Step 3: Keep Banana Slices Fresh
Just toss your banana slices in some lemon juice to inhibit enzymatic browning. Full coverage, particularly on the cut sides, will help prevent the slices from turning brown. In addition to lemon juice, vinegar will also work. So would sulfuric acid, for that matter, but you probably don't want to eat it afterwards.
The acid disrupts the enzymatic breakdown process and prevents your sweet, sweet banana slices from turning into mushy little brown hockey pucks.
A dab'll do ya, so keep your acid in the teaspoon range. Or you'll just have sour bananas.