ROLF really 35 pages and "Why" is still a mystery.
Devoutharpist & Half-Baked - you both need to understand Daltons Law, in a mixture of gasses each gas pretty much acts alone and isn't affected by the other gases (given they don't react chemically), so lots of dissolved CO2 wont reduce the amount of dissolved O2.
One gas can displace another physically, basically a large flow of CO2 will "blow" O2 out of the fermenter with it, Nitrogen (N2) does it better if you are thinking of purging to reduce O2.
Which raises some interesting questions about why you would bung up the fermenter so gas cant escape.
Going back to brewing basics, We only want O2 in the wort for that very brief time while yeast is reproducing, at every other point in the process it does harm. I know how fast O2 picked up in packaging can turn a NEPA into dish water, appears to be a pretty good rule of thumb that the hoppier the beer the more damage it does and the faster.
If I was planning an extremely hoppy beer I would start working on O2 exclusion from malt milling on.
Consider using an air stone and a trickle of CO2 in the mash and kettle.
Avoid aggressive stirring, or pouring liquids so that you pick up O2, consider preparing all your liquor (strike and sparge water) by purging with CO2 for ~10 minutes before using (put your water in some cubes/kegs/jerries...). Have a read up on Low DO brewing!
When it comes to pitching the yeast, my normal practice is to aerate with O2, for a super hoppy beer I would seriously think of skipping aeration, either use dry yeast that doesn't require aeration or build up a liquid starter. In either case think seriously of pitching at higher rates so you don't end up under pitching (pitch at the high end of the recommended ranges for the yeast you choose) without the recommended 10ppm or so of DO the yeast wont reproduce as much.
When you transfer, make sure that the kegs/bottles and all your lines are thoroughly flushed out (more CO2).
World wide Commercial Lager makes up about 90% of the beer sold, so most of the research is done on this type of beer.
One of the main aims of a Lager brewer is to minimise Esters. Most of these are produced during yeast reproduction and in the first 48 Hours of fermentation. Commercial brewers generally allow the fermenter to vent freely (or close to) for the first couple of days (remember that this has been pretty heavily researched). During the early stages of the ferment we want the fermenter to vent easily, this carries out any residual O2 as well as quite a few other undesirable volatiles, after that its pretty common to apply a bit of over pressure, to save money on CO2 as much as anything, the Reinheitsgebot precludes bringing CO2 into the brewery, prevents embarrassing tank damage when cooling...
The CO2 produced in the first 48 Hours isn't regarded as being pure enough to be used for conditioning beer. No one is pressurising early in the ferment.
Bunging the fermenter (usually with a PRV) is done when there are enough fermentables left to condition the beer (plus a touch), usually based on a forced ferment (AKA fast ferment) test. At this end of the ferment ester production isn't really an issue and the undesirable volatiles have already been scrubbed out. Whether you are talking about adding specie, sugar or just bunging the fermenter, this is a continuation of the initial ferment and wont make much in the way of off flavours.
The other big aim of lager brewers is to reduce (eliminate) Diacetyl, Pressure fermentation has been explored to this end, but at pressures in Pa's not kPa's ranges have been applied. This is a fraction of what some homebrewers are talking about.
Measurable rises in acetaldehyde were recorded, there is even an equation that calculates how much Diacetyl you will reduce for a given pressure/temperature and how much Acetaldehyde you will gain. but it appears to be a trade off.
Bunging late to condition beer, I get that, its an old and well tested process.
Personally I cant see the point in pressure fermenting, except as part of conditioning beer.
Some (very small) over pressure to make sure nothing undesirable is getting into your fermenter is good, above that Meh.
Mark
Grok
People can survive without food for two weeks, using your version of logic, one meal a fortnight is all you need.
Brave to ask for an opinion - mine is you have rocks in your head!
M
Devoutharpist & Half-Baked - you both need to understand Daltons Law, in a mixture of gasses each gas pretty much acts alone and isn't affected by the other gases (given they don't react chemically), so lots of dissolved CO2 wont reduce the amount of dissolved O2.
One gas can displace another physically, basically a large flow of CO2 will "blow" O2 out of the fermenter with it, Nitrogen (N2) does it better if you are thinking of purging to reduce O2.
Which raises some interesting questions about why you would bung up the fermenter so gas cant escape.
Going back to brewing basics, We only want O2 in the wort for that very brief time while yeast is reproducing, at every other point in the process it does harm. I know how fast O2 picked up in packaging can turn a NEPA into dish water, appears to be a pretty good rule of thumb that the hoppier the beer the more damage it does and the faster.
If I was planning an extremely hoppy beer I would start working on O2 exclusion from malt milling on.
Consider using an air stone and a trickle of CO2 in the mash and kettle.
Avoid aggressive stirring, or pouring liquids so that you pick up O2, consider preparing all your liquor (strike and sparge water) by purging with CO2 for ~10 minutes before using (put your water in some cubes/kegs/jerries...). Have a read up on Low DO brewing!
When it comes to pitching the yeast, my normal practice is to aerate with O2, for a super hoppy beer I would seriously think of skipping aeration, either use dry yeast that doesn't require aeration or build up a liquid starter. In either case think seriously of pitching at higher rates so you don't end up under pitching (pitch at the high end of the recommended ranges for the yeast you choose) without the recommended 10ppm or so of DO the yeast wont reproduce as much.
When you transfer, make sure that the kegs/bottles and all your lines are thoroughly flushed out (more CO2).
World wide Commercial Lager makes up about 90% of the beer sold, so most of the research is done on this type of beer.
One of the main aims of a Lager brewer is to minimise Esters. Most of these are produced during yeast reproduction and in the first 48 Hours of fermentation. Commercial brewers generally allow the fermenter to vent freely (or close to) for the first couple of days (remember that this has been pretty heavily researched). During the early stages of the ferment we want the fermenter to vent easily, this carries out any residual O2 as well as quite a few other undesirable volatiles, after that its pretty common to apply a bit of over pressure, to save money on CO2 as much as anything, the Reinheitsgebot precludes bringing CO2 into the brewery, prevents embarrassing tank damage when cooling...
The CO2 produced in the first 48 Hours isn't regarded as being pure enough to be used for conditioning beer. No one is pressurising early in the ferment.
Bunging the fermenter (usually with a PRV) is done when there are enough fermentables left to condition the beer (plus a touch), usually based on a forced ferment (AKA fast ferment) test. At this end of the ferment ester production isn't really an issue and the undesirable volatiles have already been scrubbed out. Whether you are talking about adding specie, sugar or just bunging the fermenter, this is a continuation of the initial ferment and wont make much in the way of off flavours.
The other big aim of lager brewers is to reduce (eliminate) Diacetyl, Pressure fermentation has been explored to this end, but at pressures in Pa's not kPa's ranges have been applied. This is a fraction of what some homebrewers are talking about.
Measurable rises in acetaldehyde were recorded, there is even an equation that calculates how much Diacetyl you will reduce for a given pressure/temperature and how much Acetaldehyde you will gain. but it appears to be a trade off.
Bunging late to condition beer, I get that, its an old and well tested process.
Personally I cant see the point in pressure fermenting, except as part of conditioning beer.
Some (very small) over pressure to make sure nothing undesirable is getting into your fermenter is good, above that Meh.
Mark
Grok
People can survive without food for two weeks, using your version of logic, one meal a fortnight is all you need.
Brave to ask for an opinion - mine is you have rocks in your head!
M
