Repitch On Stressed Yeast Cake

[Kidagora]

The Situation

Brewed two separate batches of a high gravity RIS 13 days ago with 1.106 and 1.104 O.G.s Expected OG was 1.111.

Two separate 2L starters were made for each batch using 1.060 OG wort and two packets of S-04 per 2L.

First Batch: Oxygenated the 1.106 well and pitched a 2L starter. Nice vigorous fermentation s/p 36 hours with a temp set at 60F and slowly increased to 68F by day 10. Sample on day 10 was 1.030. Contemplating adding another 2L yeast starter but not convinced it's finished yet. Tasted pleasant, smooth, very little acetaldeyde and no fusels. I'm a believer it can make it another 10 points for 1.020 although it was calculated to finish at 1.028.

Second Batch: Oxygen stone BLEW OFF INTO THE WORT . Barely oxygenated to the extent I wanted or it needed. Pitched the 2L starter. As expected, significantly less activity with NO wort/krausen blow off into the jug. Batch 1 blow off jug was black and batch 2 blow off jug was pure starsan. Gravity on day 10 was 1.040 and had a distinct "sharper" quality that I perceived as acetaldeyde and slightly fusel while still retaining some of the similar malt qualities of the other. Also maintained in the same chamber as the first batch and regulated at 60F to 68F.

Questions:
I was on a brew schedule and wanted to use the cakes of each of these batches for another 2 batches of the same RIS. I'm looking to fill a barrel and would like to fill within the next month. Given the lack of promising fermenation, possibly stalled FG, and potential for off flavors of batch 2...would it be advisable to continue using the yeast? I may end up dumping the beer if it doesn't improve in another 2 weeks. General thoughts and most importantly EXPERIENCES on using high gravity yeast cakes for high gravity beers?

 

[porterpounder]

Just split the cake from the better fermenting batch and use it on the next 2 batches, dumping the other. More yeast is not necessarily better and you very likely have enough to split and have a very healthy fermentation for both the next batch.

 

[Calder]

Good advice from PP on splitting the better cake.

Adding more of the same yeast to lower the gravity if it doesn't finish low enough is probably not going to do anything. You got decent fermentation as noted by your latest gravity reading, so you have plenty of healthy yeast. Your FG is due to a combination of yeast selection, OG, and wort fermentability. If you want to get it lower, try using a more attenuating yeast; something like 3711.

 

[hottpeper13]

I can't say about repitching from such a large beer,but my 1.100 ones are in primary for 4 weeks.

 

[KepowOb]

First off, generally speaking dry yeast manufacturers don't recommend starters, and if you don't make a starter, they also say you don't need to oxygenate.

That said, is there a reason you want to pitch on the stressed yeast other than saving money?

If so, and you're already making starters, just make a bigger starter and save some of it, and use that as your starter for the next batch.

I'd be worried that if you keep pitching onto stressed yeast cakes that you might run into other issues with such high gravities involved.

 

[Kidagora]

@KepowOb

Yea. Mostly time and money. Just wanting to evaluate cost/benefit based on experience rather than my own assumptions or non referenced statements.

Making a starter, in my mind, is a scaled version of a beer. So I find it odd that a manufacturer WOULDN'T recommend it. I could see why they may say it isn't necessary. But what problems arise from propagating packets of dry yeast and proliferating? Even yeast pitch calculators have dry yeast programmed as an option.

The Brewer's Friend yeast calculator I used by the site suggested 220 billion est. with two dry yeast packets which falls short of my estimated need of 652 billion needed for 1.106. Using the calculator to adjust for a 2L starter of 1.060 and 2 packets with a stir plate gives me an estimated finish of 699 billion which should be sufficient according to the site.

I'm assuming the majority of fermentation has completed with batch one (1.030 from a 1.028 target) I'm willing to secondary and let the remaining yeast that's alive ferment out what it can prior to barreling.

As far as primary for 4 weeks, I would like to do that but fermentor space and time is an issue and I'm trying to see if this is a viable option. The FG is close to projected in batch one and I'd like to reduce yeast contact time with high ABV to avoid premature autolysis (had a 12% batch for 2 months exhibit the rubber/sulfur quality).

That's why I'm asking about personal experience regarding pitching "possibly" stressed yeast. It's early in the process to tell but most likely based documented issues that batch two had complications. If I create a favorable environment next time, will it matter? Is the damage done with the second batches yeast? I guess with the amount and potential I'm second guessing but looking for definitive advise so as not to kill another batch.

"I'd be worried that if you keep pitching onto stressed yeast cakes that you might run into other issues with such high gravities involved." What kind of issues? Have you experienced some problems?

I'm brewing today and will most likely transfer the good (batch 1) to secondary and pitch onto the cake. And go to the LHBS to pick up yeast for another healthy starter. to be done on Thursday based on statements. I may just do a mild/porter with the stressed yeast but not sure I can afford that extra batch right now.

 

[Calder]

I don't put much into the theory of 'stressed' yeast. Yes, it has worked hard and is worn out, but provided you don't over-pitch on the next batch, the yeast will reproduce and you will have fresh yeast to work on the next beer. Remember pitching on too much yeast is not good as it reduces the amount of new yeast produced. It is probably more important to pay attention to proper pitching rates when re-pitching on high gravity beers than on normal beers.

That said, re-pitching on yeast used in high gravity beers is not really a good idea. I think high gravity increases the potential for mutation, and it certainly selects cells with particular qualities (high gravity, and probably low flocculating properties). With increased risk of mutation, and selection of certain properties in the yeast, you accelerate changes in the character of the yeast. After a couple of generations at high gravity, it may have little of the original character and properties of the original yeast.