Hey fellow homebrewers!
I’ve got a hop rocket that I rarely use for its intended purpose, so I’ve decided to repurpose it as a yeast brink to harvest, store, and pitch yeast. Everything seems to be working well so far, but one thing I’m still unsure about is:
How do you determine pitching rate based on the weight of yeast slurry?
Are there any formulas or guidelines for calculating pitch rate by weight (grams or mL) rather than cell count?
flappy dunk
I’m harvesting the slurry straight into the hop rocket from the conical fermenter and keeping it cold between brews.
The real way to do it is to take a sample and do a cell count on the slurry. You can use that to calculate cells /ml and then how many ml’s of slurry you’d need to pitch to be accurate.
But as with most things in brewing there’s the “this is the correct way to do it” and the short hand dad-to-day way a lot of brewers will do which is “Use X% of the slurry and let it rip”
I think Jamil Zainasheff’s yeast calculator on mrmalty.com would let you calculate how many ml of slurry to add to your wort in the fermenter based on OG. But Jamil no longer has the time to support refining the code for his calculator and it is no longer available. I looked a couple other places on the internet to see if there was something similar that would let you do this but didn’t find anything.
Drew is correct about counting the yeast cells to determine the amount of yeast you would need. But you would need a hemocytometer, a microscope and some other things like methyl blue reagent to do this to do this accurately. I used to do yeast counts when I was doing my pro-brewer gig some years back.