Infected harvested slurry?

[jojacques]

Hi.
A month ago I transfered the slurry that was in the bottom of my Baltic Porter fermenter (Fermentis S-23)
I used two sanitized (starsan) masson jar, and put in the fridg right away.

Now, the content of the two masson jars looks different one from the other.
One has some kind of slurry on top of the liquid and the lid is bent from inside pressure.

Is one of the jars infected?

 

[jojacques]

Picture of it

View attachment 1481847214262.jpg

 

[passedpawn]

Hard to say. I would not use yeast that was suspect though. When it doubt, throw it out.

That one on the left doesn't look right. My jarred yeast is very clear above the yeast/trub line.

 

[IslandLizard]

There may have been some fermentation activity after you harvested, causing CO2 to raise the yeast cake, and swelling the lid. Not necessarily from infection, although it is possible too. The one on the right maybe a better choice but...

...regardless of possible infection, reusing harvested yeast from high gravity ales, such as your Baltic Porter, is usually not advised. Depends on the final alcohol %.

 

[jojacques]

It does look weird indeed.

I was not informed of that, the Porter ended at 8.15%... too high to re use? Considering its not an Ale, but a Lager

 

[IslandLizard]

8-9% is about the limit. Depends on the yeast strain.

Although you could probably pitch the slurry on the right as is, it's generally preferred to make a starter from 1/2 the slurry in the jar on the right. Run it through a yeast calculator, like Brew United's or Mr.Malty. But first taste the beer that's on top (decant some). If it smells or tastes like a$$, infected or severely autolyzed (marmite, bouillon cube flavor, burnt rubber, or worse) get a fresh pack.

Depending on the availability and cost of a package of fresh dry yeast, making a starter of a (harvested) dry yeast can cost you more and takes time. There's always the chance on an infection riding in with it too.

The advantages of reusing yeast, including dry varieties, are possibly better flavor, higher attenuation and other profile characteristics. You can also acclimate your yeast to a certain wort profile, and even push her limits a bit, for example selecting for those cells that can survive higher alcohol content and/or attenuation and propagate those. Now in turn, those may not give you better flavor.

 

[jojacques]

That's good info! Thanks a lot, I'll do that!

I recently re-pitched on a fresh yeast cake, and wow! Fermentation started right away with no starter, I was amazed!

I have a one week old yeast cake in a fermenter, do you recommend pitching on it or it's getting a bit old?

 

[IslandLizard]

When pitching directly onto a whole fresh yeast cake, you may risk overpitching. Typically only 1/4-1/3 of the (fresh) cake is plenty, unless you have a very high gravity beer or a much larger batch. Some brewers will do this purposely, first brew a 1.045-1.055 Stout or Porter, then pitch a RIS wort on top of the cake. 2 beers and only a small starter or one single dry yeast pack needed.

When racking always leave some beer on top of the yeast cake, a quart or so. It's actually hard to avoid this while preventing any of the dense yeast slurry from being transferred. You can then easily swirl it to homogenize the slurry and pour all, or the part you don't need, into a large jar (I use a 1/2 gallon pickle jar).

A week old slurry is fine, as long as it isn't infected from being handled and sitting there. After racking there's a huge headspace left, filled with air (O2) and whatever bugs floated in with it. Many homebrewers seem to fare well with that method, though. The layer of beer on top is a decent protective barrier to keep many bugs from taking over since it contains alcohol and hop compounds.

If the slurry was stored in the fridge, it would still be good and very pitchable after a month, like what you did with those 2 jars above.

 

[jojacques]

Good to know, thanks.

The fermenter with the yeast cake has been sitting with a sanitized foil as a cap and is in my garage, sitting at around 45Far.

 

[Kampenken]

Few thoughts and questions here. I harvest yeast into mason jars and pitch without a starter, have had great results. I too have heard about the perils of using higher gravity yeast sources but with no experience I can't confirm if that's nonsense. I can confirm I've reused yeast from 070 OG with no issues and have read limits lower than that. So it's a bit of buyer beware here. If/when I do a RIS, I will indeed save to test this out. In fact I'm getting two mini brew buckets (Christmas!), just to split batches and test different yeasts.

I haven't pitched on yeast cake, but that's coming too in 2017!

My question to IslandLizard, besides what island(s!), is since I see you've posted a lot I suspect you likely have a fair amount of brew experience, have you had bad experience in reusing high gravity yeast? And I've used harvested yeast 4+ months old without issue, if you don't, again, why not? Bad experience? Or was the ok after one month not meant to be a limit? I'm presuming the latter, and how long have you used harvested yeast (in this manner, not slants)?
Thanks!