Yeast in larger batches

[Pewter_of_Deodar]

I am discussing hard cider with a friend that makes 250 gallon batches. He basically throws a brick of yeast into the vessel with the raw juice along with some nutrients.

While we have discussed what constitutes adequate yeast for a 5 or 10 gallon batch, I would like to ask exactly what it is we are shooting for in terms of the yeast we pitch for any size batch, but especially those large enough that a packet or two is supposedly not sufficient.

For instance, I know from the yeast tests that every yeast we tested LOVES the raw juice and goes bananas... So theoretically, I could pitch a single packet in a gallon of juice and dump the gallon into the 250 gallon batch after a day or so? What are the concerns? What is the actual goal that determines the right amount of yeast to pitch?

Thanks in advance,
Pewter

 

[Jmattioli]

(snip) So theoretically, I could pitch a single packet in a gallon of juice and dump the gallon into the 250 gallon batch after a day or so? What are the concerns? What is the actual goal that determines the right amount of yeast to pitch?

Thanks in advance,
Pewter

Yes, you could pitch it and it would do the trick as long as the large batch is sufficiently aerated and has the required nutrients for the yeast to reestablish and multiply. However, it is usually superior to add a 250g pack or brick to the 250 gallon batch. Why? Because the yeast in the pack will be first generation strain and probably superior to those you created from the first 5g pack.
Afterall they were created under tight laboratory conditions and packed with the ideal nutrients to get them started. Some of yours will be 10th generation or higher as they double approximately every 2 hours under ideal conditions.
Joe

 

[jab]

So is it safe to say, as a rule of thumb, 1 gram per gallon for a good start?

I realize that most people pitch a 5g pack at the minimum regardless of the batch size but is there some 'magic' formula for figuring starting quantities for a good fermentation?

 

[JamesP]

Maybe a better measure is the quantity of Krausen (foam) in a yeast starter, rather than a "dry quantity" - that way you know it is active before pitching, and isn't dependant on an quantity of yeast with an unproven "potential" to ferment.

 

[Oskaar]

Here's a post from Mike Faul of Rabbit's Foot Meadery that I found on the usenet mead group.

====================================================
Subject: Re: New York City Homebrewers Guild
From: MeadMax
Newsgroups: rec.crafts.brewing,rec.crafts.meadmaking

Well, this all depends on how you create your starter, what type of
yeast you use and the temperature you ferment at.

Most yeasts in virtually any fermentation will have a lag phase as it
grows and depletes the available O2 as well as a portion of the sugar.
Once you deprive the yeast of the O2 you start producing CO2 and alcohol(s)

If you prepare a good starter 24 hours in advance using 10% of your
batch size and at 15 brix you will have a good strong active culture tha
twill start fermenting immediatley upon innoculation into the primary must.

Then once you have a good, well aerated, proper nutrients etc must it
will ferment out to completion in under 10 days.

I ferment all of my meads in under 10 days (most under 7) and up to 18% abv

Mike

Rabbit's Foot Meadery
http://www.rabbitsfootmeadery.com
=================================================

Hope that helps,

Oskaar

 

[Pewter_of_Deodar]

Hey all,

Thanks for the answers. Let me recap what I am hearing and throw it out for a second round of comments.

1. There is a concern about either weakening or change in the yeast strain as it reproduces in order to create the number of cells necessary for a good fermentation. (from JMat's comments)

2. I need to use adequate initial yeast to achieve a good, quick ferment. (from Rabbit's Foot comments, although they recommend a 24 hour headstart, which ignores Joe's issue)

3. You need to have adequate yeast to use up the free oxygen in order to start fermenting so there needs to be a balance between amount of yeast initially, minimum amount of nutrients available, and amount of oxygen. (my derived thoughts from what was posted)

4. You need to be careful not to overdo the yeast and end up with "yeastiness" in the taste characteristics of the resulting mead. (something that wasn't mentioned)

Comments?

Let me toss out the question another way. For "optimum" fermentation, is there a specific concentration level that is desired (ie. so many yeast cells per milliliter of must)? As jab points out, we seem to have adopted an informal 1 gram of yeast per gallon of must, or at least that number seems to approximate what we all use except in smaller than 5 gallon batches.

