Aeration - Check This....

[bear09]

Very interesting experiment....

What do you think?

 

[Kingy]

was a good video and results were what i was hoping for as ive just started to use in airstone lol

 

[kirem]

My thoughts are and in my opinion;

If you use the correct size starter to achieve the correct cell count in the fermenting wort then the starter is the best place to aerate. It is here that the cells need the oxygen for building strong and flexible alcohol tolerant walls (sterols).

Oxygen is good for yeast but bad for flavour and aroma molecules. So I believe limiting the essential aeration to a yeast starter and getting that right, prevents the damage to the whole batch of wort.

 

[Darren]

My thoughts are and in my opinion;

If you use the correct size starter to achieve the correct cell count in the fermenting wort then the starter is the best place to aerate. It is here that the cells need the oxygen for building strong and flexible alcohol tolerant walls (sterols).

Oxygen is good for yeast but bad for flavour and aroma molecules. So I believe limiting the essential aeration to a yeast starter and getting that right, prevents the damage to the whole batch of wort.

Ah,
Great to see someone else "ranting" the obvious

cheers

Darren

 

[tangent]

not really a rant Darren , but always nice to hear the science behind the folklore.
Nice one Kirem.

 

[Kingy]

ive definatley noticed huge results in using an airstone for my wort and starters,am i wasting my time airating the wort if i use a well airated starter?

So basically i dont need to airate the wort if im airating my starter?

 

[Darren]

ive definatley noticed huge results in using an airstone for my wort and starters,am i wasting my time airating the wort if i use a well airated starter?

So basically i dont need to airate the wort if im airating my starter?

Kingy,

If you are organised enough to pitch your starter at high-krauzen, there is no need to airate your wort (especially for ales)

cheers

Darren

 

[hughman666]

Kingy,

If you are organised enough to pitch your starter at high-krauzen, there is no need to airate your wort (especially for ales)

cheers

Darren

or let it ferment out completely, pour off 80% of the starter wort, agitate the rest and pitch that.

 

[Phrak]

The way I'm seeing the evidence that the video guy presented is that there's only a very small difference between not aerating at all, and using O2 injection.

From the youtube description:
Wort1=No aeration
Wort2=Shaken(, not stirred)
Wort3=O2 injection

There is a lot of discussion going on in the homebrewing community about the necessity of getting oxygen back into your wort after a full boil. There are several methods being used and not everyone agrees on the best bang for the buck (shaking the fermenter or pure O2 injection). I personally experienced some empirical evidence that O2 injection was benefitial but I was hoping to confirm or deny this in a more scientific way.

Ok, so it's been six days since I pitched on this experiment.

If you recall, I posted that at 45 hours after pitching (remember the OG was 1.050):

#1 = 1.018 (64% attenuation)
#2 = 1.019 (62% attenuation)
#3 = 1.016 (68% attenuation)

After 70 hours, the SGs were:

#1 = 1.016 (68% attenuation)
#2 = 1.015 (70% attenuation)
#3 = 1.013 (74% attenuation)

After 144 hours or 6 days, the SGs are:

#1 = 1.012 (76% attenuation) 5.1% ABV
#2 = 1.013 (74% attenuation) 4.9% ABV
#3 = 1.011 (78% attenuation) 5.2% ABV

So for one more gravity point, is the expense of an O2 injection system really worth it?

 

[roger mellie]

The way I'm seeing the evidence that the video guy presented is that there's only a very small difference between not aerating at all, and using O2 injection.

From the youtube description:
Wort1=No aeration
Wort2=Shaken(, not stirred)
Wort3=O2 injection

So for one more gravity point, is the expense of an O2 injection system really worth it?

Spot on Phrak

Good video footage - I would happlily settle for number 2 anytime - Oxygen injection - FFS!

Nooooooooooo Neeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeed!

Or Something

RM

 

[bayWeiss]

Kingy,

If you are organised enough to pitch your starter at high-krauzen, there is no need to airate your wort (especially for ales)

cheers

Darren

I can not say i agree with this. Some research (starting on page 33) has shown that even when fairly large (too large) pitching rates are used, there are yeast that still multiply to some extent given there is oxygen available. It seems that if "flavor-based" overpitching yeast cells still multiply, that they would need some oxygen to accomplish this. So, I would think aeration via shaking would be enough, and no aeration of a just boiled wort would not do the trick. Perhaps the heavy splashing of the wort as it goes into the fermenter might be adequate...

