On the stability of oil-in-water emulsions to freezing

Abstract

Oil in water emulsions (40 wt%) were prepared from a homologous series of n-alkanes (C10–C18). The samples were temperature cycled in a differential scanning calorimeter (two cycles of 40 °C to −50 °C to 40 °C at 5 °C min −1) and in bulk (to −20 °C). The emulsions destabilized and phase-separated after freeze–thaw if the droplets were solid at the same time as the continuous phase and were more unstable if a small molecule (SDS or polyoxyethylene sorbitan monolaurate) rather than a protein (whey protein isolate or sodium caseinate) emulsifier was used. The unstable emulsions formed a self-supporting cryo-gel that persisted between the melting of the water and the melting of the hydrocarbon phase. Microscopy provides further evidence of a hydrocarbon continuous network formed during freezing by a mechanism related to partial coalescence which collapses during lipid melting to allow phase separation.