At its heart, making a good cup of coffee is about extraction. The water has to be hot enough, and the beans ground at the right consistency, with both components at the right ratio, to create just the right flavor of sweet, sweet caffeine water. Coffee is made up of more than 1800 chemical components, so it’s a pretty complicated thing to study.
With an eye toward making the perfect cup, a group of mathematicians recently tried to come up with a mathematical model that can describe the various factors that influence the cup of coffee that comes out of the brewing process, as the BBC reports. The paper was published in the SIAM Journal on Applied Mathematics [PDF]. They admit that “defining what makes a good cup of coffee is a nontrivial matter and to some extent a matter of personal preference,” but attempted nonetheless to figure out how variations in the brewing process can change the taste of coffee.
"The really surprising thing to us is that there are really two processes by which coffee is extracted from grains,” co-author William Lee told the BBC. “There's a very quick process by which coffee's extracted from the surface of the grains. And then there's a slower tail-off where coffee comes out of the interior of the grains."
The researchers took into account the grind and porosity of the beans; the temperature and velocity of the water; and the concentration and surface area of the grounds, among other factors. The models they came up with could potentially be used to improve the way drip coffee makers work, though they may not mean much to the average French press user. For instance, whether the water comes through a single fluid stream or multiple jets changes the process. “For fluid delivery with a single jet, the evolution of the coffee bed shape is important, as a central cavity may form in the bed which shortens the path fluid has to travel through the bed to exit the filter,” ultimately influencing the brew process, they write.
But unless you're a mathematician or a coffee machine manufacturer, you're probably best just brewing your coffee the way you've always done—as long as you have a good grinder, of course. Otherwise, just go ahead and visit a shop.