FTIR-ATR was used to study the effect of roasting conditions on the flavor of brewed coffee using Guatemala Antigua coffee beans. The 1800-1680 cm(-1) carbonyl region for vinyl esters/lactones, esters, aldehydes, ketones, and acids was found to provide a flavor-print of the brewed coffee. A study of light, medium, and dark roasts indicated that when the rate of heating to the onset of the first and second cracks was kept constant, the types of carbonyl compounds formed were similar, varying only in their concentration. This difference in concentration is apparently due to the additional heating of the coffee bean beyond the second crack. When the heating rate to the onset of the first and second crack was varied, both the types and concentration of the carbonyl compounds formed during roasting were affected. Thus, heating rates of green coffee beans to the onset of the first and second cracks are important determinants of the basic taste and aroma of brewed coffee.

Infrared difference spectroscopy was used to study how changes in the processing of Arabica coffee cherries into green beans affected the flavor of coffee brewed from roasted green beans. Paired samples of green beans, in which the drying step or fermentation/washing step in their processing was altered, were roasted and brewed in a standard manner and their ATR-FT-IR spectra obtained. Difference spectra of the 1800 to 1680 cm −1 carbonyl region of water-subtracted spectra of paired samples of these brewed coffees provided data which indicated differences in brewed coffee flavor due to changes in fermentation/washing steps and drying steps involved in the processing of coffee cherries. The role of acid, ketone, aldehyde, ester, lactone, and vinyl ester carbonyl components on the flavor of brewed coffee is proposed that is consistent with the flavors as perceived by the coffee tasters.