Homebrewers Association | AHA Forum

General Category => Yeast and Fermentation => Topic started by: marcopolo on January 21, 2010, 04:53:01 PM

Title: PURE O2 vs. NATURAL AIR AERATION
Post by: marcopolo on January 21, 2010, 04:53:01 PM
Does using pure O2 offer any significant advantages over aerating with plain air ?  The only advantage I can see is that pure O2 only takes seconds to oxygenate the wort whereas natural air takes minutes.  Is that the only difference ?
Thanks,
Marco
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: denny on January 21, 2010, 04:57:36 PM
I haven't done a side by side, but I can tell you that aerating with my MixStir I get results as good as friends who use O2.  If I didn't get that kind of result, I'd look at switching.  It only takes a couple minutes with the Mixstir.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: tubercle on January 21, 2010, 05:11:33 PM
My tiny mind tells me O2 is just that regardless of the source.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 21, 2010, 05:14:16 PM
The only problem with natural air is that you can’t get past 8-10 ppm. But this is what is recommended anyway. Even large lager breweries aerate with sterile air and must be getting to the recommended 12 ppm. I think this is because the wort is quite cold when they aerate.

I recently added a DO meter to my testing equipment and have started playing around with various aeration techniques. Here is data from a MixStir aeration:

Wort temp: 11 C
Gravity 11.5 Plato

Unaerated wort: 1.5 ppm DO (there is a lot of error in low DO readings, so don’t put too much into this.

30s MixStir, 2 min settling time: 5.2 ppm
another 30s MixStir, 2 min settling: 7 ppm
another 30s MixStir, 2 min settling: 7.6 ppm
additional 60s MixStir, 2 min settling: 8.0 ppm

Another batch with pure O2:

Wort temp 10C
Gravity 11.5 Plato

Unaerated: 1.6 ppm
1 min pure O2 -> 20 + ppm

In this case I maxed out the DO meter range. Based on earlier experiences with aerating starters with pure O2 I thought it would take much longer than 1 min to max out the DO meter. I’ll be oxygenating shorter next time around.

The advantage of air is that you cannot overaerate the wort. But I don’t necessarily like all that foam when using the MixStir. It makes it hard for me to see when low Kraeusen starts.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: babalu87 on January 21, 2010, 05:16:32 PM
That tube with the holes in it on the end of my kettle to fermenter hose aerates the hell out of the wort.

Foam out the top everytime
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Matt B on January 21, 2010, 05:16:55 PM
There's no real advantage. It's faster, since you have to pump less 'air' into it, and possibly more sanitary as not a whole lot can live in a pure O2 environment, but with the right precautions (sanitary filter) with a good fish tank pump is almost just as effective. For me it was more convenient, I have an O2 tank, didn't have to buy a pump, done.

Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 21, 2010, 05:21:55 PM
... and possibly more sanitary as not a whole lot can live in a pure O2 environment...

I’m trying to look at this as well. The idea is to take a wort sample before and after the aeration process and perform a wort stability test on it.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: bluesman on January 21, 2010, 05:35:35 PM
Kai,

Based on your crude experiment you are getting almost three times as much dissolved O2 in your wort using pure O2 vs mix-stir. My question to you is did you determine any flavor contribution by increased DO in the beer. Did you do a side by side tasting? By the way...nice work as usual.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: denny on January 21, 2010, 05:43:10 PM
I seem to recall reading somewhere that 8 ppm is optimal.  Can anybody confirm or correct that?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 21, 2010, 05:47:06 PM
Based on your crude experiment you are getting almost three times as much dissolved O2 in your wort using pure O2 vs mix-stir. My question to you is did you determine any flavor contribution by increased DO in the beer. Did you do a side by side tasting? By the way...nice work as usual.

I only know that I got more than 20 ppm O2 into the wort. It may have been much more since the meter quickly jumped to “overflow”. The way these meters work is by having O2 diffuse through a membrane into an electrolyte. The meter than measures the O2 content in the electrolyte. The time it takes for the O2 concentration in the electrolyte to rise or fall depends on the O2 gradient between the electrolyte and wort. Since it jumped to 20+ pretty quickly I assume that the wort may have been aerated with well over 20 ppm.

Obviously that was not my intention. The two beers are intended to evaluate the benefit of removing the Kraeusen. I wanted to aerate both to ~8 ppm DO but way overshot my target on the 2nd one. One suspicion I have with the pure O2 method is that it is difficult to set a flow rate that is constant between all the beers you brew. You may be able to set a constant pressure by making the regulator but that means nothing if your stone gets more and more clogged over time. I’ll get a better idea about that in future batches.

