Using air instead of O2...

I want to know more about the legitimacy of this thought...

I have read all over that infusion of pure O2 in cooled, post-boil wort, is the best means of generating a strong fermentation.

I wonder why it isn't just as beneficial to simply use filtered air via pump, filter, and air stone? (I know this works, but some people I've talked to frown upon it.)
I know that it would take longer to aerate wort with this method.

I wonder this because air, obviously, contains (roughly) 21% O2 and 79% N2 (ignoring other trace gases).

But won't the N2 also dissolve into the wort and provide a valuble food source for yeast?

If so, why wouldn't this be more beneficial to use than O2? (Bearing if one has an extra 20-25 minutes to use this method)

Oxygenating wort is to help yeast propagation - the little critters need it to create sterols, which are the lipids they use to create cell membranes (ie MORE yeast ).

As far as I'm aware, it's more the commercial people who like to use O2 - and it's just like you said; 'cause it's faster. There's also the added advantage of knowing the general dissolution rate of the O2 so you can calculate an approximate amount of O2 added, whereas the content in air can vary a bit.

Air, IMO, is actually better, 'cause it's super easy when using pure O2 to actually OVER oxygenate your wort. I know several commercial brewers who use air instead, and several more who don't even bother to 'aerate' (it splashes into the fermenter, and they're happy with that).

Not sure about the N2 dissolution, but if it does go into the wort I think it's in the wrong form for yeast nutrient. It CAN, however, give you a creamier head (think guiness widget). Hope that helps!

Nitrogen compounds are fine nutrients for yeast, but N2 isn't really a useful form, being way too inert. The only common processes that can make it into a nutrient are lightning and other electrical phenomena, or else certain types of nitrogen-fixing bacteria. Hopefully neither of these will be in your wort.

The only reason I can imagine a brewpub not worrying about O2 is that they pitch a massive slurry and don't need to promote yeast reproduction. It would be the same for homebrewing scale to pitch on the cake. However, if you're starting from a fresh pack of yeast like a white labs vial or propagator pack, you really do need to oxygenate the best you can. Why not use a pump? Because it takes about 30 minutes and you still can't acheive optimum dissolved oxygen.

Pure oxygen injection can acheive optimum DO in 60 seconds, it's quick and completely sterile.

But won't the N2 also dissolve into the wort and provide a valuble food source for yeast?

Click to expand...

Very few critters can deal with N2, gaseous or dissolved. Every plant on the planet is dependent on a few types of bacteria and lightening.

Gasses transfer from atmosphere to the wort along any surface area. Stirring creates more surface area and also gets the wort to turn over so more of the volume reaches the surface to take up O2. Sending bubbles also turns the wort volume over, and also adds surface area because each little bubble rising up has a little surface area on it's own. Stands to reason if those little bubbles hold pure O2, then more O2 will get in during the time that bubble takes to make it to the surface and pop. Add a higher concentration of O2 in the headspace of your fermenter during your aeration time and that makes oxygenation that much faster.

That said. I splash and stir and call it good.

Killer_Robot said:

Nitrogen compounds are fine nutrients for yeast, but N2 isn't really a useful form, being way too inert. The only common processes that can make it into a nutrient are lightning and other electrical phenomena, or else certain types of nitrogen-fixing bacteria. Hopefully neither of these will be in your wort.

Click to expand...

yep, on the money with this. Atmospheric nitrogen must first be converted to a usable form of nitrogen otherwise it's not going to react.

I've seen it written or implied that the maximum O2 concentration possible with "air" aeration is around 8ppm, which is pretty good... especially with the right size starter. Injecting pure O2 can get the concentration higher than with plain air.

Also, I believe the dissolved O2 in any wort/beer is either used up by the yeast or off-gassed in like 8-12 hours anyway.

As far as the N2 goes, even if it did combine with other compounds to form yeast nutrients, it's probably negligible compared to the amount of nutrients already in the wort... particularly from an all grain brew.

