Pitching yeast in low pH

The reason people suggest using water rather than wort is the osmotic stress the sugar brings to the yeast. It is not a pH-based argument. I think pH could play a role in ion transport across cell membranes, if pumping hydrogen ion is helpful for maintain charge balance, but am not sure of it its relevance in this circumstance. FWIW, at least one major manufacturer of dry yeast has backed off recommendations for rehydrating, and several home brew experiments show minimal or no impact. Perhaps we have placed too much emphasis on it in the homebrew-niverse. The doubt this has cast on the benefits of yeast acclimating to an osmotic gradient created by sugars makes me question -- "are you sure your yeast need to acclimate to your pH?"

 

https://www.therarebarrel.com/index...Acidic-Shock-and-Sour-Ale-Bottle-Conditioning

 

Some additional reading on the matter:

http://www.milkthefunk.com/wiki/Packaging#Acid_Shock_Starters

FWIW, Brettanomyces sp. can handle pH down to about 2.0, so if you're packaging a beer that hasn't been subject to very long term aging, your beer should carbonate just fine with normal priming.

 

If you subscribe to Brew Your Own magazine, there is an article in the December 2016 issue about the acid tolerance of yeast. It's honestly not very in depth, but it includes some experiments fermenting at different pHs. Here is a related blog post by the author of the article, Michael Tonsmeire (link).

My understanding is that saison yeasts tend to be fairly acid-tolerant. And as Jesus said, Brettanomyces strains are also very adapted to acid environments. That's about all I've got... I will say that I've used US-05 to ferment Berliner and gose beers, and it can easily handle the pH resulting from Lactobacillus. But if you're using bugs that take the pH lower than that, then you're out of the range of my experience with clean yeast.

 

Can you please provide further details here? Which yeast vendor no longer recommends rehydrating? When did they make this change? Is there something specific/unique about the manner is which this yeast vendor produces their dry yeast to warrant this change in recommendation?

I first learned about the benefits of rehydrating dry yeast by a Q & A on another homebrew forum (20 years ago?) with Dr. Clayton Cone of Danstar (Lallemand). For completeness below is what he stated:

Subject: Yeast Hydration, Infusion Mashing and England

My question to Dr. Cone regards yeast rehydration. All the packages of yeast contain instructions for rehydration yet they all ferment just fine without it. I have to believe that such a procedure may be theoretically beneficial, however it would seem to be marginally useful at least on a homebrew scale.

I own a home brew shop and a very common phone call is the ” My beer is not fermenting.” problem. I go through the list of potential causes (plastic bucket lid leaks, too cold, etc.) About twice a week the caller will indicate that he rehydrated the yeast. This is a strong signal that the yeast has been damaged and will need to be replaced. I have come to the conclusion that, since rehydration is not necessary to ferment beer properly and there is a strong chance that the yeast will be damaged in a botched rehydration, it is not desirable to recommend such a procedure.

Just how important is rehydration and is it worth the risk?

Dan,

I appreciate your dilemma It is a universal problem for those that market Active Dry Yeast.

Let me give you some facts regarding rehydration and you can decide for yourself where you want to compromise. Every strain of yeast has its own optimum rehydration temperature. All of them range between 95 F to 105F. Most of them closer to 105F. The dried yeast cell wall is fragile and it is the first few minutes (possibly seconds) of rehydration that the warm temperature is critical while it is reconstituting its cell wall structure.

As you drop the initial temperature of the water from 95 to 85 or 75 or 65F the yeast leached out more and more of its insides damaging the each cell. The yeast viability also drops proportionally. At 95 – 105 F, there is 100% recovery of the viable dry yeast. At 60F, there can be as much as 60% dead cells.

The water should be tap water with the normal amount of hardness present. The hardness is essential for good recovery. 250 - 500 ppm hardness is ideal. This means that deionized or distilled water should not be used. Ideally, the warm rehydration water should contain about 0.5 – 1.0% yeast extract.

