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Old 04-20-2010, 06:16 AM   #1
lpdb185
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Default ? about pitching washed yeast

i read the sticky and then proceeded to wash the WLP550 from my recent batch of belgian pale ale. i ended up with 2 pint jars that now contain about 1/2" or approximately 35-40ml of yeast slurry. i am about to use this washed yeast in the AHS La Chouffe clone. i believe i read that pitching rates are very important for the taste profile of this style and i want to do this correctly.

mr. malty says i need +/- 295B cells. in the pitch from slurry option, it says i need +/- 90ml of slurry to get 295B cells. so i deduce that there are roughly 100B cells (equivalent to a WLP vial) in 33ml of washed yeast slurry (is this accurate?). so if i was pitching a starter (according to mr. malty), i need a 1.8L starter with 1 vial or 1L with 2 vials. so, am i correct in assuming that i would be close enough to pitching the right amount of yeast if i threw my washed yeast (approximately 75-80ml combined) into a 1L starter? and if pitching rates are so important, wouldn't it matter if the starter was mid-fermentation versus post-fermentation when i pitch into the primary? how do you determine yeast cell reproduction rates for starters?

any input that can guide me in the right direction would be appreciated.



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Old 04-20-2010, 01:47 PM   #2
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Well, it's hard to say how many cells you have per ml of slurry. It all comes down to how well it was washed, I guess. If they say 90 ml (~300B cells) is what you need, I am sure that you will be fine with the 75ml in a 1 liter starter. As far as how to determine cell reproduction rates, it varies. Using a stir plate, shaking it and doing nothing will change the reproduction rates greatly. They say it's best to pitch a starter when it is at high krausen but I have done it post fermentation and it was fine.

I'm all over the place with this but hope I answered your questions at least a little bit.



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Old 04-20-2010, 05:57 PM   #3
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But if there's enough cells in 90 ml of slurry, then you don't need a starter at all. The starter should grow cells, but it sounds like you have enough cells already.

The trick is that how do you know how dense with yeast your slurry is or what the viability of that yeast is? I just assume that JZ's defaults on the calculator are good enough and go with his numbers.

If it were me, I'd just pitch the 90 ml of yeast you have directly.

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Old 04-20-2010, 07:13 PM   #4
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I'd make a starter with a jar what you have and pitch it. If you want your fermentation to take off more quickly then pitch at high krauesen, I however always chill then decant my starters.

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Old 04-21-2010, 05:17 AM   #5
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so, am i safe to assume that there would be roughly 100B cells per 30ml of washed yeast slurry in the bottom of my jars, or is the pitch from slurry option referring to unwashed yeast?

for those of you that wash and re-use yeast, how do you determine the volume of yeast you pitch into your starter?

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Old 04-21-2010, 05:46 AM   #6
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How long has your washed yeast been sitting? You can plug in a harvesting date in Mr.Malty and it will give you the percent viability of your washed yeast. After two weeks of sitting you will be down to about 30% viability. I'm not sure what that will do to your numbers, but you should take that into account if you haven't already.

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Old 04-21-2010, 12:45 PM   #7
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Without a microscope and a hemocytometer, it's a huge guessing game. The defaults on Jamil's pitching rate calculator on the pitch from slurry tab represent the average concentration and non-yeast percentage for slurry poured right out of the fermenter and settled for one week in the fridge. It's his calculator and he designed it for his process. If this is not the process you use, you need to adjust the sliders for your particular slurry. You will have less trub so adjust as necessary.
how to use the pitch from slurry tab



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