Stepping Up A Starter

[MikeyHomebrewer]

What I am reading is that if you start out with 100 bil cells in a 1l starter would will end up with aprox 130 bil of new cell growth. How do you calculate that out to larger starters??

That's correct, 100 billion cells into 1L of wort grows ~130 billion new cells. Your actual cell count is then the 100 billion that you started with + your 130 billion new growth, 230 billion. If you keep the same ratio of starting cell count to starter size, you can scale by just multiplying the result by your starter size. For example, if you start out with 200 billion cells and make a 2L starter, you will grow 130*2 = 260 billion new cells, for a total of 460 billion. Another example, if you start out with 100 billion cells and make a 4L starter your cell count ratio is 100/4 = 25. And that corresponds to ~80 billion new cells / L from the chart (you can plug your cell count ratio into the formula printed on the chart for a more exact number). So new growth will be 80 * 4 = 320 billion, for a total of 420 billion.

This chart is just a plot of what the mr. malty calcultor spits out, the important thing to remember is that in order to use the least amount of starter wort you want to stay around 1L/100 billion cells. For example, say you need 550 billion cells. You can make an 8L starter with 100 billion cells and be done. Alternatively, you can make a 1L starter (130 billion new cells, 230 after fermentation), then throw that into a 2.3 L starter (again sticking with the same ratio of 1L/100 billion cells) to get ~530 billion cells (230 starting + 2.3*130 new). So instead of using 8L of starter wort, you've grown almost as many cells using 3.3L. You can let the calculator do this for you by setting your viability to 230% and changing the gravity or volume until it says you need a 2.3L starter.

I am looking to brew a Baltic Porter from BCS within the next week or so and just wanted to make the math on this was right.
According to BCS, OG is around 1.089 and the pitching rate calculator spits out 697 bil yeast cells. I plan on using Wyeast 2124 Bohemian Lager, 100 bil cell count. I'll start with 2L starter, then step up to 3L

Based on your equation:
2L starter:

100 bil / 2L = 50 bil/L
Y = 35.869*ln(50) - 33.846
Y = 106.47 bil
106.47 * 2 = 212.94 bil + 100 bil = 312.94 bil

3L Starter:
312.94 bil / 3L = 104.31 bil/L
Y = 35.869*ln(104.31) - 33.846
Y = 132.85
132.85 * 3 = 398.55 bil + 312.94 bil = 711.49 bil total yeast cell count

[Nyakavt]

I am looking to brew a Baltic Porter from BCS within the next week or so and just wanted to make the math on this was right.
According to BCS, OG is around 1.089 and the pitching rate calculator spits out 697 bil yeast cells. I plan on using Wyeast 2124 Bohemian Lager, 100 bil cell count. I'll start with 2L starter, then step up to 3L

Based on your equation:
2L starter:

100 bil / 2L = 50 bil/L
Y = 35.869*ln(50) - 33.846
Y = 106.47 bil
106.47 * 2 = 212.94 bil + 100 bil = 312.94 bil

3L Starter:
312.94 bil / 3L = 104.31 bil/L
Y = 35.869*ln(104.31) - 33.846
Y = 132.85
132.85 * 3 = 398.55 bil + 312.94 bil = 711.49 bil total yeast cell count

Looks right to me, and the mr.malty calc agrees. The 3L starter is just outside the plotted range (12.5-100 bil/L) but it's close enough. If you get too far out of the plotted range I would not have much confidence in the results. Keep in mind that this is probably +/- 20%, so you don't need to carry all the decimals unless you want to.

[MikeyHomebrewer]

Looks right to me, and the mr.malty calc agrees. The 3L starter is just outside the plotted range (12.5-100 bil/L) but it's close enough. If you get too far out of the plotted range I would not have much confidence in the results. Keep in mind that this is probably +/- 20%, so you don't need to carry all the decimals unless you want to.

Cool, cool. Just wanted someone to verify that I was in the ballpark. Thank you.

