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Old 02-10-2013, 12:15 AM   #1
el_caro
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Default Generation of Yeast from Starter

I am a little unsure about the generation of yeast that have been grown in starters and never fermented out a beer as such.
For instance I take a vial or smackpack of yeast and put it into a starter then rinse and store the yeast in a couple of containers. Is this still first generation yeast?
If I take one of those containers from the fridge and grow it up in a starter and store some of the yeast again then what generation is that stored yeast?

If you step up starters rather than make a larger one does that have any impact on what generation the yeast is?


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Old 02-10-2013, 01:14 AM   #2
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As I understand it, the first starter out of the vial or smack pack is the first generation. If you split that starter off and make another starter later, that would be the second generation. Step-ups for a single starter are the same generation.

I'm sure somebody will correct me if I'm wrong.


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Old 02-10-2013, 03:42 AM   #3
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Why would stepping up a starter not be a new generation same as creating a new starter at some time in the future? All that is actually happening is that wort is being fed to the yeast in both cases.
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Old 02-10-2013, 05:10 AM   #4
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Correct me if I'm wrong, but "generations" refer to yeast collected from batches of beer. Original pitch = gen 1, collect and re-use for next batch = gen 2, etc.
But...
If I step up a starter, split it and store it (like I always do), then once it's split and in the fridge, the clock is ticking. As it ages, the viability diminishes.
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Old 02-10-2013, 08:44 AM   #5
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Quote:
Originally Posted by acidrain View Post
Correct me if I'm wrong, but "generations" refer to yeast collected from batches of beer. Original pitch = gen 1, collect and re-use for next batch = gen 2, etc.
That is the confusing bit for me. If the yeast never makes beer but is just stepped up, rinsed and stored, is it still generation 1. And if I step that stored yeast up at a later date, rinse it and split it into two samples then what generation are those samples?
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Old 02-10-2013, 02:06 PM   #6
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I haven't read any of the yeast books that are frequently mentioned on this site, assuming they even cover this subject, so I could be talking out my arse, but I think of it this way: anytime you significantly reduce the size of the colony and then build it back up, that in my mind would be a new generation. That's what happens when you split a starter. However, stepping up a starter is taking the same colony and growing it larger, so it's not a new generation with each step. The time lapse between steps also likely plays a role as well. If viability declines too much between steps due to excessive time lapse, then that could mean the difference between a single generation and two. My guess is there is a bit of grey area here.

Of course, there are certainly biological factors regarding growth phases and such that come into play as well, but that stuff is way over my head, so I just try to keep it simple so that my little brain can make some sense of it all. Perhaps one of the members who knows a lot more about yeast than I profess to know will step in and provide some much needed insight.
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Old 02-10-2013, 08:12 PM   #7
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Thanks Bean.
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Old 02-11-2013, 03:00 AM   #8
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I'd call them all first generation.

A starter is low gravity and not much head pressure. It is relatively easy on the yeast.
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Old 02-11-2013, 07:26 AM   #9
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Quote:
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I'd call them all first generation.

A starter is low gravity and not much head pressure. It is relatively easy on the yeast.
Thanks for your input Calder
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Old 02-11-2013, 12:18 PM   #10
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It's terminology. A new generation is spawned each time a cell buds. This happens 5-10 times in a normal fermentation. A new passage is created when yeast is moved from one media to another. The latter is more similar to what homebrewers refer to as a generation.

However,

What you are probably really interested in is how much the yeast has changed from the original strain. This is effected by conditions under which the yeast is propagated. In a 9P wort at 25C with constant aeration the yeast will change vary little with hundreds of cell divisions. In at 35P barley wine the same number of cell divisions can result in cells very different than the original strain.


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