FEATURE NEWS
The coffee formula Lower pressure, reduced dosage, and coarser grinds could be the key to espresso reproducibility, faster shot times, and saving thousands of dollars per year.
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oo many times, a barista will brew an excellent espresso and repeat the recipe to the exact same specifications only to end up with a different result. This drove Michael Cameron mad. During an online conversation in 2016 with Prof. Christopher Hendon of the University of Oregon, author of Water for Coffee and various coffee-related works, Michael – at the time a Café Manager at Frisky Goat Espresso in Queensland – expressed his frustration and asked how he could make better espresso more consistently. Christopher said he could start by reducing his line pressure from nine bar to six bar. “I dropped the pressure and it was amazing coffee. I talked to Chris about it a few days later, and he suggested we write a paper,” Michael says. “It started with the idea of testing if you can make high extraction coffee on a consistent basis by dropping your
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line pressure. We thought the finer you grind, the more surface area you expose to water, so the higher your extraction yield would go, and that it would be a higher extraction yield at six bar than nine bar.” Michael started going in on weekends to produce espresso in a controlled setting and identified a “tasty point” at 22 per cent extraction yield. Meanwhile, Chris developed a mathematical model which predicted how grind size, coffee mass, and water volume would affect the extraction yield. The model matched Michael’s experiments up to a certain point when extraction yields started to decline. “We were expecting this to be a quick and easy study, because we assumed that you could just grind finer and get more out the coffee,” Christopher says. “But we couldn’t pump water through at nine bar through a fine grind setting. It choked the machine. And then after we went to six bar, the extraction yield
from the ground coffee bed was actually lower than we expected. That’s when we knew we were onto something unusual and unfortunately, we had a lot more work to do.” Four years later, their work was published in ‘Systematically Improving Espresso: Insights from Mathematical Modeling and Experiment’ by scientific journal Matter. Christopher identified clumping as the issue, causing certain areas to be over extracted, others under extracted, and some untouched by water. With Michael’s tasty point on the uneven side of the peak extraction yield, Christopher realised the same yield could be achieved more consistently in less time with a coarser grind size. He says while the percentage of compounds extracted by the two shots is the same, the flavour may not be. “They’re going to taste different because they’re different types of extractions. One of them is even
