How Does Water Quality Affect Coffee Flavor?

You’ve got a French press, the finest fresh locally Ohio-roasted coffee beans, even specialty coffee syrups, but something about your coffee brews is still… off. Did you know the quality of your tap water can also affect its flavor? And not necessarily in a bad way. Maybe your coffee is awesome but every time you drink a cup at your friend’s house something is just different. It might be because harder water can actually produce a stronger tasting more flavorful coffee. If your friend lives somewhere with soft water, get used to the soft coffee. 

So say Maxwell Colonna Dashwood and Christopher H Hendon, who recently co-wrote a book, “Water for Coffee” that scientifically breaks down just why the wrong tap water can absolutely ruin even the best coffee. The book is a more readable compilation of data Hendon discussed in his 2014 paper, published in the Journal of Agricultural and Food Chemistry, on how the mineral content in water affects coffee flavor.

In his research, Hendon observed that the mineral compounds in hard water tend to attach themselves to the flavorful elements in roasted coffee beans during brewing. He found that water with higher levels of magnesium will likely extract more flavor from a coffee bean. Soft or distilled water, conversely, does the opposite and has a harder time pulling the flavor from coffee beans. Hendon describes hard water minerals as “sticky,” which is why they attract all the goodness inside the coffee bean.

Hendon is currently working on a paper to determine how brewing temperature affects flavor. “I’m trying to build a picture to show people that every aspect of coffee can be explored if you want,” Hendon told The Atlantic in a recent interview.

Hendon, the SCAA & the Art of Coffee as a Science

Coffee is packed with over 1000 vitamins, minerals and aroma compounds, so it makes sense that it has different “chemistry” with different kinds of water. Hard water is heavy in minerals like magnesium and calcium, while soft water is high in sodium. But it’s not as simple as hard water good, soft water bad. 

High calcium hard water brews a bitter coffee (no thanks), while hard water that’s high in magnesium brings out the full earthiness of a coffee bean. Likewise, the bicarbonates in soft water can take a low-acidity coffee roast to a sour taste. Okay, so maybe the “soft water bad” part is true.

But all is not lost if you live somewhere with soft water, which the USGS water map can easily tell you. Just choose your coffee beans strategically. This is another area small-batch coffee roasters shine; we’re intimately knowledgeable about every bean we source, and can point you towards single origins, blends and flavors that can make the most of your soft water problem.

Hendon is quickly becoming the residential scientist of the specialty coffee industry, a field that is still on the frontier stage of science:

“Over time, we’ve struggled to achieve the same scientific rigor behind our industry that others, like wine and beer, have,” says Emma Sage, Science Manager at the Specialty Coffee Association of America (SCAA), told The Atlantic. “Now we’re changing that.”

In a recent podcast, Hendon discussed his coffee-related research on a broader level. His big picture is achieving a better, sustainably-sourced and brewed coffee with less waste and more flavor. (Did you know that spoiled and unused coffee is one of the biggest culprits of waste in the US each year?). And it’s not just water hardness and temperature he’s got to consider. In the podcast, Hendon discusses how where the coffee bean comes from complicates the process even further. 

See? Coffee is just as much a science as it is an art.

Want to learn more about how water affects your organic java? Check out Hendon’s book on Amazon!