SALAD dressings, long-life milk and even paint could soon last much longer if
a new way for preserving oil-in-water emulsions catches on.
Chemical thickeners and other additives can be used to delay separation in
oil-in-water products鈥攂ut this only works for a short time. Now Brian
Saunders and Andrew Koh at the University of Adelaide have found a polymer
additive that makes oil-in-water emulsions suddenly turn to gels when heated
past 48 掳C, instead of separating out. The process is reversible, so it
could increase the shelf life of oil-in-water emulsions almost indefinitely.
鈥淚t鈥檚 very unusual for an emulsion to behave like this,鈥� says Saunders. The
results will appear in Chemical Communications.
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The researchers believe the polymer changes from a 鈥渟trung out鈥� molecule into
a compact one that forms a chemical scaffold, immobilising the oil droplets. By
playing with the polymer, the researchers believe that they will be able to
preset the temperature at which the emulsions become jelly-like. This means, for
example, salad dressing might turn into gel when it gets too hot鈥攊nstead
of separating out. But it would become fluid again at room temperature.
Heat-sensitive emulsions could also make better paints for hot surfaces, they
say.