VLB Berlin Tests Confirm: Petainer Kegs Preserve Beer Freshness Comparable to Bag-in-Keg Solutions

VLB Berlin Beer Study

For brewers, once they have sent their product from the brewery, they are relying on bar staff to pour a perfect pint. Many variables are now out of their hands; the temperature of the cellar and the cleanliness of the lines for example. What they can choose is the container they package their beer in. At Petainer, our kegs are tested extensively to ensure that they offer the best product protection.

We have tested our kegs across a number of real life situations such as long distance export & long storage, where they perform to BFBi & our own high standards. To add more real world testing, we wanted to investigate the longest time a beer could be coupled, and still taste as good as possible when served from a Petainer Keg. We know our customers will want to investigate all options for their products, so we evaluated Petainer Kegs against a Bag-in-Keg solution. The obvious difference here is the contact of the beer with the dispense gas in a Petainer Keg.

With the VLB, the world-renowned institute for brewing and study in Berlin, we undertook a test to compare our kegs and bag-in-keg products, coupled for 4 weeks. The VLB informed us that 4 weeks is their expected limit for a keg to be coupled on the bar, and above that would only be required in exceptional circumstances for very low rotation beers. This works out to be 9 pints served per week in a 20L keg.

The test was constructed with two beer styles, an ale and a hoppy lager. 300ml of beer was tapped daily from each keg and each Friday the sample underwent a DLG sensory test by 10 trained testers. Thorough hygiene practices were in place to ensure that only the kegs could be influencing the beer.


The results of this latest research shows conclusively that Petainer Kegs are able to preserve flavour across 4 weeks. Trained taste testers at the VLB reported in their conclusions that ‘At 4 weeks coupled, beer served from a Petainer Keg would be of high quality’, with the results returning Pure and Very Pure across key sensory metrics (taste, aroma, mouthfeel, bitterness, effervescence) even after 4 weeks. These results were comparable to a bag-in-keg solution.

Key conclusions that the VLB drew from the experiment:

  • Petainer Keg and Bag-in-Keg solutions performed comparably,
  • No discernible impact of contact with the dispense gas on carbonation,
  • Key impact for longevity therefore is proper and effective hygiene practices.
VLB Berlin Beer Study Results
DLG score after 2 weeks coupled – Hoppy Lager. Scores of 4 indicate ‘Pure’.

So what would this mean to a brewer looking to explore a one-way kegs? Firstly, it should suggest that a bag-in-keg or a bag-less keg are both sufficient to protect your product. Going for a bag-less version provides a few advantages.

When it comes to preparation, a Petainer Keg can be filled immediately as it is pre purged, and can be filled upright or inverted, meaning they can be used straight from the pallet.

With Petainer's being a transparent product, fillers can keep an eye on foaming, and adjust pressure to maintain the fastest fill possible. Without needing to pre purge, invert and fill slower to avoid foaming, Petainer’s will save operational hours and costs during the filling process.

Petainer’s also offer flexibility when filling, with options for manual, semi manual and automatic filling.

Study available on request.