What is a crema?
A crema is the layer of thick effervescent foam that sits on top of an espresso shot. It is made up by bubbles of carbon dioxide released from the beans when ground, surrounded by oils from the coffee along with other compounds. It is the result of the hot brewing water passing through the finely ground coffee particles under pressure. Ideally it should be a rich reddish brown colour, settling out like the head of a Guinness. A lighter blonde coloured crema could indicate that the water has flown too quickly through the coffee and not had chance to pull out the flavour.
