Carefully inspect your bananas before bringing them home from the store. Instead of automatically picking a ripe bunch of bananas, choose firm or green bunches, giving the fruit ample time to ripen at home. Bananas can develop brown spots overnight if brought home when too ripe.
Immediately after cutting the bananas, dribble a small amount of lemon or orange juice over the slices. The acidic quality in the juice slows down the browning of the banana. The juice preserves the banana but does not alter its taste or texture.
To prevent the rapid browning of cut bananas, you may also place the slices in a bowl of cold water before refrigerating them. For added measure, crumble vitamin C capsules into the bowl. Vitamin C, a major ingredient in citric acids like lemon and orange juice, slows down the browning process as well.
After cutting the bananas, place the fruit slices in plastic wrap. Tightly secure the slices in the plastic, making certain air cannot enter and thus preventing oxygen from reaching and browning the fruit. For added measure, you can spray the slices with lemon juice and place them in the refrigerator.