What is the difference in foamed and steamed milk?

Milk Chemistry

Milk is comprised of fats, proteins and sugars. The milk proteins are agents for milk foaming. When the air is introduced forcefully to the milk the proteins form a film around the air to create bubbles. The fats will tend to inhibit and then break down the foaming process, although whole milk will tend to have a softer foam than non-fat because of the fat content. Milk that has been "fortified" - where proteins have been added back into the milk - will tend to foam more easily and to greater volume than milk that has not. This is why non-fat milk, which is almost always fortified, will froth to the greatest volume because of the high protein and low fat content.

It is best if milk frothing is started at 40 degrees F. Once the milk temperature has reached 161 degrees F and maintains that temperature for 15 seconds it has effectively been pasteurized. Any bacteria that may have been present is killed.

Steamed Milk

Steamed milk is milk that has been heated and is the same consistency as cold milk, i.e., all liquid and no bubbles or foam (froth). Milk can be heated in several different ways, however using the steaming wand on your espresso machine is a quick and easy way. Care must be taken to ensure adequate circulation occurs during the steaming process or you may scald the milk and diminish the flavor quality. By keeping the wand below the surface of the milk, you will not allow any air into the milk and no "frothing" should occur. Do not save any extra milk after steaming that you do not use. Discard all unused milk.

Frothed Milk

Frothed milk has had air forced into it so that it has a foamy texture. By placing the steaming wand barely below the surface of the milk, the circulation of the milk will draw in air and combine it with the milk, creating a foamy froth. The texture may vary depending upon how the air was introduced and how long the frothed milk was allowed to sit.

Different textures are desired for different drinks and sometimes combinations of textures are used for multiple layers of drinks.Mastery of the creation of frothed milk can only be accomplished by practice, practice and more practice!!

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