Kegconnection Complete Starter Kit and More Giveaway!


Home Brew Forums > Home Brewing Beer > Brew Science > Purpose of wort oxygenation

Reply
 
LinkBack Thread Tools
Old 04-25-2011, 05:48 AM   #11
terrencepickles
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2010
Location: Las Vegas
Posts: 55
Default

Quote:
Originally Posted by HItransplant View Post
mmmmm... bioreactor... eeeexxcellent (wrings hands together sinisterly)


so does the mrmalty pitching calculator take into consideration aerated vs. non-aerated wort?
No. You should always aerate your wort before pitching.

From How to Brew by John Palmer

Quote:
Originally Posted by howtobrew.com
Chapter 8.1.3 - Temperature Factors

8.2.1 Lagtime or Adaptation Phase

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.
Source: http://howtobrew.com/section1/chapter8-2-1.html
__________________
terrencepickles is offline
 
Reply With Quote Quick reply to this message
Old 04-25-2011, 06:09 AM   #12
HItransplant
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2010
Location: Portlandia
Posts: 1,030
Liked 6 Times on 5 Posts
Likes Given: 6

Default

Quote:
Originally Posted by terrencepickles View Post
No. You should always aerate your wort before pitching.

From How to Brew by John Palmer



Source: http://howtobrew.com/section1/chapter8-2-1.html
now that makes sense.. so you want another generation of yeast once pitched because it is better suited to the actual wort you want it to ferment (as opposed to the starter wort).

am I understanding this?
__________________
Quote:
Originally Posted by BlindLemonLars View Post
It's comfort foam. :D
Quote:
Originally Posted by EdWort View Post
It's a gentle recipe, so your first time will be enjoyable and memorable. :D
HItransplant is offline
 
Reply With Quote Quick reply to this message
Old 04-25-2011, 03:28 PM   #13
Saccharomyces
Be good to your yeast...
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
Saccharomyces's Avatar
Recipes 
 
Join Date: Jun 2008
Location: Pflugerville, Texas
Posts: 5,443
Liked 78 Times on 52 Posts
Likes Given: 2

Default

Yes, you could pitch enough yeast that the cells would not need to grow to ferment the wort. What would most likely occur, would be yeast autolysis, and an undrinkable beer, because some yeast growth will occur anyway, and a given wort can only provide enough nutrients for a limited population of yeast.

Ideally, you want each cell pitched to bud 2-3 times, which means you need enough sterols for the yeast to be able to bud that many times, and enough nutrients available (yeast available nitrogen) for the cells to synthesize enough proteins to produce the ideal number of offspring. Yeast cannot produce sterols without O2 present in the wort.

Higher gravity fermentations benefit from the introduction of O2 in stages during the growth phase, so that yeast cells which have already budded can replenish the sterols they gave up to their daughter cells. This keeps the cell walls flexible, and thicker, allowing the yeast to counter the higher osmotic pressure from the remaining wort sugars, as well as higher ethanol concentrations later on. In other words, O2 will help the yeast ferment to a higher %ABV.

__________________
[How to Calculate Mash Efficiency | Do I Need a Yeast Starter? | My Ghetto Fermentation Chamber | Twitter | 6 Gal. HDPE Fermenters | Slanting Yeast | No Sparge Brewing]

Quote:
Originally Posted by Soperbrew
big brother only monitors facebook and untappd
Saccharomyces is offline
 
Reply With Quote Quick reply to this message
Old 04-25-2011, 03:35 PM   #14
HItransplant
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2010
Location: Portlandia
Posts: 1,030
Liked 6 Times on 5 Posts
Likes Given: 6

Default

Quote:
Originally Posted by Saccharomyces View Post
Yes, you could pitch enough yeast that the cells would not need to grow to ferment the wort. What would most likely occur, would be yeast autolysis, and an undrinkable beer, because some yeast growth will occur anyway, and a given wort can only provide enough nutrients for a limited population of yeast.

Ideally, you want each cell pitched to bud 2-3 times, which means you need enough sterols for the yeast to be able to bud that many times, and enough nutrients available (yeast available nitrogen) for the cells to synthesize enough proteins to produce the ideal number of offspring. Yeast cannot produce sterols without O2 present in the wort.

