Wort Aeration

[jonocarroll]

I was up in Clare last weekend (the town, dirty buggers ) at a few (very) lovely wineries with the Wine Guild, and got to asking a few questions about yeast. It doesn't seem to get much of a mention on the tours (and these are tours with people who know their stuff) so I asked. Apparently it is talked about a lot between winemakers.

I asked what types of yeasts the the wineries used and how they inoculate their must. Wild ferments are not so common any more, but a few places still do open ferments and use the local wild strains. For closed ferments, a neutral yeast is typically used (esp. in whites). I inquired about these yeasts and one winemaker told me they use 500g in 1000L of must - aerated with a nitrogen-oxygen mix. Essentially a giant starter. Once this has completed the aerobic phase, it is pitched to the main batch to ferment out.

I asked what they do to aerate the entire batch - they don't.

I don't know what the bigger breweries do. Perhaps someone on here does. Anyhoo - the point of this story (I like stories) is a question - if we make large enough starters, do we really need to aerate the wort at all? I know yeast need to acclimatise to their surroundings, but can they do that in the anaerobic phase, or do they really need to reproduce further? I've seen the comparisons regarding shaking vs. direct O₂ injection, and the results was that it really didn't matter which you did, or even that shaking was better. Can't recall if that used a starter or not.

If it's a dumb question, just let me know. Otherwise, I'm keen to know if anyone has any knowledge or experience with this. Remember, it's pedantic little me here, so starting a reply with 'I don't know anything about it, but this is exactly what happens' won't get you any brownie points <_<

 

[alexbrand]

Hi QuantumBrewer!

Right after pitching the yeast needs the oxygen to grow (not the single cell, but the amount of cells). So if you pitch lots of yeast into your non areated wort it will do the job because there's already enough yeast. If you don't have enough yeast ready to pitch you have to areate (or use olive oil instead) for increasing the number of cells.

This is what you winemaker did. I guess, oxygen is not wanted in the fresh grape juice for some "taste" reason.

Cheers,

Alex

 

[jonocarroll]

Hmm... Perhaps I didn't make clear enough the level of answer I'm after - I get the aerobic reproduction phase. I understand the role of oxygen here. I'm curious to know whether or not people who make a starter still do something to aerate their wort, or if they just pitch a sufficient starter and begin the anaerobic phase.

The reason the winemaker doesn't aerate the entire batch is because he feels the starter is large enough, and the yeast can go straight into anaerobic fermentation. Oxygen in wine fermentation is an easy hurdle - they just throw SO₂ at it until it isn't a problem anymore. Wine is racked often enough, and sits around in barrels for long enough, that the SO₂ comes out of solution, just like lagering.

 

[hockadays]

Was reading about this today on the wyeast website and they say to pitch a starter with the appropriate amount of yeast and then to get the dissolved O2 up to 10ppm. Their preference was to use pure O2 injection as airstone/splashing etc could only get a max of 8ppm. So to your question I think you need both.

 

[alexbrand]

Well, the bigger the starter is the less you need to areate the wort. If you have 'big enough starter' there's no need anymore to areate the wort prior to pitching.

Isn't that what you're after?

Cheers,

Alex

 

[hockadays]

If you pitch too big a starter though you run into problems from overpitching and thence poor attenuation. Check the wyeast site on yeast and o2 as it explains it pretty well.

 

[kirem]

The reason the winemaker doesn't aerate the entire batch is because he feels the starter is large enough, and the yeast can go straight into anaerobic fermentation.

Oxygen in wine fermentation is an easy hurdle - they just throw SO₂ at it until it isn't a problem anymore. Wine is racked often enough, and sits around in barrels for long enough, that the SO₂ comes out of solution, just like lagering.

The first part is the way we do it. get a 10^8 cell count in the yeast culture then innoculate. We turn approx 80000t of grapes into wine and don't get stuck, sluggish or non-typical fermentations, it would get very expensive, very quickly if we did. It is also the way I make beer, I don't aerate my wort, I aerate my starters and get the correct cell count and then add the correct volume of starter to my wort. I suppose it is the winemaker coming out in me, but I feel that aerating the wort will oxidise aroma and flavour molecules. Perhaps a brewer can explain to me why this wouldn't happen in wort like it does in grape juice.

