Rehydrate yeast for a starter

Hey,

I am going to be making a starter with some champagne yeast to pitch into a big beer because I want to get it going at high krausen before I pitch in in there.

I know rehydrating before pitching is generally a good idea but would I need to do this for a 1040ish starter? Would a good amount of the yeast still die if I pitch into wort that low?

I've read that approximately 1/2 of the dry yeast die if pitched dry (without rehydrating). I think that was in Yeast (the Chris White/Jamil Z book) but am not certain. For a smallish starter, pitching dry should be fine, although rehydrating is always best practice, I suppose.

I think you should rehydrate it. It's so easy to do.

Why do we make starters? To ensure we have a healthy colony that is the right size to do the task at hand. By pitching the dry yeast into the wort without rehydrating, you are effectively choosing to kill up to half of the yeast colony as your first step towards making a healthy yeast colony. Not only that, but the survivors have already been put through a very stressful event.

Will it work? Yes. It just seems like a strange way to kick things off, IMO.

For what it's worth, you should also make sure you are making a large enough starter for the number of yeast cells you are pitching. Too small of a starter leads to more issues like stress, starvation, and death.

Rehydrating and making starters are two different things.

Dry yeast should be rehydrated prior to pitching but making starters is actually not recommended. Because of the process in making dry yeast the yeast essentially have everything they need already in reserve to simply hydrate and pitch. By making a starter you actually are forcing the yeast to use a lot of these essential reserves up in a very small beer instead of the actual batch. Also, a typical 11.5 gram pack already has 200B cells which is adequate for most beers of reasonable gravity

Liquid yeast benefits from starters because they lose cells more rapidly this reducing viable pitch rate and require a build up of everything they need to properly ferment a beer.

Right. They are prepackaged with nutrients and pitching into a starter the size you would normally make for a WL vial would be detrimental. Still there is really no reason you can't make a starter as long as it is sufficiently large to accommodate the (generally large) colony of yeast you are pitching. Wort is full of nutrients. You need only add oxygen to a sufficiently large starter wort to provide the yeast with all of the nutrition they need. If you have 200 billion cells to start with, that's probably a 3L starter to ensure healthy growth without depleting food and nutrients. It would certainly be a non-standard thing to do, but if you do it right it will work just fine.

boydster said:

Right. They are prepackaged with nutrients and pitching into a starter the size you would normally make for a WL vial would be detrimental. Still there is really no reason you can't make a starter as long as it is sufficiently large to accommodate the (generally large) colony of yeast you are pitching. Wort is full of nutrients. You need only add oxygen to a sufficiently large starter wort to provide the yeast with all of the nutrition they need. If you have 200 billion cells to start with, that's probably a 3L starter to ensure healthy growth without depleting food and nutrients. It would certainly be a non-standard thing to do, but if you do it right it will work just fine.

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sort of, it's not the packaging of nutrients per se, liquid comes with a nutrient pack if wyeast and I'm sure something with white labs too.

It's the glycol reserves and and such that dry yeast already has that liquid don't and herein lies the difference.

I recently spoke with Lynn, a leading microbiologist and COO at Siebel at a function and she reiterated to many in attendance that rehydration is the way to go, making a starter with dry is not beneficial at all, it's best to add another pack if you need a larger cell count, not make a starter.

Interesting. I'd like to hear more on that if you care to share. It's been my understanding that the yeast are packaged with nutrients including the sterols they need to form cell walls. I've actually tried gleaning information from others about the use of dry yeast in starters but typically the flow of information stops at that point, which is why I've held on to my belief that in theory a dry yeast starter could be done without compromising the health of the yeast. Mind you, I haven't actually made a dry yeast starter as I haven't ever had the need to pitch more than one satchel. Academically though, I'm interested in knowing why a starter (as before, of sufficient volume to support and grow a healthy colony that is starting at +/-200b cells) is considered so bad with dry yeast, when they can reproduce and be harvested for re-use just fine after fermenting a beer.

