DOI: 10.3303/CET2187014 Paper Received: 29 September 2020; Revised: 27 January 2021; Accepted: 10 May 2021 Please cite this article as: Farooq U., Di Mattia C., Faieta M., Sacchetti G., Pittia P., 2021, Oil-in-water Pickering Emulsions Stabilized with Starch Particles and Formulated with Olive Oil: Colloidal Properties and Stability as Affected by Olive Oil Phenolic Content, Chemical Engineering Transactions, 87, 79-84 DOI:10.3303/CET2187014 CHEMICAL ENGINEERING TRANSACTIONS VOL. 87, 2021 A publication of The Italian Association of Chemical Engineering Online at www.cetjournal.it Guest Editors: Laura Piazza, Mauro Moresi, Francesco Donsì Copyright © 2021, AIDIC Servizi S.r.l. ISBN 978-88-95608-85-3; ISSN 2283-9216 Oil-in-water Pickering Emulsions Stabilized with Starch Particles and Formulated with Olive Oil: Colloidal Properties and Stability as Affected by Olive Oil Phenolic Content Umer Farooq*, Carla Di Mattia, Marco Faieta, Giampiero Sacchetti, Paola Pittia Faculty of Bioscience and Technology for Agriculture, Food and Environment, University of Teramo Campus Coste S. Agostino, Teramo, Italy ufarooq@unite.it 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. 1. Introduction Thanks to their role in developing lipid-containing matrices and in providing desirable appearance and mouthfeel properties, oil-in-water (O/W) emulsions are amongst the structural entities in a wide range of food and non-food (e.g. pharmaceutical and cosmetic) products. Due to their physical and thermodynamic properties the development of emulsified systems requires the understanding of the mechanisms of stabilization of the dispersed state and those causing their degradation. In the last decade studies focused on the stabilization mechanism of oil/water interface by solid particles (Pickering emulsions) which adsorb onto the interfacial layer with high absorption energy and act as physical barrier, thereby a higher stability could be achieved as compared to the traditional O/W emulsions, stabilized by surfactant and biopolymers (Yang et al., 2017). Moreover, in traditional emulsions the use of low molecular weight surfactants poses the treat of toxicity, poor bioavailability, foaming and biological interactions with other compounds (Berton-Carabin & Schroën, 2015) while Pickering emulsions are obtained by surface-active natural biopolymers that make these systems more acceptable in the food and pharmaceutical industry (Dickinson, 2012). Recent researchers focused on the use of starch as a potential natural emulsifier in Pickering emulsions thanks to its non-toxicity (Ge et al., 2017), the high availability in nature (Li et al., 2019), low cost and high bioavailability (McClements & Gumus, 2016). However, native starches are not good emulsifiers and, thus, they are modified by different procedures such as dry heating or chemical modification by esterification, being 79