Coffee cherries appear on a fertilized plant, fully ripening after 7 – 8 months, depending on both the climate and the variety. As we noted earlier, coffee cherry is a small green oval-shaped berry that becomes bright red or even dark yellow when ripe.
The cherry consists of:
- peel (thin and red);
- flesh (soft and sweetish);
- two beans (the inner side of the beans is flat with a longitudinal strip, the outer is convex).
Every bean, in its turn, is protected by two membranes, a parchment coat and a silver seed coat. The length of a coffee bean varies from 7 to 15 mm (0.27 – 0.6"), the width – from 6 to 8 mm (0.23 – 0.3") and the weight – from 0.1 to 0.2 g (0.003 – 0.007 ounces).
Basic chemical components
Since coffee was discovered, it has always been associated with magical effects, medical and therapeutic properties and stimulatory action. When we drink a cup of coffee, we experience a rich combination of sensations and impressions, which only a few other products can give us. Much has been written on this topic, but sufficient knowledge on the chemical substances causing these phenomena has been acquired only recently.
The most important chemical components of coffee are:
- Caffeine. Discovered in the beginning of the XIX century, it is an element of the alkaloid family and, certainly, the most famous component of coffee. It is caffeine that makes coffee bitter. The percentage of caffeine depends on the variety of coffee – Arabica or Robusta – and it does not lose its qualities after roasting.
- Minerals. The main mineral is potassium, but coffee also contains a small amount of calcium and magnesium.
- Proteins. The natural properties of proteins are partially changed after roasting, as they are transformed into brown compounds called “melanoidins”.
- Amino acids. Destroyed in the process of roasting, evaporating carbon dioxide. They also form an aromatic component of taste and smell.
- Fats. This category is mainly represented by coffee oils contained in beans and represented largely by triglycerides and free fatty acids. Additionally, the farthest from the middle part of the bean has a small amount of wax.
- Carbohydrates. Contribute to the formation of brown pigments (melanoidins and caramel). They are represented by sucrose (water-soluble) and, largely, cellulose (insoluble in water). Sucrose, in particular, combined with amino acids, organic acids and trigonelline, contributes to the aroma during roasting, forming thousands of volatile substances (aldehydes, ketones, pyrazines, etc.)
- Water. Its percentage in green (raw) beans decreases by approximately 1% due to evaporation during roasting.
Coffee composition (average)