First Ag - A Bit Of A Disappointment

[Thirsty Boy]

Apparently - the method of propagation and drying used by the dry yeast manufacturers leaves the yeast with a surfeit of nutrients and resources. To such an extent that they dont require oxygen in the wort, they can manage the job on internal resources alone.

After doing a fair amount of research on the topic, it seems that a nice frsh packet of dried yeast, comes with enough inbuilt resources to allow the yeast to reproduce 3-4 times and still have enough internal juice left to finish the job of fermentation and shut down properly cleaning up after themselves as they go.

So the upshot is - a nice fresh pack of yeast with the majority of its contents alive and viable - should have enough yeast cells and internal resources so that they would be able to be pitched into an oxygenated wort at around 11 -13 plato - and not need any added oxygen.

So, according to the manufacturer's spiel - for quite a chunk of homebrew requirements, you shouldn't need to aerate.

I take it with the same level of "oh really" as I apply to the notion that Wyeast smack packs and Whitelabs vials, contain enough cells to pitch without a starter. Yeah - they do, if the pack is fresh, has been well looked after and your wort is no stronger than average. The dry packs, under the same sort of optimum conditions might not need the wort to be aerated.

Me - I aerate anyway. I don't know enough about the history of the yeast to assume its in optimum shape, so I assume it isn't. Besides, I dont want my yeast to have enough resources to do the job - I want them to have resources to throw away before they knock off. I want the best, least stressed yeast I can get; and to work them just hard enough to get some flavour out of their sweat - but no more than that.

Aerating isn't going to hurt your beer, not aerating just might - I know which horse I am backing

Thirsty

 

[dr K]

they would be able to be pitched into an oxygenated wort at around 11 -13 plato - and not need any added oxygen.

So, according to the manufacturer's spiel - for quite a chunk of homebrew requirements, you shouldn't need to aerate.

How do you get oxygenated wort, particularly if you have avoided HSA before the boil, boiled the crap (and the oxygen) out of the wort then chilled and transerred...now whether you aerate (and thus about 20% oxygenate) by pouring from a great height, using a diffusion stone with sterile air of med grade O2 or shaking the shirt back in again you are oxygenating, if you do none of the above you are not.

Clearly then oxygenated wort wort needs no added oxygen....

Seriously, it is good practice to give the yeast as much help by way of oxygen in its initial stages as possible, dry yeast does have reserves of glycogen and trehalose "built in" that will help it move from the dormant to active state but oxygen is still helpful.
Aeration is not mandantory but healthy yeast activity is, aeration helps as do many other factors...the same factors apply to dry and liquid yeasts.

K

 

[katzke]

I want the best, least stressed yeast I can get; and to work them just hard enough to get some flavour out of their sweat - but no more than that.

Aerating isn't going to hurt your beer, not aerating just might - I know which horse I am backing

Thirsty

Oh now that about put me off of drinking. We put all that nice stuff in wort and end up drinking yeast sweat.

 

[braufrau]

not me, I an not sure why there would be a difference.

Perhaps its not the yeast type but the wort it goes into ? I guess, I am drawing a very long bow, but most kit users will use dry yeast.

Reading the different posts, boiling seems to have the effect of draining wort of the oxygen for yeast to live on. Perhaps because there is less boiling for kits than grain, they would not be as susceptible to low oxygen.

And kit brewers add water which creates splashing .. that's how I aerate my wort. I'll need a new method when I go to AG.

 

[Thirsty Boy]

How do you get oxygenated wort, particularly if you have avoided HSA before the boil, boiled the crap (and the oxygen) out of the wort then chilled and transerred...now whether you aerate (and thus about 20% oxygenate) by pouring from a great height, using a diffusion stone with sterile air of med grade O2 or shaking the shirt back in again you are oxygenating, if you do none of the above you are not.

Clearly then oxygenated wort wort needs no added oxygen....

Seriously, it is good practice to give the yeast as much help by way of oxygen in its initial stages as possible, dry yeast does have reserves of glycogen and trehalose "built in" that will help it move from the dormant to active state but oxygen is still helpful.
Aeration is not mandantory but healthy yeast activity is, aeration helps as do many other factors...the same factors apply to dry and liquid yeasts.