I will move the other questions I have back into the "Yeasties and Beasties" section...

Thanks,
Pewter

 

[Oskaar]

You asked:

"Let me toss out the question another way. For "optimum" fermentation, is there a specific concentration level that is desired (ie. so many yeast cells per milliliter of must)? As jab points out, we seem to have adopted an informal 1 gram of yeast per gallon of must, or at least that number seems to approximate what we all use except in smaller than 5 gallon batches."

Here's my take:

I don't adhere to the 1g/gallon approach and really never have. Joe Mattioli and I have talked about this on the back-channel a few times, I'll typically pitch based on the brix or SG of the must. Even in 5 gallon batches I pitch at least 10g of yeast. In a one gallon batch I usually pitch a 5g packet. After rehydration the stuff takes off like a rocket provided you haven't got a really chilly must. I generally do not use starters either, although I do add a pinch of nutrient to the yeast I'm rehydrating. I'll just rehydrate double or more the usual amount of yeast necessary to get things going in a hurry.

I oxygenate the must well in the first 72 hours, measure the pH and dose the must with DAP and yeast hulls to keep the yeasties healthy, happy and in a rabid feeding frenzy. I'm pretty sure that's why most of my primaries only go two weeks. I have had several primaries that are done in one week.

Here's a byte of what Ken Schramm relates in his book:

Ken Schramm addesses Pewter's question/issue about cell population in the Compleat Meadmaker on page 61-62. Basically you want a 1% solution of the total volume of your must to be innoculated, and typically that means you'll have a population somewhere in the neighborhood of 1,000,000 cells/ml.

In order to create a starter that is 1% of the volume of your must, according to Ken, you'll need to create a starter 1/2 gallon in size to get that 1% slurry of cells for your starter to be in optimal range. He also addresses the issues of SG, nutrients, etc for the inevitable "what about . . .?" questions that will follow this post.

cheers,

Oskaar

 

[Pewter_of_Deodar]

Oskaar,

The last question that begs an answer in this discussion is "How much yeast is too much?". Are there some guidelines? I mean I could pitch a brick of yeast into a 25 gallon batch or 10 packets into a gallon. I would likely get a madly bubbling ferment that is rapidly complete. But there has to be a point at which I begin paying a price for having had too much yeast or too rapid a ferment. Any thoughts?

 

[Jmattioli]

So is it safe to say, as a rule of thumb, 1 gram per gallon for a good start?

I realize that most people pitch a 5g pack at the minimum regardless of the batch size but is there some 'magic' formula for figuring starting quantities for a good fermentation?

Each yeast is different and I recommend following manufactures recommendations. No, I would not use 1 g for a one gallon batch but I would use a 5g pack for 1 to 5 gallons if that is the yeast recommendation.

Also there is a study that shows there is some yeast degradation from generation to generation. So the 20th generation of yeasts would not be as superior as the first. That is why I recommend starting with the manufacturers packs rather than trying to mutiply them yourself to save a few bucks. Granted, if you have everything just perfect as they do in a laboratory, you might not even notice a difference but unless your conditions are perfect, each new generation will have more mutants (lol). True on a serious note but do whatever seems to work best for you and I will be glad to share a drink of your mead with you.
Joe

 

[Oskaar]

Joe and I have talked about this before and he knows I'm kind of unorthodox when it comes to pitching yeast. I like to have my must within a few degrees of the reydrated yeast, so if the must is too cool I'll run it through my counterflow chiller with warm/tepid water circulating to bring the temperature up to where I want it and pitch.

I stir the snot out of my must before, during and after the pitch, and then again about hourly for the first few hours. I use generally double what is called for in yeast, I beleive in massive overkill most of the time, unless I'm trying a new recipe or following a quantitative method, then I'll play by the rules.

I just do what I feel is right based on what I've done in the past, so a lot of times I don't even check the OG before I pitch until recently. Now I am checking the OG and SG as I rack, but I'm moving toward brix. I've had a refractometer that was kind of old and I put it out to pasture recently when I bought a new one, along with a new pH meter. I figured if I was spending the coin I shoud at least use the stuff.

Mostly I go by taste. If it tastes right at the beginning it'll taste right at the end as long as you monitor it throughout the cooking process

Cheers,

Oskaar