Higher gravity fermentations benefit from the introduction of O2 in stages during the growth phase, so that yeast cells which have already budded can replenish the sterols they gave up to their daughter cells. This keeps the cell walls flexible, and thicker, allowing the yeast to counter the higher osmotic pressure from the remaining wort sugars, as well as higher ethanol concentrations later on. In other words, O2 will help the yeast ferment to a higher %ABV.
I see... does this also explain why we dont want to overpitch

thanks for the thorough education. I plan on picking up "yeast," will I learn more about this from reading it?
__________________
Quote:
Originally Posted by BlindLemonLars View Post
It's comfort foam. :D
Quote:
Originally Posted by EdWort View Post
It's a gentle recipe, so your first time will be enjoyable and memorable. :D
HItransplant is offline
 
Reply With Quote Quick reply to this message
Old 04-25-2011, 03:43 PM   #15
Saccharomyces
Be good to your yeast...
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
Saccharomyces's Avatar
Recipes 
 
Join Date: Jun 2008
Location: Pflugerville, Texas
Posts: 5,443
Liked 78 Times on 52 Posts
Likes Given: 2

Default

Quote:
Originally Posted by HItransplant View Post
thanks for the thorough education. I plan on picking up "yeast," will I learn more about this from reading it?
The "Yeast" book is definitely an excellent resource. I also recommend reading anything you can find online from Dr. Raines, she is a microbiologist who really knows how to write well.

http://www.maltosefalcons.com/tech/y...-and-practices
__________________
[How to Calculate Mash Efficiency | Do I Need a Yeast Starter? | My Ghetto Fermentation Chamber | Twitter | 6 Gal. HDPE Fermenters | Slanting Yeast | No Sparge Brewing]

Quote:
Originally Posted by Soperbrew
big brother only monitors facebook and untappd
Saccharomyces is offline
 
Reply With Quote Quick reply to this message
Old 04-25-2011, 03:45 PM   #16
giligson
Feedback Score: 0 reviews
Recipes 
 
Join Date: Oct 2008
Location: Vancouver Area - Canada
Posts: 755
Liked 4 Times on 4 Posts
Likes Given: 1

Default

Quote:
Originally Posted by HItransplant View Post
now that makes sense.. so you want another generation of yeast once pitched because it is better suited to the actual wort you want it to ferment (as opposed to the starter wort).

am I understanding this?
With all due respect to Palmer,
His text is an excellent one for the beginner and intermediate brewer but for the sake of clarity and brevity he is forced to simplify a number of technical points.

I would be grateful if you could quote a primary source who shows that oxygenation during growth of pitching yeast gives inferior results to oxygenation of the bulk wort. However I don't feel that assertion is true. There is no plausible mechanism for wort oxygenation to be a superior approach.

The yeast does not have to "adapt" to the wort in which it is fermenting if it is already in log phase. The statement presumes the use of dormant yeast which the brewer may be using from a dry pack or from a smack pack.

Not to pick nits but I just want to make it clear that a cell with an ideal plasma membrane can easily do 3-4 generations before running into trouble with autolysis. Given an ideal large population of yeast cells, the wort would not require oxygenation.
__________________

We who are about to Brew, salute you!

giligson is offline
 
Reply With Quote Quick reply to this message
Old 04-25-2011, 04:08 PM   #17
theredben
Feedback Score: 0 reviews
Recipes 
 
Join Date: Dec 2010
Location: Langley, BC
Posts: 934
Liked 23 Times on 22 Posts
Likes Given: 9

Default

If you over-pitch (somewhere around final amount of yeast), and not a "normal sized" starter, you will not need the yeast to reproduce. This lack of reproduction will change the amounts of yeast by-products and metabolites produced. For some beers this would be a benefit, but for most I would say that would be detrimental.

I would not say that any one method is better than another, but it seems that if you are looking for yeast flavours while saving money at the same time, then the normal rates of 1million cells/*P and 8-12 ppm O2 is a good compromise. You can use a larger starter, but it requires more expense in materials/flasks and only saves you the expense of either some elbow grease (pouring between buckets) or an aquarium pump and a sterile filter. You can go with a lower pitch rate (lots of new brewers seem to think that the Wyeast "propogator" packs are ready to pitch), but you risk a stuck fermentation and under-pitching off-flavours.

