Abstract
In the last years, research has focused on the technological properties of olive oil polyphenols which have been proven to exert surface activity and emulsifying capacity in both model and real emulsified food matrices; however, to date, the effect of olive oil polyphenols in Pickering emulsions has not been explored yet. Aim of the work was to study the colloidal properties and physical stability of oil-in-water (O/W) Pickering emulsions made with esterified corn starch particles as emulsifiers and olive oil characterized by different polyphenols content (low, medium and high). Emulsions (30 % v/v oil) were obtained by using high pressure (HPH) homogenization (55 bar, 5 min). Colloidal properties (droplet size and distribution), stability (e.g. creaming index), rheological properties (flow curves and frequency sweep test), and microstructure of the emulsions were evaluated.
Starch particles and HPH allowed the formation of finely dispersed emulsions with droplet sizes with a median d3,2 of 13±2 µm. Olive oil polyphenols affected significantly the colloidal properties of the emulsions as olive oils with higher polyphenols content showed narrower droplets distribution. All emulsions showed a non-Newtonian shear thinning behavior; moreover, samples with higher polyphenols content showed lower apparent viscosity. The Creaming Index (CI) indicated a good physical stability for all the systems with no phase separation over 30 days of storage, while emulsions made with oil with higher polyphenols content showed a lower CI confirming a positive effect of the bioactive in the stabilization of o/w emulsions. The results of this study highlight the feasibility of the preparation of O/W Pickering emulsions made of olive oils and the positive role of polyphenols on their colloidal and physical properties.
