Espresso Crema

Espresso must be topped by a foamy, reddish-brown, consolidated surface layer called crema. This metastable foam with a specific lifetime of ≤ 40 min is a marker of quality for expresso. But: what does the crema consist of and how is it formed? ChemistryViews.org explains this phenomenom. Find out here and surprise your colleagues with your knowledge during the next coffee break!