Is my yeast propagation correct?

Where did you get this procedure? That is a LOT of steps and more time than is necessary for each step. Most propagation steps use 10x for each step, so if you need a 2L starter, the step before it would be 200 ml. Also, you should only need one day for each step. Without a microscope and hemocytometer though, your best bet is to use a yeast calculator like on Mr. Malty. I would also recommend just using Imperial Organic's A38 Juice (same strain) and then you'd be starting with double the amount of yeast you'd get from Wyeast.

 

Hmm... 48-72 hours is double the ammount of time that I recommend. You should have logarithmic growth in 24 hours at most unless you are starting with unhealthy yeast. If that is the case, I personally would just buy a fresh pack. At 48-72 hours, you've passed the log phase. If I was doing 15 gallons, I'd probably do a 500 ml starter, 24 hours later step up to 5L and then brew 24 hours after that. That said, I would rather use Imperial Organic yeast and go straight to 5L

 

Agree with @honkey, you dont need these multiiple steps or the longer times. Your basis for starter size is innoculation rate. Go to yeastcalculator.com, Brewers Friend, or Brewcipher and in the fine print it will show you inoc rate (number of cells per ml of wort). Your best range is 40 - 125 milliion cells of yeast per ml of wort. Don't let this be confusing, the calculatior does all the work.

Use date of packet to determine number of viable cells, then let the calc compute your starter size. I would never arbitarily suggest a specific size, rather let the calc compute the starter size based on total number of cells required. Again, this is easy, the calc does all the heavy lifting.

If you pitch a new packet into a 125ml starter this will probably not start at all, it is the equivalent of inviting the defensive line of the Packers over for dinner and serving a packet of twinkies, they ain't gonna be happy. For a five gallon batch typically you'll only need a single starter. Maybe a two-stepper if the yeast is old or OG is very high ... again, let the calc help you. For 15 gal keep stepping it up (at 40-125 rate) till you reach the target computed by calc.

With a stirplate you'll be finished around 16 hours after it actually starts. I typically give it a few hours more. I always chill and decant before starting a second step. It pays to give yourself a little extra time before brew day.

Here's two good articles: http://mrmalty.com/article.php

 

Very good points here.

I'm of the opinion, however, that you don't need to step up your starters at all. Just figure out how big of a starter that you need and pitch your source yeast into that volume. It'll get you to maximum cell density more quickly overall without using multiple vessels and you will end up with yeast that are just as healthy as if you used step ups.

 

There is a practical limit to how low you can go with inoculation rate. According to Jamil Z. and Chris W. in "Yeast," anything below 4 million cells/ml will result in no additional growth no matter how much additional wort you add. (And higher (but still low) rates give diminishing returns as they get lower, i.e. as more wort is added.) There are also arguably yeast health related reasons (maximum budding (and thinning of cell walls) before needing to "reset" with a new starter cycle) to not go too low.

BrewCipher's default for minimum inoculation rate for a starter step is 25 million cells/ml. I believe YeastCalc also recommends 25 minimum. Mr. Malty also has a default minimum inoculation rate (implied in its "Growth Factor" default setting (though I forget what it is), causing it to recommend multiple packs of yeast instead of more wort once a certain minimum inoc rate is breached). I think it might be higher than 25 though.

ETA: It's not my intent to use BrewCipher as an "appeal to authority."

 

When I make starters, I always aim for a little extra to save for the next time. You can pour off the extra 500ml into a sanitized container and then keep in the refrigerator. You will need to do another starter the next time, but I have kept and restarted the extras after 5-7 months without any problems. If you wait a long time 6 months, you will probably want to do a 2-step starter.

 

I do this all the time with good results. The advantages are cost savings, easier to manage sanitation, and ideally you are getting a true cross section of the yeast's characteristics. No magic number on how much to save, theoritically you could save as little as 100ml. But that pretty much guarantees the next brew will need multiple steps. I don't mind biting the bullet and adding a step to have enough to save . . . review the optimum inoc rates and try to target starter steps that fall in this range. Another trick is to use your second runnings for starter wort for the yeast you just pitched. Often I'll restart a tiny quantity immediately on brew day.

It's not unusual for me to start my yeast steps a week before brew day. I'm a decant'er before pitching so that adds another day('ish), You didn't ask, but the yeast will tell you when they have finished growing. It's not uncommon to have no (or little) krausen with the stir plate whirring. My technique is to cut off the stir plate for about 45 minutes and let everything settle down. You should notice a larger quantity of solids and a hard shake should produce CO2 off-gassing. Gradually this off-gassing will reduce to zero . . . this means the yeasties are no longer exhaling which means they've zoned out. You should always have a pleasant aroma when giving it this shake. I also mark my flask with masking tape to have a volume reference of 100ml, this helps tell you how much (volume) of yeast solids you have..

 

No doubt.

However, if you're brewing on the homebrew scale and using fresh yeast from a lab, those rates shouldn't ever be an issue.

 

There is a pretty thorough writeup on Brulosophy about how to go about doing this. I have not tried it out myself, though.