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gkeusch · 11-19-2012, 05:43 PM

My AG ale has that banana thing again. I think it is diacetyl. I'm pretty sure I pitched an adequate amount of quality yeast (made a starter of WLP-005, had good activity early on, calculated attenuation at 72%). Grain bill was 6# 2-row, 2# Light Munich and 1/2# carapils from which I calculated 29 ppg extraction. Mash temp was 150 for 1 hour. Added 1# of honey during the boil. Hop schedule was 1 oz of Nugget at start and 1/2 oz Cascade last five minutes. Left it in primary (closed bucket) for two weeks, then bottled some and kegged the rest. Opened a bottle after 1 1/2 weeks and noticed the banana. Waited another week, then tried the first sample from the keg- same thing.

I don't try to control my fermentation temperature, but my basement in Michigan this time of year is not over 70. When this batch was fermenting (late October) it was probably 65 or so.

I've had this before, but not always. Can anyone tell me what the culprit is?

Thanks in advance.

Chugmaster · 11-19-2012, 05:55 PM

Has a monkey or family of monkeys had access to your basement in the last six months?

gkeusch · 11-19-2012, 05:58 PM

No, but this might attract them. So far only a few mice who really like malted barley when they can get it.

**helibrewer** · 11-19-2012, 06:07 PM

Diacetyl generally isn't a problem with ale yeast. That banana flavor is a fermentation temp issue caused by the yeast. Try keeping those ferm temps below 68...that's the beer temp, not ambient.

WoodHokie4 · 11-19-2012, 06:12 PM

Try monitoring the temperatures of your brew. If you can, try to keep the temperatures below 65°. You may also want to try a different strain of yeast, since that is likely where you are getting the banana flavors from. I also read a tip in another thread (can't remember which one) to put boiled bread yeast in the primary to absorb toxins and other impurities that might affect the yeast.

grimstuff · 11-19-2012, 06:23 PM

You should give it more time in the primary. Taste it before you bottle. Some diacetyl will always be produced, but giving it at least a few days after fermentation is complete should clean it up. Again, taste it before you rack it off the yeast. If it tastes estery or buttery or whatever, give it more time. Also, this strain has high floculation, which could mean that the yeast are settling out before fermenting completely and removing the diacetyl. Next time, try rousing the yeast when the gravity gets near expected FG.

gkeusch · 11-19-2012, 06:50 PM

Thanks all for the responses. How do most homebrewers control the temperature of the fermentation?

grimstuff · 11-19-2012, 06:59 PM

Quote:

Originally Posted by gkeusch

Thanks all for the responses. How do most homebrewers control the temperature of the fermentation?

Aside from refrigeration with a thermostat, you can use a water bath, which works very well. I've been able to achieve temp control within 2-3 degrees with it. Get a big receptacle large enough for your ferment vessel and water. I use a 20 gallon pot. Others use a big plastic storage container. Put your ferment vessel in, fill it with water, then use plastic 2-liter bottles of soda filled with water and frozen to keep the temp of the water down. Two of those bottles in my 20 gallon pot is plenty to keep temps down. In any case, the water is what buffers temp swings, acting as thermal mass.

jsv1204 · 11-19-2012, 07:13 PM

Most of my banana beers have cleared up after a few weeks in the bottle. I have chalked it up to being too green. I second the comment about ferment temps, but I wouldn't expect that until you are hitting the mid-70's.

brewmadness · 11-19-2012, 11:18 PM

I had this issue once, but it wasn't with the whole batch. I had one bottle that wasn't completely full that I had sitting in the fridge for a few months. the rest of the batch was great, I just never opened this bottle because it wasn't a full bottle. Maybe 3/4 full. When I did finally decide to finish that bottle.....big time banana flavor. I was puzzled as all the other bottles didn't have that flavor and were very enjoyable. oops, sounds like I'm trying to hijack the thread...just saying...it happens. Just didnt have it happen to the whole batch. I posted this before myself, didnt get much response so I'm assuming everyone was as puzzled as me.