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?
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.