Does yeast need oxygen at the start of fermentation?

[Headlands]

I was talking to a Chemistry teacher last night about how we homebrewers and Commercial breweries oxygenate the wort prior to fermentation. He insisted that as yeast works anaerobically it really isn't necessary and the presence of oxygen is a bad thing.

So I found this article this morning which sheds some light on things

https://www.morebeer.com/articles/how_yeast_use_oxygen


This is probably the most relevant part about why we oxygenate:

"The cell membrane is the structure that controls what flows into and out of the cell. If these membranes lack sufficient sterols, the yeast cells become weak, leaving the cells susceptible to a variety of problems. Weakened cells can become intolerant of alcohol, and the alcohol can kill them (5). Weakened cells can also result in stuck fermentations and numerous off-flavors. If the membranes contain sufficient levels of sterols, however, the cells are much stronger, more cells will thrive to finish the fermentation, and the yeast may complete the fermentation significantly faster.

The real requirement for oxygen, then, is to help produce fatty acids and sterols, which are very important components of the cell membrane. The reason wort aeration (or oxygenation with pure oxygen) is considered so important to brewery fermentations is that yeast can synthesize the lipids needed for membrane biosynthesis only when dissolved oxygen is available. If yeast had an independent source of these important lipids, however, the so-called requirement for oxygen could theoretically be eliminated completely"

 

[Razor]

Guess the chemistry teacher is wrong. :lol:


Sent from my iPhone using Tapatalk

 

[Covrich]

Before fermentation it certainly needs it and to be honest most of us probably do not do enough, this can lead to like you say weaker and lazier yeast cells..

It doesn;t just affect this brew, but if you plan to harvest your viability of future yeast will also be affected.

 

[geetee]

Limiting oxygen in the wort and depriving the yeast will drive the fermentation reactions towards production of esters, something that is not needed in all beers.

 

[terrym]

But bear in mind that O2 does not dissolve very well in water or wort (unlike CO2). When the solution is saturated with O2 that's it, it's saturated and no amount of extra O2 bubbled through or beaten in will make any difference because it will just bubble out.
That said if you boil your wort as in AG or full extract brewing and have driven most of the O2 out of solution, you should spend more time than a partial mash extract or kit brewer oxygenating the wort, because cold tap water is already partially oxygenated.

 

[geetee]

But bear in mind that O2 does not dissolve very well in water or wort (unlike CO2). When the solution is saturated with O2 that's it, it's saturated and no amount of extra O2 bubbled through or beaten in will make any difference because it will just bubble out.
That said if you boil your wort as in AG or full extract brewing and have driven most of the O2 out of solution, you should spend more time than a partial mash extract or kit brewer oxygenating the wort, because cold tap water is already partially oxygenated.

I always stir during steeping which adds air/oxygen back and then allowing to drop into the FV aerates the wort for fermentation.

 

[Honk]

I sometimes wonder if the need for oxygenating wort is over exagerated on homebrew forums. I recently spent a day at a brewery and was surprised how little they bothered about it. the wort had maybe a 6 inch drop from the copper into a hopback and was then pumped into the fermentation vessel via the bottom tap when they could easily have fed into the top of the vessel and let it drop to aerate it that way. In fact they were quite relaxed about a lot of things that i've read MUST be done on homebrew forums and their beer tastes great.

I let my wort drop into the fv with tap fully open but thats all the aeration it gets but I come on here and read of people useing aeration stones which all seems like overkill to me (as well as an infection risk).

 

[markcc]

I let my wort drop into the fv with tap fully open but thats all the aeration it gets but I come on here and read of people useing aeration stones which all seems like overkill to me (as well as an infection risk).

Probably fine for a "regular" beer, but if you want a big beer to attenuate well then aeration really helps.

