What is the cause of tap beer spoilage?

Lines require cleaning due to a build-up of organic growth that occurs between line cleans. Beer is a live food source and brewing itself is a science of managing bacterias, in fact many keg beers may even have some counts of bacteria at the time of arrival.

A single bacterial cell is relatively harmless, but that changes when they bind together and form a biofilm. This occurs when the first bacterial cell attaches to the  wall lining, they are social and invite others to join them, a protein substance forms to bind all the bacteria together, this is the formation of a biofilm. It is widely  considered that the adhesive nature of these proteins are of the strongest adhesives known.

The below illustration indicates the cycle of a single cell attaching to the wall and growing into biofilm.

The key to a successful line clean is to remove 100% of all organic matter from the lines at each event, if this doesn’t occur, ‘anchors’ can remain behind, allowing  for prompt reattachment post clean. Factors that influence the success of a line clean are primarily attributed to the cleaning frequency and the quality of the cleaner used.

There has been many developments in beer styles and seasonal brews of recent time, that have varying bacterial activity. Combined with more discerning beer drinkers that have a greater awareness and expectation of exceptional tap beer quality.