Making the perfect cup of coffee is a trial. There can always be something off in the coffee-making process that ruins the entire cup. A new study suggests that the answer to inconsistent coffee woes is down to an inherent inconsistency of common brewing methods.
Published in the journal Matter, the study outlines the critical role the brewing method used plays in the overall flavour.
The research team, made up of mathematicians, chemists, materials scientists and baristas, came up with a mathematical model to simulate the brewing of espresso in realistic cafe conditions.
“We used this to make predictions of how much of the solid coffee ultimately ends up dissolved in the cup. This percentage – known as the extraction yield – is the key metric used by the coffee industry to assess different coffee recipes,” the team said.
Through a series of equations, the team found their model predicted extraction yields relative to real life. This included issues such as unpredictable water flow through the espresso bed which result in under-extracted (low extraction yield), while others are over-extracted (high extraction yield) coffee.
To keep the consistency of each shot, the team found the barista should use less coffee and grind the coffee marginally coarser. By doing so, they are able to achieve very reproducible, high-yielding shots.
“The mathematical theory tells us that this is because reducing coffee mass means that the water flows faster through the shallower coffee bed. The coarse grind results in a relatively permeable bed, such that water flow and extraction are uniform and predictable. This method leads to fast, bright, sweet and acidic shots that taste the same each time,” they said.
In addition to finding the solution to the perfect brew every single time, the team’s result of using less coffee allowed for a reduction of coffee waste by up to 25% per shot. This would assist with profits and help the environment by reducing waste.