(Credit: Shaiith/Shutterstock) You can have it dark, light, sweet, bitter, steamed with milk or served with ice. But the perfect cup of coffee remains elusive — perfection is, of course, subjective. We must determine for ourselves what best satisfies our taste buds. But there is a way to objectively approach this task. Writing in the journal of the Society for Industrial and Applied Mathematics, researchers claim to have derived an equation that optimizes the quality of coffee brewed in drip machines. By altering parameters to your liking, you should be able to perfect your home brew. Optimizing coffee takes some heady math, however. The researchers' equation contains over 20 parameters, and the derivation appears more akin to math charting the path of spaceships. If anything, brewing a perfect cup of coffee seems even harder now. Coffee beans contain over 1,000 compounds, and extracting the right amount of flavor is complex — hence the math. In a typical drip coffee maker, everything from the coarseness of the grind, the filter housing, water temperature and the rate at which the coffee drains out all affects the brew, often in interconnected ways. What baristas have honed through trial and error over the course of centuries, they are trying to put into hard numbers.
The coffee bed consists of (intergranular) pores and grains. The grains consist of (intragranular) pores and solids. The schematic shows the breakdown of this coffee in the grains (intragranular poresare not represented for clarity). (Credit: Kevin M. Moroney) While the researchers don't offer a hard and fast solution to brewing ideal coffee, they do shed some light on how the process of extraction works during the brewing process. When water hits a filter filled with coffee grounds, soluble molecules are first leached from their surface, and then the process continues more slowly as compounds are drawn from within them. This helps to explain why coffee that is ground too finely will result in a bitter brew, while coarser grinds create a watery beverage. Balancing the ratio of quickly dissolved compounds to more slowly extracted solubles is what creates delicious coffee. The researchers hope that their equation, which puts down these extraction rates on paper, will help to quantify exactly what makes a good cup of coffee. Next up, the researchers hope to examine how the filter bed and drip mechanism affect coffee flavor. Most coffee makers, for example, add water to the grounds from a single spout in the middle of the bed. Using a shower-head design could spread the water more evenly. For now, it appears that the perfect cup of coffee eludes even scientists.