You could, I usually leave the tin foil on the flasks and jars, but you could put a lid on it. Just spray Starsan on and around the foil liberally before removing it and spray the opening and neck after. Then recap.
I also use 1/2 gallon pickle jars, they have the twist-off lids and make a darn good seal for longer storage. Great for making starters in.
Beware, if you store yeast in the fridge for long periods of time. I've had a few Mason jars where the lid (under the ring/band) had bulged or even contorted to let the pressure out. Even at 36-38°F there can still be some activity.
What I also discovered is that the thin kitchen quality aluminum foil used as caps develops dozens of pin holes, as quickly as in 1 day, worse over time. Hold it up to a light. I assume it's the Phosphoric acid in Starsan corroding it. I now use "heavy duty" foil, and that remains solid and light tight, even after repeated use.
Now those pinholes can be used in some photographic applications perhaps. It's nearly impossible to make holes that small with mechanical means.