The second part is wrong. I don't know any winemaker male or female that adds SO2 to a fermentation. It does have a role pre fermentation, but very limited.
SO2 does not come out of solution. you have molecular SO2 (a fraction of the FSO2 and is pH dependent), Free So2 and total SO2. FSO2 is SO2 that is not bound (ie free to scavenge oxygen) and Total SO2 is a combiantion of Free SO2 and bound SO2(already done its job scavenging oxygen). Molecular SO2 is the bomb, it is the antimicrobial form.

We also use ascorbic acid to prevent oxidation in white wine, although you need SO2 to work with it.

I think in your lagering comparison, you are confusing H2S and SO2

Oxygen and SO2 in winemaking can be very simple or extremely complex, depends how far you want to take it. Introduce redox potentials, tannins etc and it gets very complex. Oxygen can be a very good thing in winemaking (especially reds) but it has to be controlled and you have to know exactly what you are doing and trying to achieve.

You mentioned barrels, barrels basically have two functions oak flavour and slow introduction of oxygen into wine, micro oxygen imitates this function in tanks.

these attachments explain it.
View attachment 24727
View attachment 24728

I posted a bit about so-called wild ferments in this thread - http://www.aussiehomebrewer.com/forum/inde...st&p=413784

 

[kirem]

http://www.danstaryeast.com/library/aeration_vs_wort.html

AERATION AND STARTER VERSUS WORT

Can you please comment on the strategy of trying to aerate/oxygenate the yeast while they are in a STARTER rather than aerating the wort itself. (Please let me abuse the language and science a bit and just say that yeast need "a big swallow of oxygen" before they ferment beer.)

I understand that this is exactly your strategy in the production of dry yeast--i.e. dry yeast can be pitched into unaerated wort because they have already taken their big swallow of oxygen. How feasible is it for a homebrewer to grow up a starter in similar fashion? Is continuous aeration of the starter required? A stir plate?

If I have no stir plate, and no gas transfer equipment of any kind, is there a practical procedure I can follow to grow yeast whose oxygen requirements are already met? Letting air into the starter jug and shaking it, repeating this over several days, etc? Any temperature dependency? Any minerals or nutrients I can add to the starter to increase the yeast's efficiency at storing up oxygen-related compounds? Thank you for sharing your expertise.

- Matt


RESPONSES:

Yeast need a trace amount of oxygen in an anaerobic fermentation such as brewing to produce lipids in the cell wall. With out O2 the cell cannot metabolize the squalene to the next step which is a lipid. The lipids make the cell wall elastic and fluid. This allows the mother cell to produce babies, buds, in the early part of the fermentation and keeps the cell wall fluid as the alcohol level increases. With out lipids the cell wall becomes leathery and prevents bud from being formed at the beginning of the fermentation and slows down the sugar from transporting into the cell and prevents the alcohol from transporting out of the cell near the end of the fermentation. The alcohol level builds up inside the cell and becomes toxic then deadly.

Lallemand packs the maximum amount of lipids into the cell wall that is possible during the aerobic production of the yeast at the factory. When you inoculate this yeast into a starter or into the mash, the yeast can double about three time before it runs out of lipids and the growth will stop. There is about 5% lipids in the dry yeast.

In a very general view:

At each doubling it will split the lipids with out making more lipids (no O2). The first split leaves 2.5% for each daughter cell. The second split leaves 1.25% for each daughter cell. The next split leaves 0.63%. This is the low level that stops yeast multiplication. Unless you add O2 the reproduction will stop.

When you produce 3-5% alcohol beer this is no problem. It is when you produce higher alcohol beer or inoculate at a lower rate, that you need to add O2 to produce more yeast and for alcohol tolerance near the end of fermentation. You definitely need added O2 when you reuse the yeast for the next inoculum.

