The average protein content of coffee beans is 10%. The free amino acid content of green coffee beans shows a wide range, from 0.001% for methionine in Robusta to 0.1% for glutamic acid in Arabica.
Proteins are composed of different amino acids which are the main compounds contributing to the formation of the typical aroma during roasting, and previous studies have reported that alanine is the amino acid with the highest content (1.2 mg/g) in Robusta coffee beans, followed by asparagine (0.68 mg/g).
During roasting, volatile aromatic compounds and polymeric brown pigments are formed in the beans, while water and carbon dioxide are released. The principal thermally reactive constituents of the raw bean are the monosaccharides and sucrose, free amino acids, chlorogenic acids and trigonelline, and the newly formed precursors of degraded carbohydrates and denaturated proteins.
Protein in coffee beans
