The quality of the coffee beans used to make coffee is directly related to their chemical composition. The constituents of coffee that are important in making a good beverage are the flavor substances, the bitter substance and caffeine which is responsible for the stimulating effects.
Compared with robusta green beans, arabica green beans have substantially higher lipid, sucrose and trigonelline contents but lower caffeine and chlorogenic acid (CGA) contents.
Caffeine is present in the coffee bean in both the free and combined states. Its content in the bean varies in different species – C. arabica contains 1.0 – 1.2; C. robusta 1.5 – 2.5 and C. liberica 1.4 – 1.6 per cent.
Caffeine, in addition to stimulation, also contributes to the bitterness of the coffee.
Several organic acids are present in the aqueous extract from green coffee beans, the predominant being chlorogenic acid and the least acetic acid.
Coffee beans contains between 8% and 18% (dry basis) fat depending on a variety and species. Green robusta beans generally have lower lipid contents than arabica coffee beans.
Around 75% of coffee oil is in a triglyceride form, with linolenic and palmitic acids being the main fatty acids.
The composition of roasted coffee will vary according to the raw material, roasting degree and roasting parameters such as time, temperature and speed in which the process occurs.
Chemical composition coffee beans
