Pitching Rate

[Bud]

Hey everyone,

I am curious about the pitching rate of yeast. It was mentioned that you can see the viable cells once the yeast is pitched on the wort. How does one specifically denote live versus dead yeast cells? Also, what sort of scale is used to analyze the rate for reference.

 

Thanks for the good words of advice.

[PB2]

You need a microscope to look at yeast cells.

 

To determine the viability (ratio of live cells to total cells), we use a blue dye (dead cells take up the dye). We count the total amount of cells on a grid and the amount of blue cells on the same grid.

 

Dry yeast contains as much as 10 billion cells per gram with the amount of live cells dependant on the viability at the time.

 

[ChrisK]

On hopefully a similar topic: What's the benefit of refridgerating yeast and what's the downside (if any) to not refridgerating?

 

The under-lid yeast is obviously stored at room temp, where as the US-05 I bought a week or two ago was refridgerated, so I continued to do so though I admit I don't really understand why.

 

 

[PB2]

We tell home brewers to put the yeast in the fridge as soon as they get it home.

[ChrisK]

Event the under-lid stuff?

 

And I was more interested in why it should be refrigerated than the fact it should.

[PB2]

Yeast is a living organism and will survive for a longer period at lower temperatures.