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Physics

Unevenly packed coffee to blame for weak espresso, say mathematicians

A mathematical model shows that even small inconsistencies in how coffee is packed into an espresso machine can lead to weaker brews and watery flavour

By Karmela Padavic-Callaghan

9 May 2023

Finely ground coffee is dispensed into an espresso filter

The flavour of your espresso may depend on how evenly packed the coffee grounds are before brewing

Shutterstock/PixelsMD Production

Grinding coffee beans too finely makes espressos weaker and now mathematics can explain why.

Inside of an espresso machine, boiling water moves through a bed of ground coffee under high pressure. One factor used to rate the resulting espresso is called extraction yield, which is a measure of how much of the coffee dissolves in boiling water during the brewing.

In 2020, William Lee at the University of Huddersfield in the UK and …

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