A Dry Yeast Rehydration Experiment

Interesting experiment. However, it would be nice to see the experiment also done at much lower temperatures, with a lager. My guess, based on my limited experience, is that the results will show differences more significantly than with the ale dry yeasts, especially in terms of the time that signs of fermentation are observed.

For everyone's interest, I also posted in another thread, after getting a response from the people at Fermentis, that the instructions on the 11.5 gm packages of S-189 are wrong. It wrongly suggests that one package (at 12-15 C) is sufficient for 20 - 30 liters. In fact, the instructions were misprinted and should read that one package is sufficient for 10 - 15 liters. Thus, at 12 C, two packages are generally required, rather than one. At 48 C, about 4-6 packages are required.

I'm curious as to how others rehydrate dry lager yeast. If it is done at the higher temperatures as generally recommended, it apparently causes the yeast to be shocked, when it is then suddenly pitched into the much cooler wort. Rehydrating at a cooler temperatures, say 55 F, causes the yeast to remain clumped for a long time, even when stirring for a length of time.

 

Wouldn't it be a hoot if you actually demonstrate that not hydrating dry yeast can result in a better beer? Even I have never been so bold!

 

I recently followed the specific instructions from the Fermentis data sheet for W-34/70:

“REHYDRATION INSTRUCTIONS: Sprinkle the yeast in minimum 10 times its weight of sterile water or wort at 21 to 25 °C (70°F to 77°F). Leave to rest 15 to 30 minutes. Gently stir for 30 minutes, and pitch the resultant cream into the fermentation vessel.”

I pitched the dry yeast (one sachet) on the sterile water at 73 °F.

I did not pitch the resulting yeast cream into cold wort (e.g., 48 °F) but instead pitched within the “ideally” recommended fermentation range of this yeast (53.6 – 59 °F); specifically I pitched at 59 °F. Over the next 24 hours I cooled the wort down to the mid-50’s and I observed signs of fermentation (bubbling through the airlock) in less than 24 hours from pitching. Last week I transferred that beer to a secondary for lagering. The beer had a specific gravity reading of 1.012 (from an original gravity of 1.055) and I performed a taste test of the hydrometer sample and the beer tasted very good.

Cheers!

 

While I won't argue that all these recommendations for rehydrating and blah, blah, blah are for anything but ideal fermentation, I maintain that a packet of dry yeast sprinkled into the wort as per the package directions is sufficient to ferment five gallons of wort satisfactorily. My own experience supports that. This is all much ado about nothing.

IMNSHO

 

Mike, what is the highest gravity batch that you have done this?

Cheers!

 

That suggests two separate experiments: 1) to see what happens with lagers when using yeast rehydration vs. sprinkling the yeast on the surface, and 2) what difference is there in the final taste, when making lagers, whether using relatively warmer fermentation (e.g. 60 F) vs. cooler fermentation (e.g. 50 F), assuming both are still similarly lagered afterwards.

 

My maibock with S-189 fermented in the 60s took a Silver medal in a BJCP comp. Sprinkled on the top of the wort, no aeration.

 

An exBEERiment has already been done for W-34/70:

“To evaluate the differences between 2 beers of the same recipe split into separate fermentors and fermented with the same yeast with half fermented at traditional lager temperatures (50˚F/10˚C) and the other half fermented much warmer (70˚F/21˚C).”

“RESULTS:

The participant pool for this xBmt consisted of 26 people including BJCP judges, experienced homebrewers, craft beer enthusiasts, and a few Brewcasters. Each participant was blindly served 2 samples of the warm ferment beer and 1 sample of the cool ferment beer in different colored opaque cups then instructed to identify the one that was different. In order to achieve statistical significance given the sample size, 13 participants (P<0.05) would have had to correctly identify the cool ferment sample as being unique, while only 12 (p=0.083) were capable of doing so, meaning 14 tasters selected one of the other samples. Although close, these results suggest tasters in this xBmt were unable to reliably distinguish between pale lagers of the same recipe fermented 20˚F/11˚C apart,”

http://brulosophy.com/2016/02/08/fe...ager-yeast-saflager-3470-exbeeriment-results/

Cheers!

 

I have seen that write-up. However, if that was the case, why wouldn't even some of the Breweries who brew well-known lagers ferment at the higher temperatures? It would save them much time and cost.

There must be some factors in that exBeeriment that were not considered.

As the author states: "Perhaps the character expressed as a function of fermentation temperature is yeast dependent, with some strains such as 34/70 and WLP800 performing similarly without such tight constraints. Or, as Warren on The Session suggested, maybe the difference would have been more stark if the cool ferment beer had been left to completely ferment out at the lower temperature rather than ramping it up after 50% attenuation."

It might also have something to do with the amount of yeast. Using the exact same amount of yeast pitched in a warm lager as opposed to a cool one could result in a less than perfect cool lager but a properly pitched warmer lager, making the difference between the two less noticeable. It is well-known that the cooler the fermentation temperature, the more the amount of yeast that must be used. Had the proper amount been used for the cooler lager, would it have improved the taste significantly, resulting in a more noticeable difference with the warmer-fermented lager?

 

Conclusions like that one drive me up the wall. There is in fact 91.7% confidence that there might be a detectable difference between the samples, but they say there's not. Whatever.

 

Brulosophy is in business because people don't understand this. And they choose not to explain it along with each experiment.

 

I look forward to reading your write up for the experiment that you conduct.

Cheers!

@pweis909

 

That will never happen. A true experiment requires equipment, time and resources that I don't have. For example, I would need two fermentation chambers. I would have to try out numerous different types of yeast. I would have to do numerous tests. I would need numerous professional judges, especially with specialty in lagers. Etc., etc., etc.

The best that most of us could do are experiments such as the exBeeriment. And just look at the endless criticism that generous experimenter gets!

Thus our hobby will have to continue to endlessly rely on anecdotal reports.

 

As @dmtaylor pointed out, it is not the case that they showed it to be unlikely that there's a difference. Quite the opposite, though you'd never know it from a casual read, i.e. without thinking critically about what the results actually mean.

It's not that quite that bleak. The experiment in question showed that it's very likely there was a detectable difference between the beers. If you could take P=0.083 to Vegas, you'd get stinking rich.

 

They also might get different results with a trained tasting panel, rather than various skill levels.

 

This is true. The thing about this kind of test is that the confidence derived will almost always be understated as compared to a result with a panel of "perfect tasters." Panel incompetence can compromise the result, and when it does, it will skew it toward the null hypothesis.