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The effect of yeast on the flavor development of Doppelbocks

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Kaiser:
I just posted a write-up on comparing a bottle of Doppelbock that was bottles w/o yeast and one that was bottled with yeast:

The effect of yeast on the flavor development of Doppelbocks

The idea for this experiment came from an online discussion that we had either here or on the NB forum.

Here is the conclusion:


--- Quote ---Conclusion:
The result of this tasting did surprise me yet supports my thinking that the hallmark flavor of German Bocks and Doppelbocks is in fact the product of oxidation and staling of the beer. It is assumed that the yeasted beer sample did not exhibit that flavor as strongly since the yeast was able to scavenge the oxygen that had been introduced during the bottling process.

The added yeast did not affect the head retention negatively in this case. One way it can do this is by releasing excessive amounts of Proteinase A into the beer which can break down foam proteins.

The pH was not negatively affected either which is a sign that there was not an excessive amount of yeast autolysis or not enough yeast to make a difference.

The idea that big dark beers benefit from small amounts of post fermentation oxygenation has also been brought up by fellow home brewer Fred Bonjour and warrants further investigation into optimal oxygenation rates ad well as aging times.
--- End quote ---

a10t2:
Thanks for writing this up, Kai. The first doppelbock I brewed (and kegged) was fantastic, but the next year's batch (identical recipe, but bottled) just didn't have quite the same "pop". I'd wondered if some aspect of yeast metabolism could explain the difference, and this would seem to confirm that.

It would be really interesting to see what the difference was on, say, five one-gallon batches that had different amounts of oxygen added before force-carbonating. If I could get some blind tasters to evaluate them I'd be willing to brew those beers, although I'd have to get an oxygenation setup first. Do you have any idea what sort of oxygen concentrations would be needed?

Kaiser:
I think the amount of oxygen we are talking about here is very small. Too small to be measured with the O2 meters some of us have. Varying amount of headspace or various levels of bottle purging could be one approach.

Fo the Dopprlbocks that you mentioned, could there have been a difference in O2 uptake post fermentation? Were they bottle conditioned?

Kai

a10t2:

--- Quote from: Kaiser on July 05, 2010, 09:42:46 PM ---I think the amount of oxygen we are talking about here is very small. Too small to be measured with the O2 meters some of us have. Varying amount of headspace or various levels of bottle purging could be one approach.
--- End quote ---

That's what I was worried about. I was thinking that maybe a reasonably accurate regulator on an O2 tank might be enough. 5, 10, 15 mL/L, etc. Rather than relying on a DO meter.


--- Quote from: Kaiser on July 05, 2010, 09:42:46 PM ---Fo the Dopprlbocks that you mentioned, could there have been a difference in O2 uptake post fermentation? Were they bottle conditioned?
--- End quote ---

The second was bottle conditioned, with added yeast after about three months lagering. The first was kegged right out of the secondary/lagering carboy. Otherwise the beers were as identical as I could make them.

The whole reason for bottling the second batch was that everyone loved the first. Most people I distributed the bottles to didn't say anything, but there were several experienced brewers/tasters who said the bottle-conditioned batch was missing "something" the first had had. Granted, no one tasted them side by side, but these are people whose opinions I trust.

pyrite:
Kai, Interesting experiment, I always wondered about these specifics. I have a few questions.

1.Attenuation delta.  Is this the attenuation that took place after bottling?
2. Which beer do you prefer for smoothness or are you looking for Hallmark flavors, non-yeasted or yeasted?  
3. If other people have done a side-by-side comparison which do they favor?
 

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