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Old 12-02-2011, 06:14 AM   #1
boss429
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Default why does fermentng under pressure or under hydrostatic pressure does yeast produce..

less ethers and phenols?

Any Biochem or Organic chemist with an education want to clear this up?

if you are not educated please give me sources does not necessarily have to be online it can be text I can buy etc..

another question relevant

Why can stone brewing company ferment their pale ale in 3-4 days CLEANLY?

If youd like (if you can) explain to us homebrewers the difference between ethanol, esters, and phenols...in a nutshell without any gobedygook..

I know what I'm asking for is extremely hard to explain as I have searched the net but it would be greatly appreciated.

Thanks,

Boss 429 a car from 1970

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Old 12-02-2011, 12:40 PM   #2
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According to Briggs (Brewing: Science and Practice, p. 482), increased hydrostatic pressure slows yeast growth, thus suppressing the production of phenols and esters.

When you're asking for the difference between ethanol, esters, and phenols, what are you hoping to learn? Ethanol is your primary alcohol, and both esters and phenols are metabolic byproducts/intermediates that contribute distinct flavors to beer. Esters tend to be fruity and phenols tend to be spicy or astringent.

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Old 12-03-2011, 12:54 AM   #3
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Thanks I also found this..what do you guys think?

More significantly, good mixing increases the suspended yeast count and
this results in high fermentation rates and enhanced yeast growth. Increases in biomass
yields are associated with greater utilisation of wort nitrogen, elevated levels of higher alcohols and reduced pH. In addition, a greater proportion of the intracellular
pool of cytosolic acetyl-CoA is used to fuel growth at the expense of ester formation.


pg 273 Chris Boultan, Brewing Yeast and fermentation.

I'm not the one to interpret this so let me know if you guys got any more information.

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Old 12-03-2011, 03:16 AM   #4
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This is a pretty cool link: Esters In Home Brewed Beer

In very simple terms, esters are just the combination of an alcohol and an acetate. The linkage to the higher pressure vessels and esters is that the higher the pressure, the higher the concentration of oxygen in solution. From the link above, one cellular job of oxygen is during the synthesis of fatty acids. Acetyl CoA is a building block of fatty acids, so if fatty acid synthesis is running full speed, there's no Acetyl CoA for ester formation.

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Old 12-03-2011, 05:24 AM   #5
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so if i may sum it up

Pressure goes up...O2 Solubility goes up...Synthesis of Fatty acids goes up...esters can no longer form without fatty acids...

I don't have time to study the science but I think your answers pretty clear

Thanks

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