Slurry re-pitch timing

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Hedo-Rick

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I usually harvest about 100-125 ml of lager yeast from my fermenter 2-3 days before I brew again.

The yeast has been harvested, but unfortunately I can't get to my next brew day for two weeks now.

Should I be concerned about the yeast health/vitality considering I've harvested and am holding the yeast two weeks instead of re-pitching 2-3 days from harvesting?
 
Two weeks is still OK for slurry, I've used much older slurry but would normally make a starter for anything older than about 2 weeks. You'd want about a cup (250mL) for 5 gallons of a 1.050 lager with two week old yeast though (depending on thickness and non-yeast percentage), so a starter might be needed.
 
Harvest some more? Is this from a conical?

As long as it's stored in a fridge it should remain fine for 2 weeks. You could do a vitality starter on brew day, 4 hours before pitching. That would be my route.
 
You could do a vitality starter on brew day, 4 hours before pitching. That would be my route.

It's not from a conical. I carefully harvest out of the bottom of by brewing bucket. What would be your suggested process be for building a 'vitality starter' out of the 125 ml of (very clean and dense) yeast I have harvested?
 
A vitality starter is just a starter that's pitched as the yeast are becoming active (about 4 hours up to about 12 hours) - the entire starter is pitched and may need to be considered in the recipe design. I like using them because the lag phase is reduced and the starter doesn't need to be as big as with a traditional starter. Per Mr Malty, your 1/2 cup of two week old slurry has about 200 billion cells; in 5.5 gallons of 1.050 lager you need close to 400 billion cells which needs a 3.5 litre simple starter. Using a vitality starter, I'd suggest using 1.5 to 2 litres. IME it doesn't really matter if you use a stir plate or not with vitality starters - they still take off strongly.
 
@Gnomebrewer pretty much answered it. A 1.5-2 liter vitality starter should be plenty. Pitch the whole thing, no cold crashing and decanting.

If you have a stir plate use it, it reduces the chance of volcanic eruption. If you have it, add a drop of Fermcap to reduce foaming.
Also use a vessel with a large enough headspace.
 
FWIW, I pitched yeast yesterday that had been in my fridge for 4 weeks. It was pitched around 1pm yesterday, and there was bubbling in the morning. It's obviously too early to know how vigorous the fermentation will be and whether I'll get down to the proper FG, but the early signs are good. I pitched about 8 ounces that was poured directly from the trub of a prior batch.
 
125mL sounds low for a Lager.

I repitch ale yeast pretty often and use a rate of about 1/2 cup per five gallons for yeast harvested on brew day and 1.5x to 2x that amount for yeast 2-4 weeks old. My experience with lagers is not large but I'd expect needing twice as much yeast I'd need for ales.

Vitality starter sounds like a good idea. Just make it on morning of brew day. Boil a filtered water and DME (10% DME by weight), cool to room temp. Stir Plate and an erlenmeyer flask is great but a mason jar and swirling by hand will work fine too. Given you have 125mL yeast probably will want a 1 liter starter.
 
I dip a 1 qt mason jar into the wort after 10 min on the boil,and put in freezer. When chilled I pitch the saved yeast,let it get foamy ~ 4 hrs then pitch the whole thing. Ends up being ~ 1 liter.
 
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Maybe it is. I've read a lot of Kai's work at http://braukaiser.com, and worked of his information and have brewed so tasty lagers.

If your interested and have the time, below is a good read on lager production.

http://braukaiser.com/wiki/index.php/Fermenting_Lagers

Anyway, thanks for taking the time to reply and the information!

Thanks that was a good read. He mentioned for conventional fermentation at a traditional german brewery...
"Yeast is pitched at about 500 ml thick yeast slurry per 100 l 12 °P (1.048 SG) wort (this equals about 100ml or 3oz yeast slurry per 5 gal)."

Unless you also matched the professional's ability to remove hot and cold break and trub before fermenting the batch you are harvesting from the slurry you collect is probably has fewer viable cells per mL than what the pros are using. If you are brewing in a conical and settling/dumping the cold break before pitching yeast you might come close but otherwise I think it is pretty hard for homebrewers to really eliminate cold break.
 
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