Citation: Bruno, E.; Lupi, F.R.; Mammolenti, D.; Mileti, O.; Baldino, N.; Gabriele, D. Emulgels Structured with Dietary Fiber for Food Uses: A Rheological Model. Foods 2022, 11, 3866. https://doi.org/10.3390/ foods11233866 Academic Editor: Barbaros Özer Received: 10 November 2022 Accepted: 26 November 2022 Published: 30 November 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). foods Article Emulgels Structured with Dietary Fiber for Food Uses: A Rheological Model Elisabetta Bruno, Francesca Romana Lupi * , Domenico Mammolenti, Olga Mileti, Noemi Baldino and Domenico Gabriele Department of Information, Modeling, Electronics and System Engineering, (D.I.M.E.S.), University of Calabria, Via P. Bucci, Cubo 39C, 87036 Rende, Italy * Correspondence: francesca.lupi@unical.it; Tel.: +39-0984-494011 Abstract: Emulgels are biphasic emulsified systems in which the continuous phase is structured with a specific gelling agent. In this work, a rheological and microscopic investigation of O/W emulgels prepared by structuring the aqueous (continuous) phase with citrus fiber was carried out with the aim of designing their macroscopic properties for food uses and predicting their characteristics with a rheological model. According to previous investigations, fiber suspensions behave as “particle gels” and, consequently, the derived emulgels’ properties are strongly dependent on the fiber concentration and on process conditions adopted to produce them. Therefore, a rotor–stator system was used to prepare emulgels with increasing fiber content and with different levels of energy and power used for mixing delivered to the materials. An investigation of particle gels was then carried out, fixing the operating process conditions according to emulgel results. Furthermore, the effect of the dispersed (oil) phase volume fraction was varied and a modified semi-empirical Palierne model was proposed with the aim of optimizing a correlation between rheological properties and formulation parameters, fixing the process conditions. Keywords: emulgels; dietary fiber; particle gels; suspensions; rheological modelling; microstructure 1. Introduction Emulsion gels or emulgels are biphasic systems formed by dispersing a viscous un- structured phase in a structured continuous phase [1,2]. The structuration of the continuous phase can reduce the movement of the dispersed phase, increasing its stability [3,4]. Emulgels are widely used in pharmaceutical and cosmetic preparations as controlled- release materials [5–7] and, in the case of dermatological use, they have several favorable properties such as spreadability, removability, emollience and water solubility (in the case of O/W systems) [8]. The main properties of emulgels (such as spreadability, texture, control of delivery rate of active components, etc.) are strictly related to rheological characteristics and, in turn, to microstructure; therefore, the proper design of emulgels, having the desired sensorial and functional properties, needs the knowledge and control of their rheological characteristics [9,10]. Regarding this, the rheological, mechanical and textural properties can be tuned by varying the properties of the structured phase and the volumetric ratio between phases; this also makes these systems interesting and versatile for food uses where different types of emulsions are widely used [1]. In the last few years, emulsion gels have been used as fat replacers in the production of functional foods. Chen et al. [11] investigated the effect of emulgels enriched with β-carotene as a margarine alternative for sponge cakes to decrease the total saturated or trans-fat content in bakery products. Nasirpour-Tabrizi et al. [12] studied the rheological and physicochemical properties of low-fat spreadable emulgels containing ω-3 fatty acids in a matrix of carrageenan, xanthan gum and maltodextrin. Foods 2022, 11, 3866. https://doi.org/10.3390/foods11233866 https://www.mdpi.com/journal/foods