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United Kingdom: A new study has provided fresh insight into what shapes the taste of a perfect cup of espresso, identifying the flow of water through tightly packed coffee grounds as a key factor.

Published in Royal Society Open Science, the research highlights the role of the “puck”, the compact bed of coffee through which water passes under pressure.

Researchers developed a model to predict how permeability changes with grind size and packing conditions, examining two roasted coffee varieties, Tumba from Rwanda and Guayacán from Colombia.

Using X-ray computed micro-tomography, they created three-dimensional maps of the coffee grounds and observed microscopic pore spaces that influence how water flows through the puck.

The study found that factors such as connected pore space, surface area, grain size and packing density affect flavour extraction, and said the findings could help baristas refine techniques and support more precise machine design.