The two major tastes in a balanced cup of (black) coffee are bitter and sour with a balanced cup having an equal amout of both. An unbalanced cup would be either very bitter or very sour. Some people like their coffee mostly bitter, and some like it mostly sour (“bright” and “fruity” are other words used to describe the sourness), but the goal of most professional Barista’s is to create a cup that contains bitterness and sourness (in a balanced way) with many more complex flavors also present underneath these two major ones.
If coffee is mostly bitter it may be because of a few factors. Dark roasted coffee is more bitter because the sour tastes have been eliminated through roasting too long. Conversely, a light roasted coffee is more sour because the sour tastes are still present. Other factors such as processing also affect the bitter / sour balance. A dry processed coffee (also called a “natural” processed) is inherently more sour than a washed “wet” processed coffee.
Another very important factor is when the coffee is consumed after it is roasted. Coffee consumed immediately, or very shortly, after it is roasted is much more balanced than coffee that has been sitting for awhile post roast. Roasted coffee naturally becomes more and more bitter the longer it sits after roasting. This is because the sour tastes deteriorate and decompose fairly quickly after the coffee is roasted leading to a very bitter brew. Most coffee drinkers are not aware of this factor which is the most common cause of a bitter unbalanced cuppa. If the coffee you are drinking is bitter tasting, the very first thing to investigate is when that coffee was roasted. If within 3 days, the sourness should still be present. The very next thing to check is how dark the roast is. Most likely it is an espresso roast, or a french roast, with the coffee beans appearing shiny on the surface due to the oils being exposed.
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