Fewer Coffee Beans Ground Coarsely Brews the Best Espresso, New Research Shows

Researchers at the University of Portsmouth set out to see why two cups of espresso brewed the same tasted differently.
Donna Fuscaldo
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Forget coffee sommeliers, scientists think they found the answer to brewing the best shot of espresso. 

A team of mathematicians, physicists and materials experts at the University of Portsmouth in the UK, found the secret to the best cup of espresso lies in the number of coffee beans and how they are ground. 


Fewer coffee beans ground more coarsely is the answer

According to the researchers which included Dr. Jamie Foster, a mathematician at the University of Portsmouth, fewer coffee beans and grinding them more coarsely is the secret.

The researchers started with the question many espresso drinkers have: why do two shots of espresso made the same way taste very different. They applied mathematical theory to the question and when they began to look at a single grain, many of which create the coffee bed found in the basket of an espresso machine, they found the answer. It's more reliable from one cup to the next if fewer beans ground coarsely. 

"When beans were ground finely, the particles were so small that in some regions of the bed they clogged up the space where the water should be flowing," Dr. Foster said in a press release announcing the research. 

Researchers can save the industry money 

"These clogged sections of the bed are wasted because the water cannot flow through them and access that tasty coffee that you want in your cup. If we grind a bit coarser, we can access the whole bed and have a more efficient extraction. It's also cheaper, because when the grind setting is changed, we can use fewer beans and be kinder to the environment. Once we found a way to make shots efficiently, we realised that as well as making coffee shots that stayed reliably the same, we were using less coffee."

The theory is being tested in a small coffee shop located in the U.S. The researchers found over a year, the coffee shop saved thousands of dollars using fewer coffee beans. The researchers noted the entire U.S. coffee market could save $1.1 billion a year if they followed their recommendations. 


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