Microfoam is a byproduct of heating milk with a steam wand on an espresso machine. Microfoam is created by denaturing proteins such as casein and whey, by which the protein attracts and hold to its surface a gas, creating microfoam. The quality of microfoam is actually a very fine emulsion of denatured milk protein and air, that has little or no visible bubbles. The qualitative opposite of microfoam is macrofoam, which has visibly large bubbles.

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Milk