If you a medical O2 bottle and regulator you can set a flow rate but I don’t think that flow rate will be accurate once you force the O2 though an aeration stone since that will restrict the flow by an unknown amount.

I’ll see if I can taste anything that I could attribute to the excess O2.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 21, 2010, 05:49:10 PM
I seem to recall reading somewhere that 8 ppm is optimal.  Can anybody confirm or correct that?

8 - 10 is considered optimal for ales and 10-12 is optimal for lagers. I think these numbers are in line with the air saturation DO values at their respective pitching temperatures.

Once you go to high gravity beers you want more than that. But I don't know how much more.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: bluesman on January 21, 2010, 05:49:43 PM
I seem to recall reading somewhere that 8 ppm is optimal.  Can anybody confirm or correct that?

Good Question Denny.

Here's a study on the effect of DO on wort fermentation and yeasy health. Unfortunately, one must pay to get it.

http://cat.inist.fr/?aModele=afficheN&cpsidt=1355176
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 21, 2010, 05:54:04 PM
Here's a study on the effect of DO on wort fermentation and yeasy health. Unfortunately, one must pay to get it.
http://cat.inist.fr/?aModele=afficheN&cpsidt=1355176

This is a really good one. It's from the MBAA and you'll have to find someone who is a MBAA member. There aren't many papers that are readily apllicable to home brewing, but this one looks like one that would be.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: beerocd on January 21, 2010, 06:00:37 PM
http://www.wyeastlab.com/hb_oxygenation.cfm/1949-aerating-wort-techniques (http://www.wyeastlab.com/hb_oxygenation.cfm/1949-aerating-wort-techniques)

There's a table of DO towards the bottom.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: babalu87 on January 21, 2010, 06:13:05 PM
Quote
On the Wyeast table:
Sierra Nevada uses just air (filtered of course) but then again do they make any lagers...............?

Top of my head I cant remember.

I recently brewed a Pils and using just the tube with holes at angles on the end of my hose, had it just hanging in the carboy neck.

5.25 gallons of wort went into this carboy and wort foam came out the carboy neck during the last 1/2 gallon or so.
I'd say thats pretty well aerated. We'll see in about 6 weeks I guess.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: denny on January 21, 2010, 06:30:55 PM
So the Wyeast info says that 10ish ppm is good.  And yes, SN does make a lager....Glissade.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: tygo on January 21, 2010, 06:39:03 PM


I’ll see if I can taste anything that I could attribute to the excess O2.

Kai

I definitely be interested to hear the results of that taste test.  Up until the last batch I've just been shaking the hell out of the carboy for maybe a minute.  I'm guessing that method gets you less than 8 ppm.

For the last batch I aerated with pure O2 and based on this discussion I'm sure I over-aerated.  It'll be interesting to see what the effects on the beer will be.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: denny on January 21, 2010, 06:46:46 PM
According to Wyeast (sorry for the poor formatting)

Method     DO ppm     Time
Siphon Spray    4 ppm    0 sec.
Splashing & Shaking    8 ppm    40 sec.
Aquarium Pump w/ stone    8 ppm    5 min
Pure Oxygen w/ stone    0-26ppm    60 sec (12ppm)

It was concluded that pumping compressed air through a stone is not an efficient way to provide adequate levels of DO. Traditional splashing and shaking, although laborious, is fairly efficient at dissolving up to 8 ppm oxygen. To increase levels of oxygen, the carboy headspace can be purged with pure oxygen prior to shaking. The easiest and most effective method remains injecting pure oxygen through a scintered stone.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 21, 2010, 06:49:41 PM
Here is a page from a German brewing text that I still aspire to own: Technologie der Wuerzebereitung: http://books.google.de/books?id=rlcwl7aS8KYC&lpg=PA791&ots=HfVnzIkiIn&dq=w%C3%BCrzebel%C3%BCftung%20venturi&pg=PA661#v=onepage&q=w%C3%BCrzebel%C3%BCftung%20venturi&f=false

Tab 8.1 shows how much O2 (mg/l = ppm) can be dissolved in water and wort based on its temperature if air is used.

Kai

Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: a10t2 on January 21, 2010, 06:55:44 PM
It was concluded that pumping compressed air through a stone is not an efficient way to provide adequate levels of DO.

