Yeast Starter Cell Count

I'm putting this page together because I see a lot of folks wondering how to bridge the gap between estimating cell counts in a yeast starter, and how many they mathematically need for a good pitch. Not everyone out there has a microscope and hemocytometer to do a proper cell count, so I've listed a few of my runs here in hopes that it will help estimate the number of cells you are pitching. This is a work in progress, and I invite others to share their data as well.

Proper Pitching Rates

I've seen a lot of variance on what is a "good" number of cells to pitch for a batch of wort. I think the consensus would agree with the following:

Ales: 5-10 million cells/ml wort OR 0.75-1 million cells * Plato/ml wort

Lagers: 10-15 million cells/ml wort OR 1.5-2 million cells * Plato/ml wort

These are just guidelines, but getting your cell count will ensure the yeast are happy in the fermentation and lessen the chance of wild yeast or bacteria taking over the batch.

Materials

Wort Starter

1.043 gravity hopped wort (10 IBUs)

Agar plates

For culturing yeast, stored at 4C

Stirplate

With stirbar

Mason jars

16 oz

Microscope

100-200x good enough for counting

Hemocytometer

For counting cells/ml

Methods

For these experiments, the cells were spread onto 1/3 of a 10cm agar plate, fully covering that surface, allowed to grow for 3 days, then stored at 4C for the time indicated. The initial cell count from these plates innoculated into around 14oz of oxygenated (shaken) wort was fairly consistent. For cell counts, I would take 20ul of the yeast culture and count the cells in 2 chambers of the hemocytometer for accuracy. The culture was incubated at room temperature with the stir bar stirring gently.

Results

Wyeast 1056

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