the recovery of leaf phenolic compounds, which have a great interest for food industries, due to their antioxidant and antimicrobial activities. Thus, this study aims at comparing the effects of encapsulated (e-OLE) and free olive leaf extract (f-OLE) on storage stability of salad dressings prepared as single and double emulsion systems. Creaming, rheological properties, double emulsion yield, pH, total phenol content (TPC), antioxidant activity, and peroxide value (PV) of the dressings were monitored over 90 days at 4 °C. Microstructure examination showed a more homogeneous distribution of the droplet size with the inclusion of OLE. No creaming and very little variations in rheological parameters (<10%) were observed. OLE enrichment and double emulsion systems significantly (P<0.05) improved the rheological behavior, with a higher effect of e-OLE due to the alginate-pectin beads. OLE-enrichment extended the oxidation induction period from 15-20 days to 50 days. In conclusion, the work demonstrated that OLE encapsulation by emulsification-internal gelation technique was effective in gradually releasing polyphenols during salad dressing storage, thus increasing product protection toward oxidation phenomena.