Concensus on rehydrating dry yeast, yes or no?

It's still being debated, and probably always will be. I'd say that sprinkling directly onto wort has become more and more popular, in part because Fermentis, who for years said rehydration was important, now claims that it doesn't matter. And that claim just happens to be part of their "E2U" (easy to use) marketing campaign.

The amount of yeast to use should be based on your selected pitch rate, i.e. some number of cells per milliliter of wort per degree Plato. So, higher gravity worts get more cells than lower gravity. Bigger volumes get more cells than smaller volumes.

Ales and lagers typically get different pitch rates. It's common to use a pitch rate for lagers that's about double the rate for ales.

And to complicate it just a little more, some strains/styles can benefit from higher or lower pitch rates. That said, here are what I consider to be good, default rates. Many world class beers have been brewed using these rates:

Ales: 750K cells / ml / ºP
Lagers: 1.5M cells / ml / ºP

It sounds complicated, but a good yeast pitch calculator makes it pretty simple.

 

1.5 Million Cells per milliliter per degree Plato

So, a 5 gallon batch is ~18,927 milliliters
And let's assume your wort will have an OG of 1.055 (~13.6 degrees P)

1.5M x 18,927 x 13.6 = ~386B Cells

 

There is no consensus. Maybe never will be.

Many of us who use dry yeast most or all of the time, like me, know that we can use much less yeast than specified by most yeast calculators. My rules of thumb: half a pack per 5 gallons of ale, or a whole pack per 5 gallons of lager, with no rehydration, just sprinkle on top. If you want to treat your yeast like a baby and rehydrate or make a starter or whatever, you can either half these amounts again, or consider it insurance that my previous recommendations are safe. I would only use 2 packs for a really strong lager. Otherwise one is good enough for a standard strength lager. Or rehydrate and then it's almost definitely good enough. This is all based on actual cell counts -- not the cell counts provided by manufacturers, but rather by people who have been interested enough to actually measure such things. I don't do cell counts, but I know people who do, and..... the amount of viable yeasts in the packs are more than double what any manufacturer will tell you. And this makes sense, because hey, they want to sell more yeast, right?!

Any way you choose, consistent with these recommendations, or above & beyond these recommendations, based on experiences of myself and many, is 99.9% guaranteed to make great beer, assuming you're an average brewer who fairly well knows what he/she is doing.

 

18927 ml = 5 gallons not counting for trub loss, which typically amounts to 10%. If you are brewing a high gravity beer and have a heavy hop schedule including dry hopping, trub will be much greater in volume and can reach 20%.

 

Certainly some wort is lost to kettle trub and some beer is lost to fermenter trub. But 5 gallons (~18927 ml) of wort into the fermenter is 5 gallons of wort for yeast pitch purposes.

Most people understand a recipe for X gallons to mean X gallons of wort into the fermenter. Or at least the brewing software that's most commonly used defines it that way.

 

I mostly did rehydrate for a long time and now I mostly don't. The fermentis propaganda appealed to me and I did several side by side experiements rehydrating vs. not rehydrating.while making cream ale. I never observed a difference. For me, the 34/70 strain worrks sufficiently at low or even mid range ale temperatures that I wouldn't be uncomfortable using 1 pack in the low-mid 60s F. Will it be the best lager you ever had? I doubt it, but if you like beer, it will proabably still be to your liking.

 

I agree with all of this. W-34/70 is okay but not outstanding. If you want a better dried yeast for lagers, try Lallemand Diamond instead. Also S-189 is good too. And any/all of the above can be fermented cleanly even at room temperature. How do I know? Well this is what I've been trying recently. I see little or no reason to go back to cold fermentations, these come out great in 60s or even as high as 70 F. And, lower pitch rate required, and reduced fermentation time -- basically just one big long diacetyl rest.

 

I'm glad you like the results. My experience is maybe a little different. Good beer, yes. Cleanest lagers, no.

