Why does foil work better than air lock on starter?

[traviswalken]

I know that benefit of using foil vs. an air lock is that o2 is allowed into the Erlenmeyer. However, it seems like the Co2 produced by the yeast would produce positive pressure in the flask. It doesn't seem like much O2 would really make it into the flask.

I don't have a stir plate, but I swirl my Erlenmeyer many times while the starter does its work. I just wonder if I am really accomplishing anything.

 

[Facinerous]

Of course your accomplishing something. If you fiddle with it, it always works better. Right?

 

[Facinerous]

Sorry for only a smart ass remark. I had to look up aerobic fermentation really quick to make sure I had my facts right.

Apparently yeast produce more co2 during their aerobic respiration than anaerobic. Which I had totally forgotten. So I guess the biggest reason to shake the little guys up is to keep them in suspension.

 

[helibrewer]

I know that benefit of using foil vs. an air lock is that o2 is allowed into the Erlenmeyer. However, it seems like the Co2 produced by the yeast would produce positive pressure in the flask. It doesn't seem like much O2 would really make it into the flask.

I don't have a stir plate, but I swirl my Erlenmeyer many times while the starter does its work. I just wonder if I am really accomplishing anything.

I use an airlock. I also infuse with pure O2, so that combined with CO2 production negates the "let air in" methodology for me. The real benefit is a stir bar keeping the yeast in suspension.