How to tell the citrus flavor of hand-made coffee? why light roasted coffee beans are citrus?

I remember once discussing the flavor of coffee with a friend, and made a quipping conclusion at that time, that is, when you drink sour coffee, even if you really can't tell what flavor it is, it's always a to say "citrus".

There is a basis for this. You can look up the flavor description of light-roasted coffee beans with conventional treatment on the shopping platform, nine times out of ten with the words "orange, lime, grapefruit". The first and second flavors of some coffee beans are not described as "citrus" (the order in the flavor description), but are also written on the last flavor description. Why is it citrus? The most important point is that the recognition and popularity of citrus flavor is too high. Citrus fruit is almost a national fruit, can be bought at any fruit stall, and the price is close to the people, but also an important source of vitamin C supplement, it is also very difficult to forget the citrus flavor.

The second is the aroma of citrus fruits, which is very "domineering". Even without peeling, you can smell fresh orange fragrance on the surface, because the peel is rich in d-limonene, showing a light and fresh citrus aroma. Peeling off the peel, a small amount of juice is sprayed into the air, which contains small amounts of alcohols, aldehydes, ketones and esters, which are the source of pulp (juice) aroma. Some light roasted coffee contains more decyl alcohol, n-hexanol, vinyl formate, isopentenol and so on, which makes us feel the citrus flavor. In addition to citrus acid, there should be many fruits that represent sour taste, such as pear, apple, peach, apricot, cherry, plum, plum, begonia, loquat, Hawthorn, strawberry, raspberry and other Rosaceae plants, which also have corresponding flavor in coffee, but the flavor of these fruits in coffee is far less obvious than that of citrus (except for some coffee beans that use special treatment techniques to highlight a certain flavor).

In judging the flavor of coffee, it is often based on the performance of the coffee (acidity and sweetness) and the aroma emitted by the coffee (smell before and after the nose). In terms of acidity, citrus covers the range from lemon to sugar orange. the aroma is also easier to perceive than other fruits, coupled with the astringency of some light-roasted coffee, which is very similar to the astringency of citrus. Therefore, when we taste a coffee with excellent acidity, it is easy to think of "citrus".