If you prepare a starter culture you will need added O2. in the starter and perhaps in the main mash as a precaution. You will need to follow the precautions as mentioned above. If the mash is designed to produce 3-5% alcohol you may not need added O2. Brewing above that needs added O2.

Regarding your comment about growing your own yeast that will not need added O2 in the fermenter; The Lallemand yeast factory grows yeast under a different metabolic pathway than you will have in your starter culture. We feed the media to the aerobic fermentation at a rate that will keep the sugar levels below 0.2% at all times to maintain the Pasteur Effect. This builds cell mass with minimum to no alcohol production. As the sugar level rises above 0.2% the Crabtree Effect begins and no matter how much air you feed the fermentation, alcohol + CO2 are the main by-products. Your starter culture will have a much higher level of sugar. You will produce some cell mass but mostly alcohol and CO2 no matter how much air you add by stirrer or bubbles.

Dr. Clayton Cone


As Clayton mentioned oxygen is absolutely necessary to produce biomass. So I would aerate your starter as much as possible (stirrer or an aeration system used in fish tanks.)As nutrients I would add a product like FermaidK or GoFerm who add extra nitrogen, minerals and vitamins which are necessary for biomass production. These nutrients also contain some precursors that are needed for lipid production. The best temperature to build a starter is 20-28 degree Celsius. The higher the temperature the faster you build biomass. If you use higher temperatures (28 C) I would recommend separate the yeast from the media as much as possible (decanting) because at this high temperature you build up a lot of higher alcohols and esters which you don't want in your beer.

If you want to pitch your yeast without aerating the wort you need to prep your yeast in the starter for that. Aerate well so that the yeast can build enough unsaturated fatty acids. There are commercial breweries who aerate the yeast before pitching and not the wort. They believe they can increase the flavor stability of their beer this way.

Tobias

 

[kirem]

and this one. http://www.fermentarium.com/content/view/254/58/
Should you put olive oil in your homebrew? E-mail
Written by DJ Spiess
Monday, 29 September 2008


There are many things you can add to your homebrew, but the most interesting addition might be olive oil. It sounds crazy, but does it make any sense?
Why use olive oil in your homebrew?
Your yeast need oxygen for a happy and healthy fermentation. Yeast use oxygen during the lag phase to synthesize sterols and unsaturated fatty acids for its cell walls. If there is not enough oxygen, the yeast can not grow and die off early. Low oxygen leads to stalled fermentations and off-flavors. This is the reason you need to shake the carboy before pitching your yeast.



The problem is with too much oxygen your wort can become oxidized. An oxidized beer will taste like cardboard ass (or sherry but not in a good way). Any time you add oxygen to your beer, you run the risk of some oxidation. The olive oil solution is an attempt to avoid oxidation.

So why would you add olive oil? The idea behind olive oil is instead of giving the yeast oxygen to manufacture the unsaturated fatty acids, give the yeast an unsaturated fatty acid. Your wort doesnt get oxidized and your yeast get what they need for their growth.

* Oxygen is used by yeast to synthesize sterols and unsaturated fatty acids for its cell walls
* Ale yeasts need about 5 parts oxygen per million in wort, while lagers can need 10 to 12 parts oxygen per million.
* Olive oil gives yeast the compounds synthesized for cell wall construction


Where did this crazy idea come from?
Adding unsaturated fatty acids like linoleic acid to wort was attempted in several studies, but in 2005 Grady Hull, with the help of New Belgium Brewery, decided to try using olive oil. Olive oil was chosen because it is much more readily available and olive oil contains the same unsaturated fatty acid beer yeast produce. Linoleic acid is not naturally produced by yeast. It would seem olive oil was the perfect choice.

* The olive oil experiment was in a 2005 thesis by Grady Hull
* The experiment was conducted at New Belgium Brewery in Fort Collins, Colorado


With the help of New Belgium, brewers tested adding olive oil to beer.
With the help of New Belgium, brewers tested adding olive oil to beer.


How well did it work?
The experiment worked quite well for Grady Hulls goals. The original goal was to compare the effects of adding olive oil to storage yeast vs. traditional wort aeration. They found they could achieve similar results in the final product using olive oil. The paper did note ester production was higher than the traditional aeration beer, but the additional esters were within production limits; in fact the flavor panel at New Belgium preferred the higher ester flavored beer. They also found the fermentation times were slower.

