Why would an aged beer explode?

Question

I had a bottle of Westvleteren XII aging in my fridge. As I was putting some other bottles next to it, I nudged it slightly and the bottle shattered violently. I'm certain that I didn't hit it with enough force to do that kind of damage, so I'm thinking that there was pressure that had built up inside the bottle.

Is this something that's plausible? Could it mean that the beer had gone "off" and so I should not feel bad that my prized beer ended up as a sticky puddle?

Answer 1

I've been homebrewing and winemaking for almost 25 years and there are 3 reasons why a bottle might explode.

1. Too much sugar for the secondary fermentation in the bottle. Homebrewers do this ALL THE TIME. Turns your beer into little hand-grenades. Sometimes fermentation is not complete and with the normal addition of sugar at bottling can cause problems. This happens frequently in high gravity beers.
2. Infection - by this I mean something other than yeast was in the beer and started eating the sugar to make the carbonation in the beer. It could be a wide variety of agents from yeast to bacteria to fungus. They convert sugar to CO2 at different rates than yeast. Many times they produce more CO2 causing gushing beers and sometimes broken bottles.
3. Defective bottle. 99.99% of the time bottles are built to spec, but occasionally one slips through with a defect and many times that can lead to a bottle failing. Also, bottles are sometimes dropped or banged around causing a crack.

Answer 2

Not knowing much about the beer but the 30 second Google search - I will try to give insight as to why this may happen.

I've noticed this was a Trappist beer. As such, there is probably as much yeast in there as homebrew beers that have had sugar added to carbonize the beer during the bottling process. When too much sugar is added at this step, the homebrewing community refers to the disaster that happens next as "painting the ceiling." This comes from the present yeast having too much sugar to eat and over-pressurize the beer. The first time this happened to me I thought someone was shooting either in or right beside my house. I know that the Trappist Monks have been doing things a lot longer than homebrewers; but, the situation is still plausible.

There is also a chance for glass defects. Or perhaps, the bottle was knocked over and created a stress fracture that over time gave way with your slight nudge. You could always reach out to Westvleteren XII Gurus and ask what is the best way to store the beer so this doesn't happen again. Sorry for your loss! :(

Answer 3

Any beverage that is "bottle conditioned," with active yeast, has the possibility of this happening.

In most cases, the yeast will be limited by either -

1. Fermentable sugars already being depleted (not all sugars are readily fermentable to brewing yeasts)
2. Alcohol levels (this is the waste product of yeast) reaching levels that are toxic to the strain of yeast, and they either die or go dormant

Your typical home brew will go through fermentations so case #1 applies, and then they add just a bit of corn sugar and bottle so just a bit more fermentation occurs to carbonate the beverage in the bottle.

Other bottle conditioned brews might do an estimate of how much sugars have been used and how much remain, by measuring the specific gravity of the beer (more dense with sugars, less dense with less sugar and alcohol instead).

If their calculations were off, and there was still more sugars that could ferment, then pressure would build beyond what was needed just to carbonate.

I had a batch of stout where the yeast culture I used was pretty old, so it was less active than usual. The time when I thought it was done fermenting was actually not accurate because of the less lively activity, and my bottles of stout all started exploding in my basement, and I had to dump the rest of the batch out to save the bottles.

I also had a fruit punch recipe that my uncle used for a wedding beverage, using just fruit juice, wine and champagne. He used a much better champagne than the recipe called for, so there was live yeast. When he put the leftovers back into the wine jugs and put them in the fridge, they got very "lively", with carbonation, more alcohol content, a bit drier, and one jug shattering from the additional fermentation.