From here:

MB Raines, Ph.D. - Guide to Yeast Culturing for Homebrewers - Maltose Falcons Home Brewing Society (Los Angeles Homebrewing)

In general, it is difficult for homebrewers to achieve sufficient oxygen levels. The levels of oxygen necessary for optimal fermentation vary depending on the yeast strain. Ale strains usually need between 8-12 part per million (ppm) while lager strains require slightly higher amounts (10-15 ppm). At atmospheric pressure the maximum level of dissolved oxygen in wort is approximately 8 ppm and the saturation level decreases further as the gravity of the wort increases. Thus unless special steps are taken to introduce air or oxygen into the wort, it is difficult for homebrewers to achieve adequate aeration. Recent studies have shown that oxygenation is by far more efficient than aeration. Injection of oxygen through a 2 micron diffusing stone can actually supersaturate the wort with 10-12 ppm of dissolved oxygen being reached in 5 gallons of wort by a single 60 second blast of oxygen!

Click to expand...

Thus unless special steps are taken to introduce air or oxygen into the wort, it is difficult for homebrewers to achieve adequate aeration.

Click to expand...

When they say 'adequate aeration'...isn't that dependant on pitch rate? It seems if you pitch enough yeast that NO aeration would be 'adequate'.

I have a question about pure O2 and contamination. Below are some links to an experiment that was done in which a bunch of people brewed the exact same recipe but used whatever equipment/process they typically use. If you look at the results table it summarizes the results and the brewers that used pure O2 fared extremely poorly wrt infections. The pure O2 injected beers appeared to have a trend but it's a very small sample size. Still...seems enough to be a concern for those considering going the pure O2 route (like me...right now I just splash it around inside the carboy and my ales always finish at or very near the limit of attenuation per my fast-ferment tests).

Any guesses why the pure O2 injected beers fared so poorly regarding infection? Perhaps putting all that O2 in there exacerbates any poor sanitation problems?

The HBD Palexperiment

The HBD Palexperiement Results

Results table

SpanishCastleAle said:

When they say 'adequate aeration'...isn't that dependant on pitch rate? It seems if you pitch enough yeast that NO aeration would be 'adequate'.

Click to expand...

Absolutely. The commercial brewery pitch rate is typically 10x what homebrewers pitch. So, oxygenation is of little concern once they build a large yeast slurry. For homebrewers, who underpitch 99% of the time, oxygenation is extremely important to achieve a proper cell count.

A popular thread title in this forum is "24 hours and no airlock activity", which is usually the result of grossly underpitching, pitching poorly stored yeast, and/or poor oxygenation.

Homebrewers can achieve a commercial pitching rate by reusing the yeast cake from a previous fermentation within a couple of weeks. The rule of thumb is 25% yeast viability loss for every week at room temperature.

SpanishCastleAle said:

I have a question about pure O2 and contamination. Below are some links to an experiment that was done in which a bunch of people brewed the exact same recipe but used whatever equipment/process they typically use. If you look at the results table it summarizes the results and the brewers that used pure O2 fared extremely poorly wrt infections.

Click to expand...

Sorry, you can't draw conclusions from a small study with that many uncontrolled variables. Probably just coincidence....Perhaps they had a sale on oxygen kits that month.

In that one study, there is an obvious positive correlation between O2 use and contamination but it can be attributed to so many other things. Maybe they don't clean their stone well enough. It could have been picked up in any other post boil equipment. I wish they gathered chiller type data too because those with O2 may be more likely to use a plate chiller.

Does Pedio reproduce using oxygen like yeast does?

Some other interesting correlations that I got from playing with the table in excel (maybe they write about them in the article but I haven't read it yet):

15 of the 35 had severe contamination (42%).
Of those, 9 were hit with O2 while 6 used "other" methods. Really, that's only a 60/40 split and a pretty small sample size.

There's a much higher correlation between severe contaminant and use of secondary.
Of the 15 severe, 12 used secondaries and 3 used none. You might say that use of a secondary is the cause of contamination. Bucket vs. glass fermenters doesn't seem to matter.


So, that's severe... how about if we break it into two samples; clean vs ANY contamination.

25 out of 35 were contaminated in some way.
Of those, 10 used O2 and 15 used "other". Only ONE used an air pump.

