Pickering Water-in-Oil Emulsions Stabilized Solely by Fat Crystals

Abstract

Water-in-oil (W/O) emulsions have attracted heightened attention because of the ever-increasing interest in using non-calorific water to replace calorie-dense fat in food. However, designing clean-label and ultra-stable W/O emulsions is a longstanding challenge in colloid science. Herein, a novel, facile approach is introduced to designing cocoa butter (CB)-based crystals to stabilize Pickering W/O emulsions. Results using a combination of small- and wide-angle X-ray scattering and microscopy across length scales reveal that the fat crystals formed in an oleogel of CB with vegetable oil offer high stability to water droplets (up to 60% (v/v)) against coalescence and phase inversion, over storage for 7 months. Such extraordinary stability is attributed to the nanoplatelet-like CB crystals of βV polymorph located at the water–oil interface and to the inter-droplet fat crystal network formation, interlocking the water droplets. The increment in water volume fraction endows gel-like properties with the water droplets acting as “active fillers.” These newly designed Pickering W/O emulsions stabilized solely by fat crystals with unusual rigidity offer great promise for fabricating advanced functional materials in food, pharmaceutics, and cosmetic applications, where long-term stabilization of water droplets using sustainable particles is a necessity.