Mid-infrared spectroscopy and physicochemical analyses in the characterization of coffee roasting stages

The coffee quality results from the interaction of different processes during the production chain, among them roasting. Roasting process can be subdivided into dehydration, roasting, and cooling stages. However, establishing physical and chemical markers for these stages is a complex task, given that sensory perceptions, which can be subjective, are still used for this purpose. This study applied physicochemical parameters, spectroscopy in the mid-infrared region (FTIR) analysis, and chemometric tools to discriminate and establish technical and scientific parameters of the roasting stages of coffee beans. Thus, the objective of this study was to investigate the roasting process of Coffea canephora and Coffea arabica beans using chemical tools to monitor the roast stages. For this, a sample was taken every minute during a roasting period of 17 min for subsequent physical and chemical analyses. The pH, titratable acidity, water activity, colorimetry, and soluble solids, as well as FTIR, were able to discriminate coffee beans according to roasting stages.