Just as with red wine, cheese, whisky and almost everything else worth savouring, we can sometimes go a little overboard when discussing the flavours of coffee. I’ll try not to.
The taste of coffee can be described as combination of: flavour/aroma, sweetness, acidity, bitterness, and mouth-feel.
Some biologists (and I) argue that mouth-feel can be considered an element of taste. Mouth-feel, or what some call the coffee’s texture, can be described as creamy, buttery, syrupy, thick, or even thin/watery. So while it may not be a taste, mouth-feel will affect how we interpret and perceive coffee as we drink it and so it will affect our judgement of the taste of a coffee being drunk.
Coffee’s flavour is detected by the tongue, which senses varying strengths of sweet, sour, bitter, salty and savoury. These elements of the final flavour are created during the roasting process when the raw coffee beans are heated to initiate the Maillard reaction, i.e. the caramelising of the sugars, which also accounts for the browning of roasted beans. Between 5 and 10% of a coffee bean is sugar and the highest sugar-level is achieved by harvesting the coffee beans when the coffee cherry (the bean is the seed inside the coffee cherry) is fully ripe.
There are three different acids in coffee which, together, give coffee its varying tastes of green apples, ripe grapes, or citrus fruits. The higher the altitude the coffee plant is grown at, the more acidic the coffee tastes. Brazilian coffee is grown at low altitude and therefore tends to be low in acid. The best of the Ethiopian beans are grown at high altitudes, i.e. around 2000 metres above sea level. The acid in these coffee beans is what generates what we often perceive or describe as freshness. Coffee’s acidic freshness balances its sweetness.
There is some confusion between acidity and bitterness. Fresh, ripe pineapples, apples, lemons, oranges, grapes etc. taste pleasantly, refreshingly acidic. Consider apples and pears – both tend to have similar levels of sweetness, but apples have more acidity than pears, which explains why apples tend to have a richer, fresher taste profile than pears. Acidity in coffee gives a fresh, not a bitter, taste. Unripe fruit tastes bitter as do burnt/over-roasted coffee beans. Bitter coffee is likely made from robusta beans which are typically roasted to a much higher temperature, some might describe them as ‘burnt’. If coffee tastes bitter, we tend to want to add sugar.Good coffee is not bitter; it is sweet and acidic.
Good coffee is balanced. No one aspect should dominate the cup to a point that it becomes unpleasant and just as with cheese, whisky, and wine, what flavour suits one person may not suit another. One of the joys of coffee drinking is experiencing the many different flavours resulting from the many factors that make up each coffee’s flavour profile.