Oil or non-aqueous foams are more scarce than aqueous ones and the literature relating to them is very scant. Despite this, they are encountered in, for example, lubricating oil use and in certain aerated foods like chocolate. We describe here the stabilisation of oil foams by <i>in </i><i>situ </i>preapred particles, the latter being crystals. In the case of surfactant crystals, the oil-soluble fatty acid myristic acid forms plate-like crystals below the solubility limit which depends on temperature. Aerating a one-phase molecular solution of myristic acid in oil produces no foam whereas aerating a two-phase crystal dispersion produces much foam which is ultra-stable. The foamability depends on myristic acid concentration and temperature. The crystals adsorb at bubble surfaces and excess crystals serve to gel the continuous oil phase.  We demonstrate the stimulus-responsive nature of the oil foam by progressively heating an otherwise stable foam which collapses completely around the melting point of the crystals. Finally, we show the self-foaming of fats/oils composed mainly of saturated triglyceride molecules. By careful selection of the temperature, ultra-stable foams can be produced in the absence of any additive. The triglyceride molecules of high melting point form crystals in liquid oil of triglyceride molecules of low melting point. These fat crystal-stabilised oil foams represent one way to reduce the fat content in a food as well as being a product containing no E-number additive.

Oil foams stabilised by surfactant or fat crystals

254th National Meeting (2017)

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