The New Belgian Brewery was also looking to increase shelf life for their beers. Less oxygen means they can keep their beers on the shelf longer. Hull reported increased flavor stability in the olive oil beer. Based on the goals set out by Hull, the experiment seemed to hit a home run for macro breweries, but the question everyone wanted to know still remains. How well would olive oil work on my homebrew? No one really knows yet.

* The olive oil beer produced more esters and took longer to ferment - both were still within accepted norms


How much olive oil do I use in my homebrew?
In the study, Hull added olive oil based on the total number of cells. He didnt list actual volumes in the paper because there can be variations in yeast slurry thickness. In the first trial they added 1 mg of olive oil per 67 billion cells pitched into 360 hl of wort, and the final trial they added 1 mg per 25 billion cells pitched into 2100 hl of wort.

So how much olive oil is this on a homebrew scale? Going by their numbers you would need about 0.036 ml for a 5 gallon batch. In short, less than a drop. Probably not even that much. Most brewers adding olive oil in their homebrew are sticking a pin tip into olive oil and rinsing it into their wort. Even this small amount is likely too much if the numbers are correct.

Is this the secret ingredient for your next beer?
Is this the secret ingredient for your next beer?


The study's authors added their olive oil to the yeast slurry about 5 hours before use. To do this at home, you need to add the olive oil to your yeast starter.

* Use the tip of a pin to get a small drop of olive oil
* Add the olive oil to your starter


Questions left unanswered
The first question I had after reading the thesis is: would this work for lagers? The study reported higher esters in each of their trials, but since they were making Belgian ale the esters were desired. In the case of a lager, you do not want increased ester production. This technique would be good for big beers or ales where esters are expected, but I have to question how well it will work in lagers.

Many homebrewers in brewing forums using this method and claim wild fermentations, wonderful beers, etc but unfortunately this is anecdotal evidence. The study at New Belgian Brewery claimed their olive oil fermentations actually took 20% longer than normal fermentations. If this is accurate, your fermentation at home should be slower not faster. It would be interesting to devise an experiment to try at home to see how well this scales to homebrew breweries. If youve tried this before, let me know how well it worked for you in the comments below.

* Interesting idea, but it needs more experimentation for home use
* Increased esters might be bad for a lager

 

[hoohaaman]

I have given up on wort aeration,I instead spend my time on cell count and health in the starters .After the extra drama and extra chance of contamination associated with wort aeration,I have found no difference in either attenuation or taste.

There was a article mentioned in a thread in the last 8 weeks, regarding tests done on none aeration of wort and o2 uptake of yeast for healthy fermentation.Interesting read.

I know this is not accepted practice,but works for me.However I always pitch well aerated large starters

Info posted above while procrastinating

 

[jonocarroll]

Yes, I meant H₂S. My bad on that one. I don't make wine myself, but I'm part of a 'Winemakers & Brewers Club' so I hear a lot of talk. As for oxidation when aerating wort... that's part of the motivation behind my question. Seems like aerating the starter is the way to go then pitching that at high krausen (or whenever one prefers), perhaps without the oxidised 'beer' on top, to let the anaerobic ferment go ahead strong.

On a slight side note - to the people who use a stir-plate with their starters; the reason for stirring is to keep the yeast in suspension and to continually introduce O₂ while allowing CO₂ to escape, yes? If the starter is sealed, how does more O₂ get in? Not saying it doesn't, just asking.

Edit: Just saw your second reply... Now that's an answer! Noice. Cheers & Beers!

Edit: Just saw your third reply. You know that all my future questions are coming your way from now on, right? I have heard of that method, but not the paper. I'm not sure I'm willing to be the guinea pig brewer, but it sounds like it's worth a go. I'll stick with aerating a starter for now. Cheers!!!

