I was reading a thread on another forum about dry yeast cell counts. Now, I know it's a rock solid homebrewer "fact" that dry yeast has about 20B cells per gram (per counts done by Jamil many years ago), or 200B cells per 11.5 gram package (per urban legend). But in the thread, someone pointed out that Fermentis includes a Typical Analysis for each of their strains on their product sheets, so I looked them up. The Safale strains (US-5, etc.) list > 1.0 *10^10 cfu/g, which translates to > 115B cells per 11.5 grams. The Saflager strains (W-34/70, etc.) list > 6.0 *10^9 cfu/g, which translates to > 69B cells per 11.5 grams. It's worth noting the ">" sign in these analyses, so these are minimum numbers. Still, 115B and (especially) 69B are a far cry from 200B. If the average number of cells was really 200B, but one could only "guarantee" 115B (or 69B), that would be a huge amount of variability in the product, particularly a product with a reputation of remaining viable for years.
Didn’t Kai do some cell counts on dry yeast? Pretty sure he sampled 5 or 6 different Fermentis ones and it was all over the map. The cell Count data Lallemand published on their new strains is much much lower than some of the products they’ve had for a while.
Yes, one of the bigger brewing mysteries out there. I recently looked into this as I am currently updating my brewing spreadsheet. I don’t recall all the details of what I found, but one of the dry-yeast manufacturer’s websites basically said that if you follow standard guidelines for pitching rates (so many cells/ml/degree Plato) with their stated yeast counts, that you will be over pitching. This strongly implies that (1) either their minimum cell counts are really low (about a factor of 4 in my estimation) or (2) their dry yeast is way more robust than liquid yeast. There is also a pretty good discussion of this at Kai Troester’s Brewer’s Friend website in the yeast calculator section. I think there they compromise and set the default to 10 billion cells per gm. Lastly, I’ll mention that until very recently Fermentis specified US-05 at >6 B cells / gm, but now they say >10 B / gm. Go figure. Cheers!
Below is from my BYO article entitled “Optimizing Dry Yeast” (with emphasis in bold): “An internet forum of HomeBrew Digest (hbd.org) conducted a Q & A session with Dr. Clayton Cone of Lallemand. One of the other members of HBD asked him about the practice of rehydrating yeast. Luckily this exchange is available on the internet even today: https://koehlerbeer.wordpress.com/2008/06/07/rehydrating-dry-yeast-with-dr-clayton-cone/ I will highlight one paragraph of Dr. Clayton Cone’s response: “How do many beer and wine makers have successful fermentations when they ignore all the above (rehydrating dry yeast)? I believe that it is just a numbers game. Each gram of Active Dry Yeast contains about 20 billion live yeast cells.” The above would appear to be consistent with the cell count that Jamil conducted. FWIW I have always interpreted the values specified on the various vendors spec sheets as guaranteed minimums for ‘worst case’ conditions (e.g., package at the best by date, not optimally stored in refrigerated conditions, etc.). Cheers!
So for lager strains... Dr. Clayton: 230B cells Published "Typical Analysis": > 69B Either something is wrong, or that's the most inconsistent product ever. If the average is 230B and the minimum is 69B, what's the maximum? About 391B? Range: 69B-391B. Does that make any sense to anyone?
I have already expressed my thoughts above but one more try: A sachet of dry yeast fresh out of the factory has 20 billion viable yeast cells per gram. A yeast vendor will ‘guarantee’ a lesser value for a sachet which is x years old and has been stored on the shelf of an LHBS (i.e., room temperature). In all probability that ‘old’ sachet which was sub-optimally stored will actually have more viable yeast cells than what is listed on the sheet. While I was writing my article I was verbally told by a Fermentis person, after conducting studies, they are now using a value of 4 for x above; their yeast products manufactured today will have a best by date 4 years out. Cheers! P.S. Mark (@utahbeerdude) the update of ">10 B / gm" may be due to the results of the recent studies I referenced above. Also, both the folks at Lallemand and Fermentis discussed with me their CPI (Continuous Process Improvement) efforts.
So, it's your belief that "Typical Analysis" means guaranteed after 4 years of sub-optimal storage? Ok.
Another quote from the interview Jack mentioned: “Active Dry Yeast loses about 20% of its activity in a year when it is stored at 75 F and only 4% when refrigerated.” This implies after four years that dry yeast stored at room temperature will be (0.8)^4 = 41% viable. Note 0.41 * 200 = 82. Cheers!
So basically, buy from LHBS that keeps dry yeast refrigerated, and check dates for the most viable product? And don't buy repackaged hops in little transparent drug baggies? It all seems so simple! FWIW, I use a lot of dry yeast at work. We keep it refrigerated, and I've yet to have a problem with dough rising properly, even though we proof under refrigeration. I see activity within an hour, actually, mixing at room temp using all room temp or refrigerated ingredients, then straight into a cooler. Folks in the space that keep their's at room temp every so often have a bum batch. Maybe I'm overpitching. 55g yeast for 8500g dough
I’m under the impression that despite the variability in yeast cell count it shows no difference I can taste. I use dry yeast for 75% of my beers and don’t rehydrate and my beers consistently come out as I expect. Most of my beers are generally repeatable. To be fair I’m not a very technical brewer and maybe my palate isn’t as refined but I just don’t pick up on these differences.
@JackHorzempa how do you know they are quality? Maybe I’ll have to drop some off to you next time I’m in the philly area.
Well, one sign is that your beers consistently come out as you expect and are repeatable. And I made the presumption you enjoy drinking your beers. Sounds good to me! Cheers!
Quality is all in the eyes of the beholder. Homebrew that's tastes great is quality,,,, hi quality!! Can't say how many times I was disappointed with commercial brews and then a homebrewing pal drops off some of his wares and they are excellent. Just my taste preference,,,, perhaps but if your happy then you win.
I'm shocked . . . shocked to find that yeast producers aren't more forthcoming with their details. And this is not confined to dry yeast, the liquid guys are equally hiding behind the curtain, not really wanting to give you the details to do what you want. In truth, you are not their market target. They just want someone to buy their products and hope it makes beer good enough for them to come back. If the manufacturers were to give explicit instructions on yeast count, suggested pitch rates, viability, stepped starters, inoculation rate, ad nuseaum . . . well . . . they would probably lose market share to those who kept it dumb. So the people who make yeast calculators, have hemocytometers, measure out their starters, etc. are a niche the Big Boys are willing to sleight. Pretty sure you have already figured a work around for all of this.
I understand why you would state this but while I was researching my article on whether dry yeast needed to be rehydrated I was personally shocked how forthcoming the dry yeast vendors were in answering my numerous (and I do mean numerous) questions. In addition they volunteered to me the results of their many scientific studies (information that I would deem to be proprietary); many, many pages of this information. If you have specific questions for them I would strongly encourage you to contact them and ask them. If you mean that we homebrewers are not their primary market you are indeed correct; the majority of their business is with commercial breweries. Having stated that Fermentis made the effort to send one of their scientists (PhD type) to HomebrewCon 2019 and give a presentation with some of their scientific studies results. From my perspective that is an effort to share information with us homebrewers. I personally appreciated they did this. Cheers!
