Unraveling the dynamic impact of roasting degree on the evolution of coffee aroma profiles

Coffee gets its alluring aroma mainly from volatile compounds generated during roasting. To elucidate the impact of roasting degree on coffee aroma, the odor characteristics and sensory quality of coffee with different roasting levels were investigated. Totally 111 volatiles were found in coffee, among which ester and heterocyclic compounds were dominant, exhibiting an inverse relationship in proportions as roasting intensity increased. Thirty-four volatiles were identified as markers to distinguish coffee samples at different roasting stages using partial least squares discriminant analysis. Among 32 aroma-active compounds with odor activity value (OAV) above one, ethyl 2-methylpropanoate having the highest OAVs in each sample was the key contributor to fruity odor. High-roasting treatment proved essential for developing a coffee aroma with strong roasted, burnt, and smoky odors, yielding the highest overall sensory scores. Current findings lay a scientific foundation for producing preferred coffee and shed light on the chemical reactions unfolding during roasting.