What i got out of the report is that high pitching rates can be detrimental (in lager and ale), and you need some reproduction in the wort to accomplish good flavor. Given that knowledge (and i do this anyway), I always aerate my wort even after pitching a starter.

Although i can say, that i do not think i have ever overpitched yeast... but then again, i have not done side by side testing as has been done in that particular piece of research.

my 2 cents, cheers!

 

[Screwtop]

Those poor little Wyeast cells, locked up in the smack pack with next to no oxygen, and expected to bud/multiply and swell that bag, poor little buggers! How do they do it?

 

[kirem]

Those poor little Wyeast cells, locked up in the smack pack with next to no oxygen, and expected to bud/multiply and swell that bag, poor little buggers! How do they do it?

nutrients that include lipids and sterols can 'replace' the need for oxygen to create sterols. I don't know for sure, but I would be surprised if the wyeast smack packs don't have high quality 'dormant' yeast that are already full of lipids and sterols and the nutrient in the smack pack contains further lipids and sterols available for yeast uptake and cell wall integration.

Some further info;

http://www.fst.vt.edu/extension/enology/VC/july-aug02.html ;
Oxygen should be considered an essential yeast nutrient. Slight aeration during yeast stationary and growth phases increases the production of lipids (principally oleanolic acid) and sterols (ergosterol and zymosterol), important cell membrane constituents. It has been shown that yeast propagated aerobically contain a higher proportion of unsaturated fatty acids and up to three times the steroid level of anaerobically grown yeast. This correlates positively with improved yeast viability and fermentation.

Because yeasts are not able to synthesize membrane components in the absence of oxygen, existing steroids must be distributed within the growing populations. Without initial oxygen, yeast multiplication is usually restricted to 4 to 5 generations, due largely to diminished levels of steroids, lipids and unsaturated fatty acids. Carbon dioxide, nitrogen gas and ascorbic acid reduce molecular oxygen.

http://www.howtobrew.com/section1/chapter8-2-1.html ;
Immediately after pitching, the yeast start adjusting to the wort conditions and undergo a period of high growth. The yeast use any available oxygen in the wort to facilitate their growth processes. They can use other methods to adapt and grow in the absence of oxygen, but they can do it much more efficiently with oxygen. Under normal conditions, the yeast should proceed through the adaptation phase and begin primary fermentation within 12 hours. If 24 hours pass without apparent activity, then a new batch of yeast should probably be pitched.

At the beginning of the adaptation phase, the yeast take stock of the sugars, FAN and other nutrients present, and figure out what enzymes and other attributes it needs to adapt to the environment. The yeast use their own glycogen reserves, oxygen, and wort lipids to synthesize sterols to build up their cell membranes. The sterols are known to be critical for enabling the cell membrane to be permeable to wort sugars and other wort nutrients. Sterols can also be produced by the yeast under poor oxygen conditions from lipids found in wort trub, but that pathway is much less efficient.

Once the cell walls are permeable, the yeast can start metabolizing the amino nitrogen and sugars in the wort for food. Like every animal, the goal of life for the yeast cell is to reproduce. Yeast reproduce asexually by "budding". Daughter cells split off from the parent cell. The reproduction process takes a lot of energy and aerobic metabolic processes are more efficient than anaerobic. Thus, an oxygen-rich wort shortens the adaptation phase, and allows the yeast to quickly reproduce to levels that will ensure a good fermentation. When the oxygen is used up, the yeast switch metabolic pathways and begin what we consider to be fermentation - the anaerobic metabolism of sugar to alcohol. This pathway is less energy efficient, so the yeast cannot reproduce as proficiently as during the adaptation phase.

The key to a good fermentation is lots of strong healthy yeast- yeast that can get the job done before going dormant due to depleted resources, rising alcohol levels, and old age. As noted, the reproduction rate is slower without oxygen. At some point in the fermentation cycle of the beer, the rate of yeast reproduction is going to fall behind the rate of yeast dormancy. By providing optimum conditions for yeast growth and reproduction in the wort initially, we can ensure that this rate transition will not occur until after the beer has become fully attenuated.