I'm not sure their data really support that. Of course, they're making the assumption that 10 ppm is "adequate" and anything less than 10 ppm is therefore "inadequate". I can't argue for or against that particular target, but brewing isn't a binary process.

I've also always wondered how fast O2 will diffuse out of the wort, relative to how fast the yeast can become active and start utilizing it. I guess filling the headspace with O2 would be the best way to ensure that didn't happen.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: babalu87 on January 21, 2010, 06:58:50 PM
Here is a page from a German brewing text that I still aspire to own: Technologie der Wuerzebereitung: http://books.google.de/books?id=rlcwl7aS8KYC&lpg=PA791&ots=HfVnzIkiIn&dq=w%C3%BCrzebel%C3%BCftung%20venturi&pg=PA661#v=onepage&q=w%C3%BCrzebel%C3%BCftung%20venturi&f=false

Tab 8.1 shows how much O2 (mg/l = ppm) can be dissolved in water and wort based on its temperature if air is used.

Kai



Maybe WYeast didnt perform their tests at a cold enough temperature then?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: tygo on January 21, 2010, 07:32:47 PM

Traditional splashing and shaking, although laborious, is fairly efficient at dissolving up to 8 ppm oxygen. To increase levels of oxygen, the carboy headspace can be purged with pure oxygen prior to shaking. The easiest and most effective method remains injecting pure oxygen through a scintered stone.

Thanks Denny.  That's good to know.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: ndcube on January 21, 2010, 10:36:49 PM
I made a Tripel with pure O2 and it wasn't as estery as I expected.  I'mswitching back to whipping the wort for those styles.

Kai,
A good experiment would be to see how quickly and completely O2 is driven off by fermentation if one over oxygenates their wort.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 21, 2010, 11:28:18 PM
A good experiment would be to see how quickly and completely O2 is driven off by fermentation if one over oxygenates their wort.

I don't think any of the O2 will be driven off. The yeast consumes it well before there is enough CO2 production that would purge the O2.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: ndcube on January 21, 2010, 11:49:00 PM
A good experiment would be to see how quickly and completely O2 is driven off by fermentation if one over oxygenates their wort.

I don't think any of the O2 will be driven off. The yeast consumes it well before there is enough CO2 production that would purge the O2.

Kai

So there can never be too much O2 present that the yeast won't use it all?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 21, 2010, 11:52:38 PM
The concern with too much O2 is not beer oxidation but adverse effects on the yeast including excessive growth.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: ndcube on January 22, 2010, 12:00:08 AM
The concern with too much O2 is not beer oxidation but adverse effects on the yeast including excessive growth.

Kai

So the yeast will always grow until all available O2 is consumed regardless of gravity?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: tom on January 22, 2010, 12:40:35 AM
I used to oxygenate throughout my chilling, maybe 5-10 minutes and I got some very oxidized beers. I know everyone will say that the oxygen will dissipate, etc., but I transfer into cornies filled with CO2 (sanitizer filled to the top and then pushed out with CO2). I don't think the oxidation could come from anywhere else.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 22, 2010, 12:41:12 AM
They keep growing until one of the essential nutrients for growth is gone. Those nutrients are:

- carbon source: sugar or ethanol. The
latter only aerobically
- nitrogen source: generally amino acids but ammonium works too
- sterols: O2 is needed for their synthesis and they are accumulated during the phase when O2 is available. Later the pool is split between mother and daughter

nitrogen and O2 (sterols) tend to be the growth limiting factor in brewing.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: marcopolo on January 22, 2010, 12:49:38 AM
THANKS TO ALL FOR RESPONDING TO MY QUESTION.  Obviously this topic is subject to further research & review !  I especially appreciate your insight, Denny.  You made me a fan of batch sparging, and now the MIxStir...
Cheers !!!
Marco
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 22, 2010, 01:23:33 AM
I used to oxygenate throughout my chilling, maybe 5-10 minutes and I got some very oxidized beers. I know everyone will say that the oxygen will dissipate, etc., but I transfer into cornies filled with CO2 (sanitizer filled to the top and then pushed out with CO2). I don't think the oxidation could come from anywhere else.

In the industry there is a concern about cold side aeration as well. The concern is that the time between wort oxygenation and when the yeast finally consumed the oxygen can be long enough to promote shorter beer shelf life. As a result there have been efforts to eliminate that initial oxygenation. New Belgium's olive oil experiment was such an effort. Other efforts include oxygenation of the yeast before it is pitched into the wort.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: mikeypedersen on January 22, 2010, 02:04:47 AM
New Belgium's olive oil experiment was such an effort. Other efforts include oxygenation of the yeast before it is pitched into the wort.