So... I thought the glycol was there to provide sterols so the yeast could form cell walls upon rehydration. Hence, why I was under the impression that using a stir plate to provide oxygen would suffice as that serves the same purpose early on. Can you set me straight?

boydster said:

Interesting. I'd like to hear more on that if you care to share. It's been my understanding that the yeast are packaged with nutrients including the sterols they need to form cell walls. I've actually tried gleaning information from others about the use of dry yeast in starters but typically the flow of information stops at that point, which is why I've held on to my belief that in theory a dry yeast starter could be done without compromising the health of the yeast. Mind you, I haven't actually made a dry yeast starter as I haven't ever had the need to pitch more than one satchel. Academically though, I'm interested in knowing why a starter (as before, of sufficient volume to support and grow a healthy colony that is starting at +/-200b cells) is considered so bad with dry yeast, when they can reproduce and be harvested for re-use just fine after fermenting a beer.

So... I thought the glycol was there to provide sterols so the yeast could form cell walls upon rehydration. Hence, why I was under the impression that using a stir plate to provide oxygen would suffice as that serves the same purpose early on. Can you set me straight?

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Sure, I'll do my best (I am not a microbiologist and won't pretend to be one)

The process of manufacturing dry yeast involves processes that allow the yeast to be packaged containing all of the necessary cell reserves they require to properly ferment beer and grow during the lag phase. Simple re-hydration brings all the cells back into a pliable state so the nutrients and reserves are readily available once the yeast begins consuming the o2 in the well-aerated wort. Making a simple starter with dry yeast simply depletes all the cell reserves that the manufacturers have already packed into the yeast.

Further, because there are +/- 200B cells in a dry 11.5 gram pack, there is pretty much an adequate amount of cells present to ferment a typical 1.060 +/- wort. Because dry yeast is inexpensive, if a larger cell count is required it is actually less expensive to re-hydrate a second pack then make a starter.

As for the re-use / harvest question: Because the dry yeast was already used to ferment a beer, the harvested yeast is technically no longer a dry yeast. It is now a liquid slurry, fully depleted of the reserves and nutrients originally packaged so from that point forward it would then be necessary to create a starter or pitch the required amount of slurry to properly ferment the next batch of wort. In other words, the manufacturer has already taken into account the benefits of a starter in the prepackaged dry yeast to ensure everything the yeast needs to do its job is already present so re-hydrate it and pitch it, don't waste the time and effort trying to re-create something that is already present

Many experts state that if simply pitching dry yeast into a wort, roughly half of the cells will be killed off if not properly re-hydrated, thus increasing lag time and the overall health of the ferment of the beer. (Quoted from "Yeast" pg. 133) ("Working with dry yeast" pg. 146)

Liquid yeast strains are essentially harvested products from original slants of a yeast library mass produced into pre-packaged colonies of +/-100B cells. Because of the way they are produced and packaged they do not maintain the same viability during storage and transport as dry. Wyeast provides a nutrient pack that when smacked releases into the yeast and allows them to begin taking up the necessary nutrients and build reserves but this is not a starter wort and the cells do not multiply, they simply take up nutrients. Since nobody ever really gets a perfectly fresh from the factory pack, degradation has already occurred and thus, the starter is highly recommended to produce the proper pitch rate as well as the cells ability to create the necessary reserves to begin fermenting the wort. It is the making of the starter and the addition of o2 that then allows the cells to reproduce and multiply. Yes, I know, both Wyeast and White Labs state their packs/vials will direct pitch a 1.060 beer and I will not tell you they won't. There is a difference though between fermenting a beer and PROPERLY fermenting a beer in a HEALTHY way. (Covered in "Yeast" pg 132, "Homebrew Propagation-viability and starters)

All yeast will ferment a beer as long as they are viable but healthy yeast and pitch rates will allow for the best fermentation of the beer without stress or potential for off flavor production or poor attenuation.

Hope this helps! If you do not have the book "Yeast" I would highly recommend it as a great resource for any brewer's library!

I understand what you are saying, and I do have Yeast so I have read the passages covering a lot of what you discussed. Thanks for putting the time into your post, I appreciate it and want to bounce a little more of my thoughts off you for further discussion.

Here is what I am having a hard time processing (and it's OK for neither of us to have a satisfactory answer, I'm just trying to learn here and if we uncover a topic that needs further exploration and research before we have a true answer, I'm fine with that):

The yeast is packaged in such a way that when it is rehydrated (when first being reconstituted, it can't control what it absorbs and so will absorb anything around it until it can rebuild cell walls) it will immediately absorb the nutrients it needs for proper cell function as well as the glycol to synthesize sterols to reestablish its cells walls.

