Coffee beans used for making coffee are the seeds of coffee cherries, the fruits produced by coffee shrubs. Similarly to cherries, the coffee fruit is green when unripe, and it is during the ripening process that its colour turns from yellow into red, but varieties ripening to yellow are also known (Yellow Bourbon).
The coffee cherry has five layers
- Seed: this is the coffee bean that is used roasted and ground for making coffee
- Silver skin: this layer usually still coats raw or green coffee beans, and comes off in the form of chaff during roasting
- Parchment skin: this layer of cellulose covers each of the coffee seeds and turns into a parchment-like, hard material when dried
- Musilage: sticky, yellowish substance that is also called “honey” in English
- Skin and pulp: the external part of the fruit that makes up about 45% of coffee cherries
In the centre of each coffee cherry a seed develops that consists of two halves. Accordingly, one side of the coffee beans is flat, while the other is convex.
Occasionally – in the case of around 5% of the fruit – the two halves grow together to form one seed, called peaberry. This is a speciality coffee most typical of Tanzania, where they are sorted out by hand before marketing. However, they are increasingly present in the coffee offer of other countries as well.
Peaberry coffee beans
Normally developed coffee beans
The coffee cherries are cleaned with various methods so that by the end of the process only the seeds coated with a silver skin would remain, which are marketed as raw or green coffee.
Various processing methods are used which have an effect on the flavour and acidity of coffee, therefore it is worth enquiring about them before purchase.