New non-volatile acids in coffee

By means of gas chromatography/mass spectrometry following preseparation by free flow field step electrophoresis 38 acids have been identified and quantified in coffee. Of these, 18 acids were identified for the first time and 5 others quantified for the first time in coffee. As a rule, the contents of the acids increase slightly on steam treatment and strongly on roasting. Exceptions are acids generated from other acids or trigonelline, which are formed on roasting only. On average, the contents of a steam treated roasted coffee sample were lower than the contents of a corresponding untreated sample. Nevertheless, a distinction of the two groups of coffees is not possible. In addition to the analysis of some coffee samples of known origin, the acids contents of 6 commercial blends of medium roast, of one espresso blend and of one instant coffee were determined.