Once it is rehydrated, those reserves are depleted quickly. At that time it can then be pitched into the wort without being shocked by excess sugars or any other chemicals present in the wort because the cell walls allow it to control what it absorbs. Also at this point, it will begin reproduction until it has either A) depleted the nutrients in the wort and can no longer sustain reproduction or B) established a sufficiently large colony to consume the sugars present.

The inoculation rate of yeast into a wort, along with the presence of nutrients including oxygen, determines how much the cells divide. Once the yeast is rehydrated, I don't see how it makes a difference whether you pitch the yeast into a 5-gallon fermentor of wort or into a 3L starter (that particular inoculation rate would result in a close-to-ideal yield factor, per Yeast pg. 140, inoculation rate of 67million cells per ml). The nutrient reserves that are packaged with the dry yeast are to ensure the yeast has everything it needs to reconstitute itself in the healthiest manner possible before pitching into a wort, at which point the nutrients in the wort are going to replenish the needs of the yeast as the colony consumes and grows.

Granted, dry yeast is cheap and it makes a lot of sense to just pitch a second satchel from a cost standpoint if the gravity and/or size of the batch of beer dictate, for example, 400billion cells are needed to properly ferment a batch. But as a thought-experiment, consider someone who does not have time or ability to purchase the extra packet and also imagine that person has an overabundance of DME. What disadvantage is this person actually putting the dry yeast at by making a starter of sufficient size and with necessary aeration to allow for an ideal yield factor?

I am currently of the mindset that the cost is the factor that makes dry yeast starters an unpopular thing to do, and not that it is actually unhealthy for the yeast if done properly. If that isn't the case, I'm searching for the reason why so I can dispel this idea. I'm not so closed minded that I refuse to believe that I could be wrong about this, but I haven't heard anything compelling to lead me to believe otherwise. If it is the case that a healthy starter can be made with dry yeast, I think we need to put an end to the myth that it is unhealthy if done properly and just start saying it doesn't make sense from a cost standpoint.

The inoculation rate of yeast into a wort, along with the presence of nutrients including oxygen, determines how much the cells divide. Once the yeast is rehydrated, I don't see how it makes a difference whether you pitch the yeast into a 5-gallon fermentor of wort or into a 3L starter (that particular inoculation rate would result in a close-to-ideal yield factor, per Yeast pg. 140, inoculation rate of 67million cells per ml). The nutrient reserves that are packaged with the dry yeast are to ensure the yeast has everything it needs to reconstitute itself in the healthiest manner possible before pitching into a wort, at which point the nutrients in the wort are going to replenish the needs of the yeast as the colony consumes and grows.

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So I think that here in lies the issue. Lets put aside the whole concept of pitch rate and focus on the second and somewhat more important topic of yeast health. Everyone speaks of and concerns themselves with ensuring proper pitch rate but very few look at the aspect of growing that pitch rate up with the most healthy yeast possible. Hence the desire to use a low gravity wort and proper aeration and reasonable temperature to produce their starters. Those that are less diligent will in fact produce proper pitch rate but perhaps not the most healthy yeast in the colony.

I believe this to also be the thought process behind the making of starters for dry yeast. Think of it as being a huge overpitch in a very small beer. Will you increase cell count and pitch rate? Yes, but will those cells be the healthiest? Perhaps not. Because you are pitching a product that is properly created to have everything it needs to ferment a reasonable gravity beer to start at 5 gallon batch size, by putting it to work in a low (1.030) gravity, very low volume of wort, the cells are not working to their most efficient potential and thus replicating in less than ideal conditions to achieve their maximum output, so to speak.

I look at it as similar to under pitching. Will the beer ferment? Yes, Will the yeast do the best job possible, probably not because they were in a stressed state during the lag phase producing less healthy cells to perform. Hence the possibilities of stuck fermentation, off flavors and poor attenuation. The same possibility exists in extreme overpitching scenarios as well. It's like trying to send too many laborers to perform a job that only requires a few people, major inefficiencies occur. It's like they are expending a whole lot of resources to do very little work in a very inefficient manner. I am not sure this can even be quantitatively evaluated but it makes sense.

