About Emulsion

Emulsion

An emulsion is a smooth mixture of two liquids, such as oil and water, that normally do not mix. On a microscopic level, an emulsion consists of tiny particles of one liquid (or occasionally a solid) suspended in another. These tiny particles are kept separate from one another by an extremely fine coating of an emulsifier that surrounds each particle, keeping them from touching one another and from clumping into larger globules, which would float or sink.

Mayonnaise is an example of an emulsion in which microscopic globules of oil are suspended in a relatively small amount of water-based liquid. The suspension is held in place by the emulsifier, which, in this case is egg yolk. Other familiar emulsions are beurre blanc (globules of butter fat suspended in a medium of white wine and vinegar, emulsified by the milk solids in the butter), hollandaise (emulsified with egg yolks, like mayonnaise), cream sauces (milk solids in the cream keep the butterfat and liquid in it in a stable emulsion), vinaigrettes (mustard holds the oil and water in an emulsion), and bechamel sauce (the flour in the roux stabilizes the milk into an emulsion that can withstand heat).

Cooks rely on various emulsions to make sauces, custards, souffles, cakes and pastries. But some emulsions are undesirable. If a meat stock or jus is allowed to boil, the fat that is slowly being released by the meat is churned back into the liquid and will eventually become emulsified, resulting in a cloudy, greasy, muddy-tasting stock. (simmering allows the fat to float to the surface, where it can be skimmed off). For the same reason, the first step in making gravy from pan juices is to skim off the fat floating in the roasting pan. Otherwise, the thickener in the gravy, usually flour, will emulsify the fat into the gravy.

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