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Old 08-31-2011, 10:17 PM   #1
angrybits
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Per the Safbrew WB-06 PDF:

Viable cells at packaging: 6 x 10^9 / gramme

So, if that is an 11.5g sachet, then wouldn't that make the pitching cell count 69 billion? I understood that pitching cell count for a typical 5 gallon batch is in the neighborhood of 200 billion.

I am pretty sure I missing something, just wondering what it is.



 
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Old 08-31-2011, 11:24 PM   #2
Clementine
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Depends of what a typical batch is, a better way to check your pitch rate is to calculate it from a program like Mr Malty or use the equation

(OG-1)*1000/48*pitchrate*ml or wort=Yeast cells to be pitched

so OG 1.056
5 gallons = 19000ml approx
pitch rate for ales = 6-10 Million Yeast cells per ml
pitch rate for lager = 15 Million Yeast cells per ml

56/48*(or 6)10*19000 = Millions of yeast cells to pitch

133 - 221 (ish) Billion Yeast cells

Therefore it would take 1.9 - 3.2 packets of dry cells to correctly pitch.

So I guess you are asking why do companies give you one packet is a beer kit and say go for it.... well I don't know, what I do know is if you either calculate it or use Mr Malty it will tell you to go and buy more yeast.

The effects of under pitching are increased fusel alcohol and ester flavors and poor attenuation (possible stuck brew).

Hence a lot of people just make their own yeast and save the money. My yeast making takes me total about 1 1/2hours spread over 5-9 days to make a batch of yeast and cost me next to nothing (after initial purchases of pressure cooker, stir plate and flasks). It also give me a 99% grantee of success as I know my yeast is in good order ready to go to work for me. I also like that I have more understanding and involvement with my beer.

Clem



 
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Old 09-01-2011, 12:00 AM   #3
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I rarely pitch more than one pack of dry yeast. All it does is add a couple hours to the growth time.
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Old 09-01-2011, 12:09 AM   #4
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Right, that lines up with what I was thinking as well. But I keep seeing people being advised that dry yeasts do not require starters, and I have even seen it said that there are already 200+ billion viable cells in the typical sachet. Just trying to understand why a starter with a liquid yeast at 100 billion is universally agreed upon, but it's almost universally agreed upon that dry yeasts don't need it.

My end goal is deciding whether or not to do a starter for the WB-09 that I bought today. Thanks for the replies!

 
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Old 09-01-2011, 12:20 AM   #5
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It probably does add to your lag time, the yeast have to replicate further, this leads to more esters as they form this will reproducing also the yeast may have less numbers and therefore be more strained and strained yeast produce more fusel alcohols (that is the theory). I guess if you manage to have enough nutrients and O2 underpitching only draw back would be the higher level of esters from the increased amount of reproduction?

Until we can interview the yeast we can't be certain of what goes on in our fermenters as amateurs we are, so I look to the pros and beer science says give'm a set pitching rate, I will, until I see good science to say that it is a bad idea.

Since switching to liquid yeast I have had two stuck brews (when I first started) and that was without starters and dodgy yeast from LHBS. Since then I have cultured my own yeast and pitched according to recommended rates and not had a single problem plus to confidence in knowing my yeast is alive healthy and ready to do it job makes me not want to change my process. Most of my brews finish fermenting in 72hrs and then they clear for another week then bottled, my latest a pumpkin ale OG 1.064 when down to 1.016 in 56hrs.

In the end it is what works for you, I think if you have a process that works for you, then stick with it. I like the science side of playing with my yeast, my wife does call me an obsessed science geek, but it makes good beer.


Last minute addition I just saw the OP add another post, to address that issue the reasons I have heard about not doing a starter with dry yeast and my understanding is, it is cheap (cheaper to by another packet than make a starter) and very healthy when dried out. So when rehydrated they are ready to work for you vs liquid yeast can get a bit knocked about and loose viability in transit (time, temp light etc) so a starter increases numbers and confirms viability.

Clem

 
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Old 09-01-2011, 01:15 AM   #6
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Quote:
Originally Posted by Clementine View Post
Last minute addition I just saw the OP add another post, to address that issue the reasons I have heard about not doing a starter with dry yeast and my understanding is, it is cheap (cheaper to by another packet than make a starter) and very healthy when dried out. So when rehydrated they are ready to work for you vs liquid yeast can get a bit knocked about and loose viability in transit (time, temp light etc) so a starter increases numbers and confirms viability.
Ahhh, okay that adds some clarity around it. Thank you for posting!

 
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Old 05-09-2013, 12:47 AM   #7
jasonslay
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Turns out the density is closer to 20B/g. See http://seanterrill.com/2011/04/01/dry-yeast-viability/

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Old 05-09-2013, 03:21 AM   #8
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With dry yeast, it's more advantageous to rehydrate it (in 95-105*F boiled/chilled tap water) than to make a starter with it.


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