Crema
克丽玛（咖啡油脂）
EspressoDefinition
The golden-brown foam that sits on a freshly pulled espresso, created when pressurized water emulsifies coffee oils and traps carbon dioxide released from the roasted beans. It ranges from pale hazel to dark tan, and the bubbles collapse within a minute or two unless the coffee is very fresh.
Etymology
Borrowed from Italian and Spanish crema, literally "cream," adopted in mid-20th-century coffee writing to name the creamy-looking head on an espresso.
In use
Baristas read crema's color and persistence as a loose cue for freshness and extraction, though it is no longer treated as proof of a good shot.