coffee extraction and how to taste it

extraction problems

this post will cover some basic extraction theory and the tastes associated with over, under and ideal coffee extractions.

extraction is arguably the most important and least understood aspect of coffee brewing. ıt's everything. without extraction, you don't even get a cup of coffee. here's my super simple and not 100% accurate definition: 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. for now, i don’t want to delve into fats and lipids and the micro-componentry of extraction. i want to communicate useful and relevant information, like how to taste extraction and how to manipulate it. chemical analysis can come later.

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.

we always try to steer the coffee towards the middle; avoiding both over and under-extraction in the extraction.

writen by matt perger