 

[Simonh82]

I sometimes wonder if the need for oxygenating wort is over exagerated on homebrew forums. I recently spent a day at a brewery and was surprised how little they bothered about it. the wort had maybe a 6 inch drop from the copper into a hopback and was then pumped into the fermentation vessel via the bottom tap when they could easily have fed into the top of the vessel and let it drop to aerate it that way. In fact they were quite relaxed about a lot of things that i've read MUST be done on homebrew forums and their beer tastes great.

I let my wort drop into the fv with tap fully open but thats all the aeration it gets but I come on here and read of people useing aeration stones which all seems like overkill to me (as well as an infection risk).

Most breweries will have in line oxygen supply as the cooled wort is transferred, or once it is in the fermentation vessel.

 

[Gunge]

I sometimes wonder if the need for oxygenating wort is over exagerated on homebrew forums. I recently spent a day at a brewery and was surprised how little they bothered about it. the wort had maybe a 6 inch drop from the copper into a hopback and was then pumped into the fermentation vessel via the bottom tap when they could easily have fed into the top of the vessel and let it drop to aerate it that way. In fact they were quite relaxed about a lot of things that i've read MUST be done on homebrew forums and their beer tastes great.

I let my wort drop into the fv with tap fully open but thats all the aeration it gets but I come on here and read of people useing aeration stones which all seems like overkill to me (as well as an infection risk).

I make no effort to aerate my wort whatsoever, and get 3-5 day fermentations of the healthiest kind. The flow of wort from my small-bore counterflow chiller barely causes a ripple on the surface of the wort in the FV so picks up almost no oxygen. So ye, I think it's cobblers. Probably depends on the yeast but Notty certainly could not care less. It's a hard nut for sure, one of the reasons I like it. Maybe the chemistry teacher ought to brush up on biology.

 

[geetee]

Most breweries will have in line oxygen supply as the cooled wort is transferred, or once it is in the fermentation vessel.

Big mechanised breweries maybe but small micros definitely not.

 

[geetee]

Below a brief extract from a book called Yeast - the practical guide to Beer fermentation ( by Chris White with Jamil Zainashieff 2010 ed). One of my favourite bedtime reads!

"The one nutrient that yeast need, which is not present in wort due to boiling, is oxygen. During the lag phase, yeast cells rapidly absorb available oxygen from the wort. The cells need oxygen in order to produce important compounds, most significantly sterols, which are critical in yeast membrane permeability. It is important that you provide enough oxygen to the yeast at the beginning of fermentation. Generally, you do not want to add oxygen later, as it can disturb the delicate balance of flavor and aroma compound creation. One exception is when brewing very high-gravity, high-alcohol beers. In those cases, where the yeast need large reserves to ferment the beer to completion, a second addition of oxygen between 12 and 18 hours after pitching can make a tremendous difference in attenuating the beer to the desired level."

Big breweries handle this by automatic on-line monitoring but at a home level splashing about and stirring is probably enough for what we need. Oxygen is essential in the lag phase to allow some of the yeast to grow whilst other yeast is actually fermenting. Insufficent healthy yeast will drive the mechanism down a different pathway and you got all sorts of off flavours.

 

[Simonh82]

Big mechanised breweries maybe but small micros definitely not.

I thought that it was more common than that but I'm happy to be corrected.

 

[Manxnorton]

I was talking to a Chemistry teacher last night about how we homebrewers and Commercial breweries oxygenate the wort prior to fermentation. He insisted that as yeast works anaerobically it really isn't necessary and the presence of oxygen is a bad thing.

So I found this article this morning which sheds some light on things

https://www.morebeer.com/articles/how_yeast_use_oxygen


This is probably the most relevant part about why we oxygenate:

"The cell membrane is the structure that controls what flows into and out of the cell. If these membranes lack sufficient sterols, the yeast cells become weak, leaving the cells susceptible to a variety of problems. Weakened cells can become intolerant of alcohol, and the alcohol can kill them (5). Weakened cells can also result in stuck fermentations and numerous off-flavors. If the membranes contain sufficient levels of sterols, however, the cells are much stronger, more cells will thrive to finish the fermentation, and the yeast may complete the fermentation significantly faster.

