For decades, the specialty-coffee world has recognized that the water you brew with can dramatically change the taste of your coffee. This idea was brought into sharp focus through the groundbreaking work of MIT chemistry professor Christopher Hendon and three-time UK Barista Champion Maxwell Colonna-Dashwood, whose book Water for Coffee (2015) transformed the way professionals think about brew water. Their modeling suggested that minerals—especially divalent cations such as magnesium (Mg²⁺) and calcium (Ca²⁺)—actively attract flavor molecules from coffee grounds, influencing how much of those flavorful compounds end up in the cup. Water for Coffee Research
Now, new research from Umeå University in Sweden adds an interesting twist. The team looked experimentally at how magnesium and calcium interact with key organic acids in coffee. Their conclusion challenges long-held assumptions: the minerals in your water may influence flavor as much after brewing as during extraction. Swedish Research
Coffee contains hundreds of compounds that create acidity, sweetness, body, bitterness, and aroma. Many of the acids that contribute to a vibrant, balanced cup—such as citric, malic, quinic, and lactic acids—are highly soluble and extract early in the brewing process. Minerals dissolved in water can interact with these compounds, sometimes changing how we perceive them.
Hendon and Colonna-Dashwood’s work suggested that magnesium and calcium bind to and “pull out” flavor molecules more effectively than sodium or very soft water. This is one reason many baristas prefer water with moderate hardness and low alkalinity.
The Swedish researchers wanted to test this assumption in a real-world experiment:
Do magnesium and calcium actually change how much acidity is extracted from the coffee grounds?
The Umeå University team posed a focused question:
Do magnesium and calcium affect the extraction of organic acids in coffee, or do they influence flavor in some other way?
They brewed coffee using Specialty Coffee Association (SCA) standards, then added magnesium chloride and calcium chloride either:
Using GC-MS and NMR, they measured the concentrations of four organic acids that are central to coffee flavor:
The goal was to see whether minerals changed how much of each acid appeared in the final cup.
At mineral levels similar to normal drinking water (around 100 ppm of calcium and magnesium), the researchers found almost no effect on the extraction of organic acids. In many cases, the control samples brewed with no added minerals actually showed the highest acid levels.
This challenges the earlier assumption that minerals like magnesium and calcium “pull out” more flavor. At normal concentrations, extraction doesn’t change much, so differences in taste are not due to acids being extracted differently.
When mineral levels were increased to extreme, unrealistic concentrations (1000 ppm), acid levels changed dramatically—magnesium reduced several acids by 40–60%, and calcium reduced some by up to 70%. But these conditions do not occur in real-world brewing; they are purely laboratory extremes.
Just as important: pre-brew vs. post-brew additions produced nearly identical acid levels. If magnesium and calcium were strongly influencing extraction, you would expect clear differences between water that contained minerals during brewing and coffee dosed with minerals afterward. That pattern didn’t appear.
If minerals aren’t significantly changing extraction, what are they doing?
The researchers concluded that magnesium and calcium most likely influence flavor perception through post-brew interactions, such as:
For example, calcium and magnesium can form complexes with acids like malic and citric acid—similar to how calcium binds with citrate in milk. That complexation could make those acids less detectable or alter their perceived intensity.
This aligns with earlier sensory observations:
The Swedish research gives scientific support to the idea that flavor perception—not extraction—is the main role minerals play in the final cup.
If you want to improve your home brewing, here are some practical takeaways:
This combination preserves pleasant acidity, enhances sweetness, and avoids muddiness or bitterness.
The Swedish study doesn’t contradict this. It simply suggests that these differences arise after brewing, through interactions in the cup and in your mouth, rather than at the extraction step.
The new work from Umeå University doesn’t overturn Water for Coffee—it refines it. Hendon and Colonna-Dashwood’s modeling suggested minerals help extract flavor compounds, but real-world experiments show that, at normal water concentrations:
Rather than making water less important, this makes it even more fascinating. The minerals in your brewing water are not just passive background—they actively shape how your coffee tastes, not by dramatically changing what comes out of the grounds, but by changing how your palate experiences what’s already there.
For anyone passionate about brewing better coffee at home, this research offers a deeper appreciation for the chemistry in your cup—and a strong reason to pay attention to the water you use.
