Quirks and Quarks

Brewing a better espresso with less coffee and more math

A coarser grind of coffee bean improves extraction of coffee resulting in a more consistent espresso.

Researchers find a coarser grind improves coffee extraction resulting in a more consistent drink

University of Oregon computational chemist Christopher Hendon brewing a better espresso. (Christopher Hendon)

Originally published on Jan. 25, 2020.

Mathematicians, physicists, materials experts and a barista have joined forces to improve our lives by figuring out how to brew a more consistent cup of espresso.

Christopher Hendon from the Department of Chemistry at the University of Oregon in Eugene and his colleagues were interested in improving their favourite beverage. They'd previously studied water chemistry in coffee and the science of grinding coffee beans. 

Espresso with a shot of math. (Christopher Hendon)

In their latest study, they challenged current espresso wisdom, in particular, the idea that using a very fine grind and lots of beans results in a desirable drink. Hendon's team found that this technique is unpredictable and difficult to reproduce with any consistency, meaning that making espresso taste exactly the same from one cup to another is next to impossible.

What the team found was that grinding as fine as possible, then adding a lot of hot water under pressure tends to lead to tightly packed clumps of coffee in the espresso basket that water doesn't penetrate. As a result, there's little extraction of coffee flavours from the coffee in these clumps. 

This not only wastes coffee, it creates variation in taste as some grounds are brewed and some are missed entirely.

Hendon making sure the math is right. (Christopher Hendon)

Espresso gets a shot of math

After a lot of modelling and many shots of espresso, this team came up with a recipe that succeeds in both maximizing extraction yields and producing a cup of espresso that tastes similar cup after cup.

They used a coarser grind, and despite using a smaller amount of coffee and less water, were able to increase the extraction yield and make the flavour more consistent from cup to cup.

Christopher Hendon, a.k.a. Dr. Coffee, explains how he works