Have you tasted a cup of coffee and felt that it's bitter, & brushed it off because you've been told that coffee is sometimes bitter? All good cups of coffee should be a burst of good flavour, not an overpowering dose of bitterness. So why does it sometimes end up bitter?
Is it ok for coffee to be bitter?
Coffee is often associated with bitterness. While bitterness can play a role in a good cup of coffee, if you drink a really good cup, you'll find that that bitterness is far from the dominant taste. Instead you get a variety of flavors, from floral to spice notes to chocolate notes. In fact there's an entire flavor wheeldedicated to describing good coffee.
So if bitter is all you taste in your cup, there's a good reason for it.
Coffee brewing is a science, the main reason for bitter coffee is over extraction. This is the process that pulls the flavour out of the coffee, turning clear water into that delightfully dark brew. When water mixes with the coffee grounds, a chemical reaction happens that dissolves flavour compounds.
The trick is extracting the good ones, and not the bitter ones, which come out with more time. With that in mind, here are a few things that could account for that bitter cup, and that you can easily avoid next time around.
i) Letting it steep for too long
This normally happens when making French press coffee, people have a tendency to leave the coffee in the French press even after they have pushed the plunger down. By doing this, the coffee will continue to extract, and your second cup of coffee will inevitably be more bitter than the first. If you have the habit of having your coffee leisurely, transfer it to a thermal carafe to keep it hot & slowly sip it.
ii) Wrong grind size
Grinding coffee beans changes how the flavour compounds dissolve. What this simply means is that if it's too coarsely ground you risk under-extraction, this in turn gives you a flat or perhaps sour tasting coffee. But if they're too finely ground, you risk an over-extracted, bitter coffee. Different brewing methods will require different grinds, and sometimes you need to experiment to figure out the sweet spot, but if you're getting a bitter cup chances are your grounds are a little too finely ground. Do check on the right grind size for the various methods.
iii) Water is too hot
Water temperature plays a key role in coffee brewing, and if it's too hot you'll extract the bitter compounds. 90°C to 96°C is known as the temperature ideal for optimal extraction. Water boils at 100°C, so in layman's terms, that means not letting your water over boil, and letting it sit for just a minute before pouring over your grounds.
Look out for the above, & ensure that you never have a bitter cup of coffee anymore.