Espresso extraction is a precise process, where multiple brewing variables are finely adjusted in order to obtain a great cup of coffee. Brewing temperature is one of the important variables, and if we don’t handle it properly our espresso might be ruined, or just average.
In this post we are going to look at how the brewing temperature can change the flavor of the espresso, and how ca we teak the temperature in order to perfect our shot.
The information in this post is intended for the advanced barista, who wants to finely tune their shots.
- What is the ideal water temperature for making espresso
- Adjusting the Espresso Brew Temperature
- Temperature Stability
- Tuning Brewing Temperature for an Espresso Shot
- Does espresso extraction temperature affect crema?
What is the ideal water temperature for making espresso
Water temperature plays a critical role in espresso extraction. If the water is too hot, it can scald the coffee and produce over-extracted bitter espresso.
If the water is too cold, it won’t extract all of the desirable coffee flavors, resulting in a weak and sour espresso – under-extracted.
The ideal espresso extraction temperature falls somewhere in the middle, around 200 degrees Fahrenheit. This allows the water to extract all of the coffee’s flavors without scalding it.
Water too cold will give you a low extraction yield, whereas hot water will give you a higher extraction yield.
How you achieve this temperature will depend on your espresso machine. Some machines have built-in thermostats that allow you to set the exact temperature, while others require you to experiment a bit to find the perfect setting. Whichever type of machine you have, taking the time to dial in the perfect espresso extraction temperature will result in a better-tasting cup of coffee.
Adjusting the Espresso Brew Temperature
A properly extracted espresso is brewed at a temperature of 190°F to 205°F, (88°C to 96°C). It is not uncommon for baristas to look for retaining the origin notes in espresso. Lower temperatures favor acidic flavor notes, while higher temperatures favor roast flavors.
Brewing Temperature and other Variables
Brewing temperature doesn’t exist in a vacuum, and it depends on other variables, such as grind size, dose and tamp. But mostly it is affected by the roast degree.
Espresso brewing temperature is such a narrow range, and it almost looks like there is no difference between the two extremes. However, the 15 degrees difference can give you quite different results.
Generally speaking, when we grind finer we can decrease the temperature and vice versa, when we grind coarser we can decrease the temperature. However, we can never grind coarse enough in espresso, because we lose pressure in the puck. I would say that, even though there is a small correlation here, is almost insignificant.
The brew time is the second most important factor to tweak in correlation with temperature, right after roast color. I always recommend to stick to the 20 to 30 seconds extraction time. This is proven the best brew time for espresso.
When we pull a 30 seconds shot, it is 50% longer time than a 20 seconds one. So, if you like longer extraction times, choose a lower temperature. At the end of the day, we are looking for the perfect balance between roast flavors and origin flavors. So if you machine supports it, play with the brewing temperature.
Temperature Control Technology
The three main ways to control the temperature of an espresso machine are thermostat, pressurestat, and PID. The best method out of the three is the PID, though it’s bit more expensive.
On a boiler with a mechanical thermostat, the set temperature is the point when the thermostat turns off the heater. There are two problems with this technology: temperature precision, and temperature tuning. The heating element will overshoot up to 10%, and we explain elsewhere in the page why.
The mechanical thermostats are most often found in single boiler espresso machines.
The pressurestat works by pushing a diaphragm on and off, in order to activate or deactivate the heating element. The diaphragm is controlled by the pressure in the boiler. The pressurestat is more precise that the mechanical thermostat, and we find them in heat exchanger espresso machines.
The best technology for temperature control of a coffee maker is the PID. PID stands for Proportional Integral Derivative, and it is a is a control loop mechanism. A PID is a digital device that measures and controls the temperature in adjustable steps. The closer to the set temperature the less heating applies. This is how it avoids overshooting.
PID is becoming more and more used, since the device prices went down, they become more affordable, even in an entry espresso machine.
Brewing Temperature Precision
This problem come from the material’s property, thermal inertia (or thermal effusivity). When the thermostat measures the set temperature, it will turn off the heating element. However, at this point the heating element is very hot, so it will still transfer heat to the boiler. This will result in a small overheating of the brewing water, most of the times just enough to over-extract the espresso shot.
This problem is fixed on machines equipped with a PID. However, cheaper machine are very often designed without a PID. In this cases, the barista employs temperature surfing.
Temperature surfing is the technique where the operator flushes some water in order to decrease the temperature of the water in the boiler. If the water is too hot, a few seconds of water flushing will force the boiler to refill with room temperature from the water tank. This will lower the temperature in the boiler just enough to not set off the thermostat.
