Quality Control: 2018 Barrel Aged Penguin

It came to our attention that some bottles of Barrel Aged Penguin were tasting sour a few weeks after bottling. This, of course, was not what we had intended with this beer. We test every barrel for beer spoilage organisms before it gets blended in a brite tank, and we also follow up with microbiological testing on the blended batch as well as the packaged beer. All of those test results came back negative, yet the beer still soured, so what the heck is going on?

What happened is that there was a very low level contamination by a beer spoiler known as Lactobacillus acetotolerans. This particular beer spoiler is a bacterium that prefers to grow anaerobically (in the absence of oxygen, although technically it is a facultative anaerobe). Since most of our plating is done in an aerobic environment, we didn’t see the growth of this spoiler to any degree in the lab. However, after bottling, the bottling environment is quite anaerobic, and that, coupled with being stored at room temperature, allowed the Lacto acetotolerans to grow unchecked. In fact, the pH of one of our bottles held back for quality purposes clocked in at 3.98, while the pH of the same beer stored cold in a keg was 4.5.

Lactobacillus acetotolerans is also infamous for spoiling another beer that is quite popular: Bourbon County Stout.

Rest assured, drinking one of these contaminated bottles is not harmful to your health, it just tastes sour from the production of the lactic acid by the bacteria. Again, this is not what we had intended for this beer, hence the recall notice.

Going forward we plan to implement more anaerobic plating protocols, as well as pasteurizing beers that have been aging in barrels to prevent this from happening again.

We are always here to field your questions or hear your feedback at: quality@rhinegeist.com. We are very sorry for any inconvenience this may have caused anyone, and we hope to avoid issues like this in the future.

– The Rhinegeist Lab Team