Crystal nucleation in food colloids

• Speed of sound measurement is very sensitive to crystal nucleation.
• Isothermal nucleation rates are measured in a range of oil-in-water emulsions.
• Classical nucleation theory explains well all the measured data.
• Lowering interfacial energies may dramatically raise surface nucleation rates.

Crystal nucleation in food colloids is considered in the light of recent developments in classical nucleation theory (CNT); it is shown that CNT remains a sound basis upon which to understand nucleation in colloids and in particular nucleation in lipids such as triacylglycerols. Computation of the energy barrier to nucleation for a studied triacylglycerol system (Cocoa butter oil-in-water emulsion) indicates that whilst homogeneous nucleation is unlikely at higher surface energies the addition of surfactant, lowering the interfacial energy may have a dramatic impact on surface nucleation rates. Data is included supporting this contention. The impact of reducing the size of colloidal particles to the point where the interfacial region occupies a significant proportion of the total volume of the dispersed phase is discussed and it is suggested that in these circumstances undercooling may fall significantly in comparison with the undercooling measured in micrometre emulsions.

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