Oxygenation - necessary?

[byrnsey]

Provocative title, but what I'm really asking, is:

Is there a such thing as too little oxygen? Once the yeast use up the O2, they'll start fermenting and stop reproduction. So it seems like less O2 would only lead to less yeast, a longer fermentation time, less trub/lees, but the same beer at the end (but maybe less waste, since there's less gunk to deal with when racking).

Anyway, oxygenation has been the thing I sweat least, just fill the bucket through my grain strainer, once I'm at about 3 gals, plug the hole, and give it a few hard shakes, and top it off. Always comes out fine.

I notice people sell oxygenator kits though, which in addition to being CRAZY dangerous, again, seems unnecessary and expensive. Anyone want to enlighten me?

 

[boydster]

Not enough yeast reproduction leads to beer that isn't as good as it could have been. If you underpitch (typical scenario for a brewer that just pitches a tube of liquid yeast or pitches unhydrated dry yeast into their beers), oxygen is crucial to ensure the yeast can build a sufficient colony. Otherwise, there are flavor and attenuation issues that can affect your beer. There are answers other than hitting your wort with pure O2, though.

 

[Malticulous]

It's not so simple. Different strains act so much different with varying amounts of O2. We don't know what the cell uses all the O2 for, but we do know some strains like more than others.

 

[masskrug]

During my chill I stir oxygen into the wort with my drill motor and then I pour roughly into the bucket. I have never had an issue.

 

[boydster]

We don't know what the cell uses all the O2 for, but we do know some strains like more than others.

I've never heard that we don't know what the cell uses all the O2 for. Ale yeast is one of the most studied microbes on the planet. It uses O2 to make fatty acids used in the cell wall, with excess O2 handed from parent cell to daughter cell until it is exhausted.

I'm willing to learn more though. Can you shed some light on what else you have heard? Or sources?

 

[cease]

I have been wondering about this myself. I use an aerator (a small plastic triangle at the end of tubing that sprays the wort) when I transfer from the kettle to the fermentor then shake the carboy for a few minutes. Never had any off flavors with any of beers. I always rehydrate my US-05 or make simple starters (no stir plate) for my liquid ale yeast. I even made a California Common (hybrid yeast) which came out very clean.

I've been eyeing the oxygen systems that use the small oxygen tanks from the hardware store but am not sure how much of an impact it will have. I'm torn between a stir plate or the oxygen system.


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[boydster]

I have been wondering about this myself. I use an aerator (a small plastic triangle at the end of tubing that sprays the wort) when I transfer from the kettle to the fermentor then shake the carboy for a few minutes. Never had any off flavors with any of beers. I always rehydrate my US-05 or make simple starters (no stir plate) for my liquid ale yeast. I even made a California Common (hybrid yeast) which came out very clean.

I've been eyeing the oxygen systems that use the small oxygen tanks from the hardware store but am not sure how much of an impact it will have. I'm torn between a stir plate or the oxygen system.


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I would suggest the stirplate. Yeast can take up the necessary O2 during the starter phase if given the opportunity. It's the same principle that allows dry yeast to be pitched without requiring additional oxygen.

 

[Malticulous]

I've never heard that we don't know what the cell uses all the O2 for. Ale yeast is one of the most studied microbes on the planet. It uses O2 to make fatty acids used in the cell wall, with excess O2 handed from parent cell to daughter cell until it is exhausted.

I'm willing to learn more though. Can you shed some light on what else you have heard? Or sources?

I read a bunch of books a few years ago. I'll hunt down the quote. I should have bookmarked it.

It's definitely necessary to get it contestant if you want consistent results as it's one of the few controls we have over yeast.

...

This is from Handbook of Brewing, Second Addition. I might find the better quote soon.

The quantity of oxygen required for fermentation is yeast-strain dependent. Ale yeast have been classified into four groups based on the oxygen concentration required to produce satisfactory fermentation performance. Similar groupings for lager yeast were reported by Jacobsen and Thorne. The amount of oxygen required for sterol synthesis and satisfactory fermentation varies widely, not only with the particular yeast employed but also with time of addition, whether in increments, etc.


...A number of factors have been found to influence the amount of esters formed during fermentation. The yeast strain is very important, as are the fermentation parameters of temperature, pitching rate, and top pressure. Wort composition affects ester production: assimilable nitrogen compounds, the concentration of carbon sources, dissolved oxygen, and fatty acids all have an effect. Wort components, which promote yeast growth, tend to decrease ester levels.

I think that shows what I said but it's not the exact one I'm looking for. It must be in a different book. None the less what I quoted here is more important. Good aeration is probably good enough for most homebrew strains. It's worked well for me.

