Carnauba Wax and Beeswax as Structuring Agents for Water-in-Oleogel Emulsions without Added Emulsifiers

Abstract

This research aims to explore the potential of waxes as ingredients in the formulation of food-grade water-in-oleogel emulsions without added emulsifiers. The effects of the wax type, wax concentration and water concentration were tested on systems containing exclusively water, sunflower oil, and wax. Beeswax and carnauba wax were used in the formulation of water-in-oleogel emulsions with 20%, 30% and 40% w/w of water. For the continuous phase, three different levels of wax were used, namely 50%, 100%, and 150% of the critical gelling concentration. More specifically, carnauba wax emulsions were prepared at 2.5%, 5.0% and 7.5% of wax, while concentrations of 0.75%, 1.5% and 2.25% of wax were utilized for the beeswax experiments. Samples were assessed over time regarding stability, rheology and microstructure (polarized light microscopy, cryo-scanning electron microscopy and confocal scanning laser microscopy). Our findings suggest that, if present in sufficient concentration, carnauba wax and beeswax can stabilize emulsions in the absence of additional added emulsifiers. The resulting systems were inherently different based on the wax used, as crystal morphology and droplet configurations are determined by wax type. The yield strain was dictated by the nature of the wax, while the complex modulus was mostly influenced by the wax concentration. To test the scaling-up potential, systems were crystallized in a pilot-scale scraped surface heat exchanger, resulting in notably smaller crystal sizes, reduced rigidity and a storage stability of over one year. These findings represent a starting point for the formulation of scalable water-in-oleogel emulsions without added emulsifiers.

Development of structured W/O emulsions with the use of only candelilla wax

“…Given the composition of the CW (see Section Materials), these compounds tentatively involved the triterpenic alcohols, esters of triterpenic alcohols, aliphatic alcohols, and fatty acids. All these results contrast with the microstructure of the W/O emulsions formulated with 5% carnauba wax (40% water) or with 5% beeswax (20% water) developed through a pre-emulsification step (90 C) followed by dynamic crystallization step (5 C) (Penagos et al, 2023). These authors showed through PLM and confocal laser scanning microscopy, that the water droplets of the carnauba wax and beeswax W/O emulsions were stabilized by wax crystals surrounding the droplets (i.e., Pickering effect) and by a crystal network developed in the oil phase by the corresponding wax (Penagos et al, 2023).…”

“…All these results contrast with the microstructure of the W/O emulsions formulated with 5% carnauba wax (40% water) or with 5% beeswax (20% water) developed through a pre-emulsification step (90 C) followed by dynamic crystallization step (5 C) (Penagos et al, 2023). These authors showed through PLM and confocal laser scanning microscopy, that the water droplets of the carnauba wax and beeswax W/O emulsions were stabilized by wax crystals surrounding the droplets (i.e., Pickering effect) and by a crystal network developed in the oil phase by the corresponding wax (Penagos et al, 2023). On the other hand, as previously indicated pentacyclic triterpenes like the ursolic acid, can develop W/O emulsions tentatively stabilized also through the Pickering effect (Liu et al, 2022).…”

“…On the other hand, as previously indicated pentacyclic triterpenes like the ursolic acid, can develop W/O emulsions tentatively stabilized also through the Pickering effect (Liu et al, 2022). The different stabilizing mechanisms observed in the CW emulsions with those reported by Penagos et al (2023), might be associated with the different conditions used to develop the W/O emulsions and with the differences in wax composition. Carnauba wax consists mostly of long chain (26 to 30) aliphatic esters (≈40%) and diesters of 4-hydroxycinnamic acid (≈21.0%), and a significant amount of long chain ω-hydroxycarboxylic acids (≈13.0%) and fatty alcohols (≈12%) (Wolfmeier et al, 2016).…”

“…Based on contact angle measurement the authors discarded the CW, the berry wax, and the sunflower wax as tentative stabilizers of W/O emulsion. However, in this study no formal W/O emulsions were done to assess the emulsifying capacity of these vegetal waxes (Penagos et al, 2023). On the other hand, García-Gonz alez et al (2021) showed that in the temperature interval of 45 to 60 C, the addition of 3% CW significantly decreased the interfacial tension at the water-safflower oil interface from 26.4 (±0.9) mN/m to 5.9 (±0.5) mN/m.…”

“…Within the previous context and considering that the CW is constituted by components with molecular selfassembly and surface-active properties, this study evaluated the development of structured (i.e., gelled) waterin-oil (W/O) emulsions at room temperature (25 C) just with the use of the CW (i.e., absence of added surfactants). In a recent study, Penagos et al (2023) developed W/O emulsions at 5 C using mixtures of beeswax and carnauba wax formulated with 20%, 30% and 40% (w/w) of water in sunflower oil. Based on contact angle measurement the authors discarded the CW, the berry wax, and the sunflower wax as tentative stabilizers of W/O emulsion.…”