Pitching Dry Yeasts

[Blind Dog]

References

• Henschke, P.A. Preparing a yeast starter culture: fresh or dried yeast? Allen, M. (eds). Advances in juice clarification and yeast inoculation: proceedings of a seminar; 15 August 1996; Melbourne, Vic. Australian Society of Viticulture and Oenology: Adelaide, S.A : 17-21 ; 1997.
• Monk, P.R. Rehydration and propagation of active dry wine yeast. Aust. Wine Ind. J. 1: 35; 1986.

Yes the references are old, this topic was put to bed twenty years ago.

Both being examples of the oblique references I've come across, usually phrased as 'Monk/Henschke suggests...' with a citation to the paper, but the papers themselves seem to be unavailable and the abstracts I've seen make no mention of an actual study of sprinkle into wort/must V rehydration. The other oft quoted reference is David Jenkin's (plus others) paper published by the IBD, but again it's not a study of one method versus the other.

Personally, I routinely rehydrate yeast in boiled and cooled water as it makes sense to gently wake them from their slumber, and it works. I've do occasionally sprinkle direct, but only when I'm being super lazy, and feel guilty. I'd just like to read a proper scientific analysis, just cos that's the way i am

 

[Lyrebird_Cycles]

(Mainly @ Lyrebird Cycles: )
Out of interest, what are the strengths & weaknesses of the assumption that the optimal treatment of the wine yeasts are the same as the optimal treatment of both ale and lager yeasts? Namely in terms of what's going to produce the best ales or lagers, as opposed to the best yeast growth rates

Definitely not saying it's wrong, merely checking the veracity of what seems to be the main evidence for the way we treat our yeasts. I'm asking as I'm not knowledgeable about wine yeasts nor wine fermentation.

And i'm curious as to why all (i think) of brewing yeast suppliers would suggest 20-35°C for rehydrating (e.g.: 20-26 (fermentis lagers), 24-30 (fermentis ales), 25-30 (lallemand lagers), 30-35 (lallemand ales), yet you're reporting 38-39°C is optimal from your own studies (with wine yeasts, i assume?)?

Could it be that the beer strains are slightly different and are either optimised under slightly different conditions, &/or that though it might be sub-optimal for the growth of the yeasties, these lower temps are optimal for producing the best flavour profile in the beer? Just wondering.

The strength of the assumption is that it's based on the known physiology of Saccharomyces spp and they're all more alike than they are different.

The weakness of the assumption is that if I'm wrong the yeast will be severely compromised by the higher temperatures: the general temperature profile of things like this is a slow increase up to the optimal temperature and then a sharp decline above it as things denature.

I have tried rehydrating at 40 oC on two of the more popular lager yeasts, W34 and S189, and three of the more popular ale yeasts, US04, US05 and Nottingham; they all work well. I think this is enough to rule out denaturation of major enzymes. I did not do post-rehydration viabilities, if I get time I might do that soon.

I don't know the reasons for the rehydration recommendations, but I suspect that the companies are dumbing things down for amateur brewers and untrained craft brewers.

If you use the wine yeast recommendations for a lager yeast, for instance, you will need to attemperate before direct pitching at lager temperatures. It's easier to simply rehydrate at a lower temperature, skip the attemperating step and live with the slightly lower viability that will result.

As far as I know, rehydration temperature has no effect on the fermentation profile that is not a consequence of its effect on yeast health, so the distinction on which your last question is predicated doesn't actually exist.

 

[technobabble66]

.
As far as I know, rehydration temperature has no effect on the fermentation profile that is not a consequence of its effect on yeast health, so the distinction on which your last question is predicated doesn't actually exist.

(Heritable) Epigenetics?

Ie: that the environment can dictate the genes that the organism activates, not just temporarily but potentially for the rest of its life, or the life of that particular cell (same thing here, with yeast). And then the potential for these changes to be inherited (sort of "hard-wired") in the future generation(s).

Eg: rehydration at a higher temperature may impair that batch of yeast to produce an optimally clean/flavoursome fermentation (for beer production).
Maybe a slightly lower rehydration temperature is the best compromise between optimal hydration conditions and optimizing the cleanest/appropriate flavour profile by that batch, as determined by the testing of the yeast manufacturers?
EDIT: ie: the biochemistry/physiology of the yeast now becomes optimized for slightly lower temp conditions.
I appreciate the vast majority of yeast care is all about optimizing their basic health & growth rate, and the concern I'm raising would be superfluous to that. However I'm curious as to why all the beer yeast manufacturers recommend temperatures well below what would initially appear optimal for rehydration.
Also, my (basic) understanding of epigenetics would suggest there *might* be a need to compromise between conditioning for fermentation temps and optimal rehydration temps.