Kai

I don't mean to hijack the thread here, but have any homebrewers experimented with the whole Olive Oil for yeast thing.  I think I remember reading that as a home brewer you would only need as much as to dip a needle in olive oil and touch it to your wort......Just on memory.  Has anyone actually tried it before?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: ndcube on January 22, 2010, 10:59:15 AM
I used to oxygenate throughout my chilling, maybe 5-10 minutes and I got some very oxidized beers. I know everyone will say that the oxygen will dissipate, etc., but I transfer into cornies filled with CO2 (sanitizer filled to the top and then pushed out with CO2). I don't think the oxidation could come from anywhere else.

In the industry there is a concern about cold side aeration as well. The concern is that the time between wort oxygenation and when the yeast finally consumed the oxygen can be long enough to promote shorter beer shelf life. As a result there have been efforts to eliminate that initial oxygenation. New Belgium's olive oil experiment was such an effort. Other efforts include oxygenation of the yeast before it is pitched into the wort.

Kai

Also, If Tom is introducing O2 during chilling aren't the effects of oxydation accelerated when the wort is hot?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: hopfenundmalz on January 22, 2010, 12:09:49 PM
And yes, SN does make a lager....Glissade.

Don't forget the Summerfest.  They now make 2 lagers.

Somewhere I recently read that some yeasts are fine with filtered air, while others do better with O2.  It is not known why.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: majorvices on January 22, 2010, 01:20:24 PM
According to Wyeast (sorry for the poor formatting)

Method     DO ppm     Time
Siphon Spray    4 ppm    0 sec.
Splashing & Shaking    8 ppm    40 sec.
Aquarium Pump w/ stone    8 ppm    5 min
Pure Oxygen w/ stone    0-26ppm    60 sec (12ppm)

It was concluded that pumping compressed air through a stone is not an efficient way to provide adequate levels of DO. Traditional splashing and shaking, although laborious, is fairly efficient at dissolving up to 8 ppm oxygen. To increase levels of oxygen, the carboy headspace can be purged with pure oxygen prior to shaking. The easiest and most effective method remains injecting pure oxygen through a scintered stone.

I have seen this before about shaking for only 40 seconds and, frankly, I just never really believed it. I always wondered if the "40 sec" was a typo and should have said "40 minutes."

I aerate with pure o2 and I am pretty sure that I have over aerated in a yeast starter to toxic levels before (I have no proof, but the yeast should have been healthy and had a loooooong lag. Like over 4 days). But, in my carboys I have aerated with pure o2 from 1-3 minutes per 5 gallons and have never had a problem. A DO meter is a handy tool to have in our hobby - and an expensive one. Kai, do you mind if I ask how much you spent?

Does anyone know what ppm level o2 becomes toxic to the yeast? It seems like I read it before but I cannot remember. Also, I thought that wort could hold only a ppm level that was under the toxicity level? I know that colder wort can absorb more o2 than warmer wort, but can the colder wort absorb enough to toxicity levels?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: bluesman on January 22, 2010, 01:54:40 PM
According to Wyeast (sorry for the poor formatting)

Method     DO ppm     Time
Siphon Spray    4 ppm    0 sec.
Splashing & Shaking    8 ppm    40 sec.
Aquarium Pump w/ stone    8 ppm    5 min
Pure Oxygen w/ stone    0-26ppm    60 sec (12ppm)

It was concluded that pumping compressed air through a stone is not an efficient way to provide adequate levels of DO. Traditional splashing and shaking, although laborious, is fairly efficient at dissolving up to 8 ppm oxygen. To increase levels of oxygen, the carboy headspace can be purged with pure oxygen prior to shaking. The easiest and most effective method remains injecting pure oxygen through a scintered stone.

Does anyone know what ppm level o2 becomes toxic to the yeast? It seems like I read it before but I cannot remember. Also, I thought that wort could hold only a ppm level that was under the toxicity level? I know that colder wort can absorb more o2 than warmer wort, but can the colder wort absorb enough to toxicity levels?

