Advanced calibration: the different stages of espresso extraction

Traditionally, espresso coffee was made with a sensory approach, which would require months or even years to master. It required baristas to develop a sensitivity to the way the grind looked, the volume of coffee in the basket, the speed and time at which it extracted, and the way it looked, smelled, and tasted. 

Fast forward in time, and through the development of tools and technology, we swapped our sensory approach to espresso production for a scientific recipe of numbers, scales, refractometers, and pressure. These tools have helped baristas achieve quality control and simplified our lives by providing useful facts and numbers to work with. But imagine for a second we lost all of this technology. Could you still produce great tasting coffee?

I believe the future of quality espresso extraction comes from marrying sensory skills with the measurable variables. It’s not easy if you have spent most of your career on either side of the spectrum. I personally started at a café that took a 100 per cent sensory approach. I didn’t touch a scale until three years into my barista career. When I heard of guys who had only ever used scales, I would almost judge them. “Don’t you know how to pull great espresso without a scale?” What I didn’t realise at the time was the massive time saving and consistency benefits of working with a recipe as a starting point. 

Your roaster has most likely spent a lot of time and energy creating a recipe or guide for what they feel best represents their coffee and this should be respected. However, you as the barista are the ‘door keeper’ to the final recipe. You are the one who has the power to adjust a recipe for the best interest of the coffee and what your customers will enjoy. 

If you follow a recipe to a T and the coffee still tastes bad, what would you do? Before you get on the phone to complain to your supplier, look at the variables that could impact on the extraction and flavour outcome, and adjust. This can include humidity, temperature, time since roast, light, air, tamping technique and pressure, equipment functionality and cleanliness, dose volume, grind size, origin of bean, type of roast, heat, and milk pouring technique. 

Diagram 1.Key factors to a good espresso.

The three key factors to a good espresso extraction include: [see diagram 1]

• Dose: the amount of coffee, usually measured by weight in grams. 

• Grind: the particle size of the coffee, in regards to coarseness or fineness. 

• Time: the duration to extract the coffee. 

Everyone has their own method of calibration. Tom Hespe from Toby’s Estate has more than 20 years of experience in the coffee industry. For single origins, he likes to dose slightly lower compared to blends, and uses a naked group handle to get a better visual of the pour. He also likes to run things to the extreme by pulling shots super-fast, and then super-slow to experience the full range of flavor the coffee has to offer. He also recommends calibrating with a few people as you can bounce ideas off each other and get some exciting results.  

Now, to produce a well-rounded and balanced espresso shot, let’s understand the four stages of exaction: 

1. Initial extraction. This runs for roughly one to 12 seconds, also known as a ristretto. This stage is responsible for achieving dark, rich, and syrupy notes in the cup. 

2. Middle extraction. This occurs at about 12 to 22 seconds into the shot. It is responsible for achieving balance in the cup. 

3. Diluting the shot. This is the end phase at about 22 seconds and is where the colour of the extraction is light and a bit flat in flavour.  

4. The yield. This is the last phase where the volume of espresso is extracted coffee. 

These timings are just a guide. You may have a bean that really comes alive when dosed a bit higher and tighter, running up to 40 seconds, and that’s OK too. You may be using a different grinder where quicker shot times are the norm. The point to understand is how each stage of the extraction impacts on flavour. 

Diagram 2. How espresso extraction correlates to flavour.

Now let’s identify the key sensory factors in espresso extraction: 

• Speed of the pour. Did the espresso come gushing out of the group handle or did it drip out super slow and take a long time to come to a steady stream? 

• Colour. Did the colour change nicely over time or did it lighten up really quickly? 

• Smell. Does the espresso give off a nice aroma or is there a metallic/pungent note? Smell can be difficult to assess due to the fact that coffees are roasted from light to dark and this will impact on overall aroma.

• Taste. Look for a balance of sour, bitterness and sweetness. 

• If your espresso is tasting bitter, maybe the grind is too fine. You might have put too much coffee in the basket or run the shot too long.

• If your espresso is tasting sour, your grind might be too coarse, your dose too low, or you stopped the shot too soon. 

Unless you are using a volumetric machine you will need to learn when to stop the shot. We don’t have to be too technical about it. Once the shot starts ‘blonding’ and the stream wiggles or thins out, it’s a general sign that you have fully extracted the coffee. I encourage you to play around with this to find what works by stopping at different times and tasting the coffee. 

If you use a volumetric espresso machine that stops when a certain volume of water has gone through the coffee, you still need to observe what the shot looks like so that you are correctly setting your dose and grind, and not just running on autopilot and sacrificing flavour. 

This article appears in the August edition of BeanScene. To read the story in FULL, subscribe now.

By Kyle Rutten, National Training Manager of Suntory Coffee Australia.