Starter Aeration Question

[Facinerous]

So this may seem like a no brainer, but I have to ask.

Here are a few things I understand.

While boiling wort the action of the boil drives oxygen out of the liquid.
Oxygen is one of the biggest factors of producing a proper starter.

So if I were to boil dme in a flask, and cover with aluminum foil at the end of the boil but before the boiling has subsided. Is there oxygen in the air within the flask?

I do not have an air pump, or any other means of aerating the wort right now other than shaking, but a stir plate should help with that which I am using. The only time I removed the aluminum foil from the flask was to dump in the yeast. Then covered promptly. The foil is loosely fitted, so there should be some air transfer. This got me thinking though. Is there really any viable amount of oxygen within the flask to begin with?

I did things this way to maximize my sanitization efforts, but of course this would be utterly counter productive if I have not provided the necessary ingredients for healthy yeast.

What do you think?

I'm not afraid of dumping the starter and giving er a redo.

 

[aslander]

I wouldn't dump it. You didn't say how long it has been since you made it. It you made it within say 24 hours, I would start swirling the starter every time you walk by it. If over 24 hours, it is probably done growing. Use yeastcalculator.com and expect less output if you never shook it.

Either way, I wouldn't dump it. You could always chill, decant, and step it another time if the calculator says you need more cells.

 

[rekoob]

If your using a stir plate then it will take care of itself, meaning if you have a pretty good vortex going it will pull in O2.
turn off the stir plate and let it sit for a bit and see what falls to the bottom.
Using the stir plate I don't "see" any activity and never know if it's really done but it always is, it will finish fast.
As aslander stated you can always step it up again if your worried you don't have enough yeast.

 

[flars]

Your starter is okay. The boiling of the wort only eliminated oxygen from what you were boiling, not the flask itself. Gases in the atmosphere will always seek equilibrium unless we create a barrier for an artificial environment. The oxygen inside the flask that is metabolized by the yeast will be replaced from the atmosphere.
Shaking the flask suspends the yeast and adds air to the wort. A stir plate keeps the yeast suspended with the stirring action and in contact with the oxygen of the atmosphere.

I like this calculator for making starters, especially for stepping up the original starter. The estimated growth rate achieved is very helpful to optimize the size of the starter.
http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/

 

[Facinerous]

Thanks for the vote of confidence everyone. That was pretty much my logic after I had thought about it a bit more. Nice to have a little back up.