Author Topic: Yeast Starter  (Read 3127 times)

Offline tygo

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Re: Yeast Starter
« Reply #30 on: January 13, 2011, 05:01:08 AM »
You are probably right, however I am in the camp of it is better to over than under pitch. Looking at that calculator it says to pitch 65ml of a thick slurry into a 1060 wort. Maybe I am missing something and I should read the entire Yeast book, but 65ml is about half a smack pack?!? How is that enough yeast? Even with a much more concentrated amount of cells in a slurry, that volume just doesn't seem right. But, I haven't tried it and eveything else I have tried from MrMalty has worked so..

You're right that it's all about the concentration of the cells.  If you assume that a 125ml smack pack has 100B cells at 100% viability that's a concentration of 0.8B cells/ml.  Depending on the thickness of the slurry Jamil's calculator is assuming 1-4.5B cells/ml.  If you assume on the upper end of that range you're going to need a lot less volume of slurry to get the right pitching rate.

I think the challenge is determining what concentration you want to use as an estimate.  How thick is your slurry, how much non-yeast crud do you have in there along with the yeast?  Unless you're counting cells with a microscope it's got to be a pretty wide margin of error.  Which is going to be close enough for most of our purposes.
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Offline tomsawyer

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Re: Yeast Starter
« Reply #31 on: January 13, 2011, 06:13:59 AM »
Right theres not 65ml of SLURRY in a yeast vial/smack pack.

On the subject of trub as a percentage of east cake, I was in the habit of pitching most all my trub into the fermentor, just running the wort through a mesh screen to get rid of larger pieces of hops.  I'd get a nice healthy inch of yeast cake.  Recently I've begun colling and racking my wort off the trub prior to pitching, and I'm get about 1/3 as much in the bottom of the fermentor.  Its much lighter colored and finer.  Bottom line, I bet the slulrry volume recommendation is based on having the trub removed first so you'd be quite low on cell count if you don't remove trub via whirlpooling or some other means.

On the trub topic, I use DME to make starter wort and even with a short boil I get a pretty substantial amount of hot/cold break.  This is the stuff that drops quickly, so even if you are relying on visual volumes in these things you might be over-estimating.

Finally, if you pitch a vial in 750ml of wort will it even double once?  There was a discussion in Yeast about this, you might not get much of an increse in cell count with this method but it would at least get the yeast active and give hem a running start.  I think there's something to be said for a "running start", in the few times I've done it this way I see activity sooner.  Looks to me like there are cellular activities that take some bit of time to ramp up before even cell membrane component synthesis can begin.  You have to make some enzymes and express the right proteins before you can make triglycerides and cell membrane proteins.
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Offline tygo

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Re: Yeast Starter
« Reply #32 on: January 13, 2011, 07:21:59 AM »
Bottom line, I bet the slulrry volume recommendation is based on having the trub removed first so you'd be quite low on cell count if you don't remove trub via whirlpooling or some other means.

That's a good observation.  I've heard Jamil say on a few Brew Strong episodes that he always washes his slurry so you're probably right that's he's factoring out a good amount of trub in his calculations.  Although if you use a lower cell concentration without washing I think you could get pretty close. 

Your slurry, free of a lot of the trub is probably closer to the higher end of the spectrum at 4B or so cells per ml whereas mine, with the trub in, would be on the lower end of the range.
Clint
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Offline Kaiser

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Re: Yeast Starter
« Reply #33 on: January 13, 2011, 07:28:27 AM »
Finally, if you pitch a vial in 750ml of wort will it even double once?  There was a discussion in Yeast about this, you might not get much of an increse in cell count with this method but it would at least get the yeast active and give hem a running start.  I think there's something to be said for a "running start", in the few times I've done it this way I see activity sooner.  Looks to me like there are cellular activities that take some bit of time to ramp up before even cell membrane component synthesis can begin.  You have to make some enzymes and express the right proteins before you can make triglycerides and cell membrane proteins.

I do agree with this statement and don’t think either that there will be any appreciable yeast growth, especially if the yeast is starved. When you add yeast to this wort all living yeast cells will start consuming the nutrients at the same time. When the nutrients are then consumed hardly any of the yeast cells will have been able to take up enough nutrients to grow a daughter cell.

