Carnauba wax and beeswax as structuring agents for surfactant-free water-in-oleogels emulsions

Water-in-oil emulsions are metastable systems in which water is dispersed in an oil continuous matrix. Typical food examples are margarine and fat spreads. In recent years, the fat industry has been seeking to create surfactant-free fat-rich products. Hence, scientific efforts are needed to overcome inherent reformulation challenges. This research aims to explore the potential of waxes as ingredients in the formulation of food-grade surfactant-free water-in-oleogel emulsions. Emulsions were prepared exclusively from water, sunflower oil, and wax. The effects of wax type (carnauba wax, beeswax), wax concentration (50%, 100%, and 150% of the critical gelling concentration), water concentration (20%, 30%, and 40% w/w) and production method (lab scale and pilot scale) were assessed. Samples were evaluated over time regarding stability, rheology and microstructure (polarized light microscopy, cryo-scanning electron microscopy and confocal laser scanning microscopy). Our findings suggest that, if present in sufficient concentration, carnauba wax and beeswax can stabilize emulsions in the absence of surfactants. The resulting systems were inherently different based on the wax used, as crystal morphology and droplet configurations are determined by the wax type. Yield strain was mostly dictated by the nature of the wax, while storage modulus was primarily dependent on the wax concentration. To test scaling-up potential, carnauba wax systems were also crystallized in a pilot-scale scraped surface heat exchanger, resulting in notably smaller droplet sizes and at least three months of stability. These findings represent a starting point for the formulation of scalable surfactant-free water-in-oleogel emulsions. It is envisioned that the results of this research will assist in further understanding wax stabilized water-in-oil emulsions, as well as the development of novel fat-based food products.