Studies on coffee roasting process by means of nuclear magnetic resonance spectroscopy

The chemical composition of coffee has been widely investigated, focusing the attention both on main components and trace compounds. Most of these studies have been performed by using liquid and gas chromatography, eventually combined with mass spectroscometry. These techniques, although straight and effective, are time demanding due to the sample pretreatments. Here, we propose high-resolution-magic-angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR), a system capable of acquiring highly resolved NMR spectra of gel-like and suspension samples. This approach allowed us to determine the chemical composition of coarsely ground coffee beans of two varieties: Arabica and Robusta. Variation of the concentration of relevant species was monitored as a function of roasting temperature, from green beans to completely roasted. The HR-MAS NMR tool demonstrated to be very powerful for quick chemical composition determination, opening up possibilities for novel applications of this approach in food quality control.