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General Category => Yeast and Fermentation => Topic started by: Wort-H.O.G. on November 06, 2014, 11:05:39 AM

Title: dry yeast cell counts
Post by: Wort-H.O.G. on November 06, 2014, 11:05:39 AM
I don't use dry yeast very much, and am using it for an apple ale this weekend- using s-04.

seems like much variability in consensus of cell count per gram of dry yeast. for my 1.050 apple ale, target pitch is 185BB. 2 packs of s-04 at 6BB (manufacturer count) would require me to pitch 31g or almost 3 packs.

are the  manufacturers estimates solid or should i use higher average cell count per gram?

Kai's findings:

Dry Yeast - billions of cells per gram:

    No one agrees on the number of yeast cells per gram in dry yeast!
    This is made more confusing because each yeast strain has different size cells and clumping tendencies.
    We put in a reasonable default of 10 billion cells per gram of dry yeast.
    Kaiser located a study which reports the following data on dry yeast ranging from 8-18 billion cells per gram:
    Yeast    B cells/g
    Safale K-97    14
    Safale S-04    8
    Safbrew T-58    18
    Safbrew S-33    16
    Saflager S-23    10
    Saflager S-189    9
    Adapted from: Van Den Berg, S., & Van Landschoot, A. (2003). Practical use of dried yeasts in the brewing industry. CEREVISIA, 28(3), 25-30 (Table 1).

    Mr.Malty says that dry yeast contains 20 billion cells per gram. Unfortunately we could not find a reference to a study that supports that number.
    From the manufacturers:
        Fermentis: > 6B cells/gram for US-05 and S-04.
        Danstar: > 5B cells/gram for Nottingham yeast.
        These numbers sound conservative and do not match with the study referenced above. According to our pitching calculator, with dry yeast, using the mfg's number of 6B cells/g, to hit a pitch rate of 0.75 (M cells / ml / ° P) for a 5 gallon batch @1.050 would require 3x 11g packs!
    Link to a researcher claiming 20B, but only has an n of 1.
    Most dry yeast packs come in 5g or 11g amounts. With dry yeast, starters are typically not made because dry yeast is relatively cheap - just buy more packs to hit the target pitch rate.

Title: Re: dry yeast cell counts
Post by: hopfenundmalz on November 06, 2014, 01:09:57 PM
Good information. Thanks.
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 06, 2014, 03:48:56 PM
Good information. Thanks.

good but seemingly more difficult to determine correct pitch with so much variability in starting cell count per gram of dry yeast.
Title: Re: dry yeast cell counts
Post by: denny on November 06, 2014, 04:19:34 PM
Did Kai say how big a sample he used?  How many packs of each were evaluated to make sure he wasn't seeing an anomaly?
Title: Re: dry yeast cell counts
Post by: denny on November 06, 2014, 04:20:11 PM
Did Kai say how big a sample was used?  How many packs of each were evaluated to make sure they weren't seeing an anomaly?
Title: Re: dry yeast cell counts
Post by: archstanton on November 06, 2014, 05:13:44 PM
I would go with the manufacturers, they have phd's in microbiology and do cell counts for a living.
If you do then assume the manufacturers are correct, it will shatter the validity of the "pitching rate" and the liquid starter necessity. Which also just so happens to be what the manufacturers say. HMMMM
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 06, 2014, 05:36:37 PM
Did Kai say how big a sample was used?  How many packs of each were evaluated to make sure they weren't seeing an anomaly?

no that's all the info. mentions manufacturer data likely conservative.
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 06, 2014, 05:52:21 PM
Did Kai say how big a sample he used?  How many packs of each were evaluated to make sure he wasn't seeing an anomaly?

got a feeling you've got experience and opinion on this- what say you good sir?  trying to make sense of the dry yeast world.
Title: Re: dry yeast cell counts
Post by: denny on November 06, 2014, 06:21:07 PM
Did Kai say how big a sample he used?  How many packs of each were evaluated to make sure he wasn't seeing an anomaly?

got a feeling you've got experience and opinion on this- what say you good sir?  trying to make sense of the dry yeast world.

Nothing specific, but it just strikes me as strange that yeasts from the same manufacturer would vary so widely.  I dunno, maybe it's not weird in reality.  But unless we know the sample size, I question how much validity the data has.  I mean, what if they only tested one pack of each?  That seems unlikely, but we just don't know.
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 06, 2014, 06:25:52 PM
Did Kai say how big a sample he used?  How many packs of each were evaluated to make sure he wasn't seeing an anomaly?

got a feeling you've got experience and opinion on this- what say you good sir?  trying to make sense of the dry yeast world.

