Is a Latte (or any other milk based coffee beverages) chemically the same as your regular cup of coffee? The answer may surprise you. A latte is more than just coffee with milk; it is a carefully balanced blend of chemistry and artistry. From the creamy texture, to the silky foam a latte is the result of complex chemical interactions between milk proteins, fat, and heat.
Steamed Milk and Chemistry
When milk is steamed, proteins like casein, the protein that gives milk its white color, and whey undergo structural changes. These changes create a process called aeration, in which the molecular structure of the milk proteins expand and allow them to trap in air. This trapped air creates the velvety microfoam that sits on the top of your latte.
Milk also undergoes a Maillard reaction as it is heated. Fun fact, due to this Maillard reaction, the sweetness from a latte typically comes from the milk. As the milk undergoes heating, the proteins begin to caramelize to create a creamy and sweet taste.