Huge krausen during keg dry hopping

[Guilherme]

Dear Fellas,
I've brewed a 10 gallon batch of a session IPA (1.051 OG) about three weeks ago and a really weird thing happened and I am hoping you could help me.

Fermentation went fine (i've pitched 3 packs of US05) for a couple of weeks, starting at 62º - for like 4 days - and then raising it up to 70º, when apparently it stopped (FG was 1.013 - a little high for my mash schedule).

I then racked the beer to a couple of corny kegs (both flushed with CO2) and dry hopped each with 4-5 oz of simcoe, cascade and ahtanum. Both kegs were kept outside, with temperature varying between 60 and 80 degrees.

Today (after 5 days of dry hopping), I went to rack the beer to a serving keg to fine it and start carbonation. The beer in one of the kegs had attenuated a little (FG was 1.009) and was kinda carbonated.

The second keg, on the other hand, exploded (after a really hard time opening it) with a really crazy and foamy type of krausen. Once I took a gravity reading, the FG was 1.007.

What do you guys think happened? Was it only the end of fermentation or do you consider it might have gotten an infection? The aroma is kinda weird, but I can't quite think of it yet as spoiled or sour.

Cheers

 

[prandlesc]

Were your cornys sanitized, or just purged? I could just be an odd fermentation due to the heat of your last storage, but I would have expected both kegs to react the same way. Did you taste it?

 

[Guilherme]

They were supposed to be sanitized.
Looking back, I might have used an old batch of star san, so it may have lost its effectiveness.

One thing I didn't mention was that the bag in which the dry hops were settled in the second keg (the one that exploded) were opened during the new fermentation/infection (the bag was pretty much empty after I opened the corny). The bag in the other keg was full.

Do you think this may be related with the difference between both kegs?
Thank you very much for your response!
Cheers

 

[winterc]

Did you rack the beer into the kegs from different primaries? If they came from the same primary, was the one that exploded racked first or last?

 

[Guilherme]

Same primary but I can't say which one was racked first.
Do you believe the difference between FG's came from the amount of yeast that eventually went to the exploded corny?

 

[winterc]

I'd suspect yeast that transferred with the beer over older starsan.

 

[prandlesc]

I'd suspect yeast that transferred with the beer over older starsan.

+1 on that. It's definitely an unusual story. How did it taste?

 

[Guilherme]

+1 on that. It's definitely an unusual story. How did it taste?

I haven't tried it yet - I just sipped a little, but there was a lot of pellets mixed in the sample so I couldn't tell if there was something wrong.
I put the keg in the freezer to cold crash and try to clear it up and will see tomorrow if it's drinkable.

So let me get this right... you guys think there was some kind of infection with the yeast in contact with the old star san?

 

[prandlesc]

I haven't tried it yet - I just sipped a little, but there was a lot of pellets mixed in the sample so I couldn't tell if there was something wrong.
I put the keg in the freezer to cold crash and try to clear it up and will see tomorrow if it's drinkable.

So let me get this right... you guys think there was some kind of infection with the yeast in contact with the old star san?

I don't think the old starsan was the issue. It may be that it's just the transferred yeast working in reaction to the high temperatures (80) causing a lot of action. Or it could be that one keg was not sanitized well. The tast should tell you a lot. If it tastes mostly like beer, then it's probably the yeast responding to the high temperature. If it taste NASTY, then it's more likely an infection. I'd taste a sample from both kegs and compare.

Going forward, you should really try to keepo your beer away from those high temperatures unless the yeast specifically calls for them (like a dubbel or a saison). High temperature may make yeast give off a lot of unusual flavors.

So when you taste it, you'll need to determine if it's beer with a funny or off taste, or if it's nasty and not beer at all.

My guess is that it will be beer with an off taste. Let us know what it tastes like and you think.

 

[Guilherme]

I don't think the old starsan was the issue. It may be that it's just the transferred yeast working in reaction to the high temperatures (80) causing a lot of action. Or it could be that one keg was not sanitized well. The tast should tell you a lot. If it tastes mostly like beer, then it's probably the yeast responding to the high temperature. If it taste NASTY, then it's more likely an infection. I'd taste a sample from both kegs and compare.

Going forward, you should really try to keepo your beer away from those high temperatures unless the yeast specifically calls for them (like a dubbel or a saison). High temperature may make yeast give off a lot of unusual flavors.

So when you taste it, you'll need to determine if it's beer with a funny or off taste, or if it's nasty and not beer at all.

My guess is that it will be beer with an off taste. Let us know what it tastes like and you think.

I guess I won't dry hop outside anymore. Even if the taste isn't bad (which I will check tomorrow and let you guys know), I think the aroma was kinda ruined by this little accident.

Either way, thank you very much for the help!
Cheers