The Ideal Range
When steaming and frothing milk for drinks like cappuccinos and lattes, an important factor to consider is the temperature of your milk. Regular whole cow's milk is a beverage composed primarily of two types of proteins. Caseins, account for about 80% of the milk, and whey proteins make up the remaining 20%. Ideally, steamed or frothed milk will be between 140-160 degrees fahrenheit, depending on your preferences. It is important however not to exceed the 160 degree temperature ceiling, as the proteins in the milk will denature and the milk will begin to boil; when that happens, producing microfoam will no longer be possible.
Use a Thermometer
To avoid overheating milk during the frothing process, we strongly recommend using a thermometer to monitor the temperature while frothing. Specially calibrated thermometers are available that indicate the ideal temperature zone while for frothing milk. When frothing with a thermometer, it is important to remove the steam wand from the milk before the thermometer reaches 160 degrees, because the temperature on the thermometer will continue to rise for a few seconds after the heat source has been removed.