 

[Malticulous]

Here it is out of Brewing Science and Practice

The quantity of oxygen required for fermentation is strain-dependent. In an early study, ale strains were classified as requiring half air saturation, air saturation, oxygen saturation or more than oxygen saturation for satisfactory fermentation performance (Kirsop, 1974). Similar findings have been reported for lager yeast strains (Jacobsen and Thorne, 1980). The explanation for these differences is related to the spectrum of sterols produced by individual yeast strains. The fate of most of the oxygen utilized during the aerobic phase of fermentation is unknown. Theoretically 10% is utilized for sterol formation and 15% for the biosynthesis of unsaturated fatty acids (Kirsop, 1982). More than 50% is unaccounted for.

 

[boydster]

Thanks Malticulus! I agree about the need for consistency. My first post was simplified, and that was intentional just to illustrate in basic terms why the idea that low oxygen and limited cell growth isn't always a good thing. I also agree that good aeration is sufficient in the vast majority of cases, especially when using a healthy pitch rate of either dry yeast or liquid yeast fresh from a stirplate starter (since in both cases, the yeast pitched into the beer will have been grown with access to lots of O2 and will have sufficient reserves built up to draw from during fermentation).

I wasn't aware, though, that there is >50% unaccounted for oxygen utilization. I'll have to dig into that more. I have a copy of that book and Principles of Brewing Science that I just haven't had time to read yet, among other brewing related books I collected right before moving. It's on the to-do list, for sure.

Cheers!

 

[Shred]

I use straight O2 in any beer that I pitch liquid yeast into... even with a starter on a stir plate. You are not going to hurt your beer if you have a slightly higher than necessary concentration of O2. Once the (now much healthier) colony of yeast begins munching on the sugars the CO2 created purges your fermenter of the excess O2 anyway.

From personal experience, my beers went from good to award-winning when I started using O2 and a stir plate.

 

[Wayne1]

I suggest you all buy "Yeast" by Chris White and Jamil Zainasheff.

That has the answers to most of the questions raised.

A short quote from the book:

"For the average wort and yeast pitching rates, the proper amount of dissovled oxygen is 8-10 parts per million... The wort splashing devices employed by many homebrewers will result in approximately 4 ppm, less than half the required amount. With plenty of headspace, a strong back, and lots of vigorous shaking, a homebrewer can get levels as high as 8 ppm into the wort. This is about the maximum using air.... The only way to reach the recommended 10 ppm minimum is with the addition of oxygen...With bottled oxygen and a sintered stone it is possible to reach high levels of dissolved oxygen.

 

[boydster]

Thanks. I have the book, and it is certainly informative. The "required" level quoted doesn't take into account oxygen the yeast takes up prior to pitching. Keep in mind, White Labs encourages people to direct pitch a vial of yeast with no starter into 5 gallons of wort, thereby requiring a substantial amount of growth in most beers. In those cases, there is no debating how crucial it is to have plenty of dissolved O2 in your wort.

 

[chickypad]

Here it is out of Brewing Science and Practice

I don't know much about the subject but I can't help but notice the sources from this quote are between 32 and 40 yrs old. I suspect more has been learned since then.

 

[Malticulous]

I don't know much about the subject but I can't help but notice the sources from this quote are between 32 and 40 yrs old. I suspect more has been learned since then.

The book is only 10 years old.

 

[grathan]

I stopped aerating a year or so ago. Mainly as an experiment, but it seemed ok so I've stuck with it.

In addition to less growth, the yeast cell walls will be thinner meaning they will excrete esters more readily. Most people will tell you that fermentation temperature is the best way to control yeast flavor profiles, but I find lack of aeration to be more favorable flavor-wise.

 

[jfk69]

I bought the O2 kit from Williams brewing a couple months ago and have done maybe three batches using it. I give it about 45 seconds to a minute of O2 and then pitch. I "seem" to get slightly faster starts, but it would be pretty tough to quantify it. With that said, I think it's a practice that I will continue, as I don't really feel like breaking my back and balls shaking a 5-6 gallon pail of beer to add oxygen.

 

[zach976]

I bought the O2 kit from Williams brewing a couple months ago and have done maybe three batches using it. I give it about 45 seconds to a minute of O2 and then pitch. I "seem" to get slightly faster starts, but it would be pretty tough to quantify it. With that said, I think it's a practice that I will continue, as I don't really feel like breaking my back and balls shaking a 5-6 gallon pail of beer to add oxygen.

I have the same system and haven't done any studies with it but I like it and will keep using it too.


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[sportpak]

I'm a small batch guy, all I do is hit the cooled wort with a whisk for about 60 seconds. That's about when my arm is ready to give up. It works up a good froth on top. I "seem" to get faster starts then just shaking or swishing.

 

[Malticulous]

This video is pretty good

[ame]https://www.youtube.com/watch?v=75gpehf_6Gk[/ame]

I stir the crap out of it in the kettle as it cools with the IC. I think I'm getting the full 8 ppm and have not had fermentation problems. I'd like a dissolved oxygen meter. That would be interesting. I'm also thinking of making a CFC soon. I'm going to need a new way when I do.

