Volatile minor acids in coffee. I. Contents of green and roasted coffee

The contents of volatile acids, except for formic and acetic acids, have been determined in green and roasted coffee by means of SDE, ion exchange and GC/FID. Identificated, with GC/MS, for the first time in green coffee are 2-methylpropanoic, (S)-2-methylbutanoic, 3-methylbutanoic, hexanoic, 3-methylpentanoic, heptanoic, octanoic, nonanoic, decanoic, dodecanoic, tetradecanoic, pentadecanoic, (E)-2-butenoic, 2-methylpropenoic, (E)-2-methyl-2-butenoic and 3-methyl-2-butenoic acids, in roasted coffee 3-methylpentanoic, 2-ethylhexanoic, dodecanoic, tetradecanoic and pentadecanoic acids. All these acids, including propanoic, butanoic and pentanoic acids, were quantitated in green (as far as possible) and roasted coffee, partially for the first time. The found contents are much lower than most of the literature values. Most of the contents increase with increasing degree of roast, but those of the higher straight-chain saturated fatty acids, except for decanoic acid, do not. During storage at higher temperatures or/and high water contents, the contents of almost all the acids increase. The contents of some acids in roasted coffee are lower after steam treatment of the corresponding green coffee.