brewing coffee news

Ideal water composition for espresso extraction

The Coffee Science Education Centre (CSEC) in Australia tested the impact of a range of tap, artificially modified, and purified waters on the flavors of coffee in an espresso. The chemistry of the resulting brews and brew waters was analysed scientifically through gas chromatography with mass spectrometry, inductively coupled plasma optical emission spectrometry, a bank of photometers, and a series of pH/conductivity multi probes.

What a brilliant idea! I have long asserted certain differences in the flavors in a cup of coffee to the water used, but never really thought about it scientifically. Sometimes my favorite coffee tasted completely different when brewed at a friend’s home. Other times I simply couldn’t replicate the same great taste for a coffee I’d had at work in my home. I varied the recipe, tried to compensate for certain differences but never really solved the problem…

The study looked at how three elements of water affected flavours in extraction: hardness (the amount of calcium, magnesium, carbonate, and bicarbonate in water), pH levels, and total dissolved solids (TDS).

The biggest effect on flavour was achieved by modifying the hardness of the water

Dr Adam Carr of Seven Miles Coffee Roasters

They brewed an espresso on an industry standard machine from La Marzocco and then measured the concentration of chemicals in the coffee that are attributed to certain flavour characteristics, such as nutty/roasted (2-methylpyrazine), fruity (furaneol), vanilla/caramel (vanillin), and caffeine/bitterness (caffeine).

They found what I had sort of self-analysed by drinking coffee made with desalinated water, some mineral water and very hard (dH) water in my hometown in Bussum (dH around 9-10).

source: Seven Miles

Lessons learned:

  • Minimum hardness of 50 ppm for “best” flavors
  • Higher than 60 ppm has little effect on flavors
  • pH tends to concentrate flavors, much like salt enhances flavors in food
  • Higher pH tended to concentrate stronger flavours in coffee, though not to the same extent as hardness. However, higher pH levels also led to issues in the extraction process.
source: Reddit

Read the whole article to find out the recommended pH and what the effect on TDS was…


It just so happened that the water quality you want for coffee is what Sydney Water is pumping out of their stations!

Dr Adam Carr of Seven Miles Coffee Roasters