Worts that are underpitched or poorly aerated will ferment slowly or incompletely due to lack of viable yeast. Experienced brewers make a big point about aerating the wort and building up a yeast starter because these practices virtually guarantee enough yeast to do the job well.

 

[Screwtop]

(ergosterol and zymosterol),

Such temperamental little buggers, sure theres no estrogen :lol:

 

[kirem]

last time I asked they got up and stormed out of the room

 

[Ross]

Worts that are underpitched or poorly aerated will ferment slowly or incompletely due to lack of viable yeast. Experienced brewers make a big point about aerating the wort and building up a yeast starter because these practices virtually guarantee enough yeast to do the job well.

No reference here to aerating the starter rather than the wort, nor in the Wyeast presentation :unsure:
I'm not arguing against one way or the other, as I don't have the knowledge, but strange that the likes of wyeast are advocating wort rather than just starter. I know it's possible to over oxygenate using pure O2 but was informed at the Wyeast presentaion you couldn't over oxygenate with air (sterile).

Cheers Ross...

 

[kirem]

I suppose understanding why we are providing oxygen to yeast and what they do with it and the products they manufacture using oxygen is one part of the story and the other is once they have those products or a certain quantity of those products, do they really need more oxygen? Sure they will use it but do they need it?

I am pretty sure that if the yeast have finished using oxygen for lipids in the cell membrane/wall, they start or ramp up other metabolic pathways that use oxygen such as making glycerol instead of alcohol.

My point is and what I conclude from what I have read, is that by providing a cell count in the wort from a starter volume that is sufficient to have a very short lag/adaption phase then in my opinion any oxygen in the wort is over kill and probably detrimental.

I maintain that oxygen is great for yeast in the lag/adapation phase, it is not in other phases. This coupled with oxygen is bad for aroma/flavour molecules, makes me think that oxygenating you starter wort is better than doing it in the whole batch of wort.

this is good stuff!

Kirk

 

[Thirsty Boy]

The yeast IS after all going to grow some in the fermentor. Or are you talking about pitching as much yeast in as you expect to get out?? Assuming you aren't, then what do you want from the yeast?

I want them to grow to the required numbers, and when they are finished growing, to be in tip top fighting form and ready to ferment out my wort into nice well finished beer.

Yeast use oxygen to grow and even if they have LOTs of nice sterol etc reserves from a well aerated starter, they will use some of those to multiply in the initial stages. A bit of oxygen in the wort is going to mean that they use less of those reserves up, and they will be in a little bit better shape for the main game of attenuation.

I'm not saying that I think you should be belting the crap out of your wort with pure O2, but 20mins or so with an Aquarium pump while you clean up the brewery... not much effort to go to really.

But as the experiment above shows, probably not a whole heap of difference either way, as long as the little yeasties are getting a good shot of O2 at some point or another.

For me its reasonably simple, I think that a bit of Oxygen in the wort before you pitch is probably going to help a bit and probably not hurt. And on top of that, all the brewers amateur and pro, who I know and respect, oxygenate their wort. Doesn't mean a damn thing really, but it'll do me.

Thirsty

 

[Gulf Brewery]

Hi

There is a lot of banter about yeast and oxygen here.

The wort needs to have oxygen in it for the yeast, but the real question is how much you get into the wort. With a small container like they shook in the video, they could easily get a lot of oxygen into the wort, but could you do that with 23 or 46 litres?

Yeast will multiply 4 to 5 times over the number in the wort compared to the starter and they do need oxygen to multiply and remain healthy with the creation of lipids and sterols in the cell walls.

While the video is interesting, there are a few points that need a bit of attention.
1. The yeast was a dry yeast that was re-hydrated. I think dry yeast hold more oxygen than liquid ones.
2. No mention was made of the attenuation - one may have started and finished quicker, but what if it finished a few points higher?
3. If you pitch as much yeast as you expect to get out, then you will be overpitching and causing other issues.

Cheers
Pedro

 

[Ash in Perth]

increased wort oxygen levels reduce esters formed in the early phases of fermentation. I recommend getting as much air/oxygen into the wort as possible, it is very hard to over aerate wort, there is a much greater risk of under aerating. The gravity points are not everything. If you plan to re-use the yeast also you will find that without proper aeration the yeast only lasts a couple of generations before you have issues.