How to Taste Coffee Like A Pro
Extraction is everything that the water takes from the coffee.
It’s pretty easy to sum up, but a lot more difficult to understand and apply.
When you mix coffee and water, a lot of things happen. The most relevant and easy to understand of all these things is that water dissolves a lot of coffee’s flavours. These dissolved flavours make up (almost) everything you taste when you drink a cup of coffee. The rest is undissolved stuff. This is mostly very very small coffee grinds that affect mouthfeel, but can’t be included in extraction because they’re just floating around in the water.
Roasted coffee beans are ~28% (by weight) water-soluble. This means that you can extract ~28% of the coffee bean’s mass in water. The rest is pretty much cellulose and plant stuff that forms the structure of the seed.
Water is pretty good at dissolving those soluble chemicals, but it needs help. If you throw a handful of coffee beans in hot water, you don’t extract much more than the outside layer. This is because the coffee bean’s structure is incredibly dense and complex; water can’t just pass through and collect all the flavour on its way. To help, we have to increase the surface area of the coffee beans; we need to ‘open them up’ so the water can easily get at all of the flavour. This is achieved rather handily by the use of a coffee grinder. It crushes the beans into a powder, exponentially increasing their surface area and allowing the water to do its work.
In an ideal world, we’d crush the coffee into an extremely fine powder, throw water at it and dissolve all of its delicious flavours. Unfortunately, this results in a terribly bitter and awful cup of coffee. Not all of the coffee’s flavours are good, so we have to control the amount of flavour that we extract in order to make a palatable cup.
We also can’t just use more coffee grinds and extract less of them to avoid those over-extracted flavours. Under-extraction tastes terrible as well (more on this in a moment).
Under-extraction occurs when you haven’t taken enough flavour out of the coffee grinds. There’s still a lot left behind that could balance out the following undesirables.
Cast your mind to a shot of espresso that was far too short; a ristretto of a typical Specialty espresso roast. It’s sour, lacking sweetness, weirdly salty and has a disappointingly quick finish. These four things are the most obvious indicators of under-extraction. Let’s go through them in a little more detail.
This is a tricky one, especially with our desire for acidity in coffee. A lot of people think that acidity and sourness are the same thing. However, that couldn't be further from the truth.
To clear this up, I always define sourness as being negative. A sour flavour hits you quickly and aggressively. It creates an immediate physiological reaction, you might pucker your lips or it might feel electric or sharp on the sides of the tongue. Sourness is undesirable and distracting.
Acidity can be both a good and a bad thing, a beautifully balanced acidity can bring another dimension to an otherwise overly sweet or bitter coffee, balancing out the compounds to add a subtle, yet noticeable sparkling sort of sensory feeling.
In my opinion, the most important aspect to a coffee’s flavour is its sweetness. Sweetness is the best. Have you ever heard someone say ‘this espresso is too sweet!’? Think about that for a second. I strongly believe that we should always be chasing sweetness. It’s my holy grail: something that’s really difficult to find and stupendously rewarding once you get it. Under-extraction isn’t sweet. It’s far from it. It almost always displays an emptiness that leaves you with an unsatisfying ‘I-want-more’ feeling after drinking. The good thing about this lack of sweetness is that it also accentuates the sourness, making under-extraction much more obvious.
A well extracted coffee has a finish that lingers for minutes (or hours if you’re lucky). This finish can feel as though someone has left dark brown sugar on your tongue, or as though you’ve just finished a toffee. Yum!
An under-extracted coffee doesn’t have this finish. Once you swallow, it disappears straight away. You’re not left with any pleasant lingering sensation. It’s an abrupt and unsatisfying end to your coffee experience.
Over-extraction occurs when you take too much of the soluble flavours out of the coffee. This level of extraction results in unfavourable flavours.
Cast your mind now to an espresso of a typical specialty espresso roast that brewed for 40-50 seconds. Don’t pretend like you didn’t taste it when this happened once. It’s bitter, drying and hollow. These three things are the most obvious indicators of over-extraction. Let’s shine some light on them as well.
We’ve all been here. Coffee is bitter. Over-extracted coffee is really bitter. Unless I’m drinking Campari, I don’t want that much bitterness. A lot of this bitterness comes from caffeine, but there’s many other chemicals in coffee that contribute. A darker style roast that has achieved dry distillation will have many more of these bitter chemicals.
Dryness in coffee is so incredibly bad because it’s such a strong sensation, and it can last a long time. This sensation is called astringency and is the same as you get from unsweetened black tea, young red wine or white wines with extended maturation time. In wine, this effect is caused by polyphenols: chemicals that are readily found in plants, seeds, bark etc. These are arguably the same chemicals that cause dryness in coffee.
Polyphenols are bitter and bind to your saliva’s proteins. In simple terms, they de-lubricate your tongue, creating a sandpapery or dry sensation in the mouth.
Lack of mouthfeel
Well extracted coffee fills your mouth with richness. It’s luscious, smooth and, well, mouthfilling. Over-extracted coffee is empty, hollow, rough and just plain-old yucky. It’s this lack of flavour and character (rather than the presence of a particular flavour) that leads me to use the word ‘hollow’.
Those are the key over-extracted flavours. Of course there are more, but these are super simple to identify, and should have you identifying over-extraction in no time