Naturally occurring diacetyl and 2,3-pentanedione concentrations associated with roasting and grinding unflavored coffee beans in a commercial setting

Abstract

Over the last decade, concerns have been raised about potential respiratory health effects associated with occupational exposure to the flavoring additives diacetyl and 2,3-pentanedione. Both of these diketones are also natural components of many foods and beverages, including roasted coffee. To date, there are no published studies characterizing workplace exposures to these diketones during commercial roasting and grinding of unflavored coffee beans. In this study, we measured naturally occurring diacetyl, 2,3-pentanedione, and respirable dust at a facility that roasts and grinds coffee beans with no added flavoring agents. Sampling was conducted over the course of three roasting batches and three grinding batches at varying distances from a commercial roaster and grinder. The three batches consisted of lightly roasted soft beans, lightly roasted hard beans, and dark roasted hard beans. Roasting occurred for 37 to 41 min, and the grinding process took between 8 and 11 min. Diacetyl, 2,3-pentanedione, and respirable dust concentrations measured during roasting ranged from less than the limit of detection (<LOD) to 0.0039 ppm, <LOD to 0.018 ppm, and <LOD to 0.31 mg/m3, respectively. During grinding, diacetyl, 2,3-pentanedione, and respirable dust concentrations ranged from 0.018 to 0.39 ppm, 0.0089 to 0.21 ppm, and <LOD to 1.7 mg/m3, respectively. For any given bean/roast combination and sample location, diketone concentrations during grinding were higher than those measured during roasting. During grinding, concentrations decreased with increased distance from the source. Measured concentrations of both diketones were higher during grinding of soft beans than hard beans. The results indicate that airborne concentrations of naturally occurring diacetyl and 2,3-pentanedione associated with unflavored coffee processing: (1) are similar to the concentrations that have been measured in food flavoring facilities; (2) are likely to exceed some recommended short-term occupational exposure limits, but; (3) based on previous analyses of exposure response relationships in animal studies, are far below the concentrations that are expected to cause even minimal responses in the human respiratory tract.

Update on flavoring-induced lung disease

“…2,3-pentanedione air concentrations ranged from less than the limit of detection to 0.018 ppm during roasting, and ranged from 0.0089 to 0.21 ppm during grinding. These results are similar to concentrations measured in food flavoring facilities and exceed the NIOSH REL [9]. Pierce et al [10] evaluated diacetyl exposures that could occur in a small coffee shop during the preparation and consumption of unflavored roasted coffee.…”

Characterization of naturally occurring airborne diacetyl concentrations associated with the preparation and consumption of unflavored coffee

“…The grinding of roasted coffee beans then releases the diacetyl in vapor form. The findings of earlier investigations (e.g., [22] , [57] ) suggested that exposure to naturally occurring diacetyl might occur in retail establishments where coffee is roasted and/or freshly ground. In this study, we simulated a small coffee shop setting in which a barista ground, brewed, and poured numerous cups of unflavored coffee over a period of 3 h. To the best of our knowledge, this is the first published study to describe airborne concentrations of naturally formed diacetyl associated with the preparation and consumption of unflavored coffee.…”

“…Gaffney et al measured 0.018⿿0.39 ppm of naturally occurring diacetyl in short-term (8⿿11 min) area samples collected at breathing zone height next to a commercial grinder that processed 11 kg of freshly roasted, unflavored coffee beans during the sampling event [this corresponds to about 180 L (i.e., 300⿿400 medium-sized cups) of brewed coffee] [22] . The short-term personal diacetyl concentrations measured on the barista in this study were lower than the values reported by Gaffney et al [22 ], and this is certainly due in part to the much smaller volumes of coffee processed (approximately 1.4⿿1.5 kg total in 3 h) in the current study. In addition, the coffee beans used in the Gaffney et al study had been roasted on the premises only a few hours before grinding, while in the current study the beans were roasted 9 days prior to the study and had been shipped from a distant location; therefore, some diacetyl loss may have occurred before the beans were ground.…”

“…For example, coffee processing workers can be exposed to natural diacetyl levels well above the OELs [22] , yet the respiratory status of coffee processing workers has been evaluated in many studies [21] , [26] , [27] , [29] , [33] , [43] , [50] , [51] , [52] , [54] , [55] , [58] , [59] and the most consistent adverse effects are allergic respiratory responses to specific allergens in respirable green coffee dusts [21] , [26] , [27] , [29] , [30] , [50] , [54] , [55] , [59] . To the best of our knowledge, there are no reports of bronchiolitis obliterans or other serious, obstructive diseases occurring at elevated rates in coffee processing workers handling unflavored coffee beans or ground coffee.…”

“…This may also hold true for coffee processing workers. Indeed Gaffney et al (2015), recently found that the mean diacetyl concentration measured during commercial grinding of unflavored coffee exceeded all of the current and proposed short-term OELs, and that the 8 h diacetyl OELs could be exceeded after as little as 7⿿40 min of grinding [22] .…”