TDS? Extraction Yield %? - you may or may not have heard of these things. Well, you’ll either be glad or disappointed now but that’s the first and last time we’ll mention either of them in this series - because our aim is to keep things simple, remember?
Coffee is really no different to anything else. There are rabbit holes a plenty, littered around all over the place, ready to suck you in and chew you up. Extraction is one of those things that really does have the potential to cause some serious brain ache. So, what I’m going to try to do here is give you some basic information that is useful to you, information that you can take and use straight away to enable you to make better coffee. It will involve the use of imperfect analogies and we’ll definitely be leaving a lot of stuff out, because at this stage it’s really not important that you understand all the in-depth stuff, trust me.
Here goes. Once coffee has been roasted, it becomes soluble - or at least somewhere between a quarter and a third of each bean does. The rest is just the woody, organic matter that carries all those delicious flavours, sugars and aromatic compounds.
At this point it can be really helpful to keep one thing at the forefront of your mind. We’re not really drinking coffee at all, we’re drinking water. Now hopefully our water will be carrying some of that delicious coffee flavour but it’s still almost entirely water. If we’re making an aeropress or pourover, then over 98% of what we end up drinking is water and even a really strong espresso will only be around 10% coffee. Most of the coffee that we started to brew with is still at the bottom of our brewer, or in our filter paper, or in our espresso basket and it will soon be in the compost heap.
So, how do we ‘extract’ flavour from our roasted coffee and get it into our water? It’s time for an imperfect analogy!
It’s snowing outside but imagine that the snow is actually coffee (stay with me people). We’re going to go outside and fill a bucket with our snoffee (patent pending).
With me so far? - ok, so next we are going to make snowballs from all the snow we have in our bucket. We’re going to try to make them roughly the same size. We now have a bucket of snoffeeballs. Imagine that something magical happens when we make our snoffee into balls - the core of each ball (which makes up around two thirds of the whole ball) transforms into granite and around that granite core, there is a thin layer of ice which turns bright green and tastes unpleasant. Around that bright green layer, another layer of delicious sweetness followed by other layers which have distinctly fruity, floral, acidic and other flavours/characteristics. So, perhaps our snoffeeballs would look something like this if we were to slice them down the middle.
So, quick recap. Our snoffeeball is now made up of a hard core that won’t melt. This is surrounded by an ice layer that will melt but which tastes horrible and this in turn is surrounded by other layers that have various distinct flavours and/or characteristics.
Imagine we have a giant pan of water that is sitting at say 90 degrees. We’re going to brew our snoffee for 30 seconds, so we start a timer and we empty our bucket of multi-coloured snowballs into the big pan of water. After 30 seconds, we pour out our pan of water and snoffeeballs through a sieve. The water now contains some of our multi-coloured snoffee. What’s left of our snoffeeballs is caught in the sieve - including those granite cores, the bright green horrible stuff and, almost inevitably, some of our delicious snoffee. Now remember, this is an imperfect analogy. It’s not exactly what happens when we brew coffee but, for now, let’s keep going with this and have a think about what has been happening in the process we just completed so that we can improve the brew we make next time.
At this point it is good to state our goal:
We want to get as much of the delicious tasting snoffee into our water as possible whilst leaving behind only the stuff that tastes unpleasant.
Brewing coffee is similar in this respect. A tasty brew is actually comprised of a mixture of the fruity, acidic, floral, sweet and maybe even a little of the bitter stuff (the bright green snoffee). Our bright green layer is the last of the soluble material that we can access so in one way or another, we want to halt the brewing process before that part of our snoffeeball melts. At this same time, we need to make sure that we get as much of the other tasty stuff as possible. Remember, we’re looking for a balanced mixture of most of the soluble material that we have available. If we ‘under-extract’, then we may just have the acidic, floral bits but not the sweet and fruity bits that make the overall drink taste so wonderful. If we ‘over-extract’ then we get all the bright green stuff in there too and all our delicate other flavours are ruined by the drying, bitter notes which this layer contains.
We want to extract most but not all of the available soluble material. So, how do we make this brewing process more efficient? - There are a few ways, so let's look at the things that are easiest to control. It’s important that we think about these variables in isolation if we’re going to avoid confusion. So, as we look at each of these factors in turn, I want you to assume that EVERYTHING else is staying exactly the same as it was in our previous brew.
We can increase the temperature of the water in our pan. Easy one right? - hotter water means that our snoffee is going to melt into our water quicker. Conversely, if the water isn’t hot enough, then our snoffee will take ages to melt or it may not even melt at all, leaving all that delicious flavour locked away in our snoffee and destined for compost.
We can increase the amount of time that our snoffee is in contact with the water. As long as our water is hot enough, the more time that we leave our snoffee and water together, the more melting (or extraction) will occur.
We can make our snoffeeballs smaller. - so that they melt quicker. With coffee, we use a grinder to make changes to the size of the snoffeeballs - er, I mean the coffee particles.
We can put more water in our pan or use fewer snoffeeballs. It’s the same thing, right? This one may be worth dwelling on for a minute though as it’s one of those things in coffee that has the most potential to confuse. If we use more water but everything else remains the same, then we’ll get more of our ice (flavour) in our water BUT the resulting solution will be more diluted. So, here we have a slightly mind-bending idea that we have just created a drink that uses less snoffee but ends up being more flavoursome and weaker at the same time. If we turn this on its head and use more snoffee (or less water) then we’ll end up with a drink that may be ‘stronger’ (more concentrated) but less flavoursome. This is because in the first instance, we will have melted MORE of the snoffeeball into our water, so we will have more of the available flavour in our water and therefore more complexity and a better-balanced drink. In the second instance, we may well have more snoffee overall in the water but we may only have the blue and orange material and not the sweet/fruity pink layer.
Next time we’ll conclude this mini-series by applying this stuff more directly to how you might go about brewing coffee at home. We’ll look at a couple of different brewing methods and see how they differ and we’ll consider how you can work within your own limitations, whether those are caused by lack of knowledge or super basic equipment.
If you want to dig deeper into any of this stuff and share your thoughts, ideas and wisdom with others, why not check out our Discord server. Until next time, Happy Brewing!