This is my thinking anyway and what I have extrapolated from conversations with those far more intellectual on this than I will pretend to be. I will say also that I do think there is some merit to the economy argument as well. Marketing always seems to have a hand in everything.

Look forward to your thoughts............

duboman said:

So I think that here in lies the issue. Lets put aside the whole concept of pitch rate and focus on the second and somewhat more important topic of yeast health. Everyone speaks of and concerns themselves with ensuring proper pitch rate but very few look at the aspect of growing that pitch rate up with the most healthy yeast possible. Hence the desire to use a low gravity wort and proper aeration and reasonable temperature to produce their starters. Those that are less diligent will in fact produce proper pitch rate but perhaps not the most healthy yeast in the colony.

I believe this to also be the thought process behind the making of starters for dry yeast. Think of it as being a huge overpitch in a very small beer. Will you increase cell count and pitch rate? Yes, but will those cells be the healthiest? Perhaps not. Because you are pitching a product that is properly created to have everything it needs to ferment a reasonable gravity beer to start at 5 gallon batch size, by putting it to work in a low (1.030) gravity, very low volume of wort, the cells are not working to their most efficient potential and thus replicating in less than ideal conditions to achieve their maximum output, so to speak.

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I agree that the focus needs to be on yeast health. That is exactly why I brought up the topic of yield factor with the starter. With liquid, pitching 100 billion cells into a 0.5L starter vs. a 1.5L starter vs. a 4L starter results in increasing amounts of yeast cells as the starters are made larger, but the yield factor peaks around 1.5L. The book essentially says that yeast grown at peak yield factor will result in the most, healthiest yeast. Lower yield factors indicate either there was either not enough food or the starter was too large for the colony, both scenarios resulting in unnecessary stress on the yeast, while the biggest yield factor would indicate the least amount of stress placed upon the yeast.

So this idea of getting the peak yield factor is really the thing to focus on if you want to grow your yeast colony in the most responsible way. This is why I think a packet of dry yeast can be used in a starter just fine, but care needs to be taken to make sure you hit the right inoculation rate to achieve the greatest yield factor. Therefore, if you are starting with 100 billion cells of liquid yeast, you would ideally want your first step starter to be 1.5L, thus growing your colony to 181 billion cells that are in peak health. I think many people jump straight to a 2L starter because it yields the magic number of 200 billion cells and the yield factor is only marginally reduced (from 7.7 to 7.6). By extension, if you are starting with 200 billion cells, you would ideally want to make your first step starter a 3L starter, thus keeping the inoculation rate the same as the example mentioned a moment ago (67 million cells per ml).

It is worth mentioning, though, that if 200 billion cells are inoculated into 3L of starter wort, the resulting number of yeast cells would be in the neighborhood of 360 billion cells. You really only need that many cells for a 5 gallon ale that has an OG of around 1.100 - this is a bigger beer than most people make, but if you are propagating with the intention of banking some of the yeast or if you are doing a 10-gallon batch, this could make sense. That is, of course, if the cost of making the starter doesn't outweigh the cost of just buying a 2nd packet of yeast. For the actor in our thought experiment, this scenario seems to makes sense.

Just as we can harvest the formerly-dry yeast from the beer in the end, we can harvest the formerly-dry yeast from a starter that has finished fermenting, and if care was taken to make sure the yeast had optimal growth conditions I just don't see how there is any harm to the yeast's health in doing so.

Agreed and I think we are pretty much on the same page. I'm not sure the original question was answered though.....

I would say that for the average experienced home brewer simple rehydration is still the best bet when dealing with dry yeast or two packs if necessary since we don't have labs or proper measuring devices to fully evaluate what's going on.

Any more in depth analysis is honestly above my pay grade perhaps an actual microbiologist will chime in and shed more light. I do have a friend that I can bounce this off of but brewer's yeast is not his specialty, I'll pose the question.......

Cheers!

Would love to know what your friend or anyone else thinks on the matter, I'm always happy to learn.

I guess for the original question from the OP... I'm still of the mindset that if you are decidedly going to do a starter, rehydrate it first so the yeast doesn't wake up to a shocking massacre leaving only 1/2 the colony to build the starter with.

I'll follow up when I can...... To the OP, didn't mean to hijack the thread
Cheers!