Recent advances in design and stability of double emulsions: Trends in Pickering stabilization

There is an increased pressure on food manufacturers to design low calorie and low fat foods to address the global obesity crisis. Designing double emulsions (DEs) is a microstructural approach to incorporate water that appears as promising fat replacement strategy. However, these complex microstructures are thermodynamically unstable and a thorough understanding of the factors that determine the stability of DEs are required to tailor their functionality. This review provides an update on the main strategies used to stabilize DEs, focusing on the developments in the last five years. Emphasis is placed on the recent use of surfactants, combination of surfactants with gelling agents, particles, fat crystals, and/or coatings. Novel processing techniques were also reviewed, and one-step processing methodologies were particularly examined. We also briefly reviewed the rheological and tribological performance of DEs. Properties and stability of the DEs depend strongly on the formulation and fabrication technique (homogenization, phase inversion, microfluidics, 3D Printing etc). Fat crystal forming a shell around the droplets offers a promising strategy to prevent diffusion of the internal phase in DEs. Pickering stabilization has captured significant research attention, though DEs fabricated solely using particle-laden interfaces are limited. A combined approach of Pickering and bulk stabilization by gelling the aqueous phase appears as a promising strategy to improve stability of DE, which needs research attention. Future studies should focus on characterizing rheological and tribological performance of DEs and link them with mouthfeel perception to accelerate their use in food applications.