A preliminary study on the feasibility of using the composition of coffee roasting exhaust gas for the determination of the degree of roast

Variations in the chemical composition profile of the gas evolved during roasting of coffee were qualitatively monitored with the aim of further establishing a chemical criterion for determination of the degree of roast. Simultaneously, the variations in the beans physical properties, such as volume, weight loss, and moisture content, were also monitored. Three hundred grams of coffee were roasted in a lab-scale roaster and the optimum degree of roast was reached in 9 min. The gas evolved during roasting was collected for gas chromatographic analysis. The chromatograms representing the evolution of the gas composition profile showed that a group of compounds will first appear close to the optimum degree of roast time. This indicated the feasibility of using such compounds as chemical descriptors when establishing a scientific criterion for determination of the degree of roast.