 

[byrnsey]

This is all really interesting, but raises a few other questions:

How can the yeast be said to 'require' 12-15 ppm if vigorous, deliberate aeration with natural air can only get to 8ppm?

How often in its evolution in the wild, or even during cultivation, would yeast be presented with levels at 12-15ppm? It sounds like it would have been impossible to get O2 levels that high until we learned to purify oxygen. We only discovered it as an element in the 1770's and have been making beer/wine since long before then.

I'm not saying more O2 doesn't lead to better beer, but any argument that good beer can't be made without techniques that probably didn't exist until the 19th-20th century sounds dubious.

It sounds like the one real effect more O2 has, other than increasing the number of yeast in the pitch is thickening the cell walls, causing the yeast to release more or less esters?

One poster mentioned that he deliberately starves his yeast to get them to release more, and I'd thought that they were generally undesirable. Why would you want a lot of esters in your beer?

 

[Shred]

I don't think the yeast "requires" 12-15 PPM to survive. It is the preferred level to produce expected/desired results from the various strains. Can good beer be made with less? Sure. But can proper oxygenation lead to potentially better beer? Absolutely. I strongly doubt a beer brewed in the 1770s would score well by today's standards. We've learned a lot more and our palates, knowledge, ingredients, equipment and expectations have evolved.

As for the question about wanting more esters - I purposely under-pitch my Belgians for the same reason I ferment them at much higher than normal temps.... the esters produced are what make Belgians special.

 

[SandstoneCityBrew]

While at NHC this year, Colin Kaminski gave a talk, and he said something interesting about oxygenation. This is his quote

"So make a starter in a 2L flask as normal. Let it settle clear. Pour off the liquid (barm beer). Add 1L of 1.040 sterile wort. Spin with continuous aeration for 4 hr. Pitch immediately. No O2 to wort. Don't use O2 at all only sterile air for 4 hr."

I like this idea, and I definitely plan on using this method on one of my upcoming brews. I'm gonna make a 10 gallon batch, split it, one batch will get the above method, the other batch will get treated the way I always do it (starter, then splash/stir while cooling, pour hard into the bucket, and then shake the bucket). Then after they are both done, do a side-by-side and notate the differences if any.

 

[MaxStout]

I notice people sell oxygenator kits though, which in addition to being CRAZY dangerous, again, seems unnecessary and expensive. Anyone want to enlighten me?

How is that "crazy dangerous"? Unless your house burns down and the tank bursts, I don't see the danger. I doubt the many people who routinely keep medical O2 tanks in their homes or those who have oxy-acetylene welding equipment in their garages would see the danger, either.

 

[grathan]

One poster mentioned that he deliberately starves his yeast to get them to release more, and I'd thought that they were generally undesirable. Why would you want a lot of esters in your beer?

Esters are what give yeast flavor. They also produce phenol which may or may not be desirable. I personally cannot stand yeast phenol. I dislike belgian beer and clove-like hefewiezen.

 

[byrnsey]

Cool, I'd heard to stay away from fermenting too warm, as I'd end up with a banana bread tasting beer. I suppose if you plan around any flavor you can make something good out of it. Generally how do you oxygenate for a Belgian, how much shaking would you recommend?

As for the O2, I'm still in shape enough that lifting and shaking 5 gallons for 45 seconds isn't too hard to do. Messing with something as flammable as pure O2 just doesn't seem worth it to me. And people with medical tanks don't have a choice, and welders are trained in safety (one hopes). My grandmother died of emphysema, and the sheer number of warning placards all over the place when she went on oxygen might have made me leery. But I guess enough people are doing it that it can be done safely.

 

[Shred]

I still use straight O2 with my Belgians. I've never really thought of it as being anymore dangerous than the 6 propane tanks I have in my garage/brewery. Just don't use if around an open flame. The tanks I use are the little red ones in the welding section at Home Depot.


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[KepowOb]

Cool, I'd heard to stay away from fermenting too warm, as I'd end up with a banana bread tasting beer. I suppose if you plan around any flavor you can make something good out of it. Generally how do you oxygenate for a Belgian, how much shaking would you recommend?

As for the O2, I'm still in shape enough that lifting and shaking 5 gallons for 45 seconds isn't too hard to do. Messing with something as flammable as pure O2 just doesn't seem worth it to me. And people with medical tanks don't have a choice, and welders are trained in safety (one hopes). My grandmother died of emphysema, and the sheer number of warning placards all over the place when she went on oxygen might have made me leery. But I guess enough people are doing it that it can be done safely.

45 seconds of shaking isn't going to get you even close to 8ppm... 45-60 seconds is needed when you directly inject O2, shaking is going to take a lot longer. In Yeast, they compare fermentation in 4 different samples, one which was shaken for 5 minutes, in which they measured only 2.71 ppm of O2. I can't remember where I read how long you have to shake for to get a decent amount of O2, but they said something like, shake it for several minutes, take a break, then shake again for several more minutes.


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[KepowOb]

Edit - double post

 

[oakbarn]

A real O2 system!