Tbh, I find it hard to accept the "they've dumbed it down" explanation - there's not really a difference in effort between telling home brewers 27 or 33*c is what they need to achieve. I'm more inclined towards assuming they've got a better reason for it.

 

[Lyrebird_Cycles]

Tbh, I find it hard to accept the "they've dumbed it down" explanation - there's not really a difference in effort between telling home brewers 27 or 33*c is what they need to achieve. I'm more inclined towards assuming they've got a better reason for it.

There is a difference: to get the benefit of using the higher temperature you have to include the attemperation which is A: an extra step and B: not called out on any of the sheets for brewing yeast I've seen.

This thread itself is testament to why the manufacturers would want to keep it as simple as possible.

Your argument from epigenetics is good if you are talking about cultures, culture conditions definitely affect yeast performance. Here we are talking about rehydration over a space of 15-20 minutes, I don't think that's enough time for anything significant to occur, this paper seems to agree with me.

To be clear: I am not certain about the applicability of wine protocols to brewing yeasts: if a manufacturer comes along and says "No, we did the tests, the temperatures we recommend are the optimal" you'd be wise to believe them. On the other hand I have tested for the most likely downside of using the higher temps and found no ill effects. YMMV etc etc.

 

[BKBrews]

So I guess for us punters using the manufacturers guidelines, we should just go at the higher end of their recommended scale? e.g. re-hydrate US-05 in 30 degree water.

 

[thefrothologist]

I rehydrate in 40˚C water based off data written in the Yeast book by Brewers Publications...(I think :-0)

 

[kaiserben]

Interesting discussion!

Fermentis suggested rehydration pitch temp is 27C +/- 3C (ie 24-30C)
Mangrove Jacks and Danstar are a bit higher at 32.5C +/- 2.5C. (ie 30-35C), nearly up at that 40C point that has been mentioned here.

It might be worth noting that in a home brewing scenario that when you're pitching into water at a temp higher than room temp, that the temp will gradually fall during the 30 minutes you're rehydrating. The bigger the difference the more it will fall. Could falling temps affect the yeast?

 

[BKBrews]

Interesting discussion!

Fermentis suggested rehydration pitch temp is 27C +/- 3C (ie 24-30C)
Mangrove Jacks and Danstar are a bit higher at 32.5C +/- 2.5C. (ie 30-35C), nearly up at that 40C point that has been mentioned here.

It might be worth noting that in a home brewing scenario that when you're pitching into water at a temp higher than room temp, that the temp will gradually fall during the 30 minutes you're rehydrating. The bigger the difference the more it will fall. Could falling temps affect the yeast?

So maybe while a starter isn't exactly necessary for dry yeast, stir plates such as the yeast forge could help us to both a) gently stir the yeast (as advised to do by the manufacturers) and B) maintain pitching temp.

 

[skb]

If nothing else there is no better brewing porn than a stir plate and starter in action... Makes my wife actually thinks I know what I am doing, so clearly a good smoke screen

 

[rude]

Interesting discussion!

Fermentis suggested rehydration pitch temp is 27C +/- 3C (ie 24-30C)
Mangrove Jacks and Danstar are a bit higher at 32.5C +/- 2.5C. (ie 30-35C), nearly up at that 40C point that has been mentioned here.

It might be worth noting that in a home brewing scenario that when you're pitching into water at a temp higher than room temp, that the temp will gradually fall during the 30 minutes you're rehydrating. The bigger the difference the more it will fall. Could falling temps affect the yeast?

I have wondered about this too

So next time might try the 40 c

To attemperate I pour my cube into FV then add wort to rehydrated yeast in the jar reducing temp at no more than 10 c
I think , with 10min intervals I think they say

 

[pcmfisher]

What is this thing called yeast you speak of?

 

[rude]

Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom

 

[Vini2ton]

100 ml of holy water per sachet in a zippy sandwich-bag, shoved in me jocks under me cassock is enough to get the little beggars going. Embarrassing during mass if the zippy gives way. I then blame Mrs Doyles cooking.