How much to pitch

Hey all,

I was in need of some yeast fast and went to the local brewery to get some fresh stuff out of the tank but they didn't have anything available. They did however have an unused direct pitch from Wyeast for their 2 bbl brew house. It has been in cold storage for about 6 weeks. I brought it home and threw it in a 2L flask to see how much I actually have. Looks like 750ml of thick slurry and about 250ml beer once it separated. I am going to pitch into 10 gallons of 1.070 wort tomorrow afternoon. I couldn't find a calculator to help me out so I thought i might ask. I was planning on adding 400ml of starter wort to wake things up since it is 6 weeks old. What do you all think? How much starter wort should I add and how much should I pitch into each 5 gallon carboy?

Use Mr. Malty. Set the harvest date as today (I really think their viability numbers are wrong, provided the yeast has been stored properly), and it should provide you with an idea of how much to pitch. If the yeast looks fine, I wouldn't bother with a starter.

Calder said:

Use Mr. Malty. Set the harvest date as today (I really think their viability numbers are wrong, provided the yeast has been stored properly), and it should provide you with an idea of how much to pitch. If the yeast looks fine, I wouldn't bother with a starter.

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I don't want to over pitch and if I have enough yeast for a 2bbl pitch according to Wyeast I am concerned if I just dump half of it per 5 gallon carboy I am going to be way over. I don't know the math to figure out what a good volume to pitch is unless I am using a smack pack or vial and the home brew calcs like Mr Malty.

Many say these calculators are too conservative but MrMalty suggests you need about 750Ml for a 10g batch based on 6 week old repitch from slurry if I am reading it correctly.

el_caro said:

Many say these calculators are too conservative but MrMalty suggests you need about 750Ml for a 10g batch based on 6 week old repitch from slurry if I an reading it correctly.

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Apart from having to guess at the yeast concentration, and dial in non-yeast percentage, Mr. Malty is really conservative with it's viability numbers. It claims a yeast harvested today has 94% viability, and one harvested 6 weeks ago has 27% viability. That means if the slurry is 6 weeks old, you need more than 3 times the amount to pitch. I just don't believe it.

At 8 weeks it is down to 10 percent ........ and guess what, it is still 10% at 11 months. So you loose 90% viability in the first 8 weeks and then it is unchanged for up to a year. The viability numbers just are not right.

I always recommend calculating as though you just harvested the yeast, and maybe bumping it up a little if you want.


So this is a direct pitch yeast pack (not slurry) from Wyeast.

1 BBL is about 31 gallons. 2 BBL = 62 gallons. You are brewing 1/6th of this, so you will need roughly 1/6th of the yeast, or about 130 ml (make it 150 ml for good measure).

Calder said:

Apart from having to guess at the yeast concentration, and dial in non-yeast percentage, Mr. Malty is really conservative with it's viability numbers. .

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Agree .
YeastCalc is even more conservative beyond 6 months - it drops viability to 1%?

I ended up throwing 800ml of 1.040 starter wort onto the yeast on a stir plate just to wake it up for about 18 hours. I split the then 1600ml of yeast slurry between the 2 carboys. There was a 17 hour lag phase before a krausen started to form. Ill take it I pitched the right amount I figure if I had over pitched there wouldn't have been a growth/lag phase at all.