Draught beer hygiene: a forcing test to assess quality

Abstract

The quality of draught beer is important to consumers but can be inconsistent, ranging from excellent through to unacceptable. The few, 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 660 nm. 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. Copyright © 2017 The Institute of Brewing & Distilling

Draught beer hygiene: a survey of on-trade quality

“…Draught beer quality is an important factor for consumers, particularly as the price differential of the brand increases between the on‐ and off‐trade. Measurement of quality post dispense, using a validated forcing test , confirms the widely held view that draught beer quality is variable. This survey of 57 accounts in the UK Midlands is suggested to be relevant to similar dispense configurations in the UK and elsewhere.…”

“…Draught beer quality was determined using a forcing test . Samples were processed on the same day as sampling or, where required, the next day after overnight storage in a refrigerator.…”

“…This inevitably damages beer quality and increases wastage. Further, managing the entry of yeast and bacteria at the ‘ends’ of the dispense system is recommended by sanitising the keg coupler/spear and tap/nozzle , but take‐up by the on‐trade is, at best, poor. Product throughput also contributes to quality and ideally a keg should be consumed within a week, which was only achieved in 39% of all keg taps in the UK, as reported in the 2017 Beer Quality Report .…”

“…Quality can be compromised by the dispense process (slow throughput, temperature, over/under carbonation), glassware (dirty, wrong glass) and hygiene (bacteria and yeast generating off‐flavours, aromas and haze). Although draught beer hygiene quality varies widely, measurement ranges from indirect (data logging) and subjective (clarity, aroma, appearance) to objective (isolation and quantification of microorganisms) . As these approaches have their limitations, a new approach has been reported to assess the hygiene quality of draught beer based on the microbial loading at dispense .…”

“…The method is based on the long established ‘forcing’ principle, in this case, forcing draught beer at 30°C for four days. The increase in turbidity of beer post incubation relates to the initial loading of beer spoilage microorganisms.…”