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Old 04-21-2010, 02:17 PM   #1
Paco
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Default "Exact" pitch rate from fridge slurry

Think I can be precise enough on my "calculated" pitch rate from a saved slurry that's been in the fridge for 5-6 months?

Here's the details:

-Thin slurry (WY 3068 - Weihenstephan Weizen) was harvest from Weizen batch (12.33 plato or 1.050) then put in 250ml jar in the fridge for future usage.

-Asked WY technicians about getting a good "banana" (isoamyl acetate) flavor. Reply is that pitch rate affect this aspect. Suggest 6 million cells/ml or a complete Activator pack. Also mentioned that "If you go above 12 million cells/ml, this flavor will not be very noticeable."

-Yesterday I got out of the fridge the jar of slurry and prepared (sterilized) a small (~750ml) starter to "wake up" the yeast. Let both the slurry jar and starter temperate and equalize for the night at ~21°C (70°F). The idea at this point is to verified the viability of the yeast and to harvest just the yeast cells in suspension to start up a new fresh starer again from ~500ml. I want to eliminate the dead cells and old trub.

-The slurry has already create a lot of pressure during the night. I crack open the jar when I got it out of the fridge so that was "new" pressure this morning. Again, this slurry was harvest on November 2009.

-I have to be somewhat accurate in my pitching rate to achieve something close to 6 million cells/ml and not getting too close or above 12 million cells/ml.

-WY technicians said that an Activator pack is about 90-100ml of thin slurry and that should be just what I want to get the flavor I want for a 20 liters batch.


Now the question... so I just need to build up roughly 100ml of thin slurry (per 20 liters batch) with my starter and I'll be fine?!

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Old 04-21-2010, 04:58 PM   #2
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This is the joy of "pitching rate calculators"... the concentation and non-yeast % of your slurry are sliders you just move around until you get the answer you like.

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Old 04-21-2010, 05:03 PM   #3
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The concentration of the slurry in your fridge should be roughly equivalent to that of a WLP or Wyeast package. If you start with about the same volume that's in one of those packages, assume you have about 100 billion cells.

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Old 04-21-2010, 06:41 PM   #4
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It's been what, 5 hours, and the yeast are already krausening and producing gas. I guess they're alive and most probably healthy.

The good and healthy ones are the one in suspension right? I'll transfer the liquid part of that starter onto new fresh sterilized wort toward diner time (in 4 more hours)...

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