Add additional oxygen to starter? - Home Brew Forums
Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > Add additional oxygen to starter?

Reply
 
Thread Tools
Old 12-03-2011, 01:18 AM   #1
bessieflames
Recipes 
 
Aug 2011
Denver, CO
Posts: 98



Hey all--longtime lurker, first time poster here. I had a question about making a starter on a stir plate. I added pure O2 through a stone and turned the stir plate on. My question is this: is it beneficial to inject pure O2 a second (or third) time? I am assuming that you want oxygen constantly present in the wort so that the yeasties multiply instead of fermenting and that is the purpose of the stir plate. It seems to me that since CO2 is coming out of solution and it is heavier than air, a stir plate won't be able to bring more O2 into solution other than what it starts with. Thanks in advance for the response.



 
Reply With Quote
Old 12-03-2011, 01:21 AM   #2
MrManifesto
Recipes 
 
Apr 2011
Brooklyn, NY
Posts: 433
Liked 10 Times on 10 Posts


i don't think it's necessary. will it hurt? i doubt it. may be more work than it's worth though.



 
Reply With Quote
Old 12-03-2011, 01:21 AM   #3
sudsmcgee
Recipes 
 
May 2010
Western Chicago Burbs, IL
Posts: 1,519
Liked 50 Times on 42 Posts


You only need oxygen during the early phases of yeast growth and development. Once it's bubbling you don't need it anymore. Oxygen is good, but too much will hurt or kill the yeast. Most stir plates don't require pure oxygen. Save your money.

 
Reply With Quote
Old 12-03-2011, 01:32 AM   #4
BBL_Brewer
HBT_SUPPORTER.png
 
BBL_Brewer's Avatar
Recipes 
 
Feb 2011
Kokomo, IN
Posts: 3,704
Liked 439 Times on 302 Posts


I do a shot of O2 whenever I add wort. Other than that I just let it spin with some foil on top.
__________________
Slots Down Brewery
Stick with the plan....not the sparge.


Never Ending Liquid Yeast - How to Farm Yeast and Freeze it.


 
Reply With Quote
Old 12-03-2011, 05:49 AM   #5
bessieflames
Recipes 
 
Aug 2011
Denver, CO
Posts: 98


OK, thanks. It isn't much more effort since I already have the equipment. I had just heard a lot about how a stir plate keeps the wort oxygenated and I didn't see how that was happening. I have been getting good results and high attenuation with the method I am using, so I guess I'll just stick with it. It was more of a question to solidify my understanding than to improve my results. Thanks for all of the responses.

 
Reply With Quote
Old 12-03-2011, 06:33 AM   #6
year2beer
Recipes 
 
Oct 2011
huntsville, alabama
Posts: 135
Liked 3 Times on 3 Posts


I agree... just swish your starter around a bit a couple of times a day, and it will multiply just fine! I did use an airlock on a 5L growler to build my first starter--and never injected oxygen. As long as your fermenter has enough head space, the yeasties will get plenty of O2...

Good luck!

 
Reply With Quote
Old 12-03-2011, 02:06 PM   #7
maxpower76
Recipes 
 
Dec 2010
Scotch Plains, NJ
Posts: 15
Liked 1 Times on 1 Posts


Just to add a little bit of background on why the stirring-- in the starter, oxygen diffuses into the wort at the surface of the wort and not much further than that (oxygen is not very soluble in water based liquid). Stirring with a stir plate does 2 things: mix up the wort making the oxygen more evenly distributed and if you stir hard enough to make a vortex, it increases the surface area exposed resulting in more oxygen diffusion

Hope that made sense...

 
Reply With Quote
Old 12-03-2011, 02:37 PM   #8
Clementine
Recipes 
 
May 2011
Waynesboro, PA
Posts: 545
Liked 12 Times on 12 Posts


I think two points need to be made here before miss information get distributed.

1) While making yeast the cells need O2 to multiply, in normal fermentation (not starters) we add O2 to get the yeast multiplying before they switch from aerobic to anaerobic metabolism making alcohol. Yeast metabolism requires oxygen to survive. When denied O2 it strips oxygen from sugar molecule turning the sugar in to alcohol the anaerobic side of their personality. The easier it is for the yeast the better they grow, and giving them O2 instead of forcing them to find other ways of finding O2 we can just give it to them and make them fat and happy so they will have babies. After all this is the whole point of using foil or foam instead of an air lock.

2) The amount of O2 usually does not require additional O2 being added to the starter but it would not hurt anything. The level of O2 needed to be come toxic is not really possible in a starter (I'm talking about a normal person not someone putting in an O2 turning it on and walking away).

Clem

 
Reply With Quote
Old 12-06-2011, 05:47 PM   #9
bessieflames
Recipes 
 
Aug 2011
Denver, CO
Posts: 98


I get that the stirring is supposed to increase the surface area to allow O2 to get into the wort. I also understand why we need O2 in a starter (and at the beginning in a regular fermentation). Maybe I am missing something, but can someone answer the following question:

On my stir plate, after about 6 hours, there is CO2 coming out of the flask. Even with foil on top instead of an airlock, the CO2 has forced the O2 out because the CO2 is heavier. Oxygen can't enter because it can't "sink" past the CO2. Now the interface is between the wort and the CO2. How does the stir plate help now? It seems to me that once fermentation starts, the stirring allows more surface area between the CO2 and the wort and that there is no oxygen in the headspace of the flask anymore.

 
Reply With Quote
Old 12-07-2011, 12:51 AM   #10
harrydrez
Recipes 
 
Jan 2009
Posts: 441
Liked 36 Times on 21 Posts


Quote:
Originally Posted by bessieflames View Post
On my stir plate, after about 6 hours, there is CO2 coming out of the flask. Even with foil on top instead of an airlock, the CO2 has forced the O2 out because the CO2 is heavier. Oxygen can't enter because it can't "sink" past the CO2. Now the interface is between the wort and the CO2. How does the stir plate help now? It seems to me that once fermentation starts, the stirring allows more surface area between the CO2 and the wort and that there is no oxygen in the headspace of the flask anymore.
It doesn't really work like that; the whole "magic co2 blanket" mantra that seems to be repeated here is something of a myth.

Take two glasses: fill one with water and one with alcohol. Add some red food coloring to the alcohol and then gently pour the alcohol into the glass of water. The same thing happens with gasses in the air.



 
Reply With Quote
Reply
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ran out of Oxygen dmfa200 Fermentation & Yeast 6 06-28-2012 10:13 PM
Help with Oxygen, please Brulosopher Fermentation & Yeast 15 11-23-2011 06:00 AM
Enough oxygen? MG1602 Fermentation & Yeast 7 09-11-2011 01:56 PM
is oxygen necessary when using slurry? martinworswick Fermentation & Yeast 5 12-30-2010 05:38 PM
Too much oxygen acleanthous Fermentation & Yeast 7 05-18-2010 06:42 PM


Forum Jump