What we can learn from the beer brewing community

There's an intersection to be had here between the beer and the coffee community.

Beer brewers have been fanatical about water composition far longer than coffee brewers, and there's knowedge to share – particularly when it comes to the anions involved.

Notably, the sulfate:chloride ratio has received considerable experimental testing by brewers – this article is worth a read for any coffee brewer interested in water composition.

The sulfate:chloride ratio

There are a few pieces of key wisdom from our beer compatriots:

• Beer typically has 50-250 ppm sulfates and 0-250 ppm chloride. In contrast, water for coffee will be in the range of 25-100 ppm sulfate and 5-50 ppm chloride
• Higher sulfate levels enhance hop character, bitterness, and contribute to a drier finish of the beer - meaning a lack of lingering sweetness/taste
• Higher chloride ratios help with a rounder, sweeter character and enhance the malt aspects of beer, as well as mouthfeel
• Typically a 2:1 ratio of sulfate:chloride is used for hop-forward beers like IPAs
• Conversely a 1:2 ratio is used for mild ales/stouts
• A ratio of 1:1 appears to be quite balanced in taste overall

In the article linked earlier, softness was perceived to go up as the concentration of chloride, relative to sulfate, went up.

So aiming for a 1:1 chloride to sulfate balance in coffee water might help if you're aiming for smooth mouthfeel.

Ultimately, it's clear that the balance is important, and that too much of either sulfate or chloride can lead to negative impacts on flavour (e.g. too much sulfate leads to harshness and bitterness).

In our experience, sulfate >1 mM can lead to excessively bitter roast flavours, so we certainly agree.