First kegged batch - tastes like banana after a week - why?

[wi_brewer]

Brewed an English Brown that was fermented with White Labs British Ale WLP005 two months ago. Had it in the primary for a month and then to a carboy for another month.

Kegged it 3 weeks ago, set it to 12psi and let it sit for a week. My brew buddy and I hooked up the beer line and indulged...tasted great, no off flavors.

After another week we went to enjoy another, but this time it had a distinct banana flavor.

I know yeast can give a banana flavor, but why would we be getting more yeast in our glasses this time around?

The only variable that I can think of that was different for the second week is that the beer line (12 ft of 1/4" ID) was hooked up to the keg/faucet, where as it was not for the first week while the beer was carbing....but I am guessing that this is not likely to be the cause of the banana flavor.

Any thoughts?!

 

[Yooper]

The only thing I can think of that causes "banana" is esters, so I suspect that this English strain got above 70 degrees during fermentation.

 

[mvanwie]

Bear (or Berra) in mind, kegging is not bottling and bottling isn't kegging. In other words, the process to clean, sanitize, prep, transfer, condition, etc. is the same, but the procedure is different, and IMO >90% of the time a "first-time" kegging issue stems from a used keg not being cleaned and sanitized properly, especially with a keg that was last filled with soda syrup and/or has been sitting for years. A single corny keg has more nooks and crannies than 50 bottles and needs to be cleaned/sanitized meticulously.

That being said, your keg could have been completely sterile and what you're experiencing is a conditioning or fermentation issue that Yooper alluded to, and perhaps might even be completely normal. As an example, I brewed a Hefe a couple months back that was tasty at carbing, horrid a week later, back to tasty after another week, and completely victimized by my wife within 10 days... and by victimized I mean she drank - no, pounded - like she had been sober for 9 months and faceplanted off the wagon (I cut her some slack... after all, she had just given birth). That's just how the Hefe strain I used matures.

Finally, the additional yeast is probably a settling issue... after a week, the yeast - which may have been mostly in suspension during your initial sampling - settled to (or towards) the bottom of the keg and was mostly pulled during your second sampling. Unlike in bottles where a little bit of residual yeast ends up in each bottle, in kegging the residual yeast all ends up in the first glass or two.