Formulation and Preparation of Water-In-Oil-In-Water Emulsions Loaded with a Phenolic-Rich Inner Aqueous Phase by Application of High Energy Emulsification Methods

Abstract

Currently, industry is requesting proven techniques that allow the use of encapsulated polyphenols, rather than free molecules, to improve their stability and bioavailability. Response surface methodology (RSM) was applied in this work to determine the optimal composition and operating conditions for preparation of water-in-oil-in-water (W/O/W) emulsions loaded with phenolic rich inner aqueous phase from olive mill wastewater. A rotor-stator mixer, an ultrasonic homogenizer and a microfluidizer processor were tested in this study as high-energy emulsification methods. Optimum results were obtained by means of microfluidizer with 148 MPa and seven cycles input levels yielding droplets of 105.3 ± 3.2 nm in average size and 0.233 ± 0.020 of polydispersity index. ζ-potential, chemical and physical stability of the optimal W/O/W emulsion were also evaluated after storage. No droplet size growth or changes in stability and ζ-potential were observed. Furthermore, a satisfactory level of phenolics retention (68.6%) and antioxidant activity (89.5%) after 35 days of storage at room temperature makes it suitable for application in the food industry.

Preparation of Water-in-Oil Nanoemulsions Loaded with Phenolic-Rich Olive Cake Extract Using Response Surface Methodology Approach

“…The dispersed phase was added dropwise to the continuous phase and the mixture was stirred for 5 min at 500 rpm. The emulsification was carried out using a high-intensity ultrasonic homogenizer (Sonics VCX500, 500 W, 20 kHz, Newtown, CT, USA) for 10 min effective time, in 5 s pulses (5 s off and 5 s on), with a 40% amplitude [23]. Then, emulsification of the optimized formulation was performed using the phenolic-rich olive cake extract as the aqueous phase and two high-energy emulsification methods: (i) high-speed homogenization using a Miccra D9 with a DS-5/K-1 rotor-stator (ART Prozess & Labortechnik, Mülheim, Germany); (ii) high-intensity ultrasonic homogenization using the aforementioned homogenizer.…”

“…The nanoemulsions were characterized by the following methods described in previous studies [16,21,23,32,33] and explained in the Supplementary Data S1: (i) droplet size distribution, mean droplet diameter, and polydispersity index (PDI) by dynamic light scattering using a Zetasizer Nano ZS (Malvern Instruments Ltd., Malvern, U.K.); (ii) TPC using the Folin-Ciocalteu standard method; (iii) AA by the DPPH method [34]; (iv) TPC and AA retained within the aqueous phase, following the method developed by Regan and Mulvihill [23,35]. All measurements were performed at least three times.…”

“…The droplet size distribution of all nanoemulsions was measured 1 and 30 days after preparation, stored at 4 • C and at room temperature, in darkness, to evaluate their stability. Optical characterization of each optimally formulated nanoemulsion was performed for 30 days at 25 • C by static multiple light scattering using a Turbiscan Lab Expert (Formulaction Co., L'Union, France) [23,36,37].…”

“…The final defatted solid residue can then be valorized by recovering the polyphenols. These compounds are prone to degradation due to adverse environmental conditions, but their stability and bioavailability can be improved by encapsulation [17][18][19], mainly in single emulsions [20][21][22], double emulsions [23][24][25], or in emulsion gels [11]. As a general trend, the smaller the droplet size, the more stable the W/O nanoemulsions and the longer their shelf life.…”

“…Response surface methodology (RSM) is an effective tool for process optimization, thereby minimizing the number of experiments required in order to achieve optimization. It has been applied in several studies examining the effects of different variables in emulsion formulations and their stability [23,[26][27][28][29]. In this study, we prepared W/O nanoemulsions loaded with a phenolic-rich aqueous phase from olive cake extract by applying the response surface methodology.…”