Nothing specific, but it just strikes me as strange that yeasts from the same manufacturer would vary so widely.  I dunno, maybe it's not weird in reality.  But unless we know the sample size, I question how much validity the data has.  I mean, what if they only tested one pack of each?  That seems unlikely, but we just don't know.

precisely- that's the dilemma. mr. malty generically list every dry yeast at 20bb/gr, and im sure other calcs use some default that varies from the others. seems like 10bb/gr would be reasonable minimum expected, but hen again reason doesn't always pan out.
Title: Re: dry yeast cell counts
Post by: a10t2 on November 06, 2014, 06:29:26 PM
I've only done counts on US-05 (and only a few) but it runs 20 billion/gram, give or take.
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 06, 2014, 06:31:47 PM
I've only done counts on US-05 (and only a few) but it runs 20 billion/gram, give or take.

and manufacturer list 6BB/gr for US-05...go figure.

so perhaps experience can weigh in here. for avg 1.050 ale with target of approx 185-200BB- a.) have you pitched 1 pack with good results or where there signs of under pitching, or b) have you pitched 2 or 3 packs with good results or where there signs of over pitching.
Title: Re: dry yeast cell counts
Post by: ynotbrusum on November 07, 2014, 03:21:44 AM
34/70 pitches fine in 5 gallons of sub 1.050 wort at lager temps, but I rehydrate :P
Title: Re: dry yeast cell counts
Post by: morticaixavier on November 07, 2014, 03:35:15 AM
I've only done counts on US-05 (and only a few) but it runs 20 billion/gram, give or take.

and manufacturer list 6BB/gr for US-05...go figure.

so perhaps experience can weigh in here. for avg 1.050 ale with target of approx 185-200BB- a.) have you pitched 1 pack with good results or where there signs of under pitching, or b) have you pitched 2 or 3 packs with good results or where there signs of over pitching.

one packet (11 grams) in 1.050 is just fine. I'd even go one packet in 5 gallons of 1.070 and not worry about it.

I suspect the manufacturers estimate low in order to prevent complains. of course they also say 200b cells per packet which, by the way is just about 20b/gram
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 07, 2014, 03:39:36 AM

I've only done counts on US-05 (and only a few) but it runs 20 billion/gram, give or take.

and manufacturer list 6BB/gr for US-05...go figure.

so perhaps experience can weigh in here. for avg 1.050 ale with target of approx 185-200BB- a.) have you pitched 1 pack with good results or where there signs of under pitching, or b) have you pitched 2 or 3 packs with good results or where there signs of over pitching.

one packet (11 grams) in 1.050 is just fine. I'd even go one packet in 5 gallons of 1.070 and not worry about it.

I suspect the manufacturers estimate low in order to prevent complains. of course they also say 200b cells per packet which, by the way is just about 20b/gram

So your experience is that one packet isn't under pitching? Just asking because 6b/gr is a long way off from 20b/g
Title: Re: dry yeast cell counts
Post by: HoosierBrew on November 07, 2014, 12:58:42 PM

one packet (11 grams) in 1.050 is just fine. I'd even go one packet in 5 gallons of 1.070 and not worry about it.


+1. I prefer liquid cultures but have used dry yeast many times for short notice brewing.  When I get up around 1.075-ish I'll use 2 packets. Up to that point 1 has worked perfectly fine for me.
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 07, 2014, 01:16:03 PM

one packet (11 grams) in 1.050 is just fine. I'd even go one packet in 5 gallons of 1.070 and not worry about it.


+1. I prefer liquid cultures but have used dry yeast many times for short notice brewing.  When I get up around 1.075-ish I'll use 2 packets. Up to that point 1 has worked perfectly fine for me.

awesome guys thanks for the info-good timing as in an hour i will be pitching the rehydrated yeast.
Title: Re: dry yeast cell counts
Post by: morticaixavier on November 07, 2014, 03:53:07 PM

I've only done counts on US-05 (and only a few) but it runs 20 billion/gram, give or take.

and manufacturer list 6BB/gr for US-05...go figure.

so perhaps experience can weigh in here. for avg 1.050 ale with target of approx 185-200BB- a.) have you pitched 1 pack with good results or where there signs of under pitching, or b) have you pitched 2 or 3 packs with good results or where there signs of over pitching.

one packet (11 grams) in 1.050 is just fine. I'd even go one packet in 5 gallons of 1.070 and not worry about it.

