How To Keep Bananas From Turning Brown While Baking
When it comes to sliced fruit, it seems bananas turn brown more quickly than other kinds. When sliced bananas are exposed to air, there's an enzymatic reaction that occurs, causing them to turn brown (via Leaf). The reaction creates melanin, which appears brown, and the longer the bananas are exposed to air, the darker they become. Though this isn't a problem of safety or even appearance, if you can't see the bananas, it's certainly one you want to avoid if you're presenting a dessert to a crowd.
While you can simply slice bananas to top a room-temperature dessert right before serving it, that isn't the case for baked banana desserts. If you are baking a banana pie, for example, you will need to know another trick or two to keep the bananas from browning while baking and being exposed to the air. Fortunately, there are a few ways you can keep the bananas from turning. This will also make the dessert look a lot more appetizing when it is time to serve it.
Tips for keeping bananas from browning
One method for keeping bananas from turning brown is to use bananas that are just the right amount of ripe (via My Recipes). You should select and use bananas that are firm and just ripe enough. Those that are too ripe will brown more quickly. Stay away from under-ripe bananas, though.
Another method is to cover the bananas in the dessert. So, if possible, cover the sliced bananas with a layer of pie filling or even meringue for a baked banana dessert. This should help keep the bananas from changing color, but it can also hide any darker spots too.
Finally, you can treat the slices of bananas with an acidic juice such as lemon, orange, or pineapple juice to keep them from browning. Keep in mind that you want to use as little as possible to avoid altering the pie's flavor. You shouldn't be able to taste the flavor of juice when eating the banana dessert. To do this, you can use a clean spray bottle to mist the slices with juice or you could use a pastry brush to lightly brush it onto the slices. Whatever method you choose, use a light hand.