For PID controlled machines, the temperature is constantly calculated by the electronic device, and continuously adjusted. As it gets closer to the set temperature, the PID makes smaller temperature changes, by finely controlling the heating element. This way the brewing temperature is very precise.
In espresso preparation, temperature stability refers to the ability of the espresso machine to deliver the set brewing temperature for the entire duration of the coffee shot extraction.
In other words, you want to have the same temperature, (about 200°F), for the entire time coffee get extracted. Otherwise, you will get a mix of correctly extracted coffee and under-extracted.
This happens most often with small boilers and with poor thermoblocks.
Temperature stability will affect the composition of the espresso shot, because we will extract different compounds, with different temperatures.
Technical Tips for Stability on Machines without a PID
If the machine is equipped with a PID, the target brewing temperature can be easily changed with the PID’s digital controls. We can achieve this on a shot by shot basis. If we have a light roasted coffee, we increase the temperature close to 205°F. If we have a very dark roast, we can lower the brewing temperature as much as 190°F, (depending on the dose, tamp and grind size).
For a machine with out a PID, we can temperature surf. We pull a short blanc shot for lowering the temperature, or we can turn the steam switch on for a few seconds just before brewing. You will have to measure the temperature when it pour out of the group head so you can calibrate your timing.
Lighter roasts, on the other hand will need a higher extraction temperature, since they are not as soluble.
Roast Degree and Temperature Suggestions
If you have a dark roast your brewing temperature should range between 190 and 195°F. A medium roast, 195 to 200°F, depending on the grind size and color. For a light roast you need to increase the temperature and go as high as 207°F. Depending how light the roast is, you can choose a temp between 200 and 207°F.
Clive Coffee has a post where they recommend how to brew various roasts, if you are interested.
The Extraction Order of the Soluble Solids – Acidity, Sweetness, and Bitterness
Because the soluble solids in the coffee bean have different solubility, they extract in a certain order. I’d say that this works in our favor, the coffee lovers, otherwise we’d hate coffee taste.
- The first to get extracted are the fats the acids and the caffeine.
- Next, we extract a bit more caffeine, and the sugars.
- At the end the plant fibers, and the phenolic compounds, which bring the most bitterness.
Why do we care about this? Because water temperature is what makes these compounds more or less soluble. At higher temperatures, the bitter compounds are just easier to extract, so the same 25 seconds extraction will get you more bitterness, compared to lower temps. The higher the temperature, the easier to extract. And, NO, it’s not good for us to extract them too easy, because then we extract all of them at once, getting an over extracted cup.
What Does the Science say?
Science has a few discoveries for us, and we can use these to perfect our coffee shot. And science shows us that a too high temperature is not good for your shot.
Dr. Monika Fekete, has conducted this espresso brewing temperature experiment, where she pulled a bunch of espresso shots at different temperatures, and measured the outcome. Her findings are probably partially surprising, or maybe not, because other scientific research before this study, found the same.
Increasing a shot’s temperature decreases the flow rate. This will result in a smaller shot with more body. Gradient brewing yielded more volume for the upward gradient, and less coffee for the downward gradient. The information seems to suggest that with higher temperatures we can clog the shot, similarly to what we do with fine grinding.
Matthew McLauchlan from Common Man Coffee Roasters conducted his own test in 2015, that concluded the same thing.
Nitpicking Brewing Temperature
This is more of an informational than practical paragraph, and it is aimed at those who chase the God shot. When aiming for the perfect espresso shot, any minor change in brewing variables will determine a change in the output.
Let’s suppose you found the perfect recipe for your espresso shot. That recipe is replicable on your machine only. Well, I exaggerate a little,. If you use a high end semi-automatic, you should be able to replicate it on any similar model.
But let’s take a recipe for a single shot. If you try to replicate the same with a triple shot, you should play with the brewing temperature. The basket for a single absorbs less heat than the filter basket for a double, or a triple. Even if you preheat the basket, you can’t preheat the coffee grounds. You have in the basket three time more coffee grounds than in a single. That is going to affect the extraction temperature at least a little.
Knowing your beans is also important, and this is why many people just don’t change beans. There is an experimentation phase with any new beans you get, if you want great coffee. If you settle with average then you are probably fine with the default settings.
If you want to extract more sweetness, you need to raise the temperature a bit. But be careful, when you 9do that you risk to extract more bitterness and astringency. Especially if you pull longer shots.
Does espresso extraction temperature affect crema?
It looks like extraction temperature within the normal range, does not affect crema. Research has shown that espresso pulled between 190°F and 208°F has the same amount of crema. So if we stick to the recommended temperature range we should get a nice amount of crema.
However, a too low brewing temperature will lead to an under-extracted shot. Under-extracted shots will produce pale crema without the typical vibrant flavors.