I guess what I am trying to say is that the pitching/oxygenation rates are not theoretically derived, they are based on observations of flavours and fermentation characteristics. If you feel that your recipe requires the use of a different set of pitching/oxygenation rates then go for it! That is the beauty of homebrewing. You get to try and outsmart what all of the commercial resources say is the "best" way of doing things. That is what science is after all!

__________________
theredben is offline
 
Reply With Quote Quick reply to this message
Old 04-25-2011, 04:50 PM   #18
Golddiggie
Feedback Score: 1 reviews
Recipes 
 
Join Date: Dec 2010
Location: Between here and there, and everywhere
Posts: 12,057
Liked 473 Times on 418 Posts
Likes Given: 266

Default

Most of us use the 'Activator' pack from Wyeast since that CAN be pitched directly without issue (depending on the wort OG). Propigator packs say to use a starter beforw pitching into a brew.

I picked up an O2 system from Williams Brewing and have used it on two batches so far. I plan to continue to use it and see how the brews come out with it in the mix. Since you can only get above 8ppm of O2 with actual O2 it means I have a more capable oxygenation system.

__________________
Hopping Tango Brewery

跟猴子比丟屎 ・ Gun HOE-tze bee DIO-se

On Tap: Caramel Ale, Mocha Porter II, MO SMaSH IPA
Waiting/Carbonating: 12.5% Wee Honey II, 8.9% Old Ale, English Brown Ale, Lickah ESB, Mocha Porter II
Fermenting
K1:
K2: Epic mead
K3: TripSix
On Deck: Caramel Ale
Aging:mead
Mead [bottled]:Oaked Wildflower Traditional, Mocha Madness, Blackberry Melomel, maple wine
Golddiggie is offline
 
Reply With Quote Quick reply to this message
Old 04-25-2011, 06:59 PM   #19
giligson
Feedback Score: 0 reviews
Recipes 
 
Join Date: Oct 2008
Location: Vancouver Area - Canada
Posts: 755
Liked 4 Times on 4 Posts
Likes Given: 1

Default

Quote:
Originally Posted by theredben View Post
If you over-pitch (somewhere around final amount of yeast), and not a "normal sized" starter, you will not need the yeast to reproduce. This lack of reproduction will change the amounts of yeast by-products and metabolites produced.....
Point taken. And I agree that your product will vary based on which path you take. I just wanted to get the point across that there was nothing particularly magical in putting oxygen directly into the wort (Hey that's what I do when I homebrew). But, oxygen is very important at some stage in the yeast lifecycle for them to build the structures they need to survive and thrive.

Let's face it, most historical brews before the end of the industrial revolution did not utilize oxygenated wort. Some brewers would add air during the first few days of fermentation (some British Ale breweries).

PS I note you are in Langley. Do you ever get out to a Vanbrewer's Meeting?
__________________

We who are about to Brew, salute you!

giligson is offline
 
Reply With Quote Quick reply to this message
Old 04-25-2011, 10:25 PM   #20
coryforsenate
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jul 2009
Location: College Station, TX
Posts: 327
Liked 4 Times on 4 Posts
Likes Given: 2

Default

The big daddy is ergosterol biosynthesis, which has multiple enzymatic steps that require oxygen.

__________________
Bottled
Merlot Barrel Russian Imperial Stout
Vanilla Belgian Stout
Hefeweizen
Hard Cider
Tripel w/wine tannins
Weizenbock


Primary
Dark Strong
Tripel
coryforsenate is offline
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
oxygenation formula DakotaPrerunner Brew Science 10 11-04-2010 03:55 AM
Wort and Beer pH Mateo Brew Science 14 09-16-2010 09:58 PM
Purpose of the boil after mashing? robertbartsch Brew Science 16 08-01-2010 05:20 PM
pH stability of wort BuzzCraft Brew Science 3 02-23-2010 09:51 PM
Purpose of lagering? brewmonger Brew Science 16 03-07-2009 04:01 PM