Water: it makes up 94–98% of your cup of coffee. But it’s not just the biggest ingredient in your beverage. Water temperature (along with its mineral composition) is also responsible for how that beverage tastes: sweet, bitter, sour…

Controlling that temperature is key for any barista or coffee-lover. Unfortunately, water temperature variation is surprisingly common in service, whether due to poor training or poor equipment.

To learn more, I spoke to Paul Stack, Operations Director at Marco Beverage Systems which produces award-winning multi-temperature water distribution systems for coffee and tea, and Nathan Retzer, Owner of Quarter Horse Coffee. They shared with me why precision brewing is so important, along with their tips for controlling water temperature in service.

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Using the Marco MIX to get temperature-controlled hot water. Credit: La Marzocco UK & Ireland

How Does Water Temperature Affect Your Coffee?

“The temperature of the water has a direct impact on the rate of extraction of different components of a brew,” Paul tells me.

During brewing, there are many complex chemical reactions happening. The water is extracting chlorogenic, acetic, and malic acids; caffeine; oils; and more. These reactions will also take place at different times: caffeine, for example, is extracted early on in the brewing. Fruity acids also start to appear towards the beginning, followed by sweetness, and with bitterness coming last.

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So, what does this have to do with water temperature? Well, the hotter the water, the quicker it is at extracting these compounds. And, since each one has a different impact on flavour, brewers need to carefully control the amount of extraction that takes place.

As Paul says, “at higher temperatures, control of extraction becomes more difficult, with undesirable flavour components being released quickly. The industry traditionally uses terms like ‘too high’ and ‘burning coffee’ to articulate the lack of control of flavour extraction at higher temperatures.”

And at lower temperatures? Paul reminds me, “As best evidenced by the explosion of cold brew, the use of the term ‘too low’ for brewing temperature is flawed.” However, anyone who’s tried cold brew will know that it’s famous for its smooth, sweet profile and reduced acidity. While brew time is normally extended to make up for the low water temperature, certain compounds are just not going to be extracted at certain temperatures. As Paul says, “Different flavour components are released at different rates at different temperatures.”

Moreover, low temperatures that aren’t compensated for by brew time and/or grind size will result in sour coffees that lack body. This is because the extracted compounds will be primarily acids, without the oils that create body or the sweetness and bitterness that give the coffee balance.

This makes precision brewing crucial. Paying attention to the water temperature will allow for better-tasting brews.

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And not only is it important to brew with the right temperature, but it’s important to do so with consistency and precision. As Paul says, “inconsistencies in water temperature is akin to baking a cake with the oven turned on and off during the baking cycle – i.e. the result is anyone’s guess.”

Coffees ready for drinking.

Poor Equipment Leads to Variation

Unfortunately, water temperature variation is always a risk. Paul tells me that it’s impossible to completely remove the causes of it – but you can control them.

Equipment is key to doing so. Nathan explains that poorly insulated boilers and low-quality heating elements or machinery often lead to inconsistency. Paul agrees: “Poor hot water delivery is usually due to the lack of precision in management of the hot water need for the catering location and the inflow of cold water to replenish the take-off…” he says.

“Use equipment that delivers consistent temperature, despite the variable volume needs of a coffee, tea, or food service location.”

A good-quality machine will resolve the issue for espresso; with manual brewing, however, it becomes more challenging.

Nathan says, “A good espresso machine controls the temperature very well and it comes out at the right temperature and straight into contact with the coffee. The problem with some pour over brewing is you have to add the water to a kettle and that will drop the temperature. We use the Marco SP-9 [a temperature-controlled brewer/hot water distributor compatible with third wave brewing devices] so we can have the exact temperature water come in contact with the coffee bed.”

Using a Marco SP-9 Single Cup Brewer with a Kalita Wave to brew temperature-controlled filter coffee. Credit: Evans Brothers Coffee

Barista Training Keeps Temperature Stable

Yet it’s not just your equipment you need to worry about. Paul explains that a high-quality water distribution system, like the SCA-award-winning multi-temperature Marco MIX, will deliver hot water to the exact degree desired. However, adding the hot water to a cold kettle or brewing in a cold dripper could then cause the temperature to drop by up to 10ºC. He emphasises the importance of heating the kettle, dripper, serving jug, and cup, if all four are used.

For this reason, good barista training is imperative – and it’s not just about processes, such as pre-heating kettles and brewers. It’s also about brewing basics.

He tells me that a barista’s pour style can also lead to water temperature variation. “If not focussed on keeping the coffee bed always wet, it can introduce variables in the coffee sludge temperature, with consequent inconsistencies.”

He recommends formal training, advising that “sitting the Foundation and Intermediate Brewing modules from the SCA Coffee Skills Programme would help”.

Pre-heating the ceramic Kalita Wave before brewing. Credit: Coffeewerk + Press

When it comes to water temperature, minute variations can have a major impact on the quality and consistency of your beverage. Make sure you use high-quality equipment capable of precision brewing. Create good protocols for pour overs. And train your staff well, whether you do it in-house or send them for external certification.

After all, good beans deserve to be brewed well.

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Please note: This article has been sponsored by Marco Beverage Solutions.  

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