[hackrsackr]

To clarify I think the pressure in the krausening or second ferment drives 4vg.

The isoA I believe is influenced by the access to oxygen through the growth phase. ie open ferm.


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I don’t notice any extra clove and I spund to 4vol. 


I don’t follow the second.  The head space of the fermenter is full of oxygen for at least a day after pitching due to the nature of gas mixing laws. Also if you oxygenate with pure o2 it’s in the liquid as well.  Active yeast will consume all o2 injected within 2 hours of pitching (verified with a DO meter).  The water column pressure on an airlock is pretty much null as well.  So not sure on that. 


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I speise to a little less than 4 vols and usually don’t notice the 4vg until after second ferment. Just an anecdotal observation and I’m using 380.


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[Robert]

To clarify I think the pressure in the krausening or second ferment drives 4vg.

The isoA I believe is influenced by the access to oxygen through the growth phase. ie open ferm.


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IsoA and 4VG are both fermentation byproducts of specific yeasts, and yeasts with a propensity to produce them can be influenced to do so in various ways.  With respect to isoA  temperature and oxygenation can drive it to a limit set by the available glucose; to surpass that limit more glucose is needed: enter the downward mash program.  The same can be said of 4VG; temperature and oxygenation can influence production but the limiting substrate is ferulic acid, produced at 114°F.

Not arguing any of that. Just saying that the 114 rest in a standard mash does not make glucose. That’s all.


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Right.  The downward mash is just the only way to increase glucose.

Yeast create biomass with the access to oxygen, aerobic fermentation. Anaerobic fermentation produces alcohol and co2.


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Remember,  it's a fuzzy gradation, not a bright line, separating the stages of yeast metabolism.  At any stage you can change conditions and influence some aspect, to some degree.  Biology's messy.

[Big Monk]

Yeast create biomass with the access to oxygen, aerobic fermentation. Anaerobic fermentation produces alcohol and co2.


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Most literature shows ester formation having an inverse relationship to yeast growth. It’s why overpitching and undercutting Oxygen is an effective way of limiting higher alcohol production and promoting ester formation using Trappist yeast.

Maybe that only works with my beloved 1214, 3787, and 1762 though. YMMV.

[hackrsackr]

To clarify I think the pressure in the krausening or second ferment drives 4vg.

The isoA I believe is influenced by the access to oxygen through the growth phase. ie open ferm.


Sent from my iPhone using Tapatalk

IsoA and 4VG are both fermentation byproducts of specific yeasts, and yeasts with a propensity to produce them can be influenced to do so in various ways.  With respect to isoA  temperature and oxygenation can drive it to a limit set by the available glucose; to surpass that limit more glucose is needed: enter the downward mash program.  The same can be said of 4VG; temperature and oxygenation can influence production but the limiting substrate is ferulic acid, produced at 114°F.

Not arguing any of that. Just saying that the 114 rest in a standard mash does not make glucose. That’s all.


Sent from my iPhone using Tapatalk

Right.  The downward mash is just the only way to increase glucose.

Yeast create biomass with the access to oxygen, aerobic fermentation. Anaerobic fermentation produces alcohol and co2.


Sent from my iPhone using Tapatalk

Remember,  it's a fuzzy gradation, not a bright line, separating the stages of yeast metabolism.  At any stage you can change conditions and influence some aspect, to some degree.  Biology's messy.

Right! I’m just saying that I’m (me just me) a firm believer in the tradition of open fermentation. I believe that is one way to affect the fuzzy gradation. Make sense?


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[Robert]

^^^^
Yep!  BTW:

I have just noticed that this thread may have set a 2018 record for most consecutive on topic, non acrimonious posts.  Yay us.

[The Beerery]

To clarify I think the pressure in the krausening or second ferment drives 4vg.

The isoA I believe is influenced by the access to oxygen through the growth phase. ie open ferm.


Sent from my iPhone using Tapatalk

IsoA and 4VG are both fermentation byproducts of specific yeasts, and yeasts with a propensity to produce them can be influenced to do so in various ways.  With respect to isoA  temperature and oxygenation can drive it to a limit set by the available glucose; to surpass that limit more glucose is needed: enter the downward mash program.  The same can be said of 4VG; temperature and oxygenation can influence production but the limiting substrate is ferulic acid, produced at 114°F.

Not arguing any of that. Just saying that the 114 rest in a standard mash does not make glucose. That’s all.


Sent from my iPhone using Tapatalk

Right.  The downward mash is just the only way to increase glucose.

Yeast create biomass with the access to oxygen, aerobic fermentation. Anaerobic fermentation produces alcohol and co2.


Sent from my iPhone using Tapatalk

Remember,  it's a fuzzy gradation, not a bright line, separating the stages of yeast metabolism.  At any stage you can change conditions and influence some aspect, to some degree.  Biology's messy.

Right! I’m just saying that I’m (me just me) a firm believer in the tradition of open fermentation. I believe that is one way to affect the fuzzy gradation. Make sense?


Sent from my iPhone using Tapatalk

Curious for your response to my open fermentation remarks.


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[hackrsackr]

Yeast create biomass with the access to oxygen, aerobic fermentation. Anaerobic fermentation produces alcohol and co2.


Sent from my iPhone using Tapatalk

Most literature shows ester formation having an inverse relationship to yeast growth. It’s why overpitching and undercutting Oxygen is an effective way of limiting higher alcohol production and promoting ester formation using Trappist yeast.

Maybe that only works with my beloved 1214, 3787, and 1762 though. YMMV.

