There are many situations in which a homebrewer might need to propagate yeast using more than one step-up – for example, building up from a bottle of commercial beer, or reviving a smack pack that’s several months old. And while I love Mr. Malty’s Pitching Rate Calculator™, doing two-stage starters with it can be frustrating.
One simple alternative is to use Wyeast’s Pitch Rate and Growth Calculator. It does have some limitations: it works only in gallons, doesn’t feature a viability calculator (although viability can be input manually as partial smack packs), gives results in fairly useless intermediate units (millions/mL) as opposed to cell count or pitching rate (millions/mL-°P), and does not allow for decanting the starter. So in my opinion the best option is to trick the MrMalty calculator into doing it. Here’s how:
- Set your production date or viability, then play with the gravity and/or volume fields until the output matches the volume of your first stage.
- Note the number of cells that result.
- Turn off the automatic viability calculation and enter that number for the viability.
- Enter your actual gravity and volume, and the calculator will tell you the volume of the second stage.
- Verify that the volumes are realistic and adjust the first-stage volume if needed. Ideally, you want to at least double the volume at each step.
For example, let’s say I want to build a six-month-old pack of Wyeast 2206 into enough yeast for a 21 L (5.5 gallon) batch of 20°P (1.084) doppelbock. The required cell count is:
(21 L)•(20°P)•(1.5 billion/L-°P) = 630 billion. And the pack’s viability is:
0.75^6 = 0.178, or about 18 billion cells.
So I need to increase the cell count by about a factor of 35. This is clearly not possible with a single starter. So I’ll start with a 3 L first stage. Using “intermittent shaking” with a viability of 18%, volume of 5.5 gallons, and gravity of 1.022, the calculator predicts 174 billion cells total. I then set the viability to 174% and the gravity to 1.084, and the calculator tells me that the second stage will need to have a volume of about 7.5 L. Clearly this is one of those situations in which I should be brewing a 2-gallon batch of light lager as a “starter”.
I’ve finished the last starter needed to round out my aeration experiments. Once again, the main post has been updated with the full data set and some additional thoughts.
Three of the four words on this tag are lies.
On my recent trip to New Orleans, given that I was only traveling for four days, and not a women, I only needed to pack one bag. I elected to take only a carry-on – an easy decision given that checking luggage costs one-fourth as [...]
I was able to brew the test beers for the Yeast Pitching Rate Experiment today. Some notes on the brew session can be found on the main experimental page.
85% efficiency on a 1.059 beer, though… I do love my Barley Crusher.
Dear Hollywood,
We have a lot of history together – not all of it good, but we’ve had some laughs over the years. Lately, though, it’s become apparent to me that we’re moving in different directions. I think it would be best if we parted ways now, rather than try to carry on in this sham [...]
Name: NOLA
Date: Feb 21, 2010 6:01 pm
Distance: 3.86 miles
Elapsed Time: 40:08.1
Avg Speed: 5.8 mph
Max Speed: 12.0 mph
Avg Pace: 10′ 24″ per mile
Min Altitude: 33 ft
Max Altitude: 108 ft
Click on this link to display the track in Google Maps. This link will be valid until Mar 23, 2010 5:47 PM PDT.
Je vais voyager en Nouvelle-Orléans de ce soir à mercredi. Laissez les bons temps rouler!
Most homebrewers, once they get seriously involved in the hobby, will make starters for their beers. While the commercial yeast products are advertised as being “pitchable”, their cells counts don’t allow brewers to inoculate a 5-gallon batch of ale at the industry standard rate of about 0.75 billion/L-°P. And the true cell counts may be [...]
I really don’t know what all the fuss is about graphic design. This was super easy and hardly looks like crap at all. (It’s also an awesome example of your tax dollars at work.)
This gag would work a lot better if it was an actual pizza.
As a quick follow-up to my starter aeration experiments, I made up a DME starter for comparison purposes. As would be expected, it produced substantially more yeast than the sugar starters. So if nothing else, don’t take the cell counts estimated in the original tests to be accurate for beer – something I probably should [...]
