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

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 degreesC to - 50degreesC to 40degreesC at 5degreesC min(-1)) and in bulk (to - 20degreesC). 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 casemate) 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. (C) 2004 Elsevier Ltd. All rights reserved.