Tailored water is the key to consistent coffee

01 October, 2019 by
Madeline Woolway

Bruce Tea Coffee opened in Glebe, Sydney, over two years ago, but owner Tony Sleiman had to spend six months getting to the root of a rather serious problem — getting the coffee right.

The lease was signed, fit-out was underway and Sleiman was in the process of finding the best beans, perfectly roasted and aged when the issue came to light. After tasting hundreds of cups of coffee over a two- to three-week period, the team still hadn’t managed to produce a great coffee.

Advertisement

“We had no idea why,” says Sleiman. “We were wracking our brains — it’s very unusual. We cut out all the variables. We asked all the experts and caught up with all the coffee companies [we work with].”

The troubleshooting process started in August 2016 and didn’t end until December. The brand new equipment was checked to reveal no problems. Brewing methods were assessed using quality control and assurance methods. Again, everything was fine. There was only one variable left. “We realised it had to be the water,” says Sleiman. “We went through filters and tried all the major brands.”

Advertisement

Nothing worked. Eventually water test results came back showing trace levels of iron attributed to a building problem. “It was contributing a lot of bitterness to the coffee and preventing water coming into the building from dissolving the [coffee] flavours.”

The example of Bruce Tea Coffee is an extreme one, but water quality should be a key concern for the entire industry, from specialty coffee shops to mom and pop cafés.

Advertisement

“Everyone should be worried about it,” says Adam Carr, head of the Coffee Science and Education Centre at Seven Miles Coffee Roastery. Carr and his team recently conducted research on the issue and says the composition of water has the ability to damage equipment and change the flavour of espresso — for better or worse.

When it comes to the longevity of coffee machines, operators need to be aware of calcium carbonate levels, which are responsible for the build up of lime scale. Over time, this can lead to costly machine failure. Filtering water can protect the machine, but the minerals that contribute to lime scale build up are the same ones responsible for extracting flavour from coffee.

Calcium, for example, contributes to water hardness, along with other elements such as magnesium, iron and copper. According to Seven Miles’ research, calcium and magnesium do the most heavy lifting when it comes to flavour extraction during the espresso-making process. Remove too much of either in the filtration process, and you’ll end up with a lacklustre cup of coffee. “To protect your machine, you go to the other side, but then your coffee starts tasting flat,” says Carr. “Where is the middle point? What is the right point to extract your coffee while protecting your machine?”

Finding the answer was the first step in a two-part project undertaken by Seven Miles. “What are those things you can manipulate in water that will make your espresso taste the best?” asks Carr. “Best is a subjective term, but we took a few flavour compounds we know are related to chocolate flavours, roasted coffee flavour, caramel and bitterness and we saw how the measured concentrations of those chemicals change with changing water chemistry.”

The study tested basic tap water and was limited to espresso, although Carr suspects the lessons could be used for other brewing methods, too. “The two big things we found affected coffee flavour were the hardness level and the acidity or pH,” he says.

For Sydneysiders, the results are a boon. “When we looked at Sydney water, we found concentrations of everything were by and large ideal. For hardness, the optimum point is almost exactly where Sydney treats its water.”

For those based in Sydney, perfect water for espresso isn’t guaranteed. Some unique circumstances, such as Sleiman’s, will significantly cost businesses in set-up costs.

Unlike calcium and magnesium, Sleiman found the iron in his water was inhibiting the extraction process. “Nothing removes it except reverse osmosis,” says Sleiman. “This way, you filter to pure water and start from zero, so it doesn’t matter what water you’re getting into the building. Then you can rebuild the water into [what] you want. “Calcium and magnesium are the two materials that bind the flavour compounds in coffee to the water, but they both have a varying affinity for those compounds.

“Magnesium has a strong affinity, it binds flavour really well, but calcium has a relatively weak affinity. [If] there’s more magnesium, it will be more potent and easier to dissolve so you could get more bitter flavours. You can compensate for that with your grind size, roasting and temperature, but I decided — for consistency’s sake — to only have calcium, not magnesium. Calcium is more costeffective and keeps me further away from bitter.”

Adjusting the magnesium or the calcium levels in water will affect pH levels, which also impact the extraction process. Generally, the higher the pH, the more likely the coffee is to be flat or bitter. A neutral pH of seven is the industry standard, but the water Sleiman uses has a pH of eight, which Carr says is also suitable.

While Carr acknowledges some cafés, like Sleiman’s, will need to opt for reverse osmosis, he argues it’s not necessarily practical for most cafés to achieve. The second part of Seven Miles’ study looked at strategies cafés can employ. “We found the best water qualities,” says Carr. “Then, we work out how to get them practically, so what filter systems we can employ that will actually give us the water quality we want.

“We tested Sydney water and the general lessons are the same for anywhere in the world, but Brisbane water, Newcastle water or Perth water will require specific testing to determine the ideal filtration system for your coffee and your machine.”

To protect coffee machines, the majority of operators in Australia can get away with installing relatively cheap carbon filtration systems, most of which don’t cost more than $80 and only need to be changed every six months depending on volume. Given taste preferences are subjective, the right water for each café, their coffee and equipment will vary, but water designed for coffee extraction could become ubiquitous, with some roasters already requiring cafés to use specific formulas.

“It takes the pressure away from the barista to make great coffee,” says Sleiman. “If you use the same water and the same equipment, you can basically copy and paste a method for brewing. It makes coffee programmable — less artisan, but more of a science. In the future, I think that’s where everyone will go.”