Battling the Ripening of Bananas

Question from a reader:  "How can I manage to keep ripe but not overripe bananas in my home?  I don't live near a grocery store and can get to one only once a week. I usually wind up with mushy, disgusting-looking bananas that I have to throw out."

My condolences.  I know that bananas can drive you bananas. You may be comforted to know that your query has given my research skills quite a workout. Online, I've found plenty of advice, some of which didn't work for me. Keep in mind this witty comment (often quoted with slight variations) by H.L. Mencken (1880-1956), journalist, satirist, and curmudgeon: "For every complex problem, there is an answer that is clear, simple, and wrong." 

In addition to the online methods for prolonging the edible life of bananas that I tested, this article includes more trustworthy wisdom from four of the scientists who serve on the Shelf Life Advice Advisory Board.

First, I should remind you (and other troubled banana-lovers) about what makes a banana ripen.  Primarily, it's time (a limited amount of it) and the ethylene gas the banana emits.  Therefore, the major emphasis is on attempts to slow down the ethylene effect.  However, (remember Mencken) other factors are involved, especially temperature as the banana is placed in various locations.   

Remember the movie "Oh, God,"?  In that movie, God (played by George Burns) admits to making one mistake: he made the avocado pit too big. Perhaps He/She should have added, "I also made the banana ripen too fast."  Considering the fact that bananas are the most popular fruit in the world, it was a significant mistake. 

At room temperature, how long will a ripened banana last?  Most sources say 3-4 days, no more than 5.  But when should you consider it ripened, and when should you conclude that it's spoiled?  It's ripe when it's all yellow, has a few black spots on the peel (or maybe not), and feels slightly soft to the touch.  It's spoiled when you see split skin and, oozing and smell an unpleasant odor that reminds you of nail polish.  At this point, your banana belongs in the garbage.

An important point: a brown or black banana peel does NOT signal that the banana's flesh is spoiled.  Even if the flesh has some light spots on it, it's safe to eat and probably also still tasty, though these spots signal that spoilage is coming in the near future.  

The average American eats 27 lbs. of bananas a year, says chiquitabananas.com.  I hate to think about how many we throw out because they spoil so quickly. 

So much for background. Now let's move on to the internet advice and my experiments, all designed to reach that one-week goal.  I reveal my results with a touch of humility; they could be flawed due to factors I didn't consider.  I'm not insisting that these internet methods don't work, only that I had little or no success with some of them. Tell me if I'm wrong.

Tip 1: Cut the bunch of bananas apart with a scissors or knife. (Tearing might open the banana, which you don't want to do). Place each banana far from the others.

My results:  A week later, the bananas, all kept at room temperature, all had partially blackened peel, but the fruit inside looked fine. They tasted passable--a bit mealy, but certainly not spoiled.  They were in slightly better shape than the control group in an uncut bunch but not much better.

Tip 2 (a variation of Tip 1):  Cut the banana bunch apart, and then wrap the stem of each banana with plastic wrap. 

My results:  Total failure.  After 1 week, the experimental group and the control group looked exactly the same both times I tested this theory.  I did it twice because the first time I started with ripe (yellow) bananas.  Then, food scientist Dr. Joe Regenstein said this: "I think the bananas need to be relatively green. Once you get some yellow, you've already gotten much of the ethylene reaction." So I did the experiment again, this time with partly green bananas.  (I didn't find any all-green ones in the store that day). Again, failure. The 2 groups looked the same.

Tip 3: Refrigerate a ripe, unpeeled banana (after separating it from the bunch) after you've wrapped it in newspaper. 

My results: This worked! After a week in the fridge, the peel had turned brown, and the flesh displayed a few light spots, but the flesh was firm and tasted delicious.  (I think bananas taste best when they're cold.)  A reader's response to the lifehacker.com article says bananas will keep for up to 2 weeks wrapped in newspaper and refrigerated. My wrapped banana certainly wouldn't have survived a second week.  My unwrapped refrigerated banana did not hold up as well as the wrapped one.  After a week, it was softer, more spotted, and less tasty than the wrapped one.  Of course, the peel was brown. 

If your banana ripens on the counter for a day or two and then remains in good condition after a week of refrigeration, the total time from purchase to spoilage would be not just 7 days but a whopping 9!  So your problem is solved.

