There’s more to water than meets the eye. Richard Padron of BRITA explores how the water cycle influences water composition and how it reacts with coffee.
You might know all about the bean-to-cup journey, but have you thought about how the other pivotal ingredient of any coffee – water – makes its way into the brew?
Water may seem pretty straightforward, but there are many steps along the water cycle and plenty of factors that can influence its chemical composition.
Let’s start with precipitation. Clouds fill with water until they get too heavy to stay afloat and rain down onto the ground or ocean below. Water that falls on land runs off until it’s absorbed into the soil, where it joins groundwater sources that flow into trees or larger water bodies. Then, the sun evaporates the water, vapour rises into the sky and forms clouds, and the cycle continues.
Water is often called the universal solvent, as it dissolves more substances than any other liquid.
Rainwater absorbs carbon dioxide from the atmosphere as it falls to the ground, becoming slightly acidic. It then seeps into soil that contains limestone. The solid limestone dissolves into the acidic water and forms calcium and hydrogen carbonate ions. The water is now hard as it contains a high volume of dissolved ions. We call this the “lime-carbonic acid equilibrium” because the two almost balance each other out.
Leaching can also occur when minerals like limestone and dolomite, components from fertilisers and pesticides, and industrial pollution like oil residues and solvents, are absorbed into the soil and mix with groundwater.
Drinking water has strict limits on what it can contain. To make it safe, water passes through treatment plants that remove anything dangerous to our health. But they don’t take everything out, and the water can be exposed to more materials on the way to our home or cafés.
Rust and scale particles can be picked up from piping after water leaves the treatment plant. The majority of these particles are harmless and not even visible, ranging in size from one to 200 micrometres. For reference, a strand of northern European human hair has about a 50-micrometre diameter. These are harmless when you drink them, but the same can’t be said for your coffee machine. These nasties can build up in mains-fed equipment, causing faults. This can mean increased equipment downtime and higher energy and maintenance costs.
SOMETHING IN THE WATER
Many natural minerals are also left in the water and treatment plants add other substances like chlorine to disinfect it. These minerals consist of cations (positively charged ions) – calcium, magnesium, sodium, and potassium – combined with anions (negatively charged ions) – hydrogen carbonate, sulphate, nitrate, and chlorine.
The concentration of dissolved calcium and magnesium in water is referred to as total hardness. The portion of this combined with carbonate, bicarbonate, or hydrogen carbonate is called carbonate hardness.
When water is heated, like in a coffee machine, hydrogen carbonate decomposes into carbonate and carbon dioxide. As the carbon dioxide gas is released, the pH level rises (a measure of acidity), making the water more alkalic, disrupting the lime-carbonic acid equilibrium mentioned earlier. This carbonate combines with calcium to form limescale in the boiler.
When the anion is something other than carbonate, bicarbonate, or hydrogen carbonate, it is called “permanent hardness” because it remains in water post-boil.
Carbonate hardness can make up anywhere between 25 and 90 per cent of total hardness. Scale water contains higher levels or carbonate hardness than permanent hardness, while the opposite is called Gypsum water. Gypsum deposits can build in a coffee machine over time too.
Because the total and types of hardness can vary widely, water filters have to be able to meet diverse requirements – and provide the right water treatment for regional conditions.
One of the aims of a water filter is to remove particles that could lead to equipment downtime and prevent mineral and limescale deposits from forming. Another target is to achieve an ideal mineral composition and prevent unintended reactions between water and the ingredients in a beverage like coffee.
The water used in coffee is important. It is, after all, the main ingredient. Even once it has left the boiler, remaining chemicals or materials can create an unpleasant taste or aroma. They can also impact what is extracted from the coffee grounds.
Moreover, substances introduced during water treatment like chloride can cause unpalatable chlorine, corky, or musty tastes – some can even influence how coffee smells. Plus, organic contaminants in water can lend an off-flavour to coffee. In particular, water with these types of solutes can produce coffee with a distinctive earthy or musty taste.
A few years ago, BRITA worked with the Specialty Coffee Association of Europe (SCAE) to develop the SCAE Water Chart, which provides an in-depth look at how water composition impacts coffee. Reach out to your BRITA representative for the full paper.
As a rough guide, when it comes to water drinking composition, cations like calcium and potassium extract bitter flavours, magnesium tends to bring bitter/sweet tastes, and sodium draws out sweet/salty compounds.
Anions like sulphate can make a chalky profile while chloride draws out bitter flavours. Hydrogen carbonate can even react with coffee acids, resulting in a flat/dry profile.
I might be making it sound like you should use mineral-less water for your coffee brewing, but that’s far from the case. If you look at coffee competitions like the Brewers Cup, you will see competitors purify their water and add minerals that will extract compounds they are looking for in their coffee. Generally, you want a low level of hydrogen carbonate and just the right amount of calcium and magnesium to bring out desirable flavours in the cup.
The exact composition of water – including hardness, chlorine levels, aroma, and taste – can even differ from city to city and state to state, so the same coffee brewed in two different parts of the country can taste completely different. Or, a roaster could be testing their coffee with a water composition completely different to the café that serves it.
To ensure cafés have the best possible water to make the most of their coffees, BRITA offers a broad range of filters to tailor H2O to their goals and preferences. The activated carbon PURITY C Fresh filters, hydrogen exchange PURITY Quell ST and PURITY C Quell ST, and sodium exchange PURITY C Finest are each developed to work best in different situations, and the BRITA PROGUARD Coffee is able to infuse the desired minerals.
Like coffee, water goes on a long journey to get to the café, picking up flavours and compounds that give it a unique terroir. Using a simple filter solution, you can choose how that is expressed in the final cup.
For more information, visit www.brita.com.au
This article appears in the February 2021 edition of BeanScene. Subscribe HERE.