 

[THE DRUNK ARAB]

and this one. http://www.fermentarium.com/content/view/254/58/
Should you put olive oil in your homebrew? E-mail
Written by DJ Spiess
Monday, 29 September 2008


There are many things you can add to your homebrew, but the most interesting addition might be olive oil. It sounds crazy, but does it make any sense?
Why use olive oil in your homebrew?
Your yeast need oxygen for a happy and healthy fermentation. Yeast use oxygen during the lag phase to synthesize sterols and unsaturated fatty acids for its cell walls. If there is not enough oxygen, the yeast can not grow and die off early. Low oxygen leads to stalled fermentations and off-flavors. This is the reason you need to shake the carboy before pitching your yeast.



The problem is with too much oxygen your wort can become oxidized. An oxidized beer will taste like cardboard ass (or sherry but not in a good way). Any time you add oxygen to your beer, you run the risk of some oxidation. The olive oil solution is an attempt to avoid oxidation.

So why would you add olive oil? The idea behind olive oil is instead of giving the yeast oxygen to manufacture the unsaturated fatty acids, give the yeast an unsaturated fatty acid. Your wort doesnt get oxidized and your yeast get what they need for their growth.

* Oxygen is used by yeast to synthesize sterols and unsaturated fatty acids for its cell walls
* Ale yeasts need about 5 parts oxygen per million in wort, while lagers can need 10 to 12 parts oxygen per million.
* Olive oil gives yeast the compounds synthesized for cell wall construction


Where did this crazy idea come from?
Adding unsaturated fatty acids like linoleic acid to wort was attempted in several studies, but in 2005 Grady Hull, with the help of New Belgium Brewery, decided to try using olive oil. Olive oil was chosen because it is much more readily available and olive oil contains the same unsaturated fatty acid beer yeast produce. Linoleic acid is not naturally produced by yeast. It would seem olive oil was the perfect choice.

* The olive oil experiment was in a 2005 thesis by Grady Hull
* The experiment was conducted at New Belgium Brewery in Fort Collins, Colorado


With the help of New Belgium, brewers tested adding olive oil to beer.
With the help of New Belgium, brewers tested adding olive oil to beer.


How well did it work?
The experiment worked quite well for Grady Hulls goals. The original goal was to compare the effects of adding olive oil to storage yeast vs. traditional wort aeration. They found they could achieve similar results in the final product using olive oil. The paper did note ester production was higher than the traditional aeration beer, but the additional esters were within production limits; in fact the flavor panel at New Belgium preferred the higher ester flavored beer. They also found the fermentation times were slower.

The New Belgian Brewery was also looking to increase shelf life for their beers. Less oxygen means they can keep their beers on the shelf longer. Hull reported increased flavor stability in the olive oil beer. Based on the goals set out by Hull, the experiment seemed to hit a home run for macro breweries, but the question everyone wanted to know still remains. How well would olive oil work on my homebrew? No one really knows yet.

* The olive oil beer produced more esters and took longer to ferment - both were still within accepted norms


How much olive oil do I use in my homebrew?
In the study, Hull added olive oil based on the total number of cells. He didnt list actual volumes in the paper because there can be variations in yeast slurry thickness. In the first trial they added 1 mg of olive oil per 67 billion cells pitched into 360 hl of wort, and the final trial they added 1 mg per 25 billion cells pitched into 2100 hl of wort.

So how much olive oil is this on a homebrew scale? Going by their numbers you would need about 0.036 ml for a 5 gallon batch. In short, less than a drop. Probably not even that much. Most brewers adding olive oil in their homebrew are sticking a pin tip into olive oil and rinsing it into their wort. Even this small amount is likely too much if the numbers are correct.

Is this the secret ingredient for your next beer?
Is this the secret ingredient for your next beer?


The study's authors added their olive oil to the yeast slurry about 5 hours before use. To do this at home, you need to add the olive oil to your yeast starter.

* Use the tip of a pin to get a small drop of olive oil
* Add the olive oil to your starter


Questions left unanswered
The first question I had after reading the thesis is: would this work for lagers? The study reported higher esters in each of their trials, but since they were making Belgian ale the esters were desired. In the case of a lager, you do not want increased ester production. This technique would be good for big beers or ales where esters are expected, but I have to question how well it will work in lagers.

