Yeast Management?

[hopfen]

I've been looking for a while and can't get the answers I'm looking for.

I'm trying to figure out how to save and reuse yeast as needed.

We brew 20 gallon batches, conical fermentor

Using MrMalty with a 1.054 OG, stir plate we need 4.65 liters of starter. We'll use 3 smack packs to create this and pitch.

After 7 days, trub was removed, fermentation is finished and yeast was removed. We had approximately 1 liter of material including some trub and a good amount of yeast with some liquid.

We repitched this into a second batch of the same beer.

1 - Can anyone tell me about how much actual yeast we had?

2 - If I wanted to save this yeast for a period of time, can I divide this into vials to create starters?

3 - How much yeast should be in a vial to create a starter? It doesn't look like there is much yeast in a White Labs vial.

Please provide any relevant information.

thanks,

eric

 

[Suthrncomfrt1884]

1 - Can anyone tell me about how much actual yeast we had?

2 - If I wanted to save this yeast for a period of time, can I divide this into vials to create starters?

3 - How much yeast should be in a vial to create a starter? It doesn't look like there is much yeast in a White Labs vial.

Please provide any relevant information.

thanks,

eric

1. Roughly, 3-4 times the amount you started with. Obviously this is one of those answers that has a ton of variables to it, but on average, most yeast cells will replicate 3-4 times during fermentation. You also need to remember that trub consists of hops, dead yeast, break material, etc. Unless you wash the yeast, there's no way to know how many healthy yeast you have. Then, you can sometimes guess by how much collects at the bottom.

2. Yes, definitely. Here's an excellent write-up on starting your own yeast bank... https://www.homebrewtalk.com/wiki/index.php/Yeast_bank

3. Refer to the above link and you should have no problem. Between Mr. Malty, and stepping up starters, it shouldn't be too hard.

 

[nefarious_1_]

Mr. Malty:

Repitching Yeast

If you've brewed more than one batch, I'm sure you've noticed that there is a huge pile of yeast in the fermenter at the end. If (and that is a big 'if') you've got excellent sanitation all the way through the process and have provided proper yeast nutrition (including O2), you have a gold mine of healthy yeast ready to reuse. Of course, you don't want to reuse the whole thing. I know a number of people dump a new batch on top of the yeast cake, but you're not going to get the best beer that way. Yeast do need some growth to result in the right kind of ester profile, etc. While too big a pitch is better than too little, it is pretty easy to figure out how much you need and pitch just that.

There are about 4.5 billion yeast cells in 1 milliliter of yeast solids (solids with no excess liquid). According to Fix, in a slurry, only about 25% of the mass is yeast solids. Of course, if there is a lot of trub in there, you have an even lower percentage of yeast solids. The bad thing is that you can't tell how viable that yeast is, unless you have the equipment to properly test and count it. So this is where it gets a little bit like black magic. There are a number of factors that affect the viability of a given pitch of yeast. How old is the yeast? How stressful was their last fermentation? Have they had the proper environment and nutrients for successful reproduction or are they too scarred and tired to go on?

When the yeast is fresh and healthy off an previous batch, viability is maybe around 90%+. It goes down from there fairly quickly without proper storage and it also really depends on the strain of yeast. Unless you're going to get into testing viability, you're going to need to make some educated guesses and keep good notes on the results. This is where being a yeast psychic really helps. Start in a range of 80 to 90% viability and you probably won't be too far off. Use the Pitching Rate CalculatorTM to help figure out how much of that yeast you need. If your yeast viability is much lower than 90%, you should probably toss the yeast. If you really want to use it, you might consider pitching it in some starter wort to get the still viable cells active. When they're in solution, decant that active part of the starter into another vessel, hopefully leaving the dead cells behind.

http://www.mrmalty.com/pitching.php

 

[Hatchbrew]

I repitch my yeast three times before starting anew. But a vial of yeast allows me yeast for about 26+ batches of beer.

 

[hopfen]

Thanks for the great info. It's exactly what I was looking for.


Another question,

What about over pitching? If we run two or three batches in a row, do we run the risk of over pitching if we just collect and repitch the slurry?

eric

 

[Clementine]

Yes, the down side of this is you might not get the flavor profile you are looking for esters are mostly made during the reproduction cycle of yeast.

Also (not sure just educated guess) they yeast will still multiply as there will be some O2 present hence you will end up with a lot more yeast and they will consume sugar making babies and not alcohol so you could end up with less alcohol.

Just use MrMalty to figure out your pitching rates and stick around the 10MYC per ml or wort.

Clem

 

[Suthrncomfrt1884]

Also (not sure just educated guess) they yeast will still multiply as there will be some O2 present hence you will end up with a lot more yeast and they will consume sugar making babies and not alcohol so you could end up with less alcohol.

You're somewhat right..

Yeast will reproduce until the oxygen supply is consumed. When there is no longer any oxygen, they will then start to convert sugar into alcohol. This is why aerating your beer is so important. If you have lots of oxygen, they will produce more yeast cells...creating a cleaner fermentation in the end.

 

[hopfen]

sorry but what is ??? stick around the 10MYC per ml or wort.

 

[Clementine]

I will see if I can get this straight...
Correct pitch rate (ALE) is around 10 Million Yeast Cells (MYC) per milliliter of wort for an OG of 1.048. If you make a spreadsheet with the formula
Cells to pitch = ml's of wort x (1-OG/48) x 10MYC and put the same numbers in to Mr Malty you can see that this how Jamil calculates the required Yeast Cell count.

If you go further and use cell concentration for different types of starters (traditional, shaken, intermittent aeration and stirplate you can get the size starter you need and again the numbers match up with MrMalty.

I made a spreadsheet and I tried to upload it however only images can be uploaded so here is an example of what I did.

 

[hopfen]

Thanks for the info.