I suspect the manufacturers estimate low in order to prevent complains. of course they also say 200b cells per packet which, by the way is just about 20b/gram

So your experience is that one packet isn't under pitching? Just asking because 6b/gr is a long way off from 20b/g

that has been my experience. I have been dinged in competition for too few esters pitching 1 packet of us-05 into 5 gallons of 1.065 IPA
Title: Re: dry yeast cell counts
Post by: S. cerevisiae on November 07, 2014, 04:10:39 PM
Nothing specific, but it just strikes me as strange that yeasts from the same manufacturer would vary so widely.

The cell count per gram delta is due to yeast cell size. 
Title: Re: dry yeast cell counts
Post by: S. cerevisiae on November 07, 2014, 04:32:23 PM
So your experience is that one packet isn't under pitching? Just asking because 6b/gr is a long way off from 20b/g

You are reading the specification incorrectly.  The number listed is the lower bound, not the upper bound or actual cell count.  For those who have studied computer science (comp sci), think of the number as Ω(cell_count_per_gram), not O(cell_count_per_gram) or Ɵ(cell_count_per_gram).  Comp sci types can also think of yeast cell growth as O(2n).  I know that comparing yeast cell counts to asymptotic growth rates is a weird analogy, but hopefully it helps a few forum readers.
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 07, 2014, 05:44:49 PM
Other than "I'm reading the specification incorrectly", I don't understand but take your experienced word!


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Title: Re: dry yeast cell counts
Post by: morticaixavier on November 07, 2014, 05:54:29 PM
Other than "I'm reading the specification incorrectly", I don't understand but take your experienced word!


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basically he's saying that 6b/gram is the lowest cell count you can expect to encounter within the best by window.
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 07, 2014, 06:32:01 PM
Other than "I'm reading the specification incorrectly", I don't understand but take your experienced word!


Sent from my iPad using Tapatalk

basically he's saying that 6b/gram is the lowest cell count you can expect to encounter within the best by window.

ok. i pitched 1 packet so lets see how she rolls. thanks again.
Title: Re: dry yeast cell counts
Post by: S. cerevisiae on November 07, 2014, 07:01:48 PM
basically he's saying that 6b/gram is the lowest cell count you can expect to encounter within the best by window.

Thanks, Jonathan!  Sometimes, it is difficult to remember that terms like "lower bound" are foreign to many people.  It's one of those terms that people with comp sci, engineering, or math backgrounds take for granted.
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 07, 2014, 08:16:28 PM
basically he's saying that 6b/gram is the lowest cell count you can expect to encounter within the best by window.

Thanks, Jonathan!  Sometimes, it is difficult to remember that terms like "lower bound" are foreign to many people.  It's one of those terms that people with comp sci, engineering, or math backgrounds take for granted.

yes sir-no engineer here  ;D i did sleep at a holiday inn last night
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 08, 2014, 05:31:27 PM
Other than "I'm reading the specification incorrectly", I don't understand but take your experienced word!


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basically he's saying that 6b/gram is the lowest cell count you can expect to encounter within the best by window.

ok. i pitched 1 packet so lets see how she rolls. thanks again.

well took off in about 7 hours and is like a tornado in there ripping through those sugars with a vengeance.
Title: Re: dry yeast cell counts
Post by: archstanton on November 08, 2014, 07:32:04 PM
Other than "I'm reading the specification incorrectly", I don't understand but take your experienced word!


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basically he's saying that 6b/gram is the lowest cell count you can expect to encounter within the best by window.

What the specification sheet from Fermentis says is- in a typical analysis you will see greater than 6 billion cells per gram at packaging.  This is different from the number of cells you can expect to get, as that number will depend on a number of factors- such as storage and rehydration.

I have pitched 1 and 2 packs of US-05 into 1.060 worts and liked the results of both, no real distinction between the two. I have also pitched 1 rehydrated and one straight into equal worts and noticed no ascertainable difference in the resulting beers.

What my experience has shown me is that there is a very wide range of "pitching rates" which will make very good beer. Chasing down a specific number that is in the billions is futile. Consistency with your processes is far more important to me. You have to decide for yourself what you like.
Title: Re: dry yeast cell counts
Post by: S. cerevisiae on November 08, 2014, 09:38:07 PM
What my experience has shown me is that there is a very wide range of "pitching rates" which will make very good beer. Chasing down a specific number that is in the billions is futile. Consistency with your processes is far more important to me. You have to decide for yourself what you like.

