For something that most of us require every single day of our lives, it seems unfair that coffee should require a fairly complex chemical extraction process. Temperature, particle size, and extraction time are the main variables one has to keep in mind when brewing the stuff and—yes—changing these variables will affect the flavour.
If, for example, your coffee is sour, your initial reaction may be to blame the beans, but there are two other parameters you may want to try adjusting first. Our own Alice Bradley was having such an issue with some coffee she received from Atlas Coffee Club, so she reached out to the company to see what was up with that.
The company explained over email that sourness could a result of two things: not brewing it long enough and too fine a grind:
If that coffee was a little sour when you tried to enjoy it straight, it may have been under extracted. When you don’t brew coffee long enough or the grounds are too large, this can easily occur. A quick fix for this is brewing your coffee for a little longer or adjusting your grind size to be a little finer.
If you have a drip coffee maker, extraction time isn’t something you can control, so try grinding it finer and see if that fixes the issue. If you use something like a French press, try letting the grounds hang out a while longer before straining them. If that doesn’t work, then maybe get new beans. Not everyone likes the same beans.