Let’s say you have a cup of coffee in the cafe. The coffee is clean and sweet, with a bright acidity. It’s balanced and enjoyable. As it cools, the coffee becomes sweeter and the acidity changes subtly. You buy a bag and take it home. Using all the right tools for the job and following your favorite brew recipe, you nail the pourover. You take your first sip. It’s dull and flat. The acidity is harsh. The overwhelming note present in the cup is one: coffee. What did the barista do that you didn’t? Is it worth buying the best coffees for home if you can’t make them taste the same way at home?
Coffee brewing is chemistry. Since making coffee is all about proper extraction, (moving all of the good flavors present in the coffee bean to the water/coffee solution) coffee makers should work to optimize how coffee flavors are extracted from the beans and preserved and perceived in the resulting cup of coffee. Variables like time, temperature, particle distribution (grind), the ratio of water to coffee, and agitation during the extraction process all help extract flavor, but it is actually the composition of the water itself that extracts flavor from the coffee bean.
The minerals in water, specifically magnesium and calcium, do a great job extracting the acids and sugars present in the bean and the Malliard reactions that have occured from roasting the bean that give sweet caramelized flavors like vanilla or nougat. So, theoretically, the more minerals like magnesium and calcium in your water, the more you will be able to extract from the coffee bean. However, since we drink coffee, and we’re primarily concerned with the taste of extraction and not just the overall ability to extract, we need a buffer, namely bicarbonate, in the water to balance the chemical changes in the water to preserve the acids as they move from bean to cup. Dashwood and Hendon’s Water for Coffee recommends a 2:1 ratio of general hardness (minerals) to bicarbonate to provide optimal extraction for specialty coffee. To hear more about Water for Coffee, check out Maxwell Colonna-Dashwood’s 2015 Re;co Symposium Lecture
What it means
Companies like Third Wave Water are working to take the research being done by coffee professionals and make it accessible to the average consumer. You can find Third Wave Water Packets for Pourovers and Espresso in the shop. The team at Barista Hustle has some great info on making your own water recipe if you’re interested in learning more about how various coffee professionals optimize their water with easy to use recipes.