Characterization of organic coffee using photothermal techniques

This chapter describes various photothermal techniques and reviews some of their applications for organic coffee characterization. These techniques measure changes in the thermodynamic state of a sample resulting from periodically modulated heating. Photoacoustic spectroscopy avoids the light dispersion problems that can interfere with conventional spectrophotometric methods, and the present paper focuses on the characterization of grains, powders and infusions of roasted and soluble coffee. Furthermore, photoacoustic is a non-invasive and inexpensive technique that allows investigations of in vivo and in situ photosynthetic activity in plants. Examples of the monitoring of photosynthetic activity of coffee plants are presented, along with the use to photoacoustic technique to show the effects of environmentally friendly bacterial inoculants. In addition, knowledge of thermal parameters is particularly important for improving the industrial roasting of coffee as well as for monitoring the degradation of the final product when, for example, it is exposed to cyclic periods of heating that can affect its quality. Finally, we also show how the photosynthetic activity of coffee plants, the thermal parameters of coffee beans, and the presence of pigments and contents of certain chemical components in ground and roasted coffee differ according to plant growth conditions.