The Speciality Coffee Association of America along with many other sources have a best practices for brewing a simple cup of joe. I, however, want to dive a tad deeper and understand how these standards improve the quality of my 4 cups of coffee a day.
Let’s start with the main ingredient, and objectively the most straightforward, quality water. If the water used to brew your coffee has existing odors or metallic flavors the resulting solution will also exhibit these characteristics. To remove metals, sediments and other unwanted chemicals use filtered water, either from a bottle or from another filtration source.
Next, still water! Or rather the ratio of coffee to water. The SCAA suggests 55 grams (2 ounces or ¼ cup) of coffee per liter of water (just over 4 cups) to achieve the “Golden Cup Standard”. When measuring your coffee grounds, weight is most accurate since bean density is dependent on the roast, light being the more dense roast. This ratio of coffee to water in combination with brewing temperatures between 91–94 °C (195–202 °F) results in 11.5 to 13.5 grams of dissolved solids of coffee in each litre of water, or 18 to 22 percent extraction. But why this precision?! Well, now we start exploring the flavor profile of the coffee and the effect of over or under extraction.
We are looking for a balanced cup where we have extracted much of the desired favors and as little of the unwanted solubles as possible. Under extracted coffee (less than 18% extraction) will be unbalanced and particularly sour since balancing sugars will be extracted later than the initial acids. Over extracted coffee (over 22% extraction) tend to be bitter since extraction of bitter components will continue after the sugars and acids have completed. Another noteworthy aspect of extraction is that caffeine is extracted early on and therefore over extraction does not result in a more potent cup.
Finally, brew time is a function of grind size. Finer grinds provide more surface area and therefore require less brew time to achieve optimal extraction. The SCAA (www.scaa.org) provides the following guidelines for brew time depending on the coffee grind: 1-4 minutes Fine, 4-6 minutes Drip, 6-8 minutes Coarse.