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

Recently described scientific literature has identified the airborne presence of 2,3-butanedione (diacetyl) and 2,3-pentanedione at concentrations approaching or potentially exceeding the current American Conference of Industrial Hygienists' (ACGIH) Threshold Limit Values (TLVs) at commercial coffee roasting and production facilities. Newly established National Institutes of Occupational Safety and Health (NIOSH) Recommended Exposure Limits for diacetyl and 2,3-pentanedione are even more conservative. Chronic exposure to these alpha-diketones at elevated airborne concentrations has been associated with lung damage, specifically bronchiolitis obliterans, most notably in industrial food processing facilities.Workers at a large commercial coffee roaster were monitored for both eight-hour and task-based, short-term, 15-min sample durations for airborne concentrations of these alpha-diketones during specific work processes, including the coffee bean roasting, blending and grinding processes, during two separate 8-h work periods. Additionally, the authors performed real-time Fourier transform infrared spectroscopy (FTIR) analysis of the workers' breathing zone as well as the area workplace air for the presence of organic compounds to determine the sources, as well as quantitate and identify various organic compounds proximal to the roasting and grinding processes. Real-time FTIR measurements provided both the identification and quantitation of diacetyl and 2,3-pentanedione, as well as other organic compounds generated during coffee bean roasting and grinding operations.Airborne concentrations of diacetyl in the workers' breathing zone, as eight-hour time-weighted averages were less than the ACGIH TLVs for diacetyl, while concentrations of 2,3-pentanedione were below the limit of detection in all samples. Short-term breathing zone samples revealed airborne concentrations for diacetyl that exceeded the ACGIH short-term exposure limit of 0.02 parts per million (ppm) in two samples collected on a grinder operator. FTIR analysis of air samples collected from both the workers' breathing zone and area air samples revealed low concentrations of various organics with diacetyl and 2,3-pentanedione at concentrations less than the limit of detection for the FTIR methods. Neither the breathing zone nor area air samples measured using the FTIR reflected airborne concentrations of organic compounds that, when detected, approached the ACGIH TLVs or regulatory standards, when available. FTIR analysis of headspace of ground coffee beans revealed ppm concentrations of expected alpha diketones, carbon monoxide and other volatile organic compounds (VOCs).Coffee roasting and grinding, with adequate building ventilation and typical roasted bean handling and grinding, appears to generate very low, if any, concentrations of diacetyl and 2,3-pentanedione in the workers' breathing zones. This study also confirmed via FTIR that roasted coffee beans naturally generate alpha-diketones and other organic compounds as naturally occurring compounds resultant of the roasting and then released during the grinding process.

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.132