If you've finished your first week of the Home Barista Bootcamp, you've now got a good understanding of how important freshly roasted coffee is to your brewing, and perhaps you've even bought some specialty coffee from Coffeefusion! These beans have hopefully arrived, and have now rested long enough that you're ready to brew. This week we're going to understand how to extract the best from these beans, and learn the three basic parts of an espresso extraction.
The best way to digest this information is with the following video. Or if you'd rather read through, scroll past the video for more info.
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There are three main things that go in to Espresso Extraction - Dose, Yield, and Time.
Dose refers to the dry coffee grounds going in to the portafilter basket. In an ideal scenario, this is weighed using a set of scales and we should be aiming for an accuracy of 0.1g. The basket in your portafilter is usually rated for a certain amount of grams. If not, a lot of baskets have a ridge in them. The tamped coffee should sit somewhere around this ridge. Once we figure out the dose for our basket, we should keep this number consistent. For example, on my machine, my basket fits 20g nicely, so I always dose 20g of coffee into the basket.
Yield refers to the espresso that falls into the cup. These days it is often measured in grams so that you can make a direct comparison to the weight of the dose, however it was often previously measured using a shot glass in mL. For better coffee, we should also keep the yield consistent. A good starting point for yield is double the amount of the dry grounds. For example, if we dose 20g into the basket, we should end up with a yield of 40g. The relationship between Dose and Yield is often expressed as a ratio, in this case it would be 1:2. You can play around with your yield, but in the beginning if you aim to keep Dose and Yield consistent, it will be a lot easier for you to understand your extraction. You can weigh the espresso after your extraction, or if you have a measuring shot glass you can substitute grams for mL pretty easily, grams are just more accurate.
The last variable in our espresso extraction is time, which can sometimes be referred to as the flow rate. The time is counted from the moment you start the extraction, to the moment you turn it back off again. A typical espresso extraction should run for approx 26-32 seconds.
If your extraction runs faster than this (25 seconds or less), chances are you're going to underextract the coffee, and flavour-wise it will tend to taste sour.
If your extraction runs slower than this (33 seconds or more), chances are you're going to overextract your coffee, and flavour-wise it will tend to taste bitter.
If you extract in the 26-32 second range, you will tend to get a balanced extraction. Flavour-wise you can expect acidity, sweetness and body all working together in harmony.
Adjusting the Grind
So we now have what we call an "Espresso Recipe" - which is how to extract our coffee. It is often Expressed as 'Dose:Yield in Seconds' for example, '20g:40g in 26-32seconds'. But what do we do if our extraction doesn't run like this? For example, our extraction is too fast or too slow? This is where adjusting the grind on your grinder comes in.
If your extraction is too fast (25 seconds or less), it means that the coffee in your portafilter is too coarse. Make it finer and it will slow down the flow rate.
If your extraction is too slow (33 seconds or more), it means that the coffee in your portafilter is too fine. Make it coarser and it will speed up the flow rate.
If you have trouble with the understanding behind this, think of a bucket of rocks and a bucket of sand. With the bucket of rocks, there are lots of gaps between the rocks, and if you poured some water in it would flow easily to the bottom of the bucket. With a bucket of sand, the grains of sand fit together a lot more snuggly. If you pour some water onto a bucket of sand, the water will slowly absorb down through the sand, but it will take a while to get to the bottom.
Lastly, when adjusting the grind, keep in mind that when you make an adjustment, any coffee which has already been ground and sitting in your grinder will be at the old grind setting. There is also a little bit of grind usually sitting in the chute of the grinder. So when you make an adjustment, it might take a couple of shots before you see the result in the extraction. For bigger commercial grinders, we often waste 3-4 double shots worth of coffee so that we can see the result in our grind change straight away.
A note on Distribution and Tamping
When we are preparing the coffee in the portafilter for extraction, it is important to not only weigh the dose for consistency, but also make sure we create an even coffee puck. This is done by first of all evening out the coffee sitting in the puck, and secondly by tamping nice and straight. A coffee puck with uneven density or an uneven tamp will cause the water to run unevenly throughout the extraction and cause some big issues with the flavour.
Hopefully this blog post has cleared up a lot on extraction for week two. Your homework is to practice these steps and get yourself to a point where you can 'dial in' your coffee. If you need some delicious coffee to do this, you can support Coffeefusion by getting your coffee from us!
Excited for the next episode? Make sure you've learnt and practiced pulling shots and then click the link to move on.