Banana in bock??

Just tasted my first german bock, a 1.076 SG, finished at 1.017, used german lager yeast. It has a decent banana essence to it... is this a desirable quality in a bock, competition or otherwise?

Is this a by-product of the yeast?

It isn't bad by any means, just a different flavor than i've tasted.

1.070 + brews create allot of heat during primary....If there was any chance that it might have got up to 80F I would say thats your culprit, I had that happen to me on a strong dark ale no temp control and it has a wonderful banana smell......Although it could just be young check out the style guidlines for bock a quick search on google will get you there. What temp was your brew during primary and secondary and how old is it?

The banana smell is isoamyl acetate and is indeed a by-product of fermentation. Like Dark Ale said, it is common to higher temperature fermentations in ales and I would think the same effect would happen with lager yeast as well. Conditioning should help take care of some of it...I used to live in Germany and don't remember Bocks as having an a lot of banana esters, but it has been awhile and I might have burned that brain cell some years back. What was your fermentation temperature?

Since bocks are lagers, any fruity esters (banana) would be a flaw. But, if you like it, that's fine.

From the BJCP style guidelines:

5B. Traditional Bock
Aroma: Strong malt aroma, often with moderate amounts of rich melanoidins and/or toasty overtones. Virtually no hop aroma. Some alcohol may be noticeable. Clean. No diacetyl. Low to no fruity esters.

Appearance: Light copper to brown color, often with attractive garnet highlights. Lagering should provide good clarity despite the dark color. Large, creamy, persistent, off-white head.

Flavor: Complex maltiness is dominated by the rich flavors of Munich and Vienna malts, which contribute melanoidins and toasty flavors. Some caramel notes may be present from decoction mashing and a long boil. Hop bitterness is generally only high enough to support the malt flavors, allowing a bit of sweetness to linger into the finish. Well-attenuated, not cloying. Clean, with no esters or diacetyl. No hop flavor. No roasted or burnt character.

Mouthfeel: Medium to medium-full bodied. Moderate to moderately low carbonation. Some alcohol warmth may be found, but should never be hot. Smooth, without harshness or astringency.

Overall Impression: A dark, strong, malty lager beer.


My guess is that you fermented over the 50-55 degree temperature range of the yeast. In my Maibock, I fermented it at 50 degrees for two weeks, did the diacetyl rest, then started secondary at 55 degrees and lowered the temperature gradually for the lagering. I used Bavarian Lager yeast, which is supposed to have a fermentation temperature range of 48-55 degrees. I didn't get any noticeable esters at all.

I lived in Germany for 9 years and dopn't remember any banana flavors except in Hefe Weizens.

I had a couple Bbocks and Double Bocks last weeka dn still no 'nanner.

As per the recipie, started warm, at 65degrees, then brought down over 2 days to 40degrees, then 40degrees for 2 weeks.

Its about 5 weeks old (still young).

Maltus McBarley said:

As per the recipie, started warm, at 65degrees, then brought down over 2 days to 40degrees, then 40degrees for 2 weeks.

Its about 5 weeks old (still young).

Click to expand...

A lot of recipes do recommend starting warmer for lagers until signs of fermentation and then reducing to the fermenting temp. However, I think you've unwittingly discovered the potential drawback to this...formation of esters during the start of fermentation due to the higher temperatures. You're in a good position to try an experiment which is to do another batch and pitch at fermentation temps and see if you eliminate the bananas.

Also, 40F would be really cold for a primary fermentation, even for lager yeasts. As a comparison, I brewed a Doppelbock at Christmas that I pitched at 50F and held there for 5 weeks of primary fermentation before lowering the temp slowly to 38F for lagering.

Tasted 2 weeks later. Most of the banana has dropped out, I'd say there isn't really even a mild essence anymore... I must not have the patience for a big lager.