6 out of 25 contaminated did NOT secondary. 19 used a secondary. Again, that's the higher positive correlation.

Of the 9 completely clean samples, 7 used glass primaries and NONE of them used buckets for both primary and secondary.

Anyway, interesting data but meh... Not many other conclusions can be drawn. You certainly have to discard anything having to do with attenuation as it relates to oxygenation method because the wort is derived from completely different mash profiles and fermented at different temps with different yeast pools.

Does Pedio reproduce using oxygen like yeast does?

Click to expand...

I'm not 100% sure Bobby but I think Lactic acid bacteria (which includes Pedio and Lacto) ferment sugars and create lactic acid...so it doesn't appear that they use oxygen like yeast does during the growth/lag phase (yeast use O2 during the growth phase but not during fermentation; as opposed to acetic acid bacteria that do not ferment but rather respire by oxidizing ethanol to acetic acid). I did notice that most of those infections were Pedio so that does seem to invalidate the hypothesis that the O2 is 'helping' the bacteria too much.

I agree you can't really draw any conclusions from that study...small sample size and too many variables. The most surprising thing to me was the number of infections relative to totally clean brews. I'm guessing that many 'mild' infections go completely unnoticed.

They do note that the bottles were sent during summer so the ones that remained local at room temp or colder probably never develop any off flavors.

The optimum level of dissolved oxygen content depends on the type of beer style that you are brewing, as it is one of the key factors in determing the amount of yeast byproducts produced (along with the other key factors of pitch rate and temperature). I am really surprised that more homebrewers do not own a dissolved oxygen meter. You can get them for about $175 and you are going to pay that much for many other standard pieces of brewing equipment.

The only way to control your dissolved oxygen levels is with oxygen and a DO meter. Aerating the wort can only generate a maximum of 8ppm dissolved oxygen, which is insufficient for certain styles. WIth a DO meter and an oxygenation system (as opposed to an aeration system), you can vary the amount of DO between 4pmm and 26ppm, according to the effect that you are trying to achieve.

I just posted this link on another thread, but here is again, as it perfectly addresses this question: http://www.bjcp.org/cep/WyeastYeastLife.pdf

Ok, so there's already a half bazillion home brewers who aren't convinced that a $50 oxygen reg/stone kit is worth the money and you want people to add another $175 piece of gear? Heck, I have oxygen and wouldn't spend on a DO meter.

Nice work disceting those stats, Bobby.

Bobby_M said:

Ok, so there's already a half bazillion home brewers who aren't convinced that a $50 oxygen reg/stone kit is worth the money and you want people to add another $175 piece of gear? Heck, I have oxygen and wouldn't spend on a DO meter.

Click to expand...

Yeah, that's a good point. There are a lot of brewers who are not really concerned about maximizing every aspect of their process, and so even a $50 investment would be seen as a large one. But what is interesting is that there are plenty of serious all-grain brewers who spend thousands of dollars on their systems, and then don't try to control DO levels. They would easily spend several hundred dollars to set up a very precisely temperature controlled mash with gas solenoid valves, Love TS controllers, etc., in order to maintain mash temps within 1 degree, but then neglect to attempt to control oxygenation levels. But I can understand the desire to keep certain variables in your system static. Some people might want to try to generate the same effects of low or high oxygenation by instead altering pitching rate and temperature. Temperature is easily controlled. However it is easier to precisely measure DO than pitching rate, since yeast cells are not easily counted and the estimates generated from pitching calculators are just estimates.

A DO meter is fairly high on my wish list. Certainly before any brewhouse upgrades.

I agree with the point that you cannot over-oxygenate with air and that’s what I see as a big benefit. Many (large) commercial breweries use air to get O2 into the wort. It’s cheaper than O2 and if the wort is cold enough the saturation level is closer to 12 ppm than 8.

Yes, you cannot draw a connection between pure O2 and contamination from this study. pure O2 is pretty much self sterilizing in the bottle. Any bacteria would simply oxidize to death. I use pure O2 and my beers are free of infections. The reason why I prefer O2 over air is that it makes less foam. But I don’t know how much O2 I actually get into the wort.

