The science behind the perfect coffee
– it’s in the
water!
Vicky Just,
A chemist at the
University has teamed up with the UK Barista Champion to find the best type of
water for making coffee. The pair are heading to the World Barista Championships
in Italy
Christopher Hendon, a PhD student from our
Department of Chemistry, embarked on the project in his spare time with friend
Maxwell Colonna-Dashwood, owner of Colonna and Small's coffee shop in Bath
Hendon used computational chemistry methods
to look at how different compositions of water affect the extraction of six
chemicals that contribute to the flavour of coffee, along with caffeine. The
study, published in the Journal of Agricultural Food Chemistry, found that water composition can
make a dramatic difference to the taste of coffee made from the same bean.
Hendon explained: “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 time, grind, temperature, pressure and brew time.
“We’ve found that the water composition is
key to the proportions of sugars, starches, bases and acids extracted from a
particular roast.”
The coffee industry uses guidelines on the
ideal water for coffee extraction from the Speciality Coffee Association of
Europe (SCAE), which measures 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.
Hendon explained: “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.”
The study also found that sodium rich
water, such as that produced by water softeners, didn’t help the taste of the
coffee either.
Hendon added: “There is no one particular
perfect composition of water that produces consistently flavoursome extractions
from all roasted coffee. But magnesium-rich water is better at extracting
coffee compounds and the resultant flavour depends on the balance between both
the ions in the water and the quantity of bicarbonate present.”
Maxwell Colonna-Dashwood, co-author on the
paper, said: “Unfortunately most of the time you are limited by the source
water available. Water from the tap varies regionally and from day to day
depending on how much it rains – the only way you can get consistent quality is
to use bottled water, but even then not all waters are the same.
“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.
“Traditionally the coffee making industry
is most concerned about using water that doesn’t scale up their machines. But
we argue that more value should be placed on the flavour of the coffee and want
to use chemistry to help people make the best coffee they can with the water
they have available.”
Maxwell Colonna-Dashwood won the UK Barista
Championship in April and will represent the UK
at the World Championships in Rimini ,
Italy
The competition takes place over four days,
with baristas from 50 countries vying to become World Barista Champion. Each
competitor must prepare four espressos, four cappuccinos, and four original
signature drinks to exacting standards in a 15-minute performance set to music.
Each entry is judged on the taste of beverages served, cleanliness, creativity,
technical skill, and overall presentation.
Hendon and Colonna-Dashwood are now
planning to share their knowledge on the science behind making the perfect
coffee in a book.
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