Re-fermentation

[Mutant]

I brewed 14.2 gallons of Doppelbock four months ago and it has been lagering for three months and normally is left alone until December when it is turned into an Eisbock. This is the third year for this recipe (maybe slight variations each year). I just pulled a sample and it seems overly sweet with a gravity of 1.025. My question is what are my options to start up fermentation again without causing any issues like oxidation. The original yeast was WLP838, but expect I'd likely need to use a different yeast at this point. The current ABV is roughly 8%.

 

[Young Brewing]

This style seems so interesting to brew and I applaud you for your patience that I certainly don’t have! What did you end up doing?

For a small restart such as this I imagine you could use whatever yeast you wanted without impacting the existing esters and flavor. I have never tried restarting a fermentation with such high existing alcohol and don’t really know what impact that plays.

Also, how does the freezing process work for this style?

 

[Mutant]

This style seems so interesting to brew and I applaud you for your patience that I certainly don’t have! What did you end up doing?

For a small restart such as this I imagine you could use whatever yeast you wanted without impacting the existing esters and flavor. I have never tried restarting a fermentation with such high existing alcohol and don’t really know what impact that plays.

Also, how does the freezing process work for this style?

I haven't yet tried to do anything. The doppelbock usually lagers for 9 months before I freeze it, so I have time. It has been too hot to want to do anything the last month or more - the last two days it was 116F. I'm probably going to have to hold off until it at least stays below 90F for a sustained timeframe - it is more about me being comfortable than anything.

I have to decide on a yeast that will pick up the fermentation without the need to oxygenate.

I freeze using a kegerator that can go to 19F when it is the middle of winter. I just let it freeze solid. The Eisbock is typically very well balanced but this year's version would come out sweeter and that would unbalance it.

 

[Young Brewing]

I’ve read that champagne yeast is pretty good at attenuating in very stressful situations which could help here. I doubt any of the yeast character will show through either.

With a well oxygenated yeast starter you could pitch with low disruption and have the yeast consume most of the oxygen before it is able to have any negative affects.

What is the usual FG for this beer? Also, does the freezing have any impact on FG?