Coffee beans are not beans. They are the seeds of a red fruit.
Coffee grows as small cherries on a shrub, and each cherry holds two seeds. The seeds are removed, dried and roasted, which is when they turn brown and start to smell like coffee.
Why is this true?
Green, unroasted coffee seeds taste grassy and sour. Roasting triggers hundreds of chemical reactions, including the same browning that gives bread its crust, and creates most of the aroma we know.
More facts in this category
More about food
Food facts sit right where biology, chemistry and history overlap. A fruit that is technically a berry, a spice worth more per gram than silver, a sweetener that never spoils in a sealed jar — the reasons usually come down to sugar, acid, water and how long humans have been moving plants around the planet. Each entry explains the mechanism in plain language, and links to a source if you want the longer version.