For the initial few minutes (perhaps seconds) of rehydration, the yeast cell wall cannot differentiate what passes through the wall. Toxic materials like sprays, hops, SO2 and sugars in high levels, that the yeast normally can selectively keep from passing through its cell wall rush right in and seriously damage the cells. The moment that the cell wall is properly reconstituted, the yeast can then regulate what goes in and out of the cell. That is why we hesitate to recommend rehydration in wort or must. Very dilute wort seems to be OK.

We recommend that the rehydrated yeast be added to the wort within 30 minutes. We have built into each cell a large amount of glycogen and trehalose that give the yeast a burst of energy to kick off the growth cycle when it is in the wort. It is quickly used up if the yeast is rehydrated for more than 30 minutes. There is no damage done here if it is not immediately add to the wort. You just do not get the added benefit of that sudden burst of energy. We also recommend that you attemperate the rehydrated yeast to within 15F of the wort before adding to the wort. Warm yeast into a cold wort will cause many of the yeast to produce petite mutants that will never grow or ferment properly and will cause them to produce H2S. The attemperation can take place over a very brief period by adding, in increments, a small amount of the cooler wort to the rehydrated yeast.

Many times we find that warm water is added to a very cold container that drops the rehydrating water below the desired temperature. Sometimes refrigerated, very cold, dry yeast is added directly to the warm water without giving it time to come to room temperature. The initial water entering the cell is then cool.

How do many beer and wine makers have successful fermentations when they ignore all the above? I believe that it is just a numbers game. Each gram of Active Dry Yeast contains about 20 billion live yeast cells. If you slightly damage the cells, they have a remarkable ability to recover in the rich wort. If you kill 60% of the cell you still have 8 billion cells per gram that can go on to do the job at a slower rate.

The manufacturer of Active Dry Beer Yeast would be remiss if they offered rehydration instructions that were less than the very best that their data indicated.

One very important factor that the distributor and beer maker should keep in mind is that Active Dry Yeast is dormant or inactive and not inert, so keep refrigerated at all times. Do not store in a tin roofed warehouse that becomes an oven or on a window sill that gets equally hot.

Active Dry Yeast loses about 20% of its activity in a year when it is stored at 75 F and only 4% when refrigerated.

The above overview of rehydration should tell you that there is a very best way to rehydrate. It should also tell you where you are safe in adapting the rehydration procedure to fit your clients.

Clayton Cone.

 

Although I'd certainly like to hear additional details, the fact that the dry yeast that I use shows active signs of fermentation in under 12 hours and produces an appropriate fermentation profile is enough proof for me that hydration is unnecessary.

 

Hi Guys,
I was actually hoping someone who knows the story better would chime in. I heard it mentioned on a podcast sometime in the last 6 months or so. I expected to hear more about it but haven't. I can't recall which podcast, maybe Master Brewers Podcast? That's about when I started to listen to it. Anyhow, my recollection is they said Fermentis. So, I did a little googling and found another tidbit that I believe is essentially the same story, reported by a different source.

Basically, what you'll hear through the link below is that an unnamed manufacturer of dry yeast revealed at a tradeshow that they will no longer recommend rehydration, based on a study that showed no significant effects of rehydrating vs. not rehydrating. That these recommendations have not yet been issued more publicly is perhaps a reason to give it pause.

https://www.homebrewtalk.com/forum/threads/dont-rehydrate-dry-and-dont-aerate-liquid-yeast.650007/

From here, listen to the video that first appears.
Scroll down and look for the link to an admittedly pretty thin white paper at Fermentis.
Then start googling E2U yeasts (easy to use). I couldn't tell if this is a new product line or a new slogan describing a process for pitching.

Imagine. Controversy about dry yeast rehydration.

 

Lallemand is still recommending yeast hydration for their products:

“Rehydration of our ale yeasts is recommended for use, and will reduce osmotic stress on the yeast when rehydrated and pitched in liquid form.”

http://www.lallemandbrewing.com/wp-content/uploads/2017/09/Rehydration-Ales.pdf

Cheers!