There's a study that I mentioned several posts back, but again you'd have to pay for it. I bet if you called or e-mailed Wyeast or White Labs they would offer that information and advice on this issue.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: beerocd on January 22, 2010, 02:08:41 PM
Aquarium pump VS splashing and shaking

Yep it's slower, but we won't get the "glass carboy almost killed me" threads.
I usually have the wort freefall about 3ft into a bucket after chilling.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: babalu87 on January 22, 2010, 02:17:58 PM
Aquarium pump VS splashing and shaking

Yep it's slower, but we won't get the "glass carboy almost killed me" threads.
I usually have the wort freefall about 3ft into a bucket after chilling.

With the cold here recently I have been chilling to pitching temps with the recirc chiller and using the drilled tube on the end of my hose.
Foam out the top of the fermenters tells me thats enough.

I'd be interested to see what temperature Wyeast used for the table being referenced.

Possibly various aeration techniques work more efficiently depending on the given temperature?
Would pure 02 not work the same regardless of the wort temperature (provided its not boiling or VERY warm)?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: ndcube on January 22, 2010, 02:33:48 PM
Would pure 02 not work the same regardless of the wort temperature (provided its not boiling or VERY warm)?

So the you can get more O2 in cooler wort using "air" is because the air is denser containing more molecules in a given space, correct?

Wouldn't the same hold true for pure O2, except that instead of talking about a difference of 8-12ppm we might be talking about a difference of 30-34 ppm (just made those numbers up) which would make no difference to us because that too much anyway.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 22, 2010, 02:43:23 PM
Somewhere I recently read that some yeasts are fine with filtered air, while others do better with O2.  It is not known why.

Different yeast strains are known to have different oxygen requirements. But we home brewers don’t worry about that as much as commercial brewers would who use the same yeast and brew the same beer all the time.

A DO meter is a handy tool to have in our hobby - and an expensive one. Kai, do you mind if I ask how much you spent?
 

I spent $150 on this one: http://www.eseasongear.com/milwaukeesm600.html

My main motivation for that purchase was to look into and evaluate different aeration techniques. I don’t think that brewers need to invest in a DO meter just because they think they might have aeration issues. Testing dissolves oxygen also takes almost a minute since the oxygen levels inside the probe have to be matched to the outside via diffusion through a membrane.

But for $150 they are definitely a worthwhile investment for any commercial brewer. Yet I was surprised to read an MBAA paper a while back that reported that many craft brewers underaerate their wort.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: majorvices on January 22, 2010, 03:24:27 PM
150 bucks? I thought they were much more.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 22, 2010, 03:41:02 PM
150 bucks? I thought they were much more.

that's what I thougt too. The link is for a place that has a big discount on them and I also bought my pH meter there.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Thirsty_Monk on January 22, 2010, 04:37:35 PM

So there can never be too much O2 present that the yeast won't use it all?
People reported solvent like taste with over O2 beers (even when fermenting at proper temp).
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: a10t2 on January 22, 2010, 05:07:20 PM
So the you can get more O2 in cooler wort using "air" is because the air is denser containing more molecules in a given space, correct?

No. Well, partly, but it's a very minor effect. The main reason is that a cooler liquid has reduced molecular energy, and so there's simply more "room" for the gas to dissolve, without the liquid molecules knocking it back out.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: prism21 on January 22, 2010, 05:39:13 PM
Does anyone use the hybrid method of filling the headspace with oxygen and then using a mixstir described here?  http://blog.flaminio.net/blogs/index.php/beer/oxygen/081408-wort-aeration
It seems to have two benefits: efficient use of oxygen (1 to 2 seconds) and consistent levels.  I'm planning to try it on my next batch.
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: majorvices on January 22, 2010, 06:01:16 PM
Interesting idea. Thanksfully our favorite brewing scientist has a DO meter. Maybe he'll find out for us.  ;)
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 22, 2010, 06:32:06 PM
Interesting idea. Thanksfully our favorite brewing scientist has a DO meter. Maybe he'll find out for us.  ;)

Thaks  :).  I have thought of that method as well and will put it on my list of things to try.

One reason why shaking is so effective is that the amount of oxygen you actually need to get to ~8 ppm in the wort only a small part of what is actually available in the head space. This is also why I have been proposing a fairly simple and foolproof procedure for a large starter:

- boil 2.5 and let cool 2 gal of water
- boil and let cool .5 – 1 gal of wort (you may combine this with the water before boiling)
- sanitize a carboy and add water and wort.
- close carboy top and shake extensively to dissolve as much head space O2 as possible.
- add yeast and let ferment it out.
- decant spent starter beer and rack “production” wort on top of the yeast. Aerate wort and resuspend the yeast.

