Effect of roasting conditions on carbon dioxide degassing behavior in coffee

CO2 is one of the major gases formed during coffee roasting, which has important implications on coffee's quality and packaging requirements. In this study, the residual CO2 content and CO2 degassing behavior of an Arabica coffee processed using a fluidized bed roaster, as affected by the roasting temperature-time conditions, were investigated. The results showed that positive correlations existed between the degree of roast (expressed as lightness value) and residual CO2, implying that lightness could be used as an indicator of initial CO2 content in roasted coffee. At the same degree of roast, coffee roasted with high-temperature-short-time process had significantly higher CO2 degassing rate than those with low-temperature-long-time process. Moreover, the CO2 releasing rate increased with the degree of roast. The degassing rate of CO2 in ground coffee was highly dependent on the grind size and roasting temperature, but less dependent on the degree of roast. The different degassing behaviors observed between roasted coffee samples were explained on the basis of chemical composition and microstructural differences.