Kinetics of volatile organic compounds (VOCs) released by roasted Coffee during the first ten days after processing

Abstract

The quality of coffee is linked to the aroma created by the chemical reactions that occur during the roasting process. While it is generally thought that roasted coffee is a stable product with a relatively long shelf-life, little information is available on the evolution (kinetic) of the volatile organic compounds (VOCs) in the days immediately following the process. The aim of this study is to determine the evolution of VOCs released by coffee beans, on samples of Coffea arabica (three different origins) and Coffea canephora (1 single origin), by using a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS) 24 hours after roasting, and for the next 9 days. Results confirmed the differences already highlighted in previous studies between the VOCs spectra of the two species. There were also significant differences in the intensity of emissions for the different origins of Coffea arabica, with the highest VOCs amount over time always detected in the Honduras Arabica samples. The involved detected protonated ions were grouped into three classes: compounds (ppbv) present with decreasing quantity ; weakly increasing; almost constant trend; or always increasing. A complex dynamic emerged for the different protonated ions over time, which not only affects the mass spectra of the different species but also influences the configuration of the mass spectra of the different geographical zones of production.