So I'll be stepping up my yeast starter for the first time and had a question. I have a 2 liter erlenmeyer (sp?) flask, and want to step the starter up from 1 liter to 2 liters. My problem is that I don't have a stir plate or aquarium pump to introduce oxygen. I have just been swirling it as often as possible. It has worked well in the past, but when I step up the starter, I won't have much head room to give it a good swirl. Will this be too much of an issue if it gets just a slight swirl as often as possible, or would this require a stir plate or pump? (understanding that the more o2 the better in starters)
Yeast Starter Question
- Thread starter trevorc13
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If you are using a foam stopper, the head space should exchange quickly enough that you'll be okay. The main think you want to do swirling is to disrupt the surface of the wort.
KJohnson said:
What makes you say that?
KJohnson said:
The Wyeast calculator actually suggests that a 1L and 2L stepped starter produces significantly greater populations than a single 2L starter, and plenty of anecdotal evidence on this board backs that up.
Obviously sanitation is still very important, and obviously a stepped starter involves more work, but where are you getting your information that a single 2000mL starter has "better results"?
As MalFet said, a 1 L starter stepped up to 2 L will significantly increase the yield relative to just a 2 L starter. I have done this many times due to not having a stir plate. However, I tried to make a 2 L starter in a 2 L flask and came in the next morning to find the krausen had overflowed and I had yeast all over the place. Beer still turned out good! Obviously, if you can avoid stepping up a starter, it is definitely the better way to go as it avoids more advanced planning and reduces the risk of contamination. I now purchased a 3 L flask and a stir plate, which should reduce the need to step up a starter in the future. I plan to try this out on my upcoming brew.
Edit: Correct me if I'm wrong, but I believe 100 billion cells pitched into 2 L should create 200 billion cells. 100 billion cells pitched into 1 L creates 150 billion and then if that is stepped to 2 L, you should get about 260 billion cells.
BoogieBrandBooze
Well-Known Member
Doesn't the amount of yeast you grow in any particular size starter depend a lot on the innoculation rate as well? I don't see where the OP told us how much yeast he started with. As far as I know, that would affect whether a 1L to 2L step or straight to a 2L is better, as far as growth rate is concerned anyway...diminishing returns and all that...I'm still trying to wrap my head around all this starter business...
You are correct. I was assuming a smack-pack or WL vial, but maybe not. If he started with less than that, though, a stepped starter would be even more important.
Don't get me wrong...I'm not trying to advocate universally for either stepped or non-stepped starters. The wyeast calculator does a nice job predicting population dynamics, and you can use that to figure out what suits your purposes better. What sjbeerman and I were objecting to was KJohnson's claim that a 2L would have better results, regardless of starting gravity, innoculation rate (as you mention), or desired pitching rate.
OP
OP
trevorc13
Well-Known Member
I'm starting up a quart mason jar of washed (rinsed) yeast that has been in The fridge since the beginning of december. Since it's been a couple of months, that's the reason I'm stepping it up. Don't have the figures on how much yeast though. I didn't have the means to measure it.
I based my statement on yield factor and pitching rates. If you pitch 1 vial In 1L you'll get a yield factor of 7.4. If you pitch 1 vial in 2L the yield factor is 7.6. Remember the higher the yield factory the better the growth. And the yield factor from 150 million cells in 2L is about 4 so you will not create another 100 billion cells you will create about 40 billion cells because of the inoculation rate. "As the inoculation rate drops the yield factor climbs." Quoted from Yeast the proper guide to beer fermentation.
I understand the math, though my numbers are more in line with what sjbeerman says. 205B cells from a 2L starter and 266B cells from a 1L to 2L starter. I understand that it doesn't double every time you step, but that is a significant enough of a difference that it is worth noting. Even if it were just 40B, as you cite, that's still a 20% difference. It may not be necessary for any particular beer, but I wouldn't say that 200B is a better result than 266B (or even 240B).
The talk of yield factor in the Chris White book always struck me as odd, and I don't think it means what you are suggesting that it does (assuming I'm understanding you right). A yield factor of 7.4 on a 1L starter vs. a 7.6 on a 2L starter means that the 2L starter will net you approximately double the yeast growth of a 1L starter.
Higher yield factor does not mean better growth. In fact, there is some talk that the opposite is true. Yield factor is a ratio of growth to sugar consumed. Why is that interesting to home brewers? I'm not sure that it is...I'm very interested in growth numbers, but don't really care about the amount of DME I need to use. Maybe that's wasteful, but it strikes me as kind of like spending an extra hour on your sparge to save 60 cents on grain. I understand why it would be an important consideration for big time brewers for whom a few points equals millions of dollars, but DME is cheap.
Anyway, to each their own. I certainly don't want to sound like I'm suggesting that stepped starters are always better, but nor do I think it is fair to tell someone doing a stepped starter that he shouldn't because a single will give him better results (in the absence of any of the important details).
Maybe I'm wrong but I think it would be 190 billion. 100 from vial and 50 from 1L and only 40 from 2 L because of the inoculation rate you only get .4 doubling. But I'm not sure on that the book doesn't really get into that. Do you get 100million cells if you pitch 150 million cells into a 2L starter cause if you do then I'm wrong?
I'm not sure I follow that last sentence. I assume you mean 150 Billion cells and the million is just a type-o. Or are you talking about inoculation rates rather than specific populations? In any case, I don't understand where the numbers are coming from.
Here's my math.
Single stage starter
100 billion cells pitched into 2L of wort is an inoculation rate of 50M/mL.
That gives a growth rate of 105%. 100B cells becomes 205B cells.
Stepped starter
100 billion cells pitched into 1L of wort is an inoculation rate of 100M/mL.
That gives a growth rate of 52%, so 100B cells becomes 152 cells.
152 billion cells pitched into 2L of wort is an inoculation rate of 76M/mL.
That gives a growth rate of ~75%, so 152B cells becomes 266B.
