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I have a can of Heady Topper sitting in my fridge, and I'd like to culture the yeast from it. I've read two methods of culturing yeast, both of which involve stepping up from a very small amount of wort to, effectively, a larger starter.
Where the methods differ is that one recommendation is to start with a small amount of wort that is 1.015 in gravity, and slowly scale up to a full sized starter of 1.040.
The other simply uses 1.040 wort from the beginning.
Thoughts? Opinions? I'd like to do this right!
Posted 34 days ago.
Using a lower gravity reduces yeast stress and allows the otherwise sluggish cells to wake up. Using those cells then to bring up a starter should result in a higher level of viability (also meaning far fewer mutations than stressed yeast).
I would suggest a few hundred ml's of 1.015-1.020 strength yeast into the can and covered for at least 24 hours, then decant into a 1 liter starter and step up from there. The can interior should be a safe spot rather than decanting into a beaker.
I also just built up some San Diego Super Yeast this way from an old slurry. Worked well. I did count before and after to get an idea of where I needed to go with it. I have stopped using wort stronger than 1.035 at the recommendation of a friend in a lab.
Posted 34 days ago.
>I have stopped using wort stronger than 1.035 at the recommendation of a friend in a lab.
This is really interesting, any more information on that? Even specific information on yeast stress?
Posted 34 days ago.
Well, I am just experimenting with the lower gravity wort based on that recommendation.
Some alleged advantages include lower osmotic pressure, which as a stress vector seems to cause DNA mutation. 1.035 is a bit arbitrary as a compromise between vectors for cell mass growth and viability. I am also seeing slightly faster starts, but that is hard to quantify. I am running counts to compare, but my home is hardly a lab.
Lower gravity wort works a charm to revive sluggish or old stored yeast. I wouldn't do it with dried yeast until propagation.
I loaned the Yeast book to this friend, and the response was, "Surprising lack of details from White Labs. They are telling you how to create biomass, but de-emphasize viability and strain purity (no real strategies laid out). This explains the comments on their site that warn about repitching more than a few times." He believes it is biased towards selling commercial yeast and lab services. He laid out a simple lab strategy that I am prepping.
His lab is tracking DNA and modeling mutation in a variety of yeast strains and application... But not brewing centric. They propagate highly viable yeasts in both stressed and non-stress environments to compare deltas in mutation and Gene expression over millions of harvests.
Posted 34 days ago.
Edited 34 days ago by mchrispen
Fantastic advice guys, thanks! And thanks for that resource ingoogni, I'll give it a read.
Posted 34 days ago.
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