I'm still waiting to see some best of show awards won by the warm lager crowd. I expect they'll turn up about the same time as the ones won by the ale strain (not including WLP800) "lager" crowd.

 

This thread seems to have evolved to a side-topic of ‘best’ lager dry yeast. I have only used liquid lager yeast strain (i.e., Wyeast, White Labs) so I have no personal experience here. I thought some folks might be interested in hearing Philippe Janssens (see bio below) who now works for Fermentis discuss the various Fermentis lager yeast strains. Below is a short summary:

· W-34/70: Ideal for neutral beers

· S-23: The solution for fruity and hoppy lagers

· S-189: A great yeast for elegant lagers with floral notes

But you can hear Philippe in his own words further discuss the above in the below linked video podcast.

Needless to say, how a given yeast strain expresses itself will be dependent upon fermentation conditions:

· Fermentation temperature can be a variable, but apparently less so for W-34/70

· Pitch rate may be impactful

· OG of the wort

· Amount of aeration/oxygenation of the wort during pitching

· Etc.

Permit me to suggest that the biggest variable is the palate and preferences of the individual. We all have our own unique palate and preferences in a given beer style so ‘best’ is indeed a subjective aspect.

Cheers!

“Philippe Janssens has more than 35 years of experience in the brewing industry, as a brewer, patent engineer, and business development manager for leading companies such as Anheuser-Busch (AB InBev) and Yakima Chief Hops. Since 2016, Philippe has been working as the Technical Manager and Brewer for Fermentis, a business unit of Lesaffre.”

 

You have a point here. I am aware that of all the NHC Gold medal lager recipes, 100% of them from the past several years have been fermented cold with traditional yeasts. I wonder if this will eventually change after homebrewers become brave enough to give warm lager ferments a try. Honestly not sure.

 

I just sprinkle on top and have never noticed any issues. Pretty sure there was a discussion on here a long time ago that convinced me to switch and I’ve never looked back.

 

used to re-hydrate but no more as turned out to be an unnecessary step at the end of a long brew day ...

 

S-23 has been a conundrum for me. I've tried it a handful of times and don't think I ever liked the results. Genetically, it appears to be a close relative of the Pilsner Urquell H strain. I'd love to hear how others have used this yeast to good effect. My attempts have been more "pee-ew" than "PU."

 

Rehydrate or pitch dry? I miss the old days when this question would practically crash the server as both sides, as if on on cue, dug in their heels and fought to the death! It was fun to pour a cold pint and watch the show. The threads would run multiple pages per day until everybody got exhausted and returned to their lives, none the worse for wear.

 

Thanks Mike.
Beat me to it. Friggin' third rail of homebrewing.

Also, not rehydrating is about the laziest thing a homebrewer could do. I mean, come on. How lazy can you be?
Cheers

 

I usually hydrate. But last batch I did I used K-97 and directions said I could just sprinkle it on wort. Did that and it was bubbling fine the next day.

 

Alrighty then, let’s keep it going……
save time and eliminate a process (lazy?), or...keep on doing it the way grandpa did because “that’s the way we’ve always done it, and by golly we liked it!” (non-lazy?)

Even Fermentis says “It’s up to you”.


Oh, and to answer your question, very lazy indeed.

 

I'm am being facetious. Mostly. Not sanitizing is the laziest thing a homebrewer could do.
But, that said, Fermentis is interested in making their product user friendly. Unless they changed the way dry yeast reacts when tossed into a sugar rich environment, it's a plain fact that more yeast cells are available for fermentation with proper rehydration.

That does not make the beer better though, and that also does not mean directly pitching yeast into wort produces sub optimal cell count. For example, simply increasing the volume of dry yeast would negate any benefits, if there are any, of rehydration.

Homebrewers will go to great lengths calculating all sorts of things in pursuit of a better way, so rehydrating is really an easy way to get a better cell count. That's all.

Cheers

edit Not a grandfather. Not yet. But I am getting old and cranky, and damnit I know how to make beer, so get the hell of my lawn kid!