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Foam 

 March 20, 2017

By  Dorian Bodnariuc

Foam is an important aspect of coffee preparation, and it determines, or validates quality in some coffee drinks

A foam is a substance that is formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas.

When steaming and frothing milk for espresso based beverages, such as latte, or cappuccino, foam is artificially created in milk, to give the beverage the specific texture. On the other hand, the layer of foam on top of the espresso is obtained as part of the brewing process. This layer is called crema, and it is one of the signs of a correctly brewed espresso.

Turkish coffee brewing also uses the foam as an indicator of quality. A Turkish coffee without the layer of froth is considered a poorly brewed drink.

Foam is created in milk for espresso based drinks by using a steam wand. A steam wand is a rod with tiny holes at the bottom that is usually made of metal  and is part of an espresso machine. This rod injects steam at high pressure into the milk. This serves the dual function of heating the milk and creating the signature foam. The amount of foam created is governed by how much air is mixed into the milk. For foamier drinks, the wand should not be submerged in the milk but rather be partially exposed to the air so that air can be incorporated into the drink. Well made foam should be smooth, shiny and velvety in texture.

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About the author

My name is Dorian and I am a former barista. I consume coffee in any form, as a beverage, in savory recipes and desserts. My favorite caffeinated beverage is the espresso.

I love to share my coffee brewing knowledge and my geeky coffee research. This blog is one of the places I write about coffee. More about Dorian... If you want to learn more about this site and how I started it, check our About Me page, where I explain all about it.