Off-flavour #3: Draught line infection

The “Off-flavours” series covers the three most common ways the flavour of beer can be ruined after it leaves the brewery and what can be done to prevent this from happening. New to the series? Start here.

Beer is a fascinating, diverse and delicious beverage, but if it’s not properly stored, it can develop some not-so-delicious off-flavours. (As a note, none of these off-flavours are health risks, but they certainly are unpleasant!) 

Beer lines at bars and pubs are subject to the same sanitation and infection issues as breweries. If they’re not kept clean, bacteria can build up in the draught lines and cause a draught line infection – our third off-flavour to explore.

What are the signs of a draught line infection?

Draught line infections can lead to buttery and sour flavours in beer:

  • Pediococcus and Lactobacillus bacteria commonly infect the beer lines themselves, producing buttery flavours (from a compound called diacetyl) and a spoiled or sour milk taste (from lactic acid).
  • Acetobacter can be found in dirty beer taps and gives beer a vinegary taste (from acetic acid).

What causes draught line infections?

As beer runs through the line from the keg to the faucet, it leaves behind carbohydrates, protein and other compounds that create a breeding ground for spoilage bacteria, like Pediococcus and Lactobacillus.

Acetobacter growth usually begins in or on drip trays, bar tops, or used bar towels and eventually spreads to the beer taps. Serving staff submerging the tap into a beer while pouring will then increase the growth rate of these bacteria. (Hence why it’s never acceptable to have any contact between the tap and the glass, or the beer in the glass, when pouring kegged beer.)

How do we prevent draught line infections?

With regular line cleaning – every 14 days at a minimum. And it’s not just about cleaning the beer lines: the couplers, FOBs and faucets need to be cleaned regularly, too. (For a recap on these different draught system components, check out this article here.)

This will keep the beer that’s running through these lines tasting the way the brewer intended and help ensure proper operation of the draught system, too.

And we made it! That’s all three off-flavours in our “Off-flavours” series introduced. Missed any topics on “Beer Service and Storage”? Head here for a recap.

Discovering Beer is not affiliated with or endorsed by the Cicerone® Certification Program.

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