When to crash chill a yeast starter

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Yorg

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I have read somewhere that after a cerain number of hours, the yeast count of a starter does not increase, but that the yeast are simply tiring and ageing as they complete the starter fermentation. The suggestion was that - I think - at high krausen the starter could be crash chilled to keep the yeast young before pitching.
Can anyone confirm / deny this as a desirable brewing practice?
 
Boy, I've never heard that. I've heard to pitch the starter at high krausen, though, if you can. If it's after high krausen, I've always let it ferment out fully, THEN put it in the fridge and decant the spent wort after the yeast all drops out.
 
It's good for 7 days if refrigerated after building the required volume for a batch. Just remember that the viability drops each day. I have had good results after 2 weeks in the fridge so I know it still will make good beer. If you want to save it for a while then wash the yeast with distilled water and save in sterilized mason jars.
 
Boy, I've never heard that. I've heard to pitch the starter at high krausen, though, if you can. If it's after high krausen, I've always let it ferment out fully, THEN put it in the fridge and decant the spent wort after the yeast all drops out.
Yeah I'm with Yooper on this one. I let it go for 24 hours and then put it in the refrigerator. I may leave it there for only a day or two before using.
 
I have actually heard this, but I don't remember enough to give any definate answers. I believe it is around the 16hr mark, but I don't know how to test, and being that yeast are living things, a timetable for their lifecycle can be pretty unpredictable. It does make since to me though, because the act of fermentation stresses the yeast, so crashing them before hey really get to fementing, just after the reproductive stage, seems like it could be beneficial.

Things I do know. According to the Dan Gordon, of Gordon Biersch and graduate of Weinstephan, it is best to pitch the yeast while in a "logarithmic growth stage". This is just before fermenting begins, as the yeast are in the peak of cell division and growth. This reduces lag to almost nothing as long as the yeast are not shocked, and aerated well when added to the wort. But, this requires the entire volume of wort to be pitched, which shouldn't be done if you have used a stirplate to grow your yeast. You get more cells using a stir plate, at the cost of having to chill and decant, because you don't want to pitch a super oxygenated, nasty tasting starter beer into your wort.

So perhaps crashing, during this logarithmic growth phase, will help preserve the yeast in their best state.
 
If you crash the starter you are basically shutting it down and getting yeast out of solution, If you crash it, you really aren't gaining anything over letting it ferment out, Pitching at high krausen will generally reduce lag time, but if you crash it and reactivate it, you lose the advantage of most of the yeast still being active when pitched.

"logarithmic growth stage". This is just before fermenting begins
That makes no sense, the yeast eat then reproduce, then eat and reproduce, the fermentation is the by product of that cycle
 
I wouldn't crash cool a starter unless it was fully fermented out and I wanted to settle the yeast and decant the beer off the top. Pitching while the yeast have gone through adaptive phase makes sense: the highest viable yeast count prior to fermentation. But practically speaking I just make a starter 2 days prior and decant most of the beer off if it's a big (+2 qt starter) otherwise the whole shebang goes in.
 
Most of my starters ferment out in 24 hours. I made a starter yesterday and will brew tomorrow. It'll go into the fridge tonight or tomorrow morning (early) depending on whether the activity has died down or not.
 
Most of my starters ferment out in 24 hours. I made a starter yesterday and will brew tomorrow. It'll go into the fridge tonight or tomorrow morning (early) depending on whether the activity has died down or not.

Is there a benefit to putting it in the fridge in the morning if you plan on brewing tomorrow?

I just put mine in the fridge for tomorrow's brew.
 
That makes no sense, the yeast eat then reproduce, then eat and reproduce, the fermentation is the by product of that cycle

Apperently, before fementation begins a rapid reproduction phase occurs in the first severl hours, due to the uptake of oxygen. I'm not arguing woth you, and I don't do it this way. I leave it on the stirplate for a day or so, crash it for a day or so, decant and pitch.

But Dan Gordon does do it this way, and he is arguably one of America's best brewers, and was the first American in many decades to graduate from the prestigious Weinstephan institue, so I trust him more than you, sorry. In an interview with him on the BN, he goes in depth into what makes a good starter, and I then discussed it with him (that was BAD ASS) at the opening of his new restaurant here. If Dan says there is a Logarithmic growth stage before fermentation reaches high krausen, then I believe him. He is the one who has watched them under a micoscope, and I mean, have you ever tasted his beers? He knows what he's doing.
 
Apperently, before fementation begins a rapid reproduction phase occurs in the first severl hours, due to the uptake of oxygen. I'm not arguing woth you, and I don't do it this way. I leave it on the stirplate for a day or so, crash it for a day or so, decant and pitch.

But Dan Gordon does do it this way, and he is arguably one of America's best brewers, and was the first American in many decades to graduate from the prestigious Weinstephan institue, so I trust him more than you, sorry. In an interview with him on the BN, he goes in depth into what makes a good starter, and I then discussed it with him (that was BAD ASS) at the opening of his new restaurant here. If Dan says there is a Logarithmic growth stage before fermentation reaches high krausen, then I believe him. He is the one who has watched them under a micoscope, and I mean, have you ever tasted his beers? He knows what he's doing.

