University of Bath chemist, Christopher Hendon, and UK Barista Champion, Maxwell Colonna-Dashwood, have studied how water composition can make a dramatic difference to the taste of coffee.
The study, published in the Journal of Agricultural Food Chemistry, looked at how different compositions of water affect the extraction of six chemicals that contribute to the flavour of coffee. “Coffee beans contain hundreds of chemicals; the precise composition depends on the type of bean and how it is roasted. The flavour of the resulting coffee is determined by how much of these chemicals are extracted by the water, which is influenced by roast profile, grind, temperature, pressure and brew time,” said Hendon, in a statement.
Hendon and Colonna-Dashwood, owner of Colonna and Small’s coffee shop in Bath, embarked on the study after a discussion about why the taste of coffee varies so much. “We’ve found that the water composition is key to the proportions of sugars, starches, bases and acids extracted from a particular roast,” said Hendon.
Guidelines on the ideal water for coffee extraction from the Speciality Coffee Association of Europe (SCAE) puts emphasis on measuring ionic conductivity to quantify the total dissolved solids. However, the researchers found that it was the proportions of these ions that affected the extraction and therefore the taste of the coffee.
“Hard water is generally considered to be bad for coffee, but we found it was the type of hardness that mattered – while high bicarbonate levels are bad, high magnesium ion levels increase the extraction of coffee into water and improve the taste,” said Hendon.
The study also found that sodium rich water, such as that produced by water softeners, didn’t help the taste of the coffee either.
“For the championships we test the local water and then select the roast that is most suitable for that particular water. For example, you could use a heavy roast with a soft water as it doesn’t extract very much, but with hard water it would extract too much and give a bitter taste, so it would be better to use a lighter roast,” said Hendon.