Why Does 92 Degree Espresso Water Temperature Matter?

Water temperature is a decisive but often overlooked variable in espresso extraction. On most machines, a boiler or brew setting between 85 and 95 degrees Celsius is a reasonable working range, and many factory defaults sit higher, near 92 to 96 degrees Celsius. Raising the temperature increases extraction efficiency and dissolves more coffee compounds, while lowering it reduces them.

The effect runs parallel to pour-over brewing: hotter water extracts faster and more completely, cooler water extracts less. Machines also distinguish boiler temperature from the actual temperature at the group, and the gap between them grows with larger doses. Grind size, dose, ratio, time and pressure still matter, but temperature changes how all of them behave.

In espresso extraction, grind size, dose, ratio, time, and pressure are often the focus of discussion, while water temperature is frequently overlooked. In fact, water temperature also has a decisive impact on aroma, flavor, and strength. This article will discuss, from Front Street's perspective, the range of boiler temperature settings, the effect of water temperature on flow rate, the difference between boiler temperature and extraction temperature, and why the larger the dose, the higher the preset temperature needs to be. At the same time, drawing on Rao's views in "The Extraction Science of Espresso," it offers temperature recommendations for daily extraction and recommends Front Street Classic Espresso Blend coffee beans suitable for a rich mouthfeel.

For more specialty coffee knowledge, please follow: Front Street Coffee ( Frontsteet Coffee )

In the past, when Front Street introduced the key points of espresso extraction, it always explained parameters such as grind size, dose, ratio, extraction time, and pressure in great detail, and also devoted considerable space to analyzing operational steps such as receiving grounds, distributing grounds, and tamping. Only extraction water temperature was rarely discussed at length.

Front Street did this not because water temperature is unimportant for espresso extraction, but because in earlier years the boiler temperature of many machines was locked at the factory, making adjustment quite difficult. Therefore, in most cases people simply treated water temperature as a fixed value and relied on other parameters to work around it.

Today, however, newly designed models, or high-end equipment released in the past decade, basically all allow users to set water temperature freely. As a result, water temperature has become an important variable that can be flexibly adjusted during extraction.

What water temperature setting is generally appropriate for a coffee machine?

Generally speaking, a coffee machine water temperature between 85 and 95 degrees Celsius is reasonable. Some machines have a default factory temperature on the higher side, leaning toward 92 to 96 degrees Celsius. When learning pour-over water temperature parameters, we already know that the higher the water temperature, the higher the extraction efficiency, and the more coffee substances can be dissolved; conversely, when the water temperature is low, extraction efficiency is low, and naturally fewer substances are dissolved.

The principle of water temperature in espresso is the same as in pour-over. If the water temperature is set too high, it is easy to taste burnt bitterness and woody flavors. But high water temperature also has benefits: it can extract richer crema. The reason espresso in the past tended to be bitter was, on the one hand, that the coffee beans were roasted very dark, and on the other hand, that the machine boiler water temperature was set relatively high, which happened to also meet the need for producing thick crema. There are also some differences in extraction, with time usually controlled at 20 to 25 seconds (if it goes longer, burnt and sawdust-like flavors easily emerge).

If the water temperature is too low, the extracted espresso will be very sour, and the crema will not be rich enough. Therefore, in the past, mainstream espresso machines rarely had a water temperature setting below 92 degrees Celsius.

Water temperature affects the flow rate of coffee extraction

When the water temperature is on the high side, the flow rate of the coffee liquid tends to be slower; when the water temperature is on the low side, the flow rate is somewhat faster. High temperature allows the coffee puck to expand faster and simultaneously release gases. These gases block the water flow until they are pressed into crema and extracted, and only then does the coffee flow rate gradually increase. The higher the temperature, the more bubbles there are, and the greater the resistance to water flow.

When the temperature is low, the coffee flow rate is fast. To give an extreme example, when the machine is just turned on and the coffee boiler begins heating, the brew head can actually extract at this time, but the water temperature is very low, only about 60 degrees Celsius. If the same parameters are used to extract espresso, the extraction time will be greatly shortened, and the coffee will flow very quickly.

By the same principle, if you use a small-boiler coffee machine to make drinks continuously at high intensity, you will also find that espresso extraction gradually becomes unstable, with the flow rate getting faster and faster. Part of the reason is that after the boiler refills with water, the temperature has not yet caught up.

Boiler temperature is not equal to extraction temperature

The water temperature we can set is actually the water temperature inside the boiler. From the boiler to the moment it truly contacts the coffee, the water still has to pass through the dispersion screen and the portafilter (filter basket). If more than 10 minutes have passed since the last extraction, the temperature of the brew head (dispersion screen) will be relatively high. At this time, if the portafilter is locked on directly for extraction, the water in the boiler will absorb heat as it passes through the dispersion screen, causing the initial water temperature to be higher than the boiler temperature.

To avoid this situation, before locking on the portafilter, the brew switch is turned on first to release water and lower the temperature, bringing the water temperature close to the set value.

The temperature of the portafilter also affects the initial extraction temperature. If the portafilter is at room temperature, then at the beginning of extraction the portafilter will draw heat away from the water, and the actual water temperature will be lower than the preset value. Therefore, before receiving grounds, hot water should be run to preheat the portafilter (this is the same principle as preheating the dripper in pour-over). Of course, some people, for convenience, leave the portafilter locked on the brew head to keep warm when not extracting. Front Street does not recommend this practice; for specific reasons, click here to view.

During the extraction process, it is also impossible for the extraction temperature to remain consistent with the boiler water temperature throughout.

What temperature setting is appropriate for daily espresso extraction?

Here, Rao's hypothetical experiment in "The Extraction Science of Espresso" is cited: Italian baristas are accustomed to extracting espresso at 85 to 91 degrees Celsius, while American baristas prefer 92 to 96 degrees Celsius. The reason behind this lies in the different ratios. The Italian standard is 7 grams of coffee grounds to extract 1 ounce of espresso, while the American standard is 18 to 21 grams of coffee grounds to extract 1 ounce of espresso.

Suppose 30 grams of 88 degrees Celsius water is mixed with 7 grams of 27 degrees Celsius coffee grounds, and 38 grams of 95.3 degrees Celsius water is mixed with 21 grams of 26.7 degrees Celsius coffee grounds; the final mixed temperature in both cases should be 82.8 degrees Celsius. Of course, this is only a hypothetical experiment. But it illustrates a principle: coffee grounds absorb temperature, and the larger the dose, the more heat they draw away. To reach a certain extraction temperature, the preset water temperature must be raised.

Book cover of "The Extraction Science of Espresso"

The ratios we use today are similar to those of American baristas, both extracting a shot of espresso with a large dose, so the temperature selection needs to be adjusted to 92 to 96 degrees Celsius.

Of course, besides water temperature, there are many other factors affecting the flavor of espresso, and the most critical one is still the coffee beans. For friends who like a rich mouthfeel, Front Street Classic Espresso Blend coffee beans are recommended. This blend is composed of beans from three origins: Brazil, Indonesia, and Vietnam. It uses a dark roast, which maximizes the rich aroma of the coffee and also allows everyone to easily extract abundant and dense crema. Whether making an Americano diluted with water or a latte paired with milk, it is very suitable. It can be purchased and ordered at the Front Street Taobao store or the Front Street Tmall flagship store.

For more specialty coffee knowledge, please follow: Front Street Coffee ( Frontsteet Coffee )

The above content is compiled by CoffeeHunters, a coffee news website.