The exponential growth phase is just common to growth of all microorganisms, bacteria and yeast alike. It's the phase when they're reproducing and will do so up to a certain population density depending on a variety of factors such as nutrient levels, oxygen, etc. After the growth phases (there are multiple ones) you're in the stationary phase and then death phase, which is guaranteed to happen in a batch process like a starter. Now, I think yeast just go dormant and will avoid that last phase for some time. Slowing increasing the volume of the starters avoids these last two phases and keeps the little yeasties happy and growing up. A continuous process could actually keep the yeast in their growth phase all the time.

When anything is put into a new environment they have a lag phase, which is where they are judging the environment they're in, absorbing oxygen, and eating food. Even during the growth phase they're eating food though.

I'm just recalling this from memory here as I'm not sure where my bio eng stuff is at currently. I've been meaning to track down where I put it during my last move.

I'm really wondering how far apart the different strains of yeast are that we end up using, as in, I wonder if they're all similar in the terms of same reproduction mechanisms and similar growth kinetics. Or even if most of the Lager yeasts are similar and most of the Ale Yeasts are similar.
 
I'm really wondering how far apart the different strains of yeast are that we end up using, as in, I wonder if they're all similar in the terms of same reproduction mechanisms and similar growth kinetics. Or even if most of the Lager yeasts are similar and most of the Ale Yeasts are similar.

I always think of them as being very similar, like people. Lager yeasts work at warm temps, and even prefer them, but we prefer the flavor the produce at lower temps. Like people, Inuits and Eskimos live where it is much colder than most of us could survive. Sure, they would probably prefer it in the 70s or 80s like everyone else, but they can deal with the cold, just like lager yeats. Belgian yeasts are like people in arid climates, because they can work when is a lot hotter than most of us would prefer.

I think of different yeast strians like different nationalities or races of the same thing.
 
I always think of them as being very similar, like people. Lager yeasts work at warm temps, and even prefer them, but we prefer the flavor the produce at lower temps. Like people, Inuits and Eskimos live where it is much colder than most of us could survive. Sure, they would probably prefer it in the 70s or 80s like everyone else, but they can deal with the cold, just like lager yeats. Belgian yeasts are like people in arid climates, because they can work when is a lot hotter than most of us would prefer.

I think of different yeast strians like different nationalities or races of the same thing.

That's probably a good way to think about it.

I wish you could get more information about the different strains when you buy them though. Of course, I'm the science/engineer type of person and think they should provide a lot of information about the yeast. :p
 
I wish you could get more information about the different strains when you buy them though. Of course, I'm the science/engineer type of person and think they should provide a lot of information about the yeast. :p

They do, on the website, and they will give you even more if you email them and ask. Wyeast and White Labs have amazing support.
 
That's good to know! I'm starting to see how much of a difference just yeast can make.

I would argue that it is the most important ingredient. Without good healthy yeast, it doesn't matter what the recipe is, it won't be good beer.
 
The general idea is to add a large number of yeast cells to fresh oxygenated wort that is being agitated (there are many acceptable ways to do this), and the pitch about 4-6 hours later (depending on the temperature). The starter should be the same temperature as the beer (unsually about 25 C, cooler for lagers). Obtaining a large number of cells can be done with 1) a smack pack or commercial tube 2) dried yeast 3) washed, sedimented slurry 4) a "crashed" culture with the supernatant decanted and fresh oxgenated wort added. Naturally, controlling bacterial growth is always a problem and I suspect that autoclaves and antibiotics are extensively use in commercial propagation.
 
Correct me if I'm wrong, but from what I know from my Cell Bio classes is that yeast are facultative aerobes (meaning they use Oxygen when they can, but in the lack of oxygen will switch to fermentation) will undergo an exponential growth period due to a surplus of nutrients (in our case malt and oxygen). Once nutrients are used up, the population levels off and starts fermenting (a less energy intensive mode of respiration).

Obviously, we want to pitch at our highest population density, which is right after our exponential growth period. This is probably signified by our krausen when yeast activity is at its highest (around 24 hr period). After krausen, the population levels off due to deficiency in either sugars or oxygen (or both) and the yeast switch into fermentation mode.

All that said, if you want a smooth and active yeast activity off the get go, pitch at high krausen (during the exponential growth phase when the yeast are still actually respiring oxygen, not fermenting.) However, you will have a trade off of adding oxygenated/diluting wort if you are using a 2 Liter starter. I think this is less important if you are making a stout, but say if you are making a clean tasting lager, then this can have a poor effect on flavor. On the other hand, you can refrigerate to precipitate out the yeast, decant off poor tasting beer, and pitch the slurry. However, you compromise the yeast being in a peak respiration state. BUT, this method usually involves warming the yeast up to your wort temp (usually ~68 deg F). This warming up period will awaken you yeast, get them in respiring mode, and they will be somewhat active by the time you pitch to your wort.

My conclusion: chilling and decanting will give you good attenuation, and eliminate the risk of introduce off flavors to your beer. Sorry if that was long-winded, but hopefully it is helpful.
 
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