A different kind of pitch rate question

Yesterday I made a Bavarian hefe with 3068. As of now, it's just transitioning from lag phase to fermentation - just a little bit of foam forming and a little movement inside the fermentor.

So today I'm brewing a weizenbock. My plan is to use the hefe like a yeast starter. I figure pouring 1-2qts of the hefe into the weizenbock is a pretty good pitch rate. Got any opinions on quantity?

The weizenbock's OG going into the fermentor will be about 1.087, but I expect it to be more like 1.081-85 after "pitching."

You say it's just starting to ferment and you want to take some wort out and use it as a your yeast supply? If so, don't do it, you'll be severely under pitching.

If I read this wrong, carry on.

_

What you are talking about will work, I would go with the 2 quarts to be on the safe side though. We are talking about 5 gallon batches here right?

Have you looked into top-cropping? That is where you remove the krausen (mostly pure yeast cells) from a fermenting ale, and use that for the next batch. Top-cropping is the traditional way to transfer yeast. Very effective.

Yeah, 5gal batches here. Top cropping would work well except i've already commited to brewing today.

I think saying this is underpitching is crazy - I basically have a 5gal starter that's been reproducing for almost 24 hours. There's got to be a reasonable amount I can pitch into the bock.

kanzimonson said:

I think saying this is underpitching is crazy - I basically have a 5gal starter that's been reproducing for almost 24 hours.

Click to expand...

In your first post you said it just started fermenting, now it's 24 hours in.
There's a big difference there. I still wouldn't recommend it.

So I ended up pitching a full 2L of the hefe into the weizenbock. At time of pitching the hefe was fully into fermentation.

I guess this brings up the question: at the approximate time fermentation begins, what percentage of the final yeast population exists? If that's not clear enough, what I mean is: let's say there's 500 billion cells in the yeast cake at the end of fermentation. When that beer was transitioning into fermentation, how many cells were present? I'm guessing it's at least 60%, if not as much as 90%.

After all, we talk about yeast first reproducing to an optimal level for their environment and then beginning fermentation. That suggests to me that a huge portion of yeast must be present at the beginning of fermentation.

At least, that's what I'm hoping for the 2L I pitched! I guess we can partially judge the pitch rate by whether or not I experience a typical lag time.

I'm about 14 hours after pitching and the bock is in the transition phase - a small krausen and some bubbles beginning to rise. The hefe is about 36 hours in and already making a machine gun of the airlock.

I know we can't completely judge by lag time but I've found that with my usual strains, when I pitch the proper amount and oxygenate I see signs of fermentation within 12-16 hours without fail. If it's ever outside this window, it's usually because I over/under pitched. I'll let y'all know how the attenuation works out as a second check.

If that's not clear enough, what I mean is: let's say there's 500 billion cells in the yeast cake at the end of fermentation. When that beer was transitioning into fermentation, how many cells were present? I'm guessing it's at least 60%, if not as much as 90%.

Click to expand...

Let's suppose all 500 billion were there. You took a 2L 'slurry' out of a ~20L batch of beer, so you collected 1/10th of the total population (at best). That's 50 billion cells (best case, and we really stretched) which is severely underpitching a 1.087 brew. Because the yeast was already actively fermenting, I would expect it to take off quicker and would not compare it to a 'typical' fermentation.

I'm just picking some numbers here, do we know how many cells are typically in the yeast cake? My guess is that we're in the trillions.

I definitely see where you're coming from - I guess I'm just likening this to top cropping. People seem to use way less yeast when they top crop and pitch. Obviously there's something to be said for pitching super-healthy, super active yeast. Again, we can make some final determinations on this when I get the attenuation numbers in.

So long as you get decent attenuation in the weizenbock, I definitely think you'll turn out ok. I like to underpitch the 3068 a little anyways. Not sure how top-cropping this yeast would change things, but I could have sworn its during the growth phase when most of the esters get kicked out, and if you're looking for those banana/clove flavors to come out in your weizenbock, I'd bet it turns out fine even if you did wind up underpitching by a tad.

I actually happened to have a email conversation with Jamil going and I threw all this scenario in and he was pretty nonchalantly encouraging about it. His words:

"If it is active fermenting beer, then 2L
into 20L is about right, assuming all the numbers in the first beer
were correct. Oh, maybe a little under, since it was a step up in gravity. I'm sure
the beer will turn out fine."

I'll make sure to report results.

Also, my basement smells like a fart sandwich with these two beers going. And the smell inside the fermentation chest is worse than diarrhea... maybe even TRIarrhea

This beer attenuated to 1.019 for a whopping 78% attenuation! Tastes nice but hard to judge because there's still so much yeast haze.

I began crash cooling and I expect to leave it in the carboy for at least a couple weeks. Yes, I realize weizen beers are supposed to be cloudy, but I expect to have this thing around for a long time. I don't like a ton of yeast in my keg or bottles so I'm trying to eliminate some of it. No gelatin though, so I expect to still have quite a nice population still floating around.

Missed this thread originally, but since this particular part of the question never got answered...

The yeast density in your hefe will be significantly impacted by your original pitching rate, but a quick back-of-the-envelope calculation (based on Chris White's yeast growth dynamics data) makes me think that 1-1.5 trillion cells is about what you'd have.

Yeah, I was looking at the Yeast book and was thinking it was closer to 800-1000billion cells in the hefe. I pitched probably a little more than .75mm/mL/*P into the hefe (I made enough yeast for a higher OG). I used yeast nutrient and yeast energizer in the starter and at pitching, and my standard 1 minute of O2 at pitching.

Between your estimates and mine it means I probably pulled 160-300mm cells for the weizenbock, which would be a pitch rate of no less than .37mm/mL/*P. At best it's about .65mm/mL/*P.

I think it's clear that I definitely underpitched when it comes to the actual number of cells, but I'm hoping the activity and the health made up for any deficiencies.

I was pretty impressed with the vitality of this yeast when I was making starters. I had to do a stepped starter because the smack pack was 2 months old, and I was making yeast for 11gal of wort. Normally I see about 24 hours of lag in my starters with a 2 month old pack, but this thing was off and running in just a few hours. The first step was 2L. I then chilled and decanted and went up to 5L. This one took off equally quickly. So I feel pretty good about overall yeast health.

This batch has been kegged and is mostly carbonated. It does have a slight flaw but pretty awesome overall. Nice creaminess and banana flavors, with a little bit of milk chocolate.

The flaw has something to do with the alcohol. I wouldn't describe it as the classic hot fusel alcohol because you don't really get that burning sensation like with liquor. It's more of a slight acidic burn on the tongue. It's very subtle and not entirely a bad thing because it works with the phenolic-spices in the beer.

It could just be a result of making a 9% weizenbock, but I wouldn't be surprised if this is a underpitching problem. Some light fusel alcohols would be the easiest explanation since it's a common result of underpitching.

I guess if I made it again in the same way, I'd plan to add 3qts of hefe for pitching.