Help with yeast calculation

[crashlann]

The main thing I am confused on is the 1.63 liter starter needed statement on Mr. Malty. What does this refer to ? I am making a two liter starter I thought if Im using a 1.040 wort in a 2 liter Erlenmeyer. I am getting confused on knowing how much of the finished starter to use. If Mr. Malty says use two vials in the starter and then use 1.063 liters of the starter, should I shake the flask, and then decant (sterile thechnique) 1.63 liters of this starter to pitch? Sorry for making this question comlicated, but thanks so much for all the feedback. I do understand how to make starters, its really the calculation of how much of theme to use that is kicking me.

[spiderwrangler]

Your question is confusing me, because you keep flipping between 1.63 and 1.063. Just do one vial in 2L at 1.040, you'll be fine.

[crashlann]

If I am brewing a Belgian Strong Ale and my OG is going to be 1.084, when I enter the data in Mr.Malty, it tells me I need 2 vials of yeast with a starter and intermittent shaking, and 1.63 liters of starter needed. I use a 2 liter starter Erlenmeyer flask. What is the 1.063 liters of starter referring to? It states a growth rate of 3.0, what is this referring to? I think I am overpitching and getting off flavors due to understressed yeast. Can anyone help me here? I get two different results whether using the website or Android. Thanks.

Thanks, my mistake, it is definitely 1.63 liters of starter. Sorry for the confusion.

[Ozwald]

I have a question, mostly related to the fact that I've never used a flask; all my starters are done in growlers, 1g 'growler' jugs & 3g carboys. Can you seriously do a 2L starter in a 2L flask? I know the 2L mark isn't at the top, but there still isn't what I would consider adequate headspace above that 2L mark.

[MRbrew]

You use all of it. Don't make a 2L starter make a 1.63L starter with the 2 vials, or a bigger one with 1 vial (slider on the calculator). If you were making a pilsner or other light flavoured beer you would make the starter then 24hrs later chill it to settle out the yeast and pour off the spent wort, then pour the yeast slurry into your fresh wort. As you're making a big belgian don't worry about it. Have the starter as close to the pitching temp as you can then put the lot in.

Re the aeration; yeast undergo an aerobic GROWTH phase for the first 12-24 hours then switch to the anaerobic FERMENTATION stage after this. It's not a clear cut point where all the yeast just switch but more of a gradual thing. If you aerate too late in the process most of the yeast have stopped using oxygen and you'll cause staling off flavours.

[spiderwrangler]

Few points to expand on...

make the starter then 24hrs later chill it to settle out the yeast and pour off the spent wort, then pour the yeast slurry into your fresh wort.

If you are going to chill and decant, you want to take the yeast to completion, not halt them midway through fermenting the starter wort. Either pitch while at krausen, or finish it out, chill and decant, pitching slurry.

Re the aeration; yeast undergo an aerobic GROWTH phase for the first 12-24 hours then switch to the anaerobic FERMENTATION stage after this.

This is a piece of misinformation that's been around for quite a while. A lot of people call the period in which yeast aren't producing CO2 the aerobic phase, and call it anaerobic when it starts bubbling. Aerobic respiration actually would produce 3x as much CO2 as fermentation, so this is patently false.

[MRbrew]

A lot of people call the period in which yeast aren't producing CO2 the aerobic phase, and call it anaerobic when it starts bubbling. Aerobic respiration actually would produce 3x as much CO2 as fermentation, so this is patently false

I've never heard this before. So you're saying there's no uptake of oxygen by the yeast? Or are you just saying that there's fermentation going on whilst the yeast are taking up O2 at the start and you can't call it aerobic? I was taught there is a reproductive/growth stage where the yeast bud and take up oxygen to produce sterols and lipids for healthier cell walls. After this stage they process sugar by cleaving off a CO2 molecule leaving alcohol. You're turning my world upside down if you're right. What does this mean for the brewing process? Do we not oxygenate the wort now?

[spiderwrangler]

I've never heard this before. So you're saying there's no uptake of oxygen by the yeast? Or are you just saying that there's fermentation going on whilst the yeast are taking up O2 at the start and you can't call it aerobic? I was taught there is a reproductive/growth stage where the yeast bud and take up oxygen to produce sterols and lipids for healthier cell walls. After this stage they process sugar by cleaving off a CO2 molecule leaving alcohol. You're turning my world upside down if you're right. What does this mean for the brewing process? Do we not oxygenate the wort now?

That is essentially correct. Calling it aerobic and anaerobic is misleading however... lots of people think that they are using the O2 in respiration (breaking down of sugar), which is more efficient than fermentation, but as you say, they are using O2 to maintain cell pliability. We for example, breath in oxygen, which is transported to our cells where it is used as a final acceptor of electrons and protons in cell respiration. If our cells are starved of oxygen (during a sprint for example), they will convert to a fermentation pathway that results in the production of lactic acid. Yeast use a similar fermentation pathway, except that a CO2 is cleaved off first and the remaining molecule is eventually converted into ethanol.
Instead of calling it aerobic and anaerobic/fermentation, the less misleading terms would be lag phase and exponential growth phase.
http://www.whitelabs.com/beer/Yeast_Life_Cycle.pdf