[dstar26t]

Woah, I think I've been doing it wrong. Last beer I made was a Dopplebock. 11.5 gallons into the fermenter at 1.082 which needs 1286 billion cells according to the PRC (Jamil's Pitching Rate Calculator).
I used yeast from 22 day old harvested WLP833. Started with 200 mL and at 22 days old it's 59% viable which effectively leaves me with 118 mL. Using the default yeast concentration of 2.4 billion cells per mL on the PRC, that leaves me with 283 billion cells (118*2.4). I put 283 into the viability for pitching liquid yeast and it spits out a 5.45 gallon starter for intermittent shaking (don't have a stir plate yet). 5.45 is too big of a volume to put that amount of yeast in so I did a 2 step starter. First step was 1.5 gallons (which is equivalent to one vial in 2 liters) and then I chilled and decanted and added 3.95 gallons more wort. I thought this would give me the 1286 billion cells I needed since all the wort adds up to 5.45 gallons but apparently I had way more? Like 1871 billion following Thirsty Boy's PRC step up procedure?

Nate

[Nyakavt]

Woah, I think I've been doing it wrong. Last beer I made was a Dopplebock. 11.5 gallons into the fermenter at 1.082 which needs 1286 billion cells according to the PRC (Jamil's Pitching Rate Calculator).
I used yeast from 22 day old harvested WLP833. Started with 200 mL and at 22 days old it's 59% viable which effectively leaves me with 118 mL. Using the default yeast concentration of 2.4 billion cells per mL on the PRC, that leaves me with 283 billion cells (118*2.4). I put 283 into the viability for pitching liquid yeast and it spits out a 5.45 gallon starter for intermittent shaking (don't have a stir plate yet). 5.45 is too big of a volume to put that amount of yeast in so I did a 2 step starter. First step was 1.5 gallons (which is equivalent to one vial in 2 liters) and then I chilled and decanted and added 3.95 gallons more wort. I thought this would give me the 1286 billion cells I needed since all the wort adds up to 5.45 gallons but apparently I had way more? Like 1871 billion following Thirsty Boy's PRC step up procedure?

Nate

283 billion cells into a 6L starter (roughly 1.5 gallons) will give you 750 billion cells with intermittent shaking. Adding another 4 gallons (roughly 16 L) will give you 2 trillion cells. So yes you did overpitch by quite a bit. How did the beer turn out, any weird esters?

If your yeast viability is that low, you may be better off taking a tablespoon from the slurry and just starting from scratch with several smaller starters. If you have 200 mL of slurry and 40% of it is dead, all that dead yeast is going to go into the next beer. May not be a huge deal, did you get any soapy or brothy flavors from the beer?

When you use the PRC to step up, make sure not to violate the minimum starter size, which is 1L/100 billion cells. So if you start with 300 billion cells, you don't want to make anything smaller than a 3L starter. The PRC will recommend less than a 3L starter if you input the right set of variables. I use this minimum size rule to determine what the two steps should be. For your case above, the least amount of wort would be a 4L starter followed by a 7.2L starter. At that point it would be really good if you could just make a 5 gal batch of lager and use the yeast from that, at least you'd get an extra beer out of it.

[dstar26t]

I pitched into the Dopplebock with all that yeast this past monday morning so I haven't tasted it yet. Regarding the amount of dead cells, I didn't think it would be an issue because out of the 1286 billion cells I was planning on having, only 82 billion would be dead from the original harvested yeast, or 6.4% of the total.

I had made a Munich Dunkel with the intention of using the resultant yeast for this Dopplebock. Long story short, I only wound up with 200 mL of harvested yeast from the Dunkel. I wanted to see what the second generation yeast would do in this Dopplebock so I used it exclusively.

Thanks for your help!

[Nyakavt]

I pitched into the Dopplebock with all that yeast this past monday morning so I haven't tasted it yet. Regarding the amount of dead cells, I didn't think it would be an issue because out of the 1286 billion cells I was planning on having, only 82 billion would be dead from the original harvested yeast, or 6.4% of the total.

The dead yeast comment wasn't in regards to having enough healthy yeast to ferment the beer, but rather just pitching that much dead or dying yeast in the next beer and maybe being able to taste it. The only time I've been able to taste autolysis was when I had a huge amount of yeast, probably 2" deep in a bottle. This was early days when I was trying to get every last scrap from the fermenter. Anyway those bottles tasted like nothing but beef broth after 3 months. Obviously 80 mL in 10+ gallons isn't going to get you to that level, but I do not know where the limit is. Let us know how the beer turns out, I'm betting you won't pick up any autolysis flavors.

[dstar26t]

Thanks, I will.