Published: Jan 30, 2017

The Most Important Thing About Brewing Coffee

This week I’d like to explain the concept of an even extraction, and what it means for flavour. The rabbit hole of evenness goes really really deep. I’m going to devote a number of weeks to discussing it. I want to drill right down into green coffee, roasting, grinding and brewing from the very specific viewpoint of evenness. Evenness is likely much more important than you have ever given it credit for. I hope to change that!

Throughout my Barista career, so many of my teachers and peers have told me to extract evenly. “Don’t do x or the extraction won’t be even” and “Do y to even out the extraction” etc. but I never really understood what an even extraction meant, and how it affected the flavour of a coffee. It’s one of those things that gets passed on mindlessly because it sounds good. So what is evenness anyway?

As I mentioned in the very first hustle, extraction is kind of like a two way street. At one end is over-extraction, and at the other end is under-extraction. Our goal, it seems, is to find the magical spot in the middle where everything tastes good so we can call it a day. Unfortunately this isn’t so accurate.

Every coffee grind is a slightly different size and shape, experiences a different flow and duration of water, and comes from a slightly different portion of the coffee bean. This means that every brew is a mixture of hundreds and thousands of individual tiny micro-extractions. Some are extracted more, some are extracted less, some sit in the middle. It’s this cacophonous mix of different extractions that all work together to make a cup of coffee. When we measure an extraction or talk about an extraction, we’re using the average of all of these micro-extractions to give us a number or general zone. Every single coffee that has ever been brewed by anyone is at least a little bit uneven. A sobering fact indeed.

An even extraction is obviously one where all (or at least a majority) of these micro-extractions sit closely together. Hopefully at a point where things are delicious.

An uneven extraction is one where there is a significant difference between large portions of these micro-extractions. This results in a cup that tastes like at least two of the three typical extractions – over, under or ideal – and everything in-between.

We’re going to brew an imaginary plunger (french press!). In it, you pour 30g of a very fine grind, and 30g of a very coarse grind. You pour 1 litre of boiling hot water in, stir it all around, and wait 1 minute. At the end of that 1 minute you have a really uneven extraction. Half of the grinds will be completely extracted, and the other half’s exterior surface area will be extracted, while their interior will still be hopelessly under-extracted. This is textbook uneven extraction; there are significant portions of coffee grinds that are sitting at different levels of extraction.

Let’s think about this plunger as if it were sitting on Extraction Street. It’s not just a point on a line anymore. It’s actually a range of extractions along that line simultaneously. Some of it is over, under and ideally extracted at the same time. It’s a street, so I’ll be using cars to communicate where a brew is. Obviously.

That limo is sitting across lots of different zones of extraction. Not ideal.

[Hustle Nomenclature] I like to call this span or range the “extraction spectrum”. An uneven extraction has a wide spectrum. An even extraction has a narrow spectrum. I’m going to use this term from time to time because it greatly simplifies sentences about complex stuff. That, and I enjoy the word nomenclature. Nomenclature.

The shape of the spectrum (car) can move around the scale to describe any kind of extraction. But the total size of this spectrum doesn’t change. That’s really important. The shape we’re seeing represents the whole brew. If more of the micro-extractions are ideal then it’s thicker at that point. If there’s lots of over-extraction then it’s thicker up there instead. So obviously the most ideal extraction would be very thick at the sweet spot right before over-extraction. This would be considered a perfectly even and indescribably delightful cup of coffee. Rest assured, you’ve never had anything close to it. Bummer.

Extraction Street vertical Limo This doesn’t happen. Most extractions look more like the following. A bit of over-extraction, an ok amount of even extraction and less under-extraction. It’s kind of like one of those awkwardly aerodynamic solar cars. Or those weird cycling helmets. Extraction Street SolarThe problem here is that this shape of extraction spectrum is kind of non-negotiable. You can’t just press the “more even” button on your grinder. Your particular combination of coffee/grinder/brewer/technique is creating that unevenness. If you extract more, the spectrum moves along the line and more of it becomes over-extracted. If you reduce the extraction, there is less over-extraction but less of the coffee is sitting at the sweetest point. The flowchart from last week aims to move this spectrum to the point where there’s the most coffee sitting at the sweetest point, without too much over-extraction. Use it.

So our goal is to make this spectrum as tight as possible. Because then more of it can exist at the sweetest spot. Every time you improve the evenness of an extraction, you move more of the coffee into the most delicious zone of extraction. This means you get more delicious flavours

. coffee extraction animation

You’re moving that coffee from a point where it contributes bad flavour to a point where it contributes good flavour! This means that for every micro-extraction that becomes even, there’s a +1 for good flavour AND a -1 for bad flavour. That’s a +2 level up for Deliciousness!!

Are you with me here? 1 unit of evenness = 2 units of deliciousness. More good stuff and less bad stuff at the same time. How many times have you ever made one improvement to coffee and received two-times the results? It’s magic. It’s the best. I’m obsessed with it. Evenness is incredible: get on board.

I really need to impress upon everyone reading this just how important evenness is for flavour. So here’s my favourite example.

VHS was really great. We got to see movies and hear sound at the same time. Then along came DVD. And Blu-ray. “Whoa” we all said, “VHS is so terrible!“. The movies didn’t change. The story-telling was the same, the actors were still beautiful. But the image and sound, the experience, was so much clearer and detailed! This is a super close analogue to the difference you experience when going from an uneven extraction to an even extraction. It’s the same coffee, with the same flavours. But now you’re getting so much more clarity, transparency and intensity of interesting flavours and so much less distracting and muddling dryness, sourness and other extraction taints.

BelleBelle in delicious High Definition, vs crummy old DVD. Kind of like going from conical to flat burrs?

Remember in the first Hustle when I talked about extraction faults being generic? They’re boring and don’t taste like the coffee you’re actually trying to present. An even extraction reduces the amount of generic, boring extraction taints and replaces them with delicious, sweet, complex and ideal extraction flavours! This is Specialty Coffee after all. We want our customers to pay more for a premium product. Even extractions deliver them more premium flavour.

The beauty of an even extraction is startling. It’s like someone has lifted the veil on a coffee.

Have you ever been frustrated with an espresso because it tastes like… espresso? That typical, boring “espresso” flavour you can’t get rid of. And behind it there are these hints of acid or sweetness but they’re not strong enough to really take shape or be identified. Well, an even extraction scrubs that generic flavour away and replaces it with the those delightful background flavours. They’re now in the fore. Instead of a coffee that “kind of tastes a bit tart” you now have an coffee that “tastes like I’m biting into a Ramson plum that’s perfectly ripe and has wonderful crystalline sweetness and perfumed skin”. It’s amazing. Who wouldn’t want this?

Tighten your extraction spectrum and deliver your customers a coffee that truly represents its provenance, rather than under or over-extraction. Make your extractions more even and the coffee will be better, every time. It’s the most important thing about brewing coffee!!

The next few hustles will be devoted to evenness. In depth at the farm, roasting, grinding and brewing stages. Get ready!


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