How do you determine pitching rates by weight?
I am looking for information on determining pitching rates by weight using a hemacytometer. Is there an magazine article or book that discusses this? Can anyone out there explain it? I know how to do it by volume, but I'm not sure how to do the dilutions by weight and I am not sure of the formula for the pitching quantity by weight.
Well Scott This is a very good question. I have found that the best way to determine the pitching rate by weight is to ask the pitcher his or her weight and then count the number of times he or she throws the ball. This seems to work for me.
Actually I was talking with a guy that brews in Idaho and he pitches 1lb/bbl for a 12 P wort 1.5 lbs/bbl over 15P. I've tried this method and it seems to work well but there is know real way of knowing your yeast viability. I don't think there is a formula for it because the cell count and viability issue is such an unknown. Hope that helps
You should email White Labs. I bet they could help you out.
1. Figure the density of the slurry by massing out a given volume. This will give you density in gr/ml,
2. Figure the cell count of the slurry as normal. This will give you cells/ml,
3. Divide the cell count by the density. (cells/ml)/(gr/ml) gives you cells/gr.
We pitch by weight and that's how we do it. We harvest our highly flocculent ale yeast into converted Sankey keg brinks. The problem we have is getting a representative sample after the yeast has settled out in the cooler for a couple days.
Of course the 1 lb/bbl rule of thumb for ales works well too.
Moose's Tooth Brewing
The following method should help you out even though I would recommend caution about pitching based on weight, unless you have some laboratory measures to assist in determining your yeast viability/vitality.
Take a sample of your yeast sluury. Count five squares in your heamocytometer(four corners and the center) and then multiple by your dilution factor(we use 256). Divide this number by twenty. This will give you your yeast density in millions. If your yeast is real healthy/thick you may get a count in the billions.
To determine your amount to pitch:
brewlength size (in bbls.) multiplied by pitch rate (we use 1M cells/ml/degree Plato). Divide this number by your yeast density (in Millions). This will give you bbls. of yeast. Mutliple this number by 31 then by 8.5 to give you pounds of yeast to pitch.
We consistently do this week in week out. We usually pitch to a 750 bbl. FV and just use the brewlength (250 bbls.) of the first brew. By the time the subsequent brews are put in the tank the yeast is already budding/multiplying. It works great for us as our yeast collection brinks are on load cells. If we have a larger brew (15+ Plato we tend to pitch a little extra, like round up to the nearest hundred). I will stress again that this works for us extremely well because we propagate yeast very often and our yeast are extremely healthy.
Best of luck and give me a shout if you have further quesitons.