Anthony Lawrence of UCC simplifies the fundamentals of calibration

Coffee calibration

Anthony Lawrence of UCC simplifies the fundamentals of calibration and the common pain points that stump new baristas and even those at the top end of their coffee career.

Preparing and serving espresso is a relatively simple procedure for a barista. Coffee is ground for us at the touch of a button, tamping is automated providing we have a Puqpress device, and when we load the portafilter into the coffee machine, the volumetric panel distributes water for us.

Despite most of the work being done by equipment, there is still an essential element during this process that will always need attention and skill from the barista, which is calibration. Coffee calibration is a necessary process when it comes to extracting our coffee correctly and consistency. Calibration, simply put, is when the barista needs to adjust the way espresso is extracting at the grinder. This is achieved by altering the rate of the flow of water by allowing it to run faster or restricting it to run slower so the flow rate aligns with the extraction time window. Coffee shops today spare no expense to ensure that this can be achieved, however the process is still deemed to be difficult and frustrating by new baristas, and seasoned veterans alike.

As a trainer for UCC Coffee, I have the opportunity of interacting with many baristas across the country with varying levels of understanding of espresso making. At the beginning of each class, I seek areas of opportunity for learning, and coffee calibration is the most common subject cited as “difficult to grasp with confidence”.

So why is it that baristas with several years’ experience and baristas who are just beginning their coffee journey stumble when it comes to calibration? How can we identify potential barriers of understanding in the calibration process, and better

understanding when and what to change so we can help baristas correctly adjust their equipment with ease and confidence?

In this article, let’s identify and breakdown calibration to the fundamentals. We need to streamline the language used around extraction definitions, analysing extracted coffee shots, and the calibration approach so baristas can check, change,
and serve coffee quicker and with more confidence. Calibration should be a platform to deepen and further a barista’s understanding and appreciation for producing coffee.

Simplifying coffee

Espresso is an incredibly expressive food. From plant to cup, each step of the journey affects the flavour in the final brew. This is essential to understand, especially when it comes to the quality of coffee served to customers. Coffee possesses thousands of flavour compounds, which are easily affected by varied environmental factors within the café. However, we can distil coffee factors to their fundamentals to define the limits for correct and incorrect extraction: Sweet, Sour, Bitter.

“Sweet” is correct. “Bitter/Sour” are incorrect. Sensory learning and understanding of what to taste in espresso is a subjective process from individual to individual, so aligning perception across a team with varying experiences and understandings of coffee flavours can be a complex process. That said, we all have a close understanding of the sensation of ‘sweet, sour and bitter’ in the food we eat, so we can use these as tools for defining the parameters we are working within during coffee service. We can approach espresso extraction as achieving “sweet” coffee and avoiding coffee that is “sour” or “bitter”. This is especially helpful when also needing to balance other events that occur during a typical coffee service.

Since there are so many events that can happen during service at any one time, it is better to focus on what you can control rather than what you can’t. For example, when a hopper runs out of beans which can cause the coffee to run quicker, or when the humidity gets higher from a sudden shower causing the coffee to run slower. Baristas cannot control when this occurs, but they can control how they respond to them, which is to make an adjustment at the grinder to correct the change that happened.

Simplifying what to check

Too often a barista runs into difficulty with successfully calibrating their grinder because the times and grind settings are not connecting correctly. For example, an underdosed coffee shot that runs too short needs to be dosed higher before the grinder settings are changed. This is the most common mistake I have observed when a barista is having difficulty calibrating.

If the coffee dose is shifting too dramatically from one fixed point, the water flow will be too inconsistent, thereby any adjustment will be imprecise. As most commercial coffee recipes have dosing limits (for example 20 grams ± 0.5 grams) anything outside of these
values cannot be considered because they produce inconsistent waterflow throughout the coffee bed. A coffee shot dosed at 19.5grams will run too quick, like an under extracted shot. Similarly, a shot dosed above 20.5grams will run too long, like an over extracted shot. This mistake happens because of a lack of understanding of the relationship between each element of the coffee brew recipe or more accurately, the relationship between coffee dose, water volume and time.

With this in mind, correct dosing is the single variable that baristas must monitor manually during calibration in order to accurately assess the recording of time to inform the subsequent grinder change.

Simplifying what to change

Many of my students can identify and differentiate when a shot is running too fast or slow and what the likely cause is, only to then make an incorrect adjustment at the grinder. A solution to avoid this crossing of wires can be to simplify the definitions of the modes of espresso to align with the grinder settings. Before we change/adjust the coffee grind, we need to think about what is happening inside the grinder. In order to visualise which choice to make and by how much, it is best to reduce definitions and descriptors to fit into the actions needed to be taken to the correct course.

Rather than having the barista assess the extraction rate, time, grind setting and then decide the appropriate grind adjustment, we can just as successfully assess, then change by redefining the states of ‘over’ and ‘under extraction’ as ‘too fine’ and ‘too coarse’ respectively.

Seeing that any typical grinder used in the industry has these settings to alter the coffee sate to be coarser or finer, if our current coffee shots are running too much on one mode, then the inverse is simply needed to be applied. This should render the whole process as a simple measurement of time and its lower and upper limits. All we must do is ensure we have dosed correctly when the shots run less than or more than those limits.

Putting it all together

We need to observe all the coffee shots we pull to ensure consistency of quality. Therefore, it could be argued that we are calibrating each time we prepare a shot of espresso. Providing we follow the steps above and apply them to our workspace, it is an achievable outcome to adjust our grinder with as minimal effort or fuss as pressing the relevant volumetric button on our coffee machine. If we can recognise and assess our coffee shots easier, than we can calibrate easier and serve delicious and consistent coffee with confidence and excitement.

This article appears in the February 2023 edition of BeanScene. Subscribe HERE.

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