I haven’t tried this yet but the idea is that you have a large volume of diluted wort which is not only less stressful on the yeast but it is also able to hold much more O2 per yeast cell and thus there should either be more growth or healthier, i.e. sterol richer, yeast cells. I don’t know how it would compare to a stirred starter though.

Kai

Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: ndcube on January 22, 2010, 06:58:53 PM
So basically your suggesting making a starter that has an OG in the 1.010 ballpark?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 22, 2010, 07:04:57 PM
So basically your suggesting making a starter that has an OG in the 1.010 ballpark?

pretty much. But not primarily for the low gravity but for the larger amount of O2 that will be available for the yeast. I do the same but constantly pump air though that starter.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: ndcube on January 22, 2010, 10:08:42 PM
The low gravity won't make the yeast want to floc out w/o a stir plate?
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 22, 2010, 10:32:01 PM
The low gravity won't make the yeast want to floc out w/o a stir plate?

Yes, it will still flocculate once most of the sugars are consumed. I guess this technique would be more for brewers who lack a stir plate.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: dean on January 23, 2010, 12:28:47 AM
New Belgium's olive oil experiment was such an effort. Other efforts include oxygenation of the yeast before it is pitched into the wort.

Kai

This is a Great thread!!  I got thinking about this the other night contemplating what I might have done difrerently with a particular batch of beer that I made and that I really liked (one Keith helped me with about a year and a half ago)... the only thing I can think of that I haven't tried is using olive oil, which I may have used at that time.  The beer in particular had more esters.  I don't know if that is worth noting or not because I didn't take good notes back then.  I sure liked that batch of beer though... it was awesome, and I'll continue to try recreating it even if I never do, it was that good.

Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 24, 2010, 03:42:11 PM
Here is quite big drawback of the DO meter I bought: The probe doesn't fit into the carboy neck :(. Oh well, I was moving to buckets anyway.

Unlike with a pH meter, a DO meter cannot be used to test small samples since it consumes the O2 in the sample and the act of pulling the sample and moving the DO probe around in it may actually aerate it further.

Kai
Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: Kaiser on January 25, 2010, 02:34:36 PM
I brewed again this weekend and got to play around with oxygenation again.

But I hit a slight snafu. The yeast was propagated in a carboy and I was feeling too lazy to move it to a flask after it had settled. The idea was that I would be able to count cells and don’t have to weigh the slurry to find out how much yeast I pitched. But after racking half the wort onto the yeast I realized that it was not un-flocculating as quickly as I hoped and that I would also not be able to take a wort stability test before and after aeration. I started doing the latter to asses how much contamination various form of aeration gets into the wort. And then the DO (dissolved oxygen)  meter probe didn’t fit into the carboy opening and I had to scratch the intend of evaluating shaking as a form of aeration.

Since I really wanted to test the DO level I moved the beer to a bucket and oxygenated with an O2 wand. Here is what I got for oxygenating the 10 l of 4 C (40 F, a bit colder than I wanted it to be) 16 Plato wort:

initial: 3.4 ppm
after 20s: 4.3 ppm
after another 20s: 5.6 ppm
Then I noticed a crack in the bottom of the racking cane that I build the O2 wand from and I had to cut it to fix the problem. The crack allowed O2 to bypass the sintered stone.
after fixing that and another 35s: 8.1 ppm

Looks like the oxygenation rate improved once I fixed the crack and more O2 was forced though the sintered stone

The ~20 hrs later I added the remaining 8 l and oxygenated again. I added the wort in 2 stages since I suspected that I didn’t have enough yeast to pitch the full wort volume.

At that point the yeast was already active but I didn’t have Kraeusen yet. The rather low pitching temp must have contributed to that.

The initial O2 reading was 2.4 ppm which might be quite imprecise since I’ll have to re-check the zero-calibration.

30s O2: 4.1 ppm
+30s O2: 4.9 ppm
+60s O2: 7.5 ppm
+60s O2: 12.2 ppm

This result is much different from what I got before where it took only 60s of pure O2 to get more than 20 ppm of DO. I wonder if the active yeast had anything to do with that. Future experiments will tell. I’ll also have to check if the time between oxygenating and testing makes a big difference. It might make a difference if there are still many O2 bubbles in suspension.

Kai





Title: Re: PURE O2 vs. NATURAL AIR AERATION
Post by: goybar on January 29, 2010, 03:59:23 PM
Wouldn't shaking/splashing the wort in the fermentor affect head retention?
 
Or are the head forming proteins created during/after fermentation?

Chris