Roast has several meanings. Firstly, it refers to the roasting of coffee, both as an English word and as a term for different degrees of roasting. Coffee beans need to be roasted to make coffee. During the roasting process, the green beans change colour from yellow to brown and can even turn black if roasted heavily. The heat during roasting releases essential oils that change the taste and smell of the beans.
When coffee is roasted, chemical reactions occur due to the heat. Sugars and proteins in the coffee beans form new compounds and roasting substances are produced. These reactions lead to the aromatic diversity of the coffee. In the past, coffee was roasted on the cooker or over an open fire, but nowadays the process is done in special roasting machines. It is important to carefully control the roasting temperature and duration, as small deviations can strongly influence the taste. Depending on the degree of roasting, the green coffee is heated to temperatures between 180 and 600 °C and then quickly cooled. There are two common roasting methods: Hot air roasting and drum roasting. Hot air roasting is economical and has short roasting times to minimise the weight loss of the green coffee. Drum roasting takes longer, but there is less loss of flavour.
Contrary to popular belief, dark roast and light roast coffees do not differ in caffeine content. The main difference lies in the taste and the roast notes. Light Roast, i.e. light roasts, are usually mild in taste. Medium roasts have a balanced flavour, a full aroma and little acidity. Dark Roast, on the other hand, has a strong, pronounced flavour that can be smoky-sweet or sometimes even slightly bitter. Coffee with this smoky note is called "roasty". Not all beans and varieties are roasted to the same degree. Light roasts are often chosen for high-quality beans to preserve the original flavour. Arabica beans, for example, should not be roasted too darkly, otherwise they can lose their properties and taste bitter.