Rehydrating Dry Yeast?

Barry, from the Fermentis spec sheet for W-34/70: “Fermentation Temperature: 9 – 22 °C (48.2 – 71.6 °F) ideally 12 – 15 °C (53.6 – 59 °F).”

It doesn’t seem to me that fermenting at 52 °F should be an issue with this yeast strain.

Unless lager fermentation is different from ale fermentation the majority of diacetyl is produced relatively early in the primary fermentation process (i.e., prior and during the exponential phase) and is ‘cleaned up’ at the end of primary fermentation (stationary phase).

It is my guess that for some reason the yeast did not ‘clean up’ after itself properly. I have no guess why this was the case.

Maybe Jim (@premierpro) can provide some insight here. He has posted in past threads that he has brewed using W-34/70 a fair amount.

Cheers!

 

To be more precise, diacetyl's precursor, alpha acetolactate, is made (with excess being dumped into the beer by the yeast) fairly early on. But the formation of diacetyl itself is an oxidation process that happens outside of the yeast cell. It continues until the alpha acetolactate is used up. The yeast absorb the diacetyl after it is formed, but it's not as if the yeast produce a one batch slug of diacetyl, switch gears, and then absorb it. My point is that diacetyl formation continues even after cleanup has started. It's the reason a forced diacetyl test can reveal new diacetyl even though there was no diacetyl taste before the test.

People think of a diacetyl rest as a way of reducing diacetyl, but it's really a way of making sure all of the diacetyl is formed and reduced.

 

maybe @OldSock can explain.

Ive been told that rehydrating was unnecessary for most beers. i did a OG 1.080 DIPA and just sprinkled two packs of us-05 and the results were great.
Though when i made my sour wort berliner weisse @OldSock told me that it was vital to rehydrate before pitching. not sure why though.
Is there a major difference in yeast cell viability if the ph is very low?

 

Barry (@GreenKrusty101),

This is how Dr. Chris White depicts diacetyl formation during primary fermentation.



http://www.whitelabs.com/files/Diacetyl_Time_Line.pdf

Cheers!

 

I think you mean that's how Dr. Chris White depicts diacetyl levels, which are a function of both formation and reduction. It would be instructive if Dr. Chris White could show the curve for each component. But I suspect Dr. Chris White's combined curve was notional anyway. I'd bet a paycheck the level doesn't approach the peak at that slope and then immediately dive with the opposite slope.

 

The diacetyl is formed at higher temps, that is where the D-rest comes in handy. The yeast will absorb and reduce the diacetyl once formed. You are correct. Covered at the last NHC by Kara Taylor of Wihite Labs.

 

Like making a starter, rehydration isn't technically required, but it is always best practice. Rehydrating in standard wort will kill cells (I've read up to 50%) because yeast have trouble regulating what passes their membrane initially. Make that high gravity or low pH wort and the problem can only be worse.

 

I have used the 34/70 strain quite a bit. This strain will ferment a clean lager in my experience from 54-66 degrees. I do not hydrate my yeast but I do conduct a diacetyl rest. This strain is excellent for malt forward lagers and equal to it's liquid brother WLP830. I am sorry you had bad luck. How do you determine when to rest your lagers? Off timing of your rest could be the reason for diacetyl. Take care.

 

im not sure i understand, so rehydrating kills up to 50% of cells? so why would i want to do that?

 

1) Sprinkling is easier.
2) There are still lots of cells left.
3) Some yeast manufacturers' instructions say to sprinkle.
4) The beer will still be either "great" or "the same."

Since I rarely use dry yeast, I don't have a strong opinion one way or the other. But I think the above points summarize the argument for sprinkling.

ETA: It's rehydrating in wort (i.e. sprinkling, i.e. not rehydrating before pitching) that kills cells. Maybe you were thinking OldSock meant rehydrating in water kills them?

 

Interesting. I had the same experience recently (~ 4 months ago) with 34/70 in a batch of pilsner. I've used this yeast a number of times in other lager styles (Maerzen, Munich Dunkel, Rauchbier) with great, clean results. But this one batch of pilsner? Butter-bomb. Like liquid movie popcorn.

