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Post by Ken on Jul 1, 2022 12:45:53 GMT -6
Okay, one more angle on this: Let's say I harvest some slurry and put it into a sanitized container, cover with foil and throw it into the fridge for a week. 2 weeks. 3 weeks. Now I want to brew and repitch it. Just pitch it and don't add any O2? Are those "dormant" cells in need of O2 to get back up and running again or no?
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Post by tommymorris on Jul 1, 2022 14:43:12 GMT -6
Okay, one more angle on this: Let's say I harvest some slurry and put it into a sanitized container, cover with foil and throw it into the fridge for a week. 2 weeks. 3 weeks. Now I want to brew and repitch it. Just pitch it and don't add any O2? Are those "dormant" cells in need of O2 to get back up and running again or no? I think those dormant cells need oxygen. At a month I would build a 1 liter SNS starter with 2 liberal TBS of slurry and pitch into aerated wort. For younger slurries I pitch directly. PS. I just use a spoon to agitate the surface to aerate. I also always leave the airlock port on my fermenter covered loosely until high krausen. So, that may also provide oxygen.
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Post by Ken on Jul 2, 2022 7:12:33 GMT -6
Okay, one more angle on this: Let's say I harvest some slurry and put it into a sanitized container, cover with foil and throw it into the fridge for a week. 2 weeks. 3 weeks. Now I want to brew and repitch it. Just pitch it and don't add any O2? Are those "dormant" cells in need of O2 to get back up and running again or no? I think those dormant cells need oxygen. At a month I would build a 1 liter SNS starter with 2 liberal TBS of slurry and pitch into aerated wort. For younger slurries I pitch directly. PS. I just use a spoon to agitate the surface to aerate. I also always leave the airlock port on my fermenter covered loosely until high krausen. So, that may also provide oxygen. At some point I asked the LO guys about this and I think my specific question was "how long would you keep slurry and just pitch it into new wort without thinking of any other things that would need to be done with the yeast [like make a starter, etc] and their answer was "three weeks". We didn't touch on the concept of O2 but I think they were heavier into the use of O2 for the purposes of yeast health than other brewers were. I should probably stop citing the LO guys and their ideas because I have been removed from their world for long enough and I remember their ideas about almost all concepts changing frequently. I brewed a beer two weeks ago today and it's still in the fermenter and I won't get to it until later this weekend and probably won't brew again for another 5-6 days so that yeast should really get some O2, IMO. YMMV.
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Post by denny on Jul 2, 2022 12:25:00 GMT -6
Okay, one more angle on this: Let's say I harvest some slurry and put it into a sanitized container, cover with foil and throw it into the fridge for a week. 2 weeks. 3 weeks. Now I want to brew and repitch it. Just pitch it and don't add any O2? Are those "dormant" cells in need of O2 to get back up and running again or no? I just pitch it. Again, think of why you oxygenate. It's for cell growth. If you pitch enough yeast, little to no cell growth is needed.
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Post by denny on Jul 2, 2022 12:27:05 GMT -6
Okay, one more angle on this: Let's say I harvest some slurry and put it into a sanitized container, cover with foil and throw it into the fridge for a week. 2 weeks. 3 weeks. Now I want to brew and repitch it. Just pitch it and don't add any O2? Are those "dormant" cells in need of O2 to get back up and running again or no? I think those dormant cells need oxygen. At a month I would build a 1 liter SNS starter with 2 liberal TBS of slurry and pitch into aerated wort. For younger slurries I pitch directly. PS. I just use a spoon to agitate the surface to aerate. I also always leave the airlock port on my fermenter covered loosely until high krausen. So, that may also provide oxygen. why do dormant cells need oxygen?
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Post by tommymorris on Jul 2, 2022 13:22:39 GMT -6
I think those dormant cells need oxygen. At a month I would build a 1 liter SNS starter with 2 liberal TBS of slurry and pitch into aerated wort. For younger slurries I pitch directly. PS. I just use a spoon to agitate the surface to aerate. I also always leave the airlock port on my fermenter covered loosely until high krausen. So, that may also provide oxygen. why do dormant cells need oxygen? There’s no science here. I don’t know.
