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Draught beer hygiene: a forcing test to assess quality

Mallett, James R.; Stuart, Melanie S.; Quain, David E.

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James R. Mallett

Melanie S. Stuart

David E. Quain


The quality of draught beer is important to consumers but can be inconsistent, ranging from excellent through to unacceptable. The few but dated studies of draught beer quality have focused on the number of microorganisms that are present in the product. Work reported here, suggests that this approach has its limitations and fails to relate to beer quality post-dispense. An alternative approach using the long-established ‘forcing’ method provides a better but still retrospective assessment of draught beer quality. Samples post dispense are ’forced’ by static incubation at 30°C for four days and beer quality is ranked by the measurement of absorbance at 660nm. The increase in absorbance reflects the growth of beer spoilage microorganisms present in the beer at dispense. Four quality bands are proposed, where quality is described as excellent (absorbance increase of < 0.3), acceptable (0.3-0.6), poor (0.6-0.9) and unacceptable (> 0.9). The method is straightforward, requires no special skills and enables, for the first time, the robust quantification of draught beer quality. It is anticipated that the method will have widespread application in the measurement and improvement of the quality of draught beer.


Mallett, J. R., Stuart, M. S., & Quain, D. E. (2018). Draught beer hygiene: a forcing test to assess quality. Journal of the Institute of Brewing, 124(1), 31-37.

Journal Article Type Article
Acceptance Date Oct 9, 2017
Online Publication Date Nov 29, 2017
Publication Date Feb 20, 2018
Deposit Date Oct 11, 2017
Publicly Available Date Nov 30, 2018
Journal Journal of the Insitute of Brewing
Electronic ISSN 2050-0416
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 124
Issue 1
Pages 31-37
Keywords Dispense, Beer spoilage, Quality, Method
Public URL
Publisher URL
Additional Information This is the peer reviewed version of the following article: Mallett, J. R., Stuart, M. S., and Quain, D. E. (2017) Draught beer hygiene: a forcing test to assess quality. J. Inst. Brew., doi: 10.1002/jib.470 which has been published in final form at This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.


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