for its presence in green tea, is reduced during the roasting process, usually about 15 minutes at , whereas the concentrations of most other alkaloids are not changed. The solubility of caffeine in water increases with temperature and with the addition of chlorogenic acids, citric acid, or tartaric acid, all of which are present in green coffee beans. For example, of caffeine dissolves in of water at room temperature, and at . The xanthine alkaloids are odorless, but have a bitter taste in water, which is masked by organic acids present in green coffee. Trigonelline (N-methyl-nicotinate) is a derivative of vitamin B6 that is not as bitter as caffeine. In green coffee beans, the content is between 0.6% and 1.0%. At a roasting temperature of , 85% of the trigonelline is degraded to nicotinic acid, leaving small amounts of the unchanged molecule in the roasted beans. Proteins and amino acids Proteins account for 8% to 12% of dried green coffee beans. A majority of the proteins are of the 11-S storage kind (alpha – component of 32 kDa, beta – component of 22 kDa), most of which are degraded to free amino acids during maturation of green coffee beans. Further, 11-S storage proteins are degraded to their individual amino acids under roasting temperature, thus are an additional source of bitter components due to generation of Maillard reaction products. High temperature and oxygen concentration and low pH degrade 11-S storage proteins of green coffee beans to low-molecular-weight peptides and amino acids. The degradation is accelerated in the presence of organic acids such as chlorogenic acids and their derivatives. Other proteins include enzymes, such as catalase and polyphenol oxidase, which are important for the maturation of green coffee beans. Mature coffee contains free amino acids (4.0 mg amino acid/g robusta coffee and up to 4.5 mg amino acid/g arabica coffee). In Coffea arabica, alanine is the amino acid with the highest concentration, i.e. 1.2 mg/g, followed by asparagine of 0.66 mg/g, whereas in C. robusta, alanine is present at a concentration of 0.8 mg/g and asparagine at 0.36 mg/g. The free hydrophobic amino acids in fresh green coffee beans contribute to the unpleasant taste, making it impossible to prepare a desirable beverage with such compounds. In fresh green coffee from Peru, these concentrations have been determined as: isoleucine 81 mg/kg, leucine 100 mg/kg, valine 93 mg/kg, tyrosine 81 mg/kg, phenylalanine 133 mg/kg.