But as tom said, the nutrients taken up by the yeast are not lost. The yeast cells are stronger and healthier than before and even though they didn’t grow in the starter they’ll start budding in your beer earlier than they would have without the starter.  In a sense you didn’t grow the number of yeast with this starter, you only grew the yeast cells themselves and brought them closer to your first bud.

Kai

 

Offline hamiltont

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Re: Yeast Starter
« Reply #34 on: January 17, 2011, 12:49:33 PM »
The reason I do it is to slowly introduce the yeast to the temp of the beer to avoid shocking it.  Read it somewhere and have adopted it into my brewing practice. I have never pitched straight from the fridge so I can't say if it works or not. YMMV. Cheers!!!

FWIW, I've done it both ways and now I'm straight form the fridge and into the beer.  The temp shock theory is outdated and has been disproved.  The current theory is that the yeast will start using up their glycogen reserves once they warm up and become active and you want that to happen in the beer, not before the yeast gets there.  I find I get far better yeast performance by pitching cold.  I'd encourage you to try it a few times and compare for yourself.  At the very least, there's no downside.

Okay, I'll try it with a slurry on Saturday.  Cheers!!!

So on Saturday I pitched a cold pint of thick slurry that was stored in the fridge for ~24 hours. It worked just fine. Noticeable fermentation within 4 hours & in full stride @ ~18 hours. Just thought I'd share that. Cheers!!!
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Offline maxieboy

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Re: Yeast Starter
« Reply #35 on: January 17, 2011, 03:46:42 PM »
We wouldn't steer ya wrong... ;D
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Offline Kaiser

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Re: Yeast Starter
« Reply #36 on: January 18, 2011, 07:23:34 AM »
Tom and Tom touch on an interesting topic that I have been thinking about as well: How to best preserve the yeast health while the yeast is dormant. I have noticed that there is a noticeable difference in the fermentation performance that I get from yeast that sat 1-2 days in the fridge after propagation vs. yeast that sat in the fridge for 4-5 days. I try to avoid letting the yeast sit dormant for too long but sometimes life gets in the way.

I generally do take the yeast out of the fridge, decant and re-suspend the yeast with 15-20 C wort. This is the temp the wort is at after I places the kettle in an ice bath to settle trub and chill it to 4-6 C for about an hour. Re-suspending the yeast allows me to count it but more importantly allows me to disperse it evenly throughout the wort. It bothers me that I have to do this in slightly warmer wort but chilling that wort would mean more effort. The whole thing is then pitched into the 4-6 C wort which may shock the yeast but I haven't seen lag time issues. In the past I found lag time to be mostly a function of the yeast amount, yeast health and wort temperature.

While the yeast will start consuming its reserves faster when warmed up I doubt a few hours will make a difference although I do concur that a simple remedy is to take the yeast out of the fridge later.

Another thing I heard is that we should avoid the introduction of O2 when harvesting yeast. That additional O2 may trigger a rise in yeast metabolism. While I do think that there is some merit to it I cannot see myself go through the effort of purging a carboy with CO2 before swirling up a yeast cake for harvest.

Kai

Offline Kaiser

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Re: Yeast Starter
« Reply #37 on: January 18, 2011, 07:29:42 AM »
I can't always brew on a schedule that allows me to make a starter 3-4 days in advance. More often I find myself having a day or so "notice" and can make a starter which I will pitch 12-18 hours after starting it. I based this on MrMalty. No decanting. No crash cooling. Just swirl and pitch.

Let me comment on this since I must have missed this initially.

There is nothing wrong with this. In fact you should make the starter part of your recipe. If your are an extract or partial mash brewer it is very easy to do.

Simply take some of the water you'll use for the recipe and some of the malt extract ad make a 2-4 qt 1040 - 1050 starter the day before. Treat this like you would be treating the beer: aerate well and pitch the yeast at or below fermentation temps. Then brew your beer with the remaining ingredients, chill, aerate and reunite all the ingredients by adding the "starter" which is likely at high Kraeusen by now.

This way you should be able to pitch from a single vial and have a proper pitching rate for your beer.

Kai