How to brew a better espresso, according to science
New research challenges conventional wisdom that brewing a strong shot of espresso requires very finely ground coffee beans. Well-ground beans typically are thought to be best for making strong shots because smaller grounds dissolve more readily, while water flows through such grounds more slowly — allowing more time for the water to soak up coffee. In brewing espresso and running computer simulations of the same process, researchers found that using finer grounds generally did allow water to absorb a higher percentage of the dried coffee — but only to a point. When filtered through beans ground to the finest setting on a standard machine, the hot water extracted a lower percentage of coffee than water filtered through slightly coarser grounds, researchers report online January 22 in Matter. Both the experiments and simulations showed that, with the finest grounds, very small particles wedge in the gaps between other particles, says Jamie Foster, a mathematician at the University of Portsmouth in England. That...