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B-Dub · 08-22-2008, 11:53 PM

So there I am taking a gravity on my last 2 Belgium brews and the triple is down from 1.078 to 1.012....nice. The quad is down from 1.094 to 1.036....not nice.

I start looking into what could have caused the apparent lack of attenuation and got to yeast pitching rates. If you type in 1.090 for 5.5 gallons of wort and try and prop up 1 vial of yeast it gives you 6.52 liters of starter. That is 1.7 gallons of starter. If I am brewing 22 gallons, ie 2-11 gallon batches, that would be about 6.8 gallons of starter!!

So the long and short of it comes down to: does this sound right? And how are other brewers building yeast and pitching for say WLP530 for a Quad? Lastly, what is the FG?

Thanks for any insight.

FYI - the triple and the quad both got the same yeast and same build up on the starter. All four ferments were very strong and the temps got into the low 80's by the end.

phissionkorps · 08-23-2008, 12:11 AM

Look at my reply in this thread:
http://www.homebrewtalk.com/f13/question-about-mr-maltys-pitching-calculator-77348/

In short, the calculation is inherently flawed because it doesn't incorporate any sort of exponential growth formula.

B-Dub · 08-23-2008, 12:21 AM

It is not growth that the calculator figures out for you? Therefore giving you the proper amount of growth for your particular needs?

How did your brew ferment? and what was your starter size, type of yeast and fg?

s3n8 · 08-23-2008, 12:46 AM

There is a good article in the current BYO. Its not online yet, so I do not know if the online article will be available. In any case, it was really good and had a good discussion about pitching rates, starter size, type of beer, etc. It was written by John Palmer. He has some brew-foo.

Edit: Here it is

http://byo.com/departments/1757.html

phissionkorps · 08-23-2008, 01:24 AM

No. The equation does not account for growth whatsoever. And seeing that it's exponential growth, which reaches and stays at a maximum for X amount of time based on a variety of factors, the equation would have to use calculus, which it does not. The only variables calculated are number of starting cells based on ale or lager, milliliters of wort, and the sweetness of the wort (if there has been actual science done behind the constants used in this calculation, someone please PM me....they seem more like "accepted" values). Harvest date is in there on the actual calculator somehow, and call me scientific, but that is an extremely rough estimate at best. Not the date, because that's on the package, but how the date and viability from a certain date figures into the equation. I have yet to see actual experiments done on these specific strains, and at what rate their viability decreases, correlated with time out from packaging date. The yeast in your package could've been packaged at a variable amount of time after propagation off mother colony date, etc, etc. Obviously a colony stored under perfect conditions will last for a lot longer than one stored under less than ideal conditions...and you have no way of knowing the exact history of every yeast packet (and they're "all" different). It's a decent enough tool to get a good estimate, but the growth rate among other things isn't accounted for, so I wouldn't rely on it.

Just looked at the BYO article. No growth rate + no calculus = not accurate (enough...for me)
If you pitch a packet of dry yeast, it will have the lag then growth phase, and take up a very small volume of the total 5 or 10g. However if you pitch a couple hundred mil's of slurry, it will already be in the growth phase, and take up a larger volume of wort = less total nutrients per cell.