Bingo!  That's what I have been saying since I joined the forum.  Far too many brewers are fretting over the numbers provided by pitching calculators.  Yeast cultures are like atomic weapons in that one does not need pin-point accuracy in order to obtain effective results, especially when using extremely forgiving yeast cultures such as Siebel Bry 96 (a.k.a. Ballantine "Beer" Brewery, "Chico," Wy1056, WLP001, US-05 ...) and Whitbread "B" (a.k.a. NCYC 1026, Wy1098, WLP007, S-04 ...).
Title: Re: dry yeast cell counts
Post by: mblanks2 on November 09, 2014, 11:26:09 AM
Other than "I'm reading the specification incorrectly", I don't understand but take your experienced word!


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basically he's saying that 6b/gram is the lowest cell count you can expect to encounter within the best by window.

ok. i pitched 1 packet so lets see how she rolls. thanks again.

well took off in about 7 hours and is like a tornado in there ripping through those sugars with a vengeance.

You should have no issues at all with this strain at this gravity. As stated earlier by others, I've had great performance up to 1.070 with one package. I do rehydrate, though.
Title: Re: dry yeast cell counts
Post by: Wort-H.O.G. on November 09, 2014, 11:27:55 AM

Other than "I'm reading the specification incorrectly", I don't understand but take your experienced word!


Sent from my iPad using Tapatalk

basically he's saying that 6b/gram is the lowest cell count you can expect to encounter within the best by window.

ok. i pitched 1 packet so lets see how she rolls. thanks again.

well took off in about 7 hours and is like a tornado in there ripping through those sugars with a vengeance.

You should have no issues at all with this strain at this gravity. As stated earlier by others, I've had great performance up to 1.070 with one package. I do rehydrate, though.

Seems so. I rehydrated yeast also.


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Title: Re: dry yeast cell counts
Post by: trentmark on November 17, 2014, 07:35:58 PM
I don't use dry yeast very much, and am using it for an apple ale this weekend- using s-04.

seems like much variability in consensus of cell count per gram of dry yeast. for my 1.050 apple ale, target pitch is 185BB. 2 packs of s-04 at 6BB (manufacturer count) would require me to pitch 31g or almost 3 packs.

are the  manufacturers estimates solid or should i use higher average cell count per gram?

Here's a link that explains the difference in counts:http://www.danstaryeast.com/articles/cell-count-and-glycogen

To summarize, Danstar (and perhaps other dry yeast companies) use plate counts to determine the number of  live cells. Plate counts are reliable to determine live cells because dead cell won't grow. The problem is that it is impossible to plate single cells consistently because they tend to stick together. So when counting what appears to be colonies formed from a single cell, often two or more cells formed that colony. According to Danstar, "For Nottingham yeast the average cell count under the microscope is around 20 to 30 billion cells per gram dry yeast." That leaves it to us to determine viability.
Title: Re: dry yeast cell counts
Post by: S. cerevisiae on November 17, 2014, 09:37:49 PM
One term that one will hear/read in discussions involving plating for single-cell isolates is morphology.   Morphology refers to the shape of a colony.  It's usually fairly easy to determine if colony was formed by more than one cell.  A multicell colony goes out-of-round fairly early in the growth process. 
Title: Re: dry yeast cell counts
Post by: archstanton on November 18, 2014, 08:45:58 PM
I don't use dry yeast very much, and am using it for an apple ale this weekend- using s-04.

seems like much variability in consensus of cell count per gram of dry yeast. for my 1.050 apple ale, target pitch is 185BB. 2 packs of s-04 at 6BB (manufacturer count) would require me to pitch 31g or almost 3 packs.

are the  manufacturers estimates solid or should i use higher average cell count per gram?

Here's a link that explains the difference in counts:http://www.danstaryeast.com/articles/cell-count-and-glycogen

To summarize, Danstar (and perhaps other dry yeast companies) use plate counts to determine the number of  live cells. Plate counts are reliable to determine live cells because dead cell won't grow. The problem is that it is impossible to plate single cells consistently because they tend to stick together. So when counting what appears to be colonies formed from a single cell, often two or more cells formed that colony. According to Danstar, "For Nottingham yeast the average cell count under the microscope is around 20 to 30 billion cells per gram dry yeast." That leaves it to us to determine viability.

Nice find. So the manufacturers numbers are based on a far more accurate means of counting cells. While they agree with what is seen under a microscope, it is not an accurate representation of the actual number of viable cells, rather far from it.