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Post by denny on Jul 2, 2022 13:39:57 GMT -6
why do dormant cells need oxygen? There’s no science here. I don’t know. The answer is that they don't.
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Post by brewbama on Jul 3, 2022 8:20:44 GMT -6
There’s no science here. I don’t know. The answer is that they don't. …based on… your opinion? Or * is* there science here? Sent from my iPhone using Tapatalk
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Post by denny on Jul 3, 2022 12:22:21 GMT -6
The answer is that they don't. …based on… your opinion? Or * is* there science here? Sent from my iPhone using Tapatalk The science is that yeast uses O2 to synthesize sterols for budding. It does nothing to wake up dormant cells. Or do you know something I don't? Always happy to learn if you have other info.
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Post by brewbama on Jul 3, 2022 16:34:22 GMT -6
No I don’t have other info but I thought you might.
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Post by denny on Jul 4, 2022 12:57:15 GMT -6
No I don’t have other info but I thought you might. I posted what I know. Since I have never seen anything to support the idea that O2 wakes up dormant cells, I have to assume there is no evidence of that. I guess that's kinda negative info, huh? Again,if anyone knows of any info about this, I'd love to see it.
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Post by Ken on Jul 5, 2022 6:27:37 GMT -6
AFAIK, we don't have a true yeast geek here on The Biergarten. Over on AHA there are a couple, including Saccharomyces. The guy has serious yeast knowledge. Denny, I'm certainly not discounting your yeast knowledge and you have far more than I do. Maybe I go back and check the one thread I started about O2 to see if there is anything about this.
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Post by Ken on Jul 5, 2022 7:45:02 GMT -6
I couldn't find that thread so instead I turned to Google. An interesting tidbit was that someone asked DOES YEAST NEED OXYGEN? and the answer was... So the yeast will ferment and make beer but the question then is "is the yeast making the best beer possible if it's operating under adverse conditions?". From Wyeast... I envision Denny saying that O2 is necessary at the beginning and that's what the SNS starter helps with... after that you don't need more O2. But the first quote above suggests that yeast cells that have been harvested and now stored have insufficient levels of various things it needs and O2 will help with that. This also brings to mind the concept of pitching the correct amount of yeast and trying not to overpitch or pitch a significant number of dead cells. There was talk about pitching "just enough" and even "slightly less" yeast than necessary because then the yeast will reproduce and create enough healthy yeast for the fermentation and that process "creates flavors that beer-drinkers find pleasing". We discussed this numerous times on AHA. I feel like that process is less likely to happen if O2 is not in decent supply during fermentation. And... all of this could be complete nonsense too.
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Post by denny on Jul 5, 2022 13:14:35 GMT -6
AFAIK, we don't have a true yeast geek here on The Biergarten. Over on AHA there are a couple, including Saccharomyces. The guy has serious yeast knowledge. Denny, I'm certainly not discounting your yeast knowledge and you have far more than I do. Maybe I go back and check the one thread I started about O2 to see if there is anything about this. Mark has pretty much withdrawn from the homebrew scene.
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Post by denny on Jul 5, 2022 13:16:13 GMT -6
I couldn't find that thread so instead I turned to Google. An interesting tidbit was that someone asked DOES YEAST NEED OXYGEN? and the answer was... So the yeast will ferment and make beer but the question then is "is the yeast making the best beer possible if it's operating under adverse conditions?". From Wyeast... I envision Denny saying that O2 is necessary at the beginning and that's what the SNS starter helps with... after that you don't need more O2. But the first quote above suggests that yeast cells that have been harvested and now stored have insufficient levels of various things it needs and O2 will help with that. This also brings to mind the concept of pitching the correct amount of yeast and trying not to overpitch or pitch a significant number of dead cells. There was talk about pitching "just enough" and even "slightly less" yeast than necessary because then the yeast will reproduce and create enough healthy yeast for the fermentation and that process "creates flavors that beer-drinkers find pleasing". We discussed this numerous times on AHA. I feel like that process is less likely to happen if O2 is not in decent supply during fermentation. And... all of this could be complete nonsense too. Note that all of those talk about oxygen in regard to cell growth. That's not what we were discussing. Maybe it's just semantics.
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