Kai

Don't get me wrong. I'd love to have a DO meter and I might be convinced to buy a used one for $50 if it ever came around. Then again, to your point about overspending on everything, I'm a cheap ass with a fully manual brew rig that I welded myself. I would buy a DO meter before a conical.

Edit; after a little reflection, I think a decent solution is to borrow a DO meter and buy a used medical O2 regulator. After a little testing, you can arrive at a typical DO level given a certain gravity, flow rate, and time. My medical reg goes as low as .25 lpm which is what I use for 60 seconds. If I know that it always gets me to like 12 ppm, I'd call it a day and give the DO meter back. I've stopped myself from building a inline oxygenator due to the fact that even though my o2 flow rate is fixed, my chiller flow isn't.

The only common processes that can make it into a nutrient are lightning and other electrical phenomena, or else certain types of nitrogen-fixing bacteria. Hopefully neither of these will be in your wort.

next time i brew, i'm going 'Ben Franklin' on my fermenter!!

I think we're missing something here.

Why don't you just spend $175 on a good erlenmayer, bung and airlock, stir magnet, and stir plate? Who cares if theres 8 ppm O2 when you've got 5x - 10x the active yeasties as a smack pack/dry packet?

menschmaschine said:

I've seen it written or implied that the maximum O2 concentration possible with "air" aeration is around 8ppm, which is pretty good... especially with the right size starter. Injecting pure O2 can get the concentration higher than with plain air.

Click to expand...

From the bit I know about dissolved gasses in solution, this doesn't make much sense to me.

A solution exposed to the atmosphere can only hold a certain amount of O2. It's all about partial pressures.

O2 is about 20% of typical air/atmosphere. Expose a solution to that atmosphere, and 20% of the pressure on top of that solution is O2, so 1 atmosphere of pressure on top of a solution is really 0.2 atmospheres of O2 "pressing down" on the top of the solution. Gasses in solution also exhibit a pressure, pushing back against the 1 atmosphere of pressure on top of that solution.

Expose a solution that is devoid of O2 to the atmosphere, and the atmospheric pressure on top of the solution will force O2 into that solution until equilibrium is reached, i.e. there is as much O2 off-gassing from the solution as there is being forced in by atmospheric pressure. Likewise, take a solution that has had O2 forced into it under pressure until it is super-saturated with O2 and expose the super-saturated solution to the atmosphere. O2 will off-gas from the solution until, once again, equilibrium is reached.

This is precisely how we can force-carbonate beer in our kegerrators. In a sealed keg, we create an environment of pure CO2 above the beer at around 12 PSI or so. After about a week, the solution is in equilibrium, i.e. there is as much CO2 off-gassing from the beer as there being forced into the beer. Increase the CO2 pressure above the beer and the amount of CO2 in the beer rises. Decrease the pressure of CO2 above the beer and you get less CO2 in the beer.

Now, take our boiled wort. At atmospheric pressure that wort can only hold a certain amount of O2, that being the amount that puts the solution into equilibrium. (Remember, equilibrium is where there is just as much O2 off-gassing from the solution as is being forced in by the atmospheric pressure above that solution.) Indeed, we could get to that equilibrium state simply by exposing the wort to the atmosphere for a long enough period of time, however the stuff would be rotten by then.

So, it's incorrect to state that an air pump cannot achieve the same amount of dissolved O2 in the wort as can an oxygen tank. The oxygen tank will get you there quicker, that's all.

Edit: I'm referring to aqueous solutions in the above example. Same probably wouldn't hold true for solvent-based stuff like paint thinner, etc.

Bobby_M said:

I'd love to have a DO meter and I might be convinced to buy a used one for $50 if it ever came around.

Click to expand...

MILWAUKEE USED DISSOLVED OXYGEN METER @ Williams Brewing

hehehehehe

drayman,
I think that you can get more O2 in solution using a pure O2 but it's just temporary...you're right that all that 'extra' O2 in solution will eventually off-gas. But just like our beer doesn't 'instantly' off-gas such that it's totally flat...the extra O2 in solution doesn't instantly off-gas either. And by that time the yeast will have hopefully consumed a lot of it.