Effect of roasting conditions on the polycyclic aromatic hydrocarbon content in ground Arabica coffee and coffee brew

Roasting is a critical process in coffee production as it enables the development of flavor and aroma. At the same time, roasting may lead to the formation of nondesirable compounds, such as polycyclic aromatic hydrocarbons (PAHs). In this study, Arabica green coffee beans from Cuba were roasted under controlled conditions to monitor PAH formation during the roasting process. Roasting was performed in a pilot spouted bed roaster, with the inlet air temperature varying from 180 to 260 degrees C, using both dark (20 min) and light (5 min) roasting conditions. Several PAHs were determined in both roasted coffee samples and green coffee samples. Also, coffee brews, obtained using an electric coffee maker, were analyzed for final estimation of PAH transfer coefficients to the infusion. Formation of phenanthrene, anthracene, and benzo[a]anthracene in coffee beans was observed at temperatures above 220 degrees C, whereas formation of pyrene and chrysene required 260 degrees C. Low levels of benzo[g,h,i]perylene were also noted for dark roasting under 260 degrees C, with simultaneous partial degradation of three-cycle PAHs, suggesting that transformation of low molecular PAHs to high molecular PAHs occurs as the roasting degree is increased. The PAH transfer to the infusion was quite moderate (<35%), with a slightly lower extractability for dark-roasted coffee as compared to light-roasted coffee.