What is "crema" in espresso?

Crema is the golden frothy layer that forms on top of a freshly pulled shot of espresso. It is created during the brewing process when hot water passes through finely ground coffee under high pressure. This interaction causes the coffee oils and air to emulsify, resulting in a creamy, rich foam that is light in color.

Crema is an important aspect of espresso as it contributes to the flavor and aroma, enhancing the overall sensory experience of the drink. A well-prepared espresso with rich crema indicates freshness and proper extraction, as it signifies that the coffee beans have been ground and brewed correctly.

Other options do not accurately represent what crema is; for instance, a thick layer of sugar does not describe crema, as it is made from the coffee oils and air rather than any sweetening agent. Similarly, a bitter residue found at the bottom refers to over-extracted coffee grounds, which has nothing to do with the desirable frothy layer of crema. Lastly, while espresso beans are essential for making espresso, referring to crema as a type of bean is incorrect, as it pertains to the foam produced during brewing rather than a specific kind of coffee bean itself.