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Diacetyl in Coffee Manufacturing

A TD-GC-MS instrument in our laboratory

The Challenge

Diacetyl is a naturally occurring substance with a butter-like odour which is present in many foods.  NIOSH (National Institute for Occupational Safety & Health) in the USA reported a link between exposure to vapours containing diacetyl and decreased lung function and disease.  Most studies have concentrated on exposure to diacetyl in the flavouring industry, but recent reports have also highlighted the possibility of exposure to diacetyl, and the related compound 2,3-pentanedione, in coffee manufacturing, particularly roasting and grinding.  Currently there are no Workplace Exposure Limits (WELs) for either diacetyl or 2,3-pentanedione but the European Commission Scientific Committee on Occupational Exposure Limits (SCOEL) has recommended an 8-hour time-weighted average (TWA) limit for diacetyl of 20 ppb (parts per billion) and a 15-minute short term exposure limit (STEL) of 100 ppb ( SCOEL, 2014).  However, there is a lack of information on airborne concentrations of these substances in the coffee manufacturing sector making it difficult to assess the potential for personal exposure in their workforce.

The Solution

Most of the methods currently available for measurement of diacetyl are awkward to use, particularly for personal sampling, and lack the sensitivity to be able to measure diacetyl and pentandione down to ppb levels.  HSE therefore developed a sampling and analytical procedure utilising well-proven sorbent tube and thermal desorption technology.  This method is capable of detecting the presence of both compounds down to sub-ppb concentrations.  In addition to pumped sampling, HSE determined diffusive uptake rates for diacetyl and pentandione which allows the sampling devices to be used to take passive (diffusive) samples.  Passive samples are well suited to long term and personal sampling as they eliminate the need for a sampling pump.  HSE used this new sampling method to carry out monitoring of both diacetyl and pentanedione at coffee manufacturing premises, using both personal and static samples.  Sampling was carried out in areas of the plant where roasting and grinding of the coffee was being carried out, as these were the areas where concentrations were expected to be the highest, as well as the packing area and control room.  Post-sampling, the samples were analysed for the presence of diacetyl and pentanedione by thermal desorption, gas chromatography and mass spectrometry (TD-GC-MS).

The Outcome

The monitoring exercise showed that airborne concentrations of diacetyl were above the proposed WEL. The highest concentrations were found in the grinding area, but airborne concentrations in excess of the 8-hr TWA limit were also detected in the roasting and packing areas and in the control room. Pentanedione was also detected, at a level of around a half to a third of those of diacetyl. These results provide evidence that improvements are required in order to control potential occupational exposure to diacetyl and pentanedione in this particular workplace. The results should also alert other coffee manufacturers to the possibility of exposure of their employees to diacetyl and pentanedione and the need for adequate control measures to prevent this and, more importantly, the ill health that may occur as a result.Graph showing substance retention measured by MS Detector Response over a period of 20 minutes. There are spikes at 4 minutes (one labelled Diacetyl), 6.5 minutes (labelled Pentanedione) and small spikes between 10 and 12 minutes (that aren't labelled).


The initial work was funded by HSE, but this is now a commercial service that we offer.

View more examples of our work in this area.

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