How does using a starter harm dry yeast?

A very recent thread (dry yeast starter) contains a statement that using a starter harms a dry yeast. I make a solution of tap water and malt extract at the same SG as the wort, boil and cool it, aerate it, and add the dry yeast to it. After a few hours I make the wort, cool it, and add the starter. Within 12 hours I get 1 to 2 inches of Krausen - which I regularly remove, but that is another story. How does this harm occur, please?

The onoly thing I can think of is that dry yeast packets have pretty high cell counts (near where you want to pitch at) so if you are using a starter you are risking over pitching, but it would have to be a fairly good size starter. The main drawbacks from overpitching is that fermentation can be so vigorous that it heats up the beer leading to increased ester production.

Here is more about overpitching https://www.homebrewtalk.com/f13/drawbacks-over-pitching-76157/

I can't think of anything about it that would harm that yeast themselves. Really it's just not necessary as the packets have plenty of cells in them and really don't need a starter to get going.

I wouldn't consider what you are doing a starter for one, more of a malt based extended rehydration. There would be no appreciable increase in cell counts over a matter of hours (considering the volume and prior cell count), but the yeast should be primed and hungry by then.

Another one of the disadvantages to making a true strarter is that the dry yeast sachets are packaged with yeast nutrient, intended for the yeast to take in during rehydration and lag phases thus reducing some of the stresses on the colony (caused by the dehyration process). If a true starter is made, then the nutrient will be well gone before the yeast see's any of the actual wort

FWIHR, this is also why many dry yeast packagers don't even recommend a rehydration.

When dried yeast cells are pitched into a solution, as they rehydrate, they don't have control (initially) of what comes through the cell membrane and what doesn't. So, if they're pitched into wort, they will let sugars through that they normally have to break down before letting through. This can kill the cells resulting in more dead yeast cells in your beer. Too many dead yeast cells can cause off flavors and a "dusty" sediment. Pitching them into water first brings them back "to life" and allows them to rehydrate without letting in things they shouldn't let in, increasing overall yeast cell viability.

However, it's not the end of the world to pitch them straight into wort. As far as cell counts go, a starter is just not necessary when compared to the cost of just buying another packet of yeast.

i've also read that the freeze drying process can cause mutations in some of the yeast cells. it's a small enough percentage that they are overpowered by healthy cells when rehydrated and pitched directly into a beer but if you allow that yeast to reproduce a couple times (say, once in the starter and again in the batch of beer) the percentage of mutated cells could possibly be much higher (like tumors in humans, some mutations can cause rapid reproduction). the idea is that the higher percentage of mutated cells could cause off flavors.

this is the justification i've read behind not making starters with or reusing dry yeast, although i know people have done both without ill effect.

john from dc said:

i've also read that the freeze drying process can cause mutations in some of the yeast cells. it's a small enough percentage that they are overpowered by healthy cells when pitched directly into a beer but if you allow that yeast to reproduce a couple times (say, once in the starter and again in the batch of beer) the percentage of mutated cells could possibly be much higher (like tumors in humans, some mutations can cause rapid reproduction). the idea is that the higher percentage of mutated cells could cause off flavors.

this is the justification i've read behind not making starters with or reusing dry yeast, although i know people have done both without ill effect.

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Aaaakk!...
That's not how mutation works.
Think, rapid evolution. Mutants that reproduce faster under certain conditions "win" and go on to make up most of the population. There is not really any significant difference in selection pressure between starter media and wort so that doesn't make any difference.
If you pitch dry yeast into wort you will just straight off kill a bunch of them. The want to be rehydrated in water for 10 minutes before you give them any nutrients. Starter solution will not harm dry yeast. The reason people don't use starters for dry yeast is that dry yeast is cheap and doesn't require the extra effort (if you really needed more cells you just pitch another packet).

thanks everybody, good answers and quick as usual. This is a great forum.

giligson said:

Mutants that reproduce faster under certain conditions "win" and go on to make up most of the population. There is not really any significant difference in selection pressure between starter media and wort so that doesn't make any difference.

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well, the difference is one more generation. the cells will reproduce some in the starter (although much less than in a batch of beer) and they'll reproduce again when you pitch the starter.

giligson said:

If you pitch dry yeast into wort you will just straight off kill a bunch of them. The want to be rehydrated in water for 10 minutes before you give them any nutrients.

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agreed 100 percent. sorry if my wording made it sound otherwise i meant directly pitching rehydrated yeast vs. making a malt starter. rehydrating dry yeast is always a good idea, regardless of package instructions.

giligson said:

Starter solution will not harm dry yeast. The reason people don't use starters for dry yeast is that dry yeast is cheap and doesn't require the extra effort (if you really needed more cells you just pitch another packet).

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agreed that the solution itself does not harm the yeast. as far as reasons for not using a starter, yes the high cell count is a good enough one.

as i said, the concern about allowing multiple generations of mutated yeast is something i read in a book, not something i believe as absolute truth or have much experience with. but i can see a logic in it so i mentioned it for discussion. i'll try to find the source for you tonight.

GilaMinumBeer said:

I wouldn't consider what you are doing a starter for one, more of a malt based extended rehydration.

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I agree. this isn't a starter, its a rehydration that barely gets to 'starter' mode when its pitched.

dry yeast sachets are optimal pitching rates too. smack packs and vials are not....and thus the benefit from a starter.

making starters from dry yeast is just extra, un-necessary effort.

There is some misleading information in this thread.

Pitching dry yeast directly into wort can result in damaged cell walls and reduced yeast viability.

Starter solution IS wort. So, if you pitch dry yeast into a starter (instead of rehydrating it in water), you will immediately reduce the yeast's viability. If you allow the starter to work over several days, the remaining yeast will reproduce, and MAY eventually outgrow the cell count that was originally available had you simply rehydrated the yeast.

Rehydrating yeast in water for 10-15 minutes prior to pitching gives the yeast its best opportunity for survival after freeze drying.

If you were to make a starter with dry yeast, you should still rehydrate it first. However, since dry yeast is pretty cheap, it's usually easiest just to pitch more than one packet (rehydrated, of course) when a high cell count is desired (i.e., lagers or high gravity recipes). For MOST recipes, a single 11 gram packet of rehydrated yeast is more than adequate to achieve a healthy fermentation.

BOBTHEukBREWER said:

I make a solution of tap water and malt extract at the same SG as the wort, boil and cool it, aerate it, and add the dry yeast to it.

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Just so you realize, when you make your wort solution, the SG changes as you boil it, the SG goes up as you boil off water. When you're finished boiling, your new SG is probably considerablly higher than what you intended it to be, much higher than what you should consider pitching into.

Bottom line, do exactly what you've been doing but don't add the malt extract.

The reason to not make a starter for dry yeast is:
An 11g packet of dry yeast contains a sufficient yeast cells to pitch for most 5 gal batches. Pitching this amount of yeast in a 1qt or even 2qt starter put way too many cells for the wort to support. They quickly exhaust the food supply without a chance to multiply. Now you have the same number of cells (or fewer) as you started with but they are going dormant due to lack of food. The dry cells are ready to multiply as soon as they rehydrate and are therefore in better shape than the ones in your starter.

So if you are going to make a couple gallon starter for a 10+ gallon batch then it is fine to make a starter with dry yeast. Otherwise it is actually detrimental and definitely does no good.

Craig