Many homebrewers in brewing forums using this method and claim wild fermentations, wonderful beers, etc but unfortunately this is anecdotal evidence. The study at New Belgian Brewery claimed their olive oil fermentations actually took 20% longer than normal fermentations. If this is accurate, your fermentation at home should be slower not faster. It would be interesting to devise an experiment to try at home to see how well this scales to homebrew breweries. If youve tried this before, let me know how well it worked for you in the comments below.

* Interesting idea, but it needs more experimentation for home use
* Increased esters might be bad for a lager

That was a great read Kirk, thanks!

C&B
TDA

 

[kirem]

I don't make wine myself, but I'm part of a 'Winemakers & Brewers Club' so I hear a lot of talk.

good old ANAWBS?

I also hear a lot of talk. I suppose everyone has their own way of doing things and if it works for them and they get the desired result then great. I would be interested to hear from thirsty_boy or DiG on this and the reason why aerating wort doesn't oxidise the same way as it does in grape juice.

 

[jonocarroll]

good old ANAWBS?

Nope.

Close, but not quite. Actually not close at all, just containing a lot of entrants, judges, stewards, and a RussTaylor.

 

[buttersd70]

QB
You thought some of my answers were long. :lol:
But understandable when you think of the complexity of yeast......Brewing Science and Practice, for example, dedicates 3 out of 23 chapters, just to yeast...Chapter 12, particularly 12.6-12.7 (and its subsequent subchapters) contain your answer in a bit more detail, which kirem has summarised very nicely indeed, from alternative sources.

 

[jonocarroll]

QB
You thought some of my answers were long. :lol:
But understandable when you think of the complexity of yeast......Brewing Science and Practice, for example, dedicates 3 out of 23 chapters, just to yeast...Chapter 12, particularly 12.6-12.7 (and its subsequent subchapters) contain your answer in a bit more detail, which kirem has summarised very nicely indeed, from alternative sources.

If I so much as open that book, it will be the end of me for weeks :nerdyicon:

One day we're all going to have to find out the rest of this 'scumbag' story from your sig. One day.

 

[hoppinmad]

To let you know of my history... I am actually a Winemaker and coincidently did one year at Jim Barry Wines (Clare Valley) in 2002. Now to answer your question about aeration of "must"... the answer is that it is not neccessary. Modern wine yeast is manafactured under highly aerobic conditions and when freeze dried have a very large concentration of O2 inside and between the individual yeast cells. Obviously it is important to get a good starter going to adapt them to the temperature and pH of the juice, but this is not oxygen related at all. The usual rate used is between 250-300mg/L

As far as wild yeast goes, well you'll find that once a winery has been using cultured yeasts for a while, it is all over the cealings, floors, walls etc.... and any uninoculated ferments are not really "wild yeasts"... just cultured yeasts that find there way into a vat of juice without being invited.

I'm not sure exactly how beer yeast is made... so to be on the safe side I do splash my wort around a bit. But as far as wine is concerned... introducing oxygen is not necessary with our yeast strains

 

[Thirsty Boy]

Actually, no one has mentioned (unless I missed it) the main reason why winemakers don't aerate the must while brewers do aerate the wort -

boiling

must isn't boiled and wort is - which drives out all the dissolved oxygen. Must has a lot more oxygen than wort in the first place. O2 does oxidize compounds in wort as it does in must.... its just that there is a lot less of it and its only "put" there just prior to inoculation when it will be fairly quickly taken up by the yeast.

you only need 3-5 generations of growth to give the appropriate flavour profile in beer ... a dried yeast has enough internal juice for about 3-4 generations of growth, so thats why the above quoted article says that with a lower ABV beer, you dont need aeration... less growth required for the cell count needed in a low abv beer. More in a high abv beer and you will require extra 02

I have no idea of the DO levels of a wine must... but it has to be more than the virtually zero in a post boil wort, that extra DO may well be the difference between the needed growth for a wine yeast and the actual pitching rates. From crush to pitch however.. I suspect the DO levels in a must are high vs wort and there would be a much higher level of oxidation (given the time) in a must vs a wort that spends 1 hr max between oxygenation and yeast pitching. Guesses only....