K

Quote me - "they would be able to be pitched into an oxygenated wort at around 11 -13 plato - and not need any added oxygen" clearly then, from the entirety of the rest of my post... I meant un-oxygenated and made a typo.. jeez

I agree 100% with your underlying sentiment though K, I was just regurgitating the spiel from the yeast makers and those who decided that said spiel means that they don't need to oxygenate. They say that the oxygen isn't needed, that the internal reserves are enough for 3-4 gens of multiplication..... so you are right, unless you do something, there is very little oxygen in the wort, but - well - apparently you don't need it.

I think that its almost certainly going to be better if you do oxygenate. I can see virtually no situation in which the yeast is not going to be healthier and in better shape for the main game of fermentation, with added oxygen, than they would be without - and that every time you get away with not doing it, you are lucky


Now - if I made another typo, could you just point it out as one - I'm trying to agree with you here.....

 

[Ducatiboy stu]

As for aeration I just drain my kettle into the fermenter will heaps of splashing. Basically if you get 1-2" of foam in the fermenter, that is enough to keep the yeasties happy

 

[mesa]

I think that its almost certainly going to be better if you do oxygenate. I can see virtually no situation in which the yeast is not going to be healthier and in better shape for the main game of fermentation, with added oxygen, than they would be without - and that every time you get away with not doing it, you are lucky

Wouldn't over oxygenation have similar effects to over pitching? I don't know much about it, but I've heard that if the yeast population is too high (and I presume over oxygenation would encourage reproduction), they will run out of sugars very abruptly during the ferment and all shutdown without cleaning up properly?

Not that I don't agree with you, aeration/oxygenation is a better bet than no aeration/oxygenation, but I do like to play devils advocate.

 

[buttersd70]

over-oxygenation, from a practical perspective, in HB terms, is something that just doesn't (usually) happen apparantly. I can't remember the numbers, but they went into it in the BB podcast that was linked earlier, how much oxygen was introduced in various methods etc, compared to oxygen levels reccomended. From memory, I think direct O2 injection was the only method that they were able to push the numbers too high, and then only through deliberate action.

 

[Adamt]

EDIT: Not sure where I read what I originally posted so I've deleted it. What should be said is: If you sparge with pure oxygen you run the risk of providing more Oxygen than required by the yeast, leaving more in solution after yeast propagation which will lead to oxidation products forming.

If you sparge/splash with air you will not over-oxygenate.

 

[katzke]

Too much oxygen is poisonous to yeast and can only really happen (as suggested) by direct oxygen injection. If you sparge/splash with air you will not over-oxygenate.

Hope you are not advocating splashing during the sparge? I am not an HSA freak but still do not believe in introducing any more air then possible before cooling the wort.

The only time to aerate is after cooling the wort.

 

[Adamt]

Absolutely not! I was referring to gas sparging, where a gas is bubbled through a liquid to dissolve, not wort sparging.

 

[katzke]

Absolutely not! I was referring to gas sparging, where a gas is bubbled through a liquid to dissolve, not wort sparging.

Never heard it called that before. Hope it does not catch on as we do not need any more confusing terms like secondary.

 

[Tim]

If no chilling, then don't bother syphoning the beer in. Just invert your cube and let it empty as fast as it can into the fermentor. That level of splashing will guarentee enough aeration.
Another factor is if you make a starter. If you add enough oxygen in the starter and pitch enough it won't make a rats arse difference if you have not oxygenated your wort enough.

 

[Thirsty Boy]

If no chilling, then don't bother syphoning the beer in. Just invert your cube and let it empty as fast as it can into the fermentor. That level of splashing will guarentee enough aeration.
Another factor is if you make a starter. If you add enough oxygen in the starter and pitch enough it won't make a rats arse difference if you have not oxygenated your wort enough.

I'd beg to differ with you there - I'm not a subscriber to the theory that oxygenating your starter is enough. Don't want to have a big debate about it, but its not a theory that is universally accepted or anything.

Otherwise lots of people and breweries have wasted their time and money on aeration gear that isn't needed. And I don't think they have.