@pweis909

 

I suspect that the insight is in the content you posted from Dr. Cone. If you can rehydrate as instructed, at the optimal temp, and then pitch at the optimal temp, taking the steps to temper down to wort temp, you’ll max cell survival. But if you pitch enough cells, and dry package do have lots of cells, it may all be the same, or close enough. The rehydration instructions he provided seem a bit intimidating. I suspect my controls are not always so precise. Maybe I’m just as well off being lazy?

 

Presuming Dr. Cone (20 years ago) spoke for Lallemand, text from the current PDF would give the impression that Lallemand has reevaluated the optimal temperature range for rehydration of their yeast.

That appears to be a moving target, but it looks like 95°F on the button is currently da bomb for rehydrating Lallemand yeast....

 

I rehydrate my yeast...not that it is critical if pitching sufficient quantities...fwiw, some enzymes (such as gamma amylase) can make a difference in a low pH environment even if the yeast doesn't particularly like it. Apologies for thread jack

 

Well, I can report that this is the process that I perform. I personally do not find taking the necessary steps (i.e., proper water amount and temperature, permit the yeast to 'sit' for 15 minutes, gently stir the yeast after those 15 minutes, attemperate prior to pitching,...) to be a difficult task. Even if a homebrewer did not follow all of the steps precisely there is likely to be more viable/healthy yeast cells in the rehydrated yeast than would exist with the sprinkling method.

It may indeed be possible to have a healthy fermentation via sprinkling.

There are folks who exercise great effort when producing yeast starters to optimize yeast cell count when utilizing liquid yeast. I too make yeast starters when using liquid yeast for batches like high gravity ales, lagers, etc. I personally find the rehydration process to be an easier task in comparison.

Cheers!

 

Not a difficult task but, minimally, it adds time or orchestrated time management to what is already a lengthy process for me. By the end of a brew day, I'm tired and more prone to making minor mistakes like missing the optimum temp window for rehydration. Maybe those minor mistakes don't matter, but maybe none of it matters.

I skipped rehydration in the past, when I first started using dry yeast. When I started rehydrating, I thought I observed faster starts to fermentation, at least based on appearance of vigor (the Fermentis ethanol graph seems to refute that, or at least makes it seem pretty minor). I can't say with any certainty that direct pitch led to noticeably inferior beer. Recently, several people who at least collectively brew more often than I do report no problems with direct pitch (Denny and Drew in Experimental Brewing podcast, Marshall and various Brulosophers, EvenMoreJesus above, etc.). With Fermentis actually putting out data that supports the anecdotes, I think it is time for me to back off my practice of rehydration, at least for a bit, to see where it gets me.

 

I noticed that Mike Tonsmeire, author of American Sour Beers and co-owner of Sapwood Cellars, has come to the same conclusion.

 

It likely comes down to how concerned you are about yeast health/viability.

As was discussed by Dr. Clayton Cone:

"How do many beer and wine makers have successful fermentations when they ignore all the above? I believe that it is just a numbers game. Each gram of Active Dry Yeast contains about 20 billion live yeast cells. If you slightly damage the cells, they have a remarkable ability to recover in the rich wort. If you kill 60% of the cell you still have 8 billion cells per gram that can go on to do the job at a slower rate."

Cheers!

 

I have no problem pitching dry yeast directly into beer wort. I rehydrate dry yeast when pitching into Mead and cider must.

Many of the pros at smaller breweries around here directly pitch dry yeast and their beers are fine. One of my friends makes legendary meads commercially, and he rehydrates using Go-Ferm (and uses stagered nutrient arditions, but that is a mead thing due to the lack of nutrients in honey).

So here is my take on it.
1. Beer yeast and wine yeast may be different in rehydration requirements.
2. Wine and mead typically have much higher Brix/OG that would be harder on the yeast.

If it works it works, as long as you know the limits.

Dr. Cone's work was in wine fermentation. I got that by looking him up when the Fortnight of yeast was going on way back when on the HBD. Fun Fact, the Dan who asked the question above was Dan Listerman.