Diacetyl and 2,3-pentanedione in breathing zone and area air during large-scale commercial coffee roasting, blending and grinding processes

Air samples collected from the enclosed headspace directly proximal to freshly ground coffee beans revealed varying concentrations of alpha-diketones. The above Figure illustrates the three major gas constituents identified in the headspace above the freshly ground beans and displays airborne concentrations of diacetyl, 2,3-pentanedione and acetaldehyde as a function of time. The FTIR measured the concentrations of the gases as the ground coffee beans exited the grinder into a plastic lined storage tote, Figure section Number 1. At approximately 12:05 P.M., the grinding was completed and the plastic bag filled with the freshly ground coffee was twisted closed with the FTIR probe inserted into the headspace, Figure section Number 2. As can be seen on Figure section Number 3, concentrations increased until approximately 12:12 P.M. when the plastic bag was opened. Airborne concentrations of for diacetyl peaked at 10.88 ppm, 2,3-pentanedione at 7.46 ppm and acetaldehyde at 16.37 ppm. As also can be seen on Fig. 1, the concentration of the gases quickly dissipated after the plastic bag was opened. While air concentrations measured by the FTIR are quantitative, the direct relationship between the mass of ground coffee and the air concentrations detected can only be inferred, thus, requiring further investigation