At what point should a microbrewery worry about overpitching??

I was recently at a new microbrewery, and there was a volunteer who was clearly very informed giving us a tour. We were having great conversational flow, but I was surprised about his answer when I asked, "How do you know when you've got too much yeast in the conical?"

He essentially told me that it's IMPOSSIBLE for a homebrewer to overpitch [which I understand], but he even said it's highly unlikely a microbrewery would be overpitching, as well.

I just find that odd, because if you're re-pitching on the same yeast over and over again, in a metal conical which you can't really see the yeast inside. I'm just going to assume that there will ALWAYS be more yeast, unless they are taking out some amount of yeast along with the trub. But how can they verify that the amount they're taking out is just enough?

Is this an oversight by a new microbrewery? Or is it really "impossible" to overpitch a perpetually used conical? And what are the potential effects of an overpitched batch, btw?

 

I think most breweries would pitch on the basis of yeast slurry. They would take the slurry from the conical and pitch it into the next batch. They probably do a cell count of some sort. I would think that the brewery would be capable of doing a semi accurate cell count.

 

Depends on the brewery, depends on the beer. If the brewery is making well attenuated beers with neutral yeast flavor (American pale ales, IPAs etc) I would mostly agree with the guide. If the brewery produces Belgian ales, German hefes etc I would disagree -- there are most definitely upper thresholds on how much yeast makes the best beer in those cases. I'm sure many microbreweries just measure yeast by the bucket and aren't breaking out the microscopes every time they pitch yeast into a new batch.

 

They don't have a clue how much yeast is inside the fermenter (from what I understand). I thought it was pretty neat when they told me they just shoot the wort up from the very bottom of the conical, and they mixed the yeast in that way. Sounded brilliant, up until the point where they told me that yeast count didn't matter. And yes, they do brew a hefe.

I guess from time to time they MUST clean out the fermenters, or at least they should. But I'm not so sure they've done that yet.

 

They aren't pumping fresh wort into the uncleaned fermenter. Below is the process they are likely using.

- Ferment wort
- harvest yeast from conical
- transfer beer to brite tank
- run cleaning/sanitizing cycle on conical
- pour yeast in through manway or pump in from propagation tank
- pump fresh wort in

 

Based on the words exchanged, I could have sworn they said something like "re-use" and then jumped to how the wort is shot up thru the bottom to mix the yeast. But I guess that still doesn't preclude them from cleaning the fermentation tanks. He even mentioned that they try not to mix the yeast from their various beers... considering they only had like 3 fermenters for 4 different types of beer they brew. They were getting like 4 or 5 more fermenters last time I checked, tho.

 

I'm sure they must drain the wort and the yeast separately and then re-pitch whatever volume of yeast they need for the next beer after cleaning the fermentor. Mostly sure.

MAYBE they put that yeast in the fermenter first and then "shoot the wort" up from the bottom as way to aerate it for fermentation?

 

Also, TRY not to mix various yeasts? I hope they are doing more than trying.

 

Either the guide wasn't explaining their process very well (likely) or I wouldn't be too keen on drinking their beer. If they're literally repitching by draining beer and adding fresh wort through the yeast cake, I'd be shocked if they didn't start having major autolysis problems. Autolysis may not be a big issue for homebrewers with 5 gallon batches in carboys, but multiple barrels in a conical is a completely different story.