The real requirement for oxygen, then, is to help produce fatty acids and sterols, which are very important components of the cell membrane. The reason wort aeration (or oxygenation with pure oxygen) is considered so important to brewery fermentations is that yeast can synthesize the lipids needed for membrane biosynthesis only when dissolved oxygen is available. If yeast had an independent source of these important lipids, however, the so-called requirement for oxygen could theoretically be eliminated completely"

Tried to reads this last nite! Brain fried lol
The guist of it is my getting the oxygen properly is in question...not that I do a crap ettempt, but just trying different ways to do it.
Document it and learn what's best..
It all boils down every single phase of a brew...the best method of everything..(sanitising m, water treatment, recipe calculations, the GF setup, no chill vs chiller, yeast starter, temp control, keg or bottling, priming calculations, primary and second fermination, racking and the times needed to do it)
This is what I love learning and putting it all together...peace of mind that I've succefully done every single thing right and the efficiency be spot on..
There's nowt wrong with being a perfectionist as long as you dont do a half hearted ettempt...
My journey has got me slowly getting the areas that needed I ironed out as far as learning...the GF and the ferm fridges has made leaps n bounds with my learning..even simple thing like no chill I'm learning all the time.
Can't be bad for a damaged brain..I think my communication and rashinal thinking needs worked on!!
But I have to realise that part of my Brain can't get fixed..so I have to settle with slowly doing thing...(seems like I'm a 100mph!)
There's worse off people out there.
So I thank the lord and the forum members for putting up with me...
Prob chippy would say "the forum would be a dull place without people like you!"
:lol:
Thx
Bri

 

[strange-steve]

If you only use dry yeast then no, it's not at all necessary because there are sufficient sterols "built in" during the production process. However if using liquid yeast or planning on reusing the trub from a dry yeast then you do need to aerate the wort to ensure healthy fermentation.

 

[Ajhutch]

If you only use dry yeast then no, it's not at all necessary because there are sufficient sterols "built in" during the production process. However if using liquid yeast or planning on reusing the trub from a dry yeast then you do need to aerate the wort to ensure healthy fermentation.

That's really interesting, I didn't know that. Thanks!

 

[Druncan]

Just to stir up more sediment. Guidance from Fermentis on dried yeasts picked up at BeerX says; "Oxygen is required to assume healthy cell multiplication. Oxygen should only be added in the first 18hrs in FV. Adding oxygen later will increase aldehyde and diacetly levels.

 

[geetee]

Just to stir up more sediment. Guidance from Fermentis on dried yeasts picked up at BeerX says; "Oxygen is required to assume healthy cell multiplication. Oxygen should only be added in the first 18hrs in FV. Adding oxygen later will increase aldehyde and diacetly levels.

As I stated above only in the first lag phase where teh yeast is growing and multiplying, not in tee fermentation process itself where it can influence the production of bi-products in a different metabolic pathway.

I have no knowledge of whether they put sterols in or not (Fermentis) but possible just covering their backs as fermentation proper does not start for a good few hours so excess oxygen probably insignificant.

 

[Pawlo7671]

I don't oxygenate my wort as I'm of the opinion that its one way of introducing an infection, why sanitize everything with the greatest care to then flood your beer with air-born microbes ? So I see not oxygenating the lesser of the evils

 

[TheQuokka]

It is essential to introduce some oxygen into the wort after a full boil unless you are pitching a full volume of yeast cells. As the quoted article states, the oxygen is used for multiplication of the yeast. I feel that many on the internet over-emphasise the oxygenatation requirements, probably due to marketing, and too much oxygen will not only cause the problems mentioned, but will encourage the growth of bacteria. I just pitched about 100ml of slurry into a wort that was simply allowed to flow from the 1/2" tap into the FV from a kitchen bench and gained a beautiful krausen within 8 hours. It will finish in about 2&1/2 days and have a diacetyl rest for another 2 - then 2-3 weeks of crash then conditioning after forced carbonation and lovely Best Bitter!