My take on it is (and I readily stand to be corrected by actual wine makers AND brewers like kirem and HoppinMad) is that the pitching rates in wine are lower than in beer, because the yeast characteristics play a much bigger part in wine flavour profiles that they do in beer. In beer, yeast characteristics are important... but in most styles it is a very subtle difference between the yeast being an important sub character to the malt and hops, and it dominating unpleasantly. Winemakers do a LOT more with their fermentation control than brewers do to manipulate things beyond just pitching rates. If it was just pitching rates and strain characteristics... I could be a wine maker, and I know bloody well that I couldn't.

Brewers on the other hand need to grow their yeast in a medium that is essentially oxygen depleted -- and the healthiest yeast you can get... has 3-4 generations of growth in it before it needs external oxygen. Do your research - if you are fairly sure that you need 3 generations or less of yeast growth in your beer, you don't need 02. If you are brewing a bigger that 3% abv....... well maybe you do.

There is also the fact that brewer re-pitch - and under oxygenation is a MUCH bigger issue if you are re-using your yeast. It's still very important for single generation brewers, but vital for re-pitchers.

I admit, most of my assurance that oxygen addition is vital to beer making, comes from commercial practice. Perhaps if you use dry yeast and are making a low abv beer you don't need it - perhaps if you use olive oil in the starter (a promising experimental technique) you don't need it - but in a more than 3% av beer, in which you would like to pitch a beer where your number of generations of growth will give you a "normal"sort of flavour profile for the beer you are making---- the standard technique of oxygenating your wort is probably your best bet.

There are a shit load of subtleties - and I truly think that beer makers have a lot to learn about yeast from winemakers. But that stuff is at the experimental edge ... way beyond my knowledge. If you are looking to make a more "standard" beer, and standard beer is what I know: then get some oxygen into your wort. Its a playing for the center of the fairway thing ---O2 will not hurt your beer and will probably help it - lack of 02 might not hurt your beer and might well actually hurt it.

If I were betting a $100 on the outcome.. I know which horse I would choose

I'm simply making some of the case for oxygenation of wort here - I don't pretend that I am 100% right, and I certainly don't pretend more yeast knowhow than the winemakers. But there are reasons why the brewing tradition adds oxygen to wort and wine tradition doesn't - those reasons are very challengeable, but its going to have to be a pretty solid challenge.

TB

over to dig for properly educated answer....

 

[newguy]

Hmm... Perhaps I didn't make clear enough the level of answer I'm after - I get the aerobic reproduction phase. I understand the role of oxygen here. I'm curious to know whether or not people who make a starter still do something to aerate their wort, or if they just pitch a sufficient starter and begin the anaerobic phase.

I give my wort a shot of pure O2; 30 seconds for the first pitch from a starter and 0-15 seconds if repitching onto a yeast cake (depends on the beer) - very high gravity brews usually get more. I've always built up pretty large starters but only relatively recently have I started using O2. I started using O2 because I was getting stuck fermentations even though my lag times after pitching were reasonable (6 - 12 hours). For me, O2 was introduced as a fix to a problem I was consistently having, not because the homebrewing literature said I needed it or because I was worried I was underpitching. Even though I have no way to confirm/count the number of active cells I pitch, I'm pretty sure it's in the proper ballpark.

 

[kirem]

Actually, no one has mentioned (unless I missed it) the main reason why winemakers don't aerate the must while brewers do aerate the wort -

boiling

must isn't boiled and wort is - which drives out all the dissolved oxygen. Must has a lot more oxygen than wort in the first place. O2 does oxidize compounds in wort as it does in must.... its just that there is a lot less of it and its only "put" there just prior to inoculation when it will be fairly quickly taken up by the yeast.

Doh. Bloody obvious. :lol: I'll get a DO on some red coming in today and some white tomorrow. We do put SO2 in the picking bins of most varieties, so that will reduce the DO and we will see to what level.