The coffee bean’s composition
The carbohydrates in the coffee bean mostly consist of water-insoluble and -soluble polysaccharides. By the roasting process, saccharose and glucose diminish almost entirely. The water-insoluble polysaccharides from the cell walls are not degraded and make up the coffee grounds.
The bean's water content is reduced from 10 - 13% to 1 – 2.5%. The lipid content in green coffee lies between 10 – 17%, depending on the variety and origin. The Arabica bean contains more lipids and coffee oils than the Robusta bean.
The “Maillard-reaction” is the most important chemical process while roasting: by the heating of carbohydrates with protein, the typical coffee flavours emerge, which to date can not be produced synthetically.
The roasting process causes the degradation of acids to two thirds. Under the effect of heat, the amount of protein decreases considerably. The coffee bean contains important minerals, such as potassium, calcium, magnesium and phosphorous. The content of minerals depends on the coffee variety and the growing region.
The best known ingredient, caffeine, has its share of 0.8 - 2.5%. The roasting process has little influence on the content of caffeine. Among experts, 850 flavour components of coffee are known. 100 flavour components are not yet determined.