What temperature did you *pitch* at?

I ask because that was one deviation from my usual practice with the batch in question. Most of the time, if I can't get my wort chilled to my desired pitching temp in a reasonable amount of time w/ my chillzilla, I'll drop it as low as I can go on the way into the fermentor, then leave the sealed fermentor in my lagering fridge overnight and pitch sometime the next day. This time around, I knew I wouldn't be home to pitch the following day. So I gambled. Pitched at 65F and moved the fermentor into the fridge (set to 50F) and hoped for the best. 'Hope' failed me, lol.

*Eventually* it cleared up somewhat - but not completely.

This one batch was very much an anomaly for me. I've enough positive experiences with 34/70 that I wouldn't hesitate to use it again - but it's one that definitely pays to rehydrate, use several packs, and pitch 'cold'.

 

Aha, ya i misunderstood that. thats what happens when i post on here before the caffeine kicks in.
thanks for clarifying

 

I don't think pitching warm is your problem. I have probably done at least 8 pilsners with this yeast and I pitch one pack between 65-75 degrees then move directly to fermentation temps. I have never tasted diacetyl in any pilsner I've brewed. Rest timing, temperature and length are key factors for cleaning up diacetyl.

 

So what were your parameters for 34/70?
I'm inclined to think you are right...I waited until 3/4 of SG drop and then raised temp to 62*F for 2 days (probably not long enough). I initially pitched at 59*F...so I know pitch temp was not the culprit. Weird though...the Baltic Porter I pitched on the cake seems to be doing fine...although I would expect diacetyl to be harder to pick up in that style...cheers

 

I think your take-aways are a little off the mark. Rehydrating isn't rocket science, and if you can use a thermometer? You can rehydrate without killing cells.

As for 'enough cells to ferment a 1.070 wort [sic]' when pitching dry? 1.070 isn't exactly 'medium gravity' and isn't something I would attempt to ferment with one package of dry yeast sprinkled on top.

Low gravity (~1.040) english ales with S-04? Absolutely. One pkg/5 gal will do it. 1.070? I'd rehydrate, and I'd probably use 2 pkg.

Of all I've tried, only S-04 and W34/70 are staples in my fridge - and then most often it's because I can use them for 'unplanned' brew days where I unexpectedly find myself with the time and inclination to brew but have no starter ready to go.

But, for as much as I stand behind pitching that one particular strain, dry, into a narrow subset of styles w/ no detectable ill effects - I'd be remiss if I left you (or anyone else) with the impression that 'what works for S-04 in a 1.044 wort works for all dry strains at all temperatures and gravities as high as 1.070'!

All of this also hasn't touched on the fact that *most* dry yeast just kind of sucks (still) compared to the diversity of liquid strains - whether you rehydrate or not!

The diversity of available dry product is increasing, but the performance & flavor profiles often just aren't there IMO. For example, WB-06 makes hefeweizen that is barely an insipid shadow of my favorite WLP380, US-05 takes forever to flocculate and seems too 'estery' no matter what I do with it (compared to 1056 or WLP001), and the 'belgian' dry strains? Nowhere close.

Obviously, this is just my own experience and I'm sure there are those who'd tell me S-04 sucks, too (I can probably name one or two), but I guess what I'd also like you to 'take away' as a new brewer is that liquid yeast is still the way to go for the majority of beer styles. Make starters. Step them up when you need to. You won't regret investing the effort.

Trust me.

 

I would say two weeks for attenuation of a 1.075 wort is pretty slow. It really shouldn't take that long with most yeast strains.

 

For a 1.075 OG in 5.25 gallons, 270B cells are recommended.

One rehydrated pack will be around 180B cells. One non-rehydrated pack will be around 90B cells. This is a significant underpitch. Underpitching can influence the way the beer tastes and smells. There is no doubt this underpitch will make beer and attenuate to the predicted FG most of the time.

If the end result is something you are happy to drink, then you did it right. It won't make the same beer as 270B cells. If you can't tell the difference between the 90B cell beer and the 270B cell beer, then it doesn't matter to you.