News

Water hardness and the perfect brew

coffee brewing

When Langdon Coffee Merchant (LCM) Account Manager, David Train, moved to Adelaide earlier this year to open LCM’s first South Australia office, purchasing a water filtration system was at the top of his To-Do list.

“South Australia’s tap water is very different to that of Melbourne, or Sydney,” explains David, a passionate brewer and experienced barista.

“The water in Adelaide is hard and chlorinated, and if you don’t manage that, it has a negative impact on the development of a coffee’s flavour and aroma.”

Coffee taste depends to a certain extent on the overall mineralisation and alkalinity, or carbonate hardness, of the water used for brewing.  Most people are familiar with the chemical structure of water, i.e. H2O but drinking water is not a pure chemical compound, containing a range of other minerals that dissolve in from the surrounding environment, or may even be deliberately added in some cities (e.g. fluoride).

Calcium, magnesium, sodium, and potassium, chloride, sulfate, and hydrogen carbonate, are all commonly found in tap water. Of these, hydrogen carbonate is responsible for alkalinity, and calcium and magnesium determine the general car­bonate hardness of the water.

Currently the #1 ranked brewer in Australia and a ‘serious coffee geek’ by his own admission, David says the best coffee starts with exceptional green coffee, and with the perfect water. In competition, this means that David will go so far as to create his own water to achieve the optimal degree of mineralisation to bring out the coffee’s full flavour and aroma.

David believes the effect of water on the taste of coffee is not well understood, even by some roasters: “We’re spoiled in Melbourne and Sydney where the mineralisation in plain tap water is almost ideal for good brewing, but in many other cities – including London where the water hardness is legendary, higher mineralisation can have a significant impact on the solvent behaviour of the water,”

“When the water is too hard, it acts as a chemical buffer, neutralising the caffeic acids, and leaving the coffee tasting bitter and flat,” explains David.

It’s a question of balance, however, and not about stripping out all the minerals which can be used to develop the full potential of the coffee bean:  “Magnesium highlights fruity and floral contributors, calcium highlights mouthfeel (texture) and bicarb works to neutralise the acidity,” says David.

Water isn’t a magic bullet. At the end of the day, the quality of the beans is what is most important for taste: “You’re only ever going to get out what’s already there,” says David, “As a roaster you are pushing the flavour profile in a certain direction. You can’t polish a…….,” David hesitates and smiles, “Well, you know what I mean!”