Splashing water on to coffee beans before grinding could be the secret to making the perfect cup of coffee, a study has found.
It is a common technique favoured by baristas hoping to keep their station tidy, as the water creates less bean mess – but it was never proven to boost taste.
Now, a study from Oregon University which drew on the science of volcanic activity has found spraying water on beans before putting them in the grinder reduces the amount of static electricity on the particles as they pass through the machine.
This not only reduces clumping and makes clean-up easier, but it also creates a finer dust which increases surface area and therefore allows for more flavour to be extracted from the beans.
Dr Christopher Hendon, associate professor of chemistry at the University of Oregon, set up a coffee lab on his campus two years ago and volcanologist Josh Méndez Harper was a regular visitor.
Dr Méndez Harper realised that there were, as unlikely as it may seem, similarities between the grinding of coffee beans and a volcanic eruption.
Ash and rocks create static
His expertise in the movement of molten rock, geological activity and rising magma meant he knew that when ash and rocks spewed out of a volcano they rubbed together and create static which can result in lightning strikes.
“It is similar to grinding coffee, where you’re taking these beans and reducing them to fine powder,” he said.
The pair investigated if the process of spraying water on to the beans before grinding can stop the static forming.
They found the technique, favoured by trendy coffee houses and hipster baristas, was effective at stopping charge building up, as believed, and also improved flavour and the strength of an espresso.
“Because the static doesn’t form, the particles also do not clump. Clumps pose problems during extraction because less surface area is available for water contact,” Dr Hendon told The Telegraph.
“Thus, adding a few drops of water to the whole beans before grinding serves many valuable purposes.
“I believe we are the first to systematically add increasing water content, and the real impact on brewing (rather than cleanliness) wasn’t realised until relatively high water content was introduced.
“With the appropriate amount of water, the brewing impact is substantial.
“By having more available surface, you end up with less wasted but extractable mass left in the coffee particles after brewing.
“As a result, by grinding with a small amount of water, you end up accessing something like 5 to 15 per cent more soluble material.”
If everyone in Europe sprayed water on their beans when making a cup of coffee it could stop product worth £200 million being wasted every year, Dr Hendon estimates.
However, the team warn that while grinding and spraying can boost flavour, the benefits will not be realised without careful calibration of a machine to exploit the finer grind.
“But, if you do that, then you have more water touching more surfaces, more evenly. This generally leads to more clarity of flavour,” Dr Hendon said.
“It’s sort of like the start of a joke – a volcanologist and a coffee expert walk into a bar and then come out with a paper,” said Dr Méndez Harper.
“But I think there are a lot more opportunities for this sort of collaboration, and there’s a lot more to know about how coffee breaks, how it flows as particles, and how it interacts with water.
“These investigations may help resolve parallel issues in geophysics—whether it’s landslides, volcanic eruptions, or how water percolates through soil.”
The study is published in Matter.