This oxidation can be prevented, or at least slowed to a crawl, with several methods. Immersion in water, sealing in an air tight container, or wrapping in plastic helps keep the air away. One of the most recommended (and tastiest, if you ask me) methods is using some kind of citrus juice. Lemon, lime, or orange juice can add a nice flavor note in some dishes. This works great for apples and avocados.
I used to pour a bunch of lemon juice over my apples and (poorly) gauge the amount to "lightly" coat all the slices. That never worked terribly well, and I'd end up with slightly soggy (though still tasty) apples. Not so bad in a pie, but a bit messy for snacking.
Then I got the bright idea of putting the lemon juice in a spray bottle. Fortunately, I could cheaply find a wide array in the "aisle of tiny, pretentious travel bottles." You know the one. They're everywhere.
The spray bottle is a perfect delivery vehicle for a light misting of juice. Just enough to fend off the icky browning. Fight science with science! It works nicely for a kick to your salad greens as well. I imagine it would work for oils and vinaigrettes as well(no more buying aerosol cooking sprays!), though you might have to find the right bottle to prevent clogging.
