Some may remember the experiment where I added life yeast to a few bottles of last year’s Imperator, my Doppelbock. I posted the rather pronounced flavor difference when I tasted 2 bottles side-by side here.
Tonight, about 1 year after they have been bottled, I opened another pair of these bottles.
The beer from the non-yeasted bottle still has a pronounced dark fruit aroma whereas the beer from the yeasted bottle has a much more subdued aroma. It seems to be catching up since I remember even less aroma at the 6 month tasting. In this beer some of the roasted character is coming though which is overpowered by the other aromas in the non-yeasted beer.
Quite dramatic this time was the difference in head retention. While it took the yeasted beer only 6 min until the head collapsed to a thin layer of bubbles. The head of the non-yeasted beer lasted about 4 min longer. This could be attributed to the release of protease-A by the yeast. This enzyme is known to degrade head retention positive proteins in beer.
As for the difference in taste, it follows the difference in aroma. The non-yeasted beer has a decidedly fuller and more complex taste than the yeasted beer. Without having experienced the difference side-by-side I would consider the yeasted beer a great Doppelbock but it is not as good as the one that was bottled without the yeast.
Conclusion: I stand by my opinion that yeast gets in the way of the proper development of the flavor profile of a Doppelbock and brewers should avoid bottle conditioning this beer.