Harvesting Yeast ?'s

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Harvesting Yeast ?'s

Postby Herr brew miester on Tue Jan 10, 2012 9:46 am

I have begun to harvest and reuse my yeast in an effort to reduce the already ridiculous per pint cost that I am presently at. On my first attempt I believe I under pitched as fermentation began slowly, (fermentation started in about 24-30 hours) fermentation was not very vigorous and 1 carboy is fermenting less vigorously than the other. So I have a few questions about how much harvested yeast to use and if you can tell how many yeast cells you have to avoid under and over pitching.

1. After harvest and washing how much yeast volume should be used to ferment a 1060 beer
2. Is a starter necessary for the same 1060 beer
3. Is there a formula for determining amount of yeast cells in a definite volume of harvested yeast
4. I harvested 4 cups of yeast from my last APA that finished at 1058; is 1 cup enough to do 2 starters for 10 gallons of beer or should I use all of the 4 cups
:cheers:
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Re: Harvesting Yeast ?'s

Postby lexuschris on Tue Jan 10, 2012 11:23 am

All your answers and more at Mr. Malty's Pitching Calculator!
Check out the tab for 'repitching from slurry'.

I would say that building a starter (with a stirplate) is the best way to ensure happy & healthy yeast.

I do not think yeast slurry keeps very long in the fridge ... most folks mention no more than 4 weeks. So, if you have a bunch, use what will get you the best healthy yeast count.

Good luck!
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Re: Harvesting Yeast ?'s

Postby BrewMasterBrad on Tue Jan 10, 2012 12:30 pm

Unless you have a microscope and a hemocytometer, there is no way to determine the yeast cell density in your slurry. As a result, re-pitching from a slurry for a homebrewer is largely a guessing game.

I am a serial re-pitcher since I believe with proper handling that third or fourth generation yeast is far superior to the first generation in regard to cell count and viability (plus I'm cheap). I ferment in converted Sanke kegs and store my harvested yeast in borosilicate flasks. I don't wash my yeast since the fewer times I handle the yeast the less chance there is for me to screw something up.
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Re: Harvesting Yeast ?'s

Postby Herr brew miester on Tue Jan 10, 2012 12:40 pm

BrewMasterBrad wrote:Unless you have a microscope and a hemocytometer, there is no way to determine the yeast cell density in your slurry. As a result, re-pitching from a slurry for a homebrewer is largely a guessing game.

I am a serial re-pitcher since I believe with proper handling that third or fourth generation yeast is far superior to the first generation in regard to cell count and viability (plus I'm cheap). I ferment in converted Sanke kegs and store my harvested yeast in borosilicate flasks. I don't wash my yeast since the fewer times I handle the yeast the less chance there is for me to screw something up.

So are you using the entire amount of harvested yeast or just a portion of it? Example if you harvest 4 cups of slurry from 10 gallons do you use all 4 cups on your next batch or just a portion of it? If just a portion how much and what are your determining factors?
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Re: Harvesting Yeast ?'s

Postby Herr brew miester on Tue Jan 10, 2012 12:50 pm

lexuschris wrote:All your answers and more at Mr. Malty's Pitching Calculator!
Check out the tab for 'repitching from slurry'.

I would say that building a starter (with a stirplate) is the best way to ensure happy & healthy yeast.

I do not think yeast slurry keeps very long in the fridge ... most folks mention no more than 4 weeks. So, if you have a bunch, use what will get you the best healthy yeast count.

Good luck!
--LexusChris

Nice link and thanks as it has already answered most of my questions. I will put it to work on my next brew day this Saturday. I’ll let you know how it works out.
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Re: Harvesting Yeast ?'s

Postby brahn on Tue Jan 10, 2012 12:59 pm

It's difficult to give you a straight answer because it really depends. How thick is the slurry? What was the gravity of the previous beer? How healthy were the yeast that were harvested? How much time is passing between harvest and re-pitching? How big of a batch are you making? Two 5 gallon batches or 1 10 gallon batch?

If you're keeping the yeast in the fridge more than a week or so, I would recommend making another starter. As a total WAG I'd probably use about 500ml of slurry in a 4-5L starter on a stir plate for 10 gallons. Then I'd toss the rest of the saved slurry and re-use the yeast from the next batch if you want.

The calculator that lexuschris linked to really is your friend. I'd also recommend looking through the podcast history of the Jamil show, there are some good conversations about yeast re-use in the archives. The Yeast book is also a good resource.

Like Brad said, you really need a scope and hemocytometer to quantify how much healthy yeast you have in the fermentation (or slurry). Using lag time or the rate of bubbles coming from your fermenter is not a great measurement. The final gravity and taste of the beer are better measurements than lag time and bubble rate, IMO.
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Re: Harvesting Yeast ?'s

Postby Herr brew miester on Fri Jan 13, 2012 10:49 am

Ok so I completed the yeast starter and not sure if the results are good or not. I was expecting to see a larger amount of yeast cake at the bottom of my flask but it has not increased in size much. I pitched 74 ml of yeast that’s about 6 tbls. I checked the gravity and after 18 hrs the gravity is 1010 and the flasks were placed in the fridge. I was even thinking about doing another step and re-pitching this yeast back onto a fresh 1500 ML of 1035 wort. Below are some pictures of the process including the amount of yeast cake after being refrigerated for 10 hours. Any opinions?
Sanatised flasks and harvested yeast Image
6000 ml boiling wort, 15 mins Image
transfered to flasks and in ice bath. Pitching temp 70 Image
yeast thickness; adjusted the calculator to thick yeast 3.5 out of 4.5 Image
2.5 hrs Image
8 hrs Image
12 hrs Image
after 10 hrs in the fridge Image
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Re: Harvesting Yeast ?'s

Postby brahn on Fri Jan 13, 2012 11:25 am

I can't see the pictures, but it sounds like it completed fermentation. In a 6L vessel, even a thin layer of yeast along the bottom actually contains quite a few cells. It can be deceptive. Going from a 6L ferment and re-pitching into a 1.5L ferment will probably do more harm than good, unless you do it only a few hours before pitching to "wake the yeast up". You won't grow healthy yeast that way though.
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Re: Harvesting Yeast ?'s

Postby Herr brew miester on Fri Jan 13, 2012 11:41 am

brahn wrote:I can't see the pictures, but it sounds like it completed fermentation. In a 6L vessel, even a thin layer of yeast along the bottom actually contains quite a few cells. It can be deceptive. Going from a 6L ferment and re-pitching into a 1.5L ferment will probably do more harm than good, unless you do it only a few hours before pitching to "wake the yeast up". You won't grow healthy yeast that way though.

I actually divided the 6000ml of boiled wort into 4 separate 1500ml starters before chilling and pitching my harvested yeast. I am probably just worrying to much about it and will be pitching this yeast tomorrow when I and Arrogant Dan brew 20 gallons of our red Ale. I'll post the conditions of the fermentation and I am hopeful this first attempt of yeast harvest goes well.
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Re: Harvesting Yeast ?'s

Postby Herr brew miester on Mon Jan 16, 2012 5:29 pm

Just wanted to report back that all went very well with our first yeast harvest and proper size starter. All 20 gallons started quick and are in active fermentation. Thanks for the comments and the Mr malty link.
Image Good fermentation.
Image Finsihing up the second boil.
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