I made an explosive beer once. I was homebrewing a dry-hopped saison at my old apartment in Watertown. I pitched the yeast, got a nice strong fermentation, transferred to the secondary for the dry-hopping when it slowed to a crawl, then bottled it a week later. After waiting the nominal 2 weeks for the bottling sugar to do it’s work I noticed immediately that the beer was over-carbonated, but the flavor was good so I ignored it even as the beer got more and more foamy. Then the explosion happened. I had a full case stored in the corner, this was an apartment so no basement or beer fridge was available. One of the bottles popped with such force that the cap bounced off the top of the case and shattered 3-4 other bottles. It was loud, terrifying, and made a huge mess. I immediately dumped the rest of the beer, which was a slow process considering the amount of force behind each cap I had to pop off plus the concern that other bottles were damaged and could potentially explode in my hand. Fortunately no one was hurt and I was able to dump everything and clean up. I talked to the guy at the homebrew store and he said the yeast strain I used was notorious for stalling out if it wasn’t fermented at a high temperature, so the beer still had unfermented sugars and the bottling process re-activated the yeast leading to the over-carbonation and explosions. I never used that yeast again and learned a valuable lesson as an amateur brewer.
Unfortunately, exploding beers have been in the news again. The recent craze of heavily fruited beers has driven brewers to experiment with different techniques to get as much fruit flavor and residual sweetness into the beer as possible. Fruited sours, where the sweetness from the fruit helps balance the acidity imparted by the brewing process, have become a big seller for many breweries. Unfortunately, this fruit addition also adds a substantial amount of fermentable sugar, and if the fruit is added late and there is still active yeast in the beer the yeast will ferment the sugars into alcohol, with the byproduct being carbon dioxide. If this continues to happen after the beer has been packaged it will result in a build-up in pressure and eventually an exploding beer. There are a few ways to prevent this, including pasteurization, a process that will kill any yeast in the beer assuming it’s done correctly. Unfortunately many brewers prefer to pass the buck to the consumers, telling them to store the beer cold (slowing or stopping any fermentation) and to drink the beer fresh before any pressure can build.
My “real job” is in the biotech industry, mostly in early research but I have a little experience with later stage development too. When we make a product it undergoes extensive testing to understand the best possible storage conditions, with the hope that hospitals and pharmacies follow the conditions exactly. We then do extensive stress-testing to understand what storage conditions could result in problems for the product, what these problems would be, and how we could mitigate them. The thing is, if anyone gets sick from our products, even if it was caused by improper storage, it is ultimately on us. I would hope that breweries would have the same mentality.
The latest discussion on exploding beers started with reports that a recent batch of Trillium Daily Serving, a heavily fruited Berliner Weisse, was having issues with exploding cans. Trillium initially insisted the beer was pasteurized and blamed the consumer if they didn’t store the beer “correctly”, and finally they offered a refund if your beer exploded. While a refund is a start, it stops way short of a full recall, a step taken by many breweries that have found this problem in their beers. Trillium insists that the beer was pasteurized, which makes you wonder how this could have happened, it must be a serious error in their process. One fortunate thing did come out of all of this, one of the best beer related memes I’ve ever seen, which also proves again that whatever happens, The Simpsons Already Did It:
Unfortunately, the exploding beer phenomenon is probably going to keep on happening, these fruited beers are immensely popular, many brewers don’t have the set up to package them safely, and there is no regulations to protect consumers yet. Relying on consumers to properly store these beers is madness, quality control is the brewers responsibility. It’s one thing when a customer drinks an out-of-code IPA, the beer is sub-par quality but nobody gets hurt. It’s almost inevitable that we will keep seeing stories about exploding beers until someone gets seriously injured (or worse) by shards of metal shooting off of a can, and then a massive crackdown by the FDA will probably follow. So it is on the breweries to keep this from happening, make sure every fail-safe is in place for their fruited beers. If you can’t package them safely just make them draft-only for the taproom until you can afford the proper equipment and training for your staff. Nobody wants to be the brewery whose reputation is destroyed because they put a customer in the hospital with their exploding fruited sour.
Lead image from Trillium Brewing social media
Hoppy Boston 
