Brewing temperature is a variable that can be readily altered with the correct espresso machine, but it’s not something that every coffee business prioritizes in the morning. On the contrary, many cafés use brewing temperature to accomplish everything else, from fine-tuning the grind to resolving issues with the grinder temperature, and so on.
However, because of the nature of espresso production, changing the temperature does not necessarily have the same straightforward effect on the extraction process as we might assume. Changing one variable in Espresso will inevitably impact many others, making it impossible to distinguish between their products. So. This post will look at some of the espresso machine temperature control challenges. The relationship between extraction temperature and other parameters and the effect of temperature on flavor extraction efficiency in coffee (e.g., coffee grind).
To better understand the effect of brewing temperature in other techniques (besides Espresso), you can also see Ideal water temperature when brewing coffee.
Temperature & Espresso
The majority of people prefer Espresso extracted between 85 and 95°C, according to decades of trial and error (A Illy and R Viana, 1995). The temperature range for specialty coffee is relatively narrow: 90 – 95°C. However, there are substantial flavor variations within that narrow spectrum to be discovered.
Ted Lingle’s research (The Coffee Brewing Handbook, 1996) clearly shows two things: higher temperatures extract higher ratios, boosting sweetness (sweetness), bitterness (bitterness), and body while somewhat lowering acidity (Acidity). Lower extraction rates result from lower temperatures, a more petite body, sweetness, anger, and more prominent acidity.
The temperature at which the brewed water leaves the group head and comes into contact with the coffee is called “extraction temperature.” Different devices control this differently, depending on the machine’s design.
Modern multi-boiler espresso machines frequently enable exact temperature adjustment at the exit. It’s critical to understand how steady your machine’s temperature is and whether hot water suction from the boiler or excessive group head discharge affects it. On the other hand, some devices may need to drain for longer than usual to keep the phase temperature stable.
Effect of brewing temperature on espresso extraction
It’s common knowledge that raising the temperature speeds the extraction process. For starters, this is due to two factors: The molecules in hotter water travel faster. This means they’re more likely to collide with the coffee’s dissolved chemicals, speeding up the extraction process. On the other hand, the temperature impacts the solubility of each substance that may be dissolved in water. This quantity is referred to as the substance’s solubility.
Each compound’s solubility is affected differently by temperature. At increasing temperatures, gases become less soluble, so boiling a kettle removes dissolved gases. Many solids become more soluble as temperatures rise, but others are less impacted, and others become less soluble.
In general coffee making, increasing the temperature means increasing the extraction rate. Most compounds in coffee dissolve faster at higher temperatures, so they are easier to extract – Baristahustle
There is an exception to this rule: gases like CO2 become less soluble at higher temperatures. As a result, CO2 plays a crucial role in espresso extraction, interfering with extraction by adding to the water flow resistance (D Albanese et al., 2009; S Anduesa) et al., 2003).
Effect of brewing temperature on taste
To begin with, raising the temperature increased not only the time and amount of substances to be extracted but also the proportions of the various compounds removed. In The Coffee Brewing Handbook (The Coffee Brewing Handbook, 1996), Ted Lingle demonstrated that increasing the brewing temperature from 70°C to 94°C increased the sucrose content while keeping the citric and malic acid levels the same. Unaltered. On the other hand, phenolic chemicals (which give off the smells of smoke, burning, bitterness, and bitterness) are susceptible to temperature changes, but chlorogenic acid or caffeine is not.
Researchers discovered increased quantities of ketones and aldehydes associated with fruity and fresh aromas in Espresso extracted at 92°C compared to 88°C ( Anduesa et al., 2003). Meanwhile, the concentration of pyrazine (roasted, earthy, and musty tastes) increased dramatically at temperatures above 96°C. This indicates that changing the extraction temperature can change the flavor balance, even if the overall extraction time stays the same.
Denaturation of flavor: As temperatures rise, some chemicals begin to denature. Because these molecules were broken down, the researchers reported decreased quantities of chlorogenic acid (CGA) and trigonelline at 96°C. CGA breaks down into caffeic and quinic acids (K Izawa et al., 2010) has a bitterer flavor than chlorogenic acid – see also Coffee Acids
The relationship between temperature and other factors
You’ve probably grasped the significance and influence of dispensing temperature, but the problem is that not all espresso machines react to temperature changes in the same way. The phase temperature is well-stabilized in most current multi-boiler devices. The temperature range in earlier dual boilers (and heat exchangers) is quite extensive.
You can refer to Compare Espresso HX and Double Boiler to understand the advantages and disadvantages of these two models.
The machine has multiple boilers allowing the extraction temperature to be set independently of the boiler. This allows for more precise control of the dispensing temperature making temperature changes much more accessible. The temperature can usually be changed in the machine’s programming menu.
Temperature and Flow
One reason the extraction process doesn’t respond to temperature in the way we expect could be the variable flow rate. Higher temperatures lead to lower flow rates in Espresso (Corrochano et al. 2015), altering the temperature on extraction.
This effect, influenced in part by gases (CO2), as mentioned above, creates additional resistance to water flow. At the same time, water also becomes less viscous at higher temperatures – enough to affect espresso brewing time (Fekete, 2019). Lower viscosity makes the flow more turbulent; increased turbulence can increase the extraction of heavier, less polar molecules, often bitter and astringent.
Temperature from the coffee grinding process.
In the end, the grinder generates a lot of frictional heat, which is absorbed by the coffee beans and changes the temperature equilibrium that we calculated earlier. A poor hero can take the ground coffee from room temperature to 50°C or higher. Enough to compensate a few more degrees for the extraction. It’s time to rethink your espresso grind.
The studies at Baristahustle can make this clear: If we use 20g of coffee powder to make 40g of Espresso (which is about ~65g of water). Where the Espresso machine is set to the standard temperature of 93˚C, and the coffee powder is at room temperature 20˚C, the result will be a cup of coffee at ~ 86.2˚C; However, in a busy coffee shop, the grinder can quickly spit out coffee beans at 50˚C, we get a cup of Espresso 89˚C.
Finally, it can be seen that temperature has a significant effect on Espresso’s flavor balance in not-so-simple ways, which is a tool to help unlock the best flavors from the coffee. But changing temperature affects different compounds in quite different ways, making it difficult to calculate the exact impact of the change on the taste of the Espresso. Finding the ideal temperature for each coffee, there’s no better way than experimentation.