INVESTIGATION OF ROASTED COFFEE FRESHNESS WITH AN IMPROVED HEADSPACE TECHNIQUE

The volatiles forming the pleasant odour arising from freshly roasted coffee beans were investigated by means of an improved headspace technique with intermediate cryo-focusing and simultaneous sniffing analysis. Shelf-life tests were carried out with whole beans in non-air tight packs and indicated that the loss of aroma freshness several days to weeks after roasting corresponded to the decrease in certain low boiling volatiles, mainly methanethiol. To validate the method, several starting parameters were investigated, specifically the influence of particle size, degree of roasting and coffee bean origin. Results reveal that this headspace technique allows an objective evaluation of the aroma freshness of whole coffee beans without exact knowledge of coffee origin, degree of roasting or starting values. In addition the method differentiates between Arabica and Robusta coffees.