Wednesday, February 29, 2012

Upward mobility (Gushing, Part II)

After my last post about gushing I got a message from my Partner in Crime. They guy sounded upset. "Infected beer doesn't taste good, it has weird flavors! Ours is good, no flavors!", he complained.

I had to admit the man had a point. The beer was gushing, but we didn't know why. Before I send him to look for a possibly non-existent infection in his equipment, I should try and figure out exactly what was wrong. The signs we had (gushing getting worse with time, beer looking weird) were inconclusive. I needed more information. If I could only taste the beer, I may be able to tell what's going on there...

Which leads to an interesting question: How do you go about tasting a beer that levitates out of the bottle when you open it? I decided to to a little experiment.

I took two bottles of the beer out of the fridge and set them side by side on the counter. For both bottles, I started to open the cap little by little, until I heard just a little bit of gas let out. Psssst...stop. Psssst...stop. I noticed that a bit of foam was building up inside the bottle, sign that the CO2 was being released. I tried to release the gas in two different rates: the bottle on the left got one release for every two the one on the right got.

At some point, I clearly overshot. The bottle on the right, that has been releasing at a faster rate, had apparently reached a tipping point. All of the sudden I noticed that the foam inside the bottle doubled and the yeast inside seemed to be traveling upwards towards the cap. Ah ha! One mystery solved. I have been wondering why it is that when I pour the beer it looks murky and smells weird. Now I knew: The pressure letting up caused CO2 to fling the yeast back into the beer, causing the murkiness and the smell.

Well the one on the right was obviously a bust. But what about the one on the left? I have been letting the gas out very slowly, and the yeast didn't seem to be disturbed. If I kept venting the beer really slowly I should be able to avoid the yeast problem. But I didn't want to spend half the night on this. Finally I had a thought: I caught one tooth on the cap with my bottle opener and bent it until I could hear just the faintest Pssssssst sound. This meant that I've created a tiny channel for the gas to escape, hopefully very slowly. I put the beer back in the fridge (figuring that that would help any yeast that becomes disturbed to settle back down) and went to sleep.

The following evening I grabbed the beer from the fridge. Opened it like I would any other, and poured it. Success! The beer poured without gushing (but still with plenty of carbonation) and settled neatly in my glass. There was a slight haze to the beer, which was what it had always had, but none of the murkiness. Time for the all-important taste test: Will the beer taste infected?

Well, no. In fact, it tasted just fine. I've had this beer many times before, over the course of several months, and I knew what it tasted like. It tasted exactly the same now. No sign of wired flavors or infection. Mystery solved! I guess I owe P.O.C. an apology :)

Moral of the story: It pays to spend the time an figure out exactly what happened to your beer. Even if it takes a whole day to open it. :)

1 comment:

  1. boaz, so the beer isn't infected. fine.
    but what is the cause for the gushing? just over carbonation? too much priming sugar or uncomplete fermentation?