Dry Yeast Pitch Rate - Am I Wrong???

[thisjrp4]

I started looking into pitching rates and see on Fermentis' website that their dry yeasts have 6x10^9 cells / gram = 6 billion /g = 69 billion / 11.5 g pack = 3.6 million / ml in a 5 gallon batch. Recommended pitch rates are 6 million / ml = 113.5 billion cells / 5 gallon batch. So is one package of dry yeast underpitching? Am I wrong? I always use either S-04 or S-05, and S-04 ferments out in 2 days and is crystal clear, S-05 doesn't even start for me for 2 - 3 days and ferments out in 10 and sometimes gives me nasty off flavors. Wondering if pitch rate has something to do with that and why S-04 and S-05 would behave differently at the same pitch rate?

 

[kh54s10]

I have never calculated the pitch rates. I have pitched single packs of US05 both dry and rehydrated and the longest lag time I have experienced was about 18 hours. I have also never gotten any off flavors from US05. Since I have never used S-04 I cannot compare but I think your results are atypical.

US05 is one of my favorite yeasts.

 

[WoodlandBrew]

I wouldn't say you are wrong, just that you are looking at the worst case scenario. In practice the viability is much higher than the minimum value listed on the data sheet that you are using.

The dry weight of yeast is 20x10^9 per gram, and viability is normally near 75% if rehydrated properly. This makes 15x10^9 viable cells per gram on average. That's 170 billion cells per package. A safe assumption is 150 billion cells.

You might be interested in these cell counts:
http://woodlandbrew.blogspot.com/2013/01/how-many-cells-are-in-package.html

Also there is more information in my book on this subject.

 

[boydster]

Someone else just posted on another thread that they contacted Fermentis to ask this same question. Fermentis told them they package 150 billion viable cells.

 

[boydster]

Here it is:

So while all this was going on, I decided to contact Fermentis and ask them about it.

As some people mentioned, the amount listed in their documentation is a minimum, normally there is more. Here is exactly what they told me:

"Our documentation is giving our guaranty. The average contain of a sachet of US05 at packaging is 150 billion of viable cells."

Sorry to revive a bit of an old thread, but I figured it's always nice to have the official answer.

 

[Yooper]

Someone else just posted on another thread that they contacted Fermentis to ask this same question. Fermentis told them they package 150 billion viable cells.

That's an average, according to Fermentis.

I have seen most people who have actually done cell counts find them closer to 200 billion.

 

[WoodlandBrew]

Cell counts I have done show that the total cell count of a package of dry yeast is about 200 billion, but the viable count is more like the 150 billion. My blog has some limited data, but there is much more extensive information in my book.

Sean Terrill, BKYeast, and Kai Troester have reported similar results.