Spontaneous Oleofoams from Water-in-Oil Emulsions

Spontaneously foaming oil systems have been formulated from water-in-oil emulsions by the controlled release and entrapment of gas in emulsified water droplets contained within the oil. The cascade of events leading to their formation is as follows: Two Span 60-emulsified populations of water droplets, one containing Na₂CO₃, the other 10% HCl and caseinate, were mixed in miglyol oil; the controlled coalescence of Na₂CO₃ droplets with the HCl ones served as a microreactor for the pH reduction and the subsequent release of CO₂ from Na₂CO₃; these gas microbubbles were arrested by sodium caseinate, stabilizing a microfoam within the water droplets; these droplets expanded under the rising gas pressure, spontaneously transforming the surrounding oil into a foamy oleogel containing water droplets.