Which of the following is NOT a layer in a shot of espresso?

In the context of a shot of espresso, crema, body, and heart are all recognized components of the espresso itself.

Crema is the golden, frothy layer that forms on the top of a well-pulled espresso shot. It is made up of emulsified oils and gases released during the brewing process, contributing to both the flavor and texture of the espresso.

The body refers to the thicker, denser part of the espresso that encompasses the majority of the shot. It carries the rich flavors and is essential to the overall mouthfeel of the drink.

The heart is the innermost layer of the espresso, where the concentrated flavors and sweetness are found. It is deeper in color and usually represents the essence of the espresso's taste.

Milk, on the other hand, is not a component of espresso itself. While milk can be added to espresso to create beverages like lattes or cappuccinos, it is not part of the espresso shot layers. Thus, identifying milk as not being a layer in a shot of espresso is accurate and signifies a clear understanding of espresso composition.