Id be interested in seeing that literature. Everything I’ve read plus personal experience points to a direct relationship between yeast growth and esters.


Sent from my iPhone using Tapatalk

[hackrsackr]

To clarify I think the pressure in the krausening or second ferment drives 4vg.

The isoA I believe is influenced by the access to oxygen through the growth phase. ie open ferm.


Sent from my iPhone using Tapatalk

IsoA and 4VG are both fermentation byproducts of specific yeasts, and yeasts with a propensity to produce them can be influenced to do so in various ways.  With respect to isoA  temperature and oxygenation can drive it to a limit set by the available glucose; to surpass that limit more glucose is needed: enter the downward mash program.  The same can be said of 4VG; temperature and oxygenation can influence production but the limiting substrate is ferulic acid, produced at 114°F.

Not arguing any of that. Just saying that the 114 rest in a standard mash does not make glucose. That’s all.


Sent from my iPhone using Tapatalk

Right.  The downward mash is just the only way to increase glucose.

Yeast create biomass with the access to oxygen, aerobic fermentation. Anaerobic fermentation produces alcohol and co2.


Sent from my iPhone using Tapatalk

Remember,  it's a fuzzy gradation, not a bright line, separating the stages of yeast metabolism.  At any stage you can change conditions and influence some aspect, to some degree.  Biology's messy.

Right! I’m just saying that I’m (me just me) a firm believer in the tradition of open fermentation. I believe that is one way to affect the fuzzy gradation. Make sense?


Sent from my iPhone using Tapatalk

Curious for your response to my open fermentation remarks.


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Sorry, which part exactly?


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[The Beerery]

To clarify I think the pressure in the krausening or second ferment drives 4vg.

The isoA I believe is influenced by the access to oxygen through the growth phase. ie open ferm.


Sent from my iPhone using Tapatalk

IsoA and 4VG are both fermentation byproducts of specific yeasts, and yeasts with a propensity to produce them can be influenced to do so in various ways.  With respect to isoA  temperature and oxygenation can drive it to a limit set by the available glucose; to surpass that limit more glucose is needed: enter the downward mash program.  The same can be said of 4VG; temperature and oxygenation can influence production but the limiting substrate is ferulic acid, produced at 114°F.

Not arguing any of that. Just saying that the 114 rest in a standard mash does not make glucose. That’s all.


Sent from my iPhone using Tapatalk

Right.  The downward mash is just the only way to increase glucose.

Yeast create biomass with the access to oxygen, aerobic fermentation. Anaerobic fermentation produces alcohol and co2.


Sent from my iPhone using Tapatalk

Remember,  it's a fuzzy gradation, not a bright line, separating the stages of yeast metabolism.  At any stage you can change conditions and influence some aspect, to some degree.  Biology's messy.

Right! I’m just saying that I’m (me just me) a firm believer in the tradition of open fermentation. I believe that is one way to affect the fuzzy gradation. Make sense?


Sent from my iPhone using Tapatalk

Curious for your response to my open fermentation remarks.


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Sorry, which part exactly?


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No problem.  It’s probably buried. 


“I don’t follow the second.  The head space of the fermenter is full of oxygen for at least a day after pitching due to the nature of gas mixing laws. Also if you oxygenate with pure o2 it’s in the liquid as well.  Active yeast will consume all o2 injected within 2 hours of pitching (verified with a DO meter).  The water column pressure on an airlock is pretty much null as well.  So not sure on that.”


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[hackrsackr]

Oh yeah. Well your DO stuff is right on point but I’m talking about the affect of atmospheric oxygen mixing with head the space. With an airlock it’s used up real quick, with open ferm the access to atmospheric oxygen IMO prolongs the growth phase a bit, produces a higher krausen as  it seems to reach for the O2. Open ferm let’s scrape the bitter hop purge brown stuff (day 2). Transfer to speise on day three, open the whole time. That’s how I do it.


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[hackrsackr]

It’s like the yeast don’t want to switch metabolic pathways until all oxygen is completely gone.


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[Robert]

FWIW significant isoA production is not limited to Weizen or Belgian yeasts; Saaz-type lager yeasts can produce it as well.  The pale lagers from the (namesake) Žateč brewery have a distinct banana note.  They still use open primaries.

[Big Monk]

Yeast create biomass with the access to oxygen, aerobic fermentation. Anaerobic fermentation produces alcohol and co2.


Sent from my iPhone using Tapatalk

Most literature shows ester formation having an inverse relationship to yeast growth. It’s why overpitching and undercutting Oxygen is an effective way of limiting higher alcohol production and promoting ester formation using Trappist yeast.

Maybe that only works with my beloved 1214, 3787, and 1762 though. YMMV.

Id be interested in seeing that literature. Everything I’ve read plus personal experience points to a direct relationship between yeast growth and esters.


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A few good ones from my stash:

https://drive.google.com/open?id=1gk0uCJdog0f3WxqMDvxfHt-j1W-NYSI7

https://drive.google.com/open?id=10kXMy5fNjvPVhPyQfN18oSUZswlIiYG-

https://drive.google.com/open?id=1pmujev58LUkO1rDbPHEAFp1u6ObvCzGC

[hackrsackr]

Oh I know all about it. Unfortunately. Warmer growth phase will make em throw isoA too.


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[Big Monk]

Oh I know all about it. Unfortunately. Warmer growth phase will make em throw isoA too.


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Just some constructive criticism: it makes it easier to read if you quote the person you are responding to.