Qtde of yeast

[robocop89]

Hi,

I have a doubt about the qtde of yeast (number of dry yeast packs).

Supposing that:
Ale with OG 1,085. - 50 liters
Fermentis S-33 - have 69 billion cell by pack

In the "yeast cell needed" recommend 760,9 billion cells, but on "dry yeast recommendation" is 4 pkgs.

To have 760,9 billion cells, I need of 13 pkgs.
If I use only 4 pkgs (as recommended by BS I will have 276 billion cells.

Why I have this difference? What of this values is more effective (yeast cell needed or dry yeast recommendation")?
'
I think that I need to disconsider the "number of pkgs recomended" and use the "yeast cell needed" to calculate the pkgs that I need.

Cheers,
Robocop.

 

[robocop89]

I searched about my doubts and I have some points to discuss ...

The pack doesn't have exactly 69 billion cells. This number is the minimum cells in the pack in low conditions. I read a lot of diferents numbers of billion cell/g (12, 15, 20). I will use the conservative value 10 billion cells/g.

The difference between yeast cell needed and dry yeast recommendations, because BS use a default value to bi/g by each yeast pack.


Ok, but after some hours reading about pitch rating I have some doubts ...

On brewersfriend calculator, I read about the manufacturing pitching recommended.

"In their defense, the product does contain extremely healthy first generation yeast. One justification might be that the 0.75 rate really applies to pro brewers – who repitch. That re-pitched yeast contains some trub, dead yeast, and other junk, so the 0.75 rate is not as pure as the 0.35 manufacturer’s rate. Repithched yeast can’t be 50% gunk, probably closer to just 10% after washing."

I understood that fresh yeast is good. But if I use a low pichting rate (underpitching) the yeast will longer time to reproduce and can be "stressed"? Why first generation can be used as "underpitching"?

I'm thinking to consider 0.75 or 1.00 as pitch rating (ales below 1.060), it are good values? I think that if use a biggest pitch rating my fermentation will finish quicly and health ... It is right? Or these pitch rating not be consider to first generation?

 

[sweetcell]

some have put the number of cells in a 11g packet of yeast at 200-220 billion cells. check out mrmalty.com.

 

[boydster]

As you saw from searching, the 6 billion cells per gram is a guaranteed minimum. Cell counts done by microbiologists that work for yeast companies and by other brewers put the number of cells closer to 20 billion cells per gram (Sean Terrill & Jamil Zainasheff, Professional Brewers; Clayton Cone & Chris White, Microbiologists for Lallemand and White Labs, respectively), while at least one dry yeast manufacturer (Fermentis) claims each 11.5g packet leaves the production line with an average of 150 billion cells.

How you store and use the dry yeast will have an impact on the viability. Storing at room temp results in a loss of viability of around 4% per month, whereas storing in the fridge reduces that to a loss of only ~4% per YEAR according to Dr. Cone. Pitching dry yeast directly into wort will reduce the viability by about another 50%. Hydrating in warm water helps ensure you get the most viable cells per gram. Check out the Dry Yeast FAQ sticky in this forum for a list of references that you can check out for more information. The Brewer's Friend calc is extremely conservative in the amount of cells per gram that it uses, but you can adjust that field. Personally, when I'm using Fermentis yeast, I go with the 150 billion cells per 11.5g sachet for my estimate. Until I can do a cell count of my own, I see no reason to distrust their claims (Sean Terrill's results that I link to in the FAQ I mentioned earlier came in very close to this figure, although that is possibly due to the age of the yeast he used).

Regarding pitch rate, I've been targeting 1 million cells per ml per degree plato for my clean American ales lately, and .75 million cells per ml per degree plato for beers where I want more yeast character like English ales. I've been really happy with the results.