Experiments with Water

Ordering coffee from different parts of the world has opened my eyes to a whole new level of difficulties of brewing coffee. While coffees sourced from local roasters consistently taste great and require only minute adjustments of brewing parameters to optimize the flavor profile, several coffees that I’ve received, in particular the Kenya Kiriaini Teresia AA roasted by Da Matteo in Stockholm, tasted unpleasantly sour cup after cup until I adjusted my grind extremely fine (number 5 on my EK43) and using water straight off boil into a preheated brewer. It then dawned on me that if it isn’t the grinder, the temperature or the brewer, it must be the water. And it makes sense, roasters in different parts of the world have different minerals in their water and would naturally roast their coffees to taste best using THEIR water.

After watching Maxwell Colonna-Dashwood’s fascinating talks on water chemistry for coffee, I decided to play around with my water. In short, he says that while we need some minerals in the water (distilled water is no good), and we already know that hard water (too many minerals) also makes coffee taste bad, which minerals are in the water and in what proportion are what make great coffee for water. In particular, we need magnesium, calcium and bicarbonate in appropriate ratios because Mg+ and Ca+ ions not only are part of the water, but they actively bind to acids in the coffee and help to extract them into solution. We need a paradigm shift from thinking about water as a mere ingredient in coffee, to an active solvent of coffee.

Experiment 1:

How to make terrible coffee using great beans equipment and equipment: use crappy water!

I wanted to know what the effect of magnesium has on coffee. For this experiment I bought a jug of USP epsom salts (MgSO4) and dissolved 3.1g into 250ml of purified water (roughly 1200mg/L of Mg+: WAY more than is reasonable and I do not recommend drinking this in more than minute amounts, but I wanted to take it to the extreme to see its effect). I brewed 7g of coffee to 100g of 95C water for 4 minutes in an aeropress to eliminate variable technique in a pourover. The coffee used was Shaye Ayra: a natural processed Ethiopian coffee from Oromia, Guji region from the Levelup group of producers, roasted by DeMello Palhetta in Toronto. It’s usually very juicy, almost jammy in its fruitiness and super sweet in a plum sort-of way with a rose and plum aroma. With this water though, the aroma was very pleasantlyl floral and had a prominent plum note, almost like a liqueur, yet the flavor was just awful. The best I can describe it is…hollow…like it’s lacking something essential that you expect and didn’t get. There was prominent acidity, a round piney bitterness but little sweetness and not a hint of the juicy plum.

Experiment 2:

Next I wanted to try water without minerals. I used the same method and coffee as before but this time using just plain Aquafina (<4ppm TDS) water. The resulting cup lacked the aromatics that were so prominent in the Mg+ heavy cup and the flavor, while being more tolerable, tasted…flat and boring. There was a noticeable lack of vibrancy and acidity with some bitterness on the finish although the cup was sweet. It didn’t taste bad, but I also found myself not caring to finish the cup either.

Finishing thoughts:

In the future I will conduct more such tasting experiments to explore the effects of calcium and bicarb and different sources (salts) for the various minerals. One confounding variable was that the addition of sulfates from the epsom salts may have also added its own flavor to the brew, especially in such high concentrations, so finding a different source for magnesium in the future would not be a bad idea to compare. For now though, I think diluting my current Brita filtered Toronto tap water with purified to reduce the total TDS and adding a pinch of epsom salt to boost the Mg+ content will get me in the ballpark of ideal water until I can nail down an exact water recipe. Expect more experimentation in the coming weeks!