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Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > Do you know how to make a yeast starter? Then why not farm yeast and freeze it?

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Old 10-06-2012, 01:44 AM   #201
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I agree. I was expecting more cells. I weighed out 150 grams of light DME and added 1.5L of water and 1/2 Tsp of yeast nutrient. Boiled for 20 min, cooled to room temp. The original gravity was 1.040 just like I read it should be. I oxygenated using a can of pure oxygen and a diffusing stone for 30 seconds. I warned the yeast for a few hours to room temp, then pitched it. I kept it loosely covered with foil at room temp on a stir plate. I'm pretty sure I did everything correctly but please correct me if I made any mistakes.

Are those yeast calculators based on the assumption that you start with 100 billion cells, or can you enter your starting cell number? I haven't seen any homebrewers validate those calculators with their own real world data.

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Old 10-06-2012, 01:59 AM   #202
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I agree. I was expecting more cells. I weighed out 150 grams of light DME and added 1.5L of water and 1/2 Tsp of yeast nutrient. Boiled for 20 min, cooled to room temp. The original gravity was 1.014 just like I read it should be. I oxygenated using a can of pure oxygen and a diffusing stone for 30 seconds. I warned the yeast for a few hours to room temp, then pitched it. I kept it loosely covered with foil at room temp on a stir plate. I'm pretty sure I did everything correctly but please correct me if I made any mistakes.

Are those yeast calculators based on the assumption that you start with 100 billion cells, or can you enter your starting cell number? I haven't seen any homebrewers validate those calculators with their own real world data.
Not sure if that was a typo, but was your starter gravity 1.014? That would definitely explain the low cell count. Starter gravity should be between 1.030 and 1.040. I keep mine close to 1.040.

Starting cell count can be manipulated with both calculators. I used a starting cell count of 50 billion.
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Old 10-06-2012, 02:02 AM   #203
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Oops that was a typo. I corrected the post. The OG was 1.040

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Old 10-06-2012, 02:12 AM   #204
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Can you give me links to those calculators. The ones I've seen are pitch-rate calculators that tell you how many cells you need depending on the beer your making, but I can't find a calculator that gives you predictions of growth rates and numbers based on starting cell number and volume of culture. Thanks. Sorry if I'm missing something obvious.

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Old 10-06-2012, 02:28 AM   #205
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Can you give me links to those calculators. The ones I've seen are pitch-rate calculators that tell you how many cells you need depending on the beer your making, but I can't find a calculator that gives you predictions of growth rates and numbers based on starting cell number and volume of culture. Thanks. Sorry if I'm missing something obvious.
Well, actually, the calculators are not designed to be used this way, but it can be done. For Mr. Malty it isn't that bad. I'm pretty sure it assumes 100 billion cells at 100% viability so you have a range of 0-100 billion cells that you can start with by adjusting the % viability. Wyeast on the other hand is a bit more of a pain to use this way. You can start with either an activator pack (100 billion cells) or a propagator pack (25 billion cells). You can use more than 1 pack in the calculation so you can start with an unlimited range of cell counts between 25 billion to infinite, but they have to be in multiples of 25 or 100 billion cells. Here are the links.

http://www.mrmalty.com/calc/calc.html

http://www.wyeastlab.com/hb_pitchrate.cfm

I guess I should explain a little further.

To use Mr. Malty to predict cell counts: Set your % viability to your starting cell count and then adjust the OG of the beer until you get the appoximate starter volume that you plan to use. At this point, the pitching rate represents the predicted cell count.

For Wyeast, it's more strait forward, sort of. Set your starting cell count by selecting the appropriate number and type of packs, then enter your starter volume in gallons. For the second step, enter an arbitrary volume that makes the end volume in the fermenter equal to an even number of gallons. The final pitching rate is reported in million cells/ml so, multiply the end volume by 3785 ml and then multply that by the reported pitching rate to get your final cell count.
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Old 10-06-2012, 02:46 AM   #206
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Thanks for the detailed explanation. I think I understand where you're getting your numbers from, but just to make sure I'm doing it correctly...

Using the Mr. Malty calculator, if I enter 1.223 for the OG, 5L, and 50% viability, stir plate, it tells me I need a 1.4L starter (which is what I did) and tells me I should have 181 billion cells from 1 vial. So my 115 billion is ~2/3 of 181 billion.

Using the Wyeast calculator, I choose Propagator (which assumes 25 billion @ 100% viability) and 2 packages, stir plate = yes, volume of starter = 0.37 gal (1.4L), it tells me my pitch rate should be 164.8 million/ml, which times 1.4L is 230 billion cells, and my 115 billion is ~1/2 of that.

This is my first starter where I've actually counted cells. Time will tell which one I believe more, my results, or the calculators. I'm sure it can vary depending on conditions between labs and homes. At least I'm not more than 2X off, I think I'm in the right ball park at least.

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Old 10-06-2012, 03:00 AM   #207
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Yup, you did it right. You took slightly differnt routes than I did, but it makes no difference.

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Old 10-10-2012, 05:49 PM   #208
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My yeast is growing really slowly. Anyone have any suggestions? I made my starter with 1.5L of bottled spring water (not distilled) + 150g light Munton's light DME from Rebel Brewer. I added 1/2 Tsp of Wyeast yeast nutrient, boiled x 20 min, cooled to room temp, oxygenated using BernzOmatic pure oxygen and a diffusing stone x 30sec. I warmed 1 vial of White Labs WLP001 to room temp for a few hours, then pitched it and kept in on a stir plate at room temp, loosely covered with aluminum foil.

I've been feeding every couple days by putting the starter in the fridge so the yeast will settle out, then decanting the wort and adding fresh wort. The starter always looks really active when I add fresh wort. I see plenty of bubbles and frothing like it's "awake". The specific gravity (the 1 time I measured it) went from 1.040 to 1.010, so the yeast is definitely active.

Is it possible that the yeast are going into fermentation mode instead of reproduction mode? I'm also worried that the quality of the DME isn't good, or my water chemistry is off. I'd really appreciate any advice

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Old 10-10-2012, 05:58 PM   #209
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I'll be interested to see what folks have to say about this. I'm kind of at a loss as to why your growth rates are low. What temperature are you keeping the starter at? Are you adding oxygen every time you step it up? Are you using the same volume of wort for every step? What's your current cell count and how many times have you stepped it?

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Old 10-10-2012, 06:19 PM   #210
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I started off keeping it at room temp (~72oF), then I moved it to 30oC (86oF) to speed up the growth. I don't think that matters much because I had poor growth at both temps. I oxygenate every batch of fresh wort before I add it. I've been adding between 1.2-1.5L of wort. I'm up to ~250 billion cells from the ~50 billion I started with, but I've had to feed the starter 3 times already. I'm averaging ~50 billion new cells per liter of wort, which is really low.

I should also mention that counting the cells has had a bit of a learning curve. I wasn't sure whether to count cells that look like they're about to divide as 1 or 2. It's difficult to tell a dividing cell from 2 cells clumped together. I'm also not sure that Trypan blue can clearly distinguish all the non-viable cells. While it's easy to see dead cells, I think the trypan might not really stain dying cells so well. I think I was over-counting on the hemocytometer because the CFU from 3 different plates has consistently given lower #s.

I'm thinking the problem is my DME or water. I'm gonna try feeding tonight with some wort made from dark DME and tap water.

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