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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, at the University of Huddersfield in the UK and his colleagues found that extraction yield decreases when …

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