Food scientist Dr. Catherine Cutter (and several of my friends) have confirmed that refrigeration does, indeed, extend the edible life of a banana for at least a few days. However, Dr. Cutter points out that some people have a bad reaction to newsprint. Therefore, next time I refrigerate a banana, I'll wrap it in all-white paper toweling.  I'll unwrap it within 3-4 days and perhaps find a spotless banana.

Tip 4: Keep your bananas away from heat and sunlight.

My results: I suppose this happens to many scientists: they discover something they weren't looking for.  When I ran out of kitchen counter space for my banana experiments, I placed some in an unoccupied bedroom.  I discovered that these bananas stayed firmer and were less blackened than the ones I had left in the kitchen, a sunnier and warmer location.

Then, I found an explanation online at sfgate.com.  Here's a paraphrase of this explanation:  During ripening, keep bananas out of sunlight, although the light itself is not the cause of the ripening. The heat from the sunlight is what affects the ripening of the bananas. Leaving bananas to ripen in direct sunlight raises the temperature of the fruit. When the fruit is warmer, it ripens faster, and it may become too soft, too quickly, resulting in bland-flavored fruit. Fruit temperatures higher than 68°F are most likely to speed up ripening if the fruit is exposed to ethylene gas. If stored above 74°F, the fruit's shelf life drops to four days or fewer.

Dr. Karin Allen agrees that temperature is an important factor:  "It helps to store bananas in a cool place.  This usually is not the kitchen.  Bananas do best at temperatures close to 50°F.  If there’s a colder room in the house where the temperature won’t get below this, your bananas may last longest there."  

Tip 5: Don't leave bananas in a closed bag--unless you want to ripen them quickly.  

If you don't want to separate the bunch, at least hang it on a banana tree, which allows circulating air to help reduce the ethylene effect.

Tip 6: Cut down on waste by freezing your extra bananas if you can't consume them before they begin to deteriorate.

Here's good advice from food process engineer Dr. Timothy Bowser: "At our house, bananas normally disappear quickly. When they do turn black, we freeze them to use later for smoothies or banana bread." Dr. Allen makes the same suggestion.

How do you freeze bananas?  Here's one common internet recommendation: Peel them, coat them with something acidic such as diluted lemon juice or pineapple juice.  Wrap them well.  When you defrost them, they'll be mush, but that works fine for recipes.

This is Dr. Bowser's favorite method for freezing a banana: before freezing, peel the banana, trim away any bad spots, and place the rest in a plastic bag.  This is a quick, easy method.

Tip 7: When selecting bananas in the store, follow this advice from Dr. Allen:

"The problem with very green bananas is that they may have been exposed to cold temperatures during shipping.  This has the same bad effect as putting an unripe banana in the fridge.  Those green bananas may never ripen; they’ll just spoil.  I always pick out light yellow bananas with just a hint of green on the ridges of the peel and no brown spots.  Hopefully, these will still ripen, but I'll have at least 3 or 4 days to use them."

My thanks to the reader who raised this stimulating question.  If nothing mentioned above works for you and your doctor has guaranteed that a fresh banana every day will keep you alive to 100, perhaps you should consider moving closer to a grocery store.  

Readers, please share your experiences battling bananas, and tell Shelf Life Advice who's winning, you or the bananas.

To reach more Q/As that answer important questions about bananas, go to this product section. Links to the Q/As are along the right margin.

Source(s):

Karin E. Allen, Ph.D., Utah State University, Dept. of Nutrition, Dietetics, and Food Sciences

Timothy J. Bowser, Ph.D., Oklahoma State University, Dept. of Biosystems and Agricultural Engineering

Catherine N. Cutter, Ph.D., Pennsylvania State University, Dept. of Food Science

Joe Regenstein, Ph.D., Cornell University, Dept. of Food Science

lifehacker.com "Keep bananas fresh longer by separating them and wrapping the stems in plastic wrap"

http://lifehacker.com/5967424/keep-bananas-fresh-longer-by-separating-them-and-wrapping-the-stems-in-plastic-wrap

(Note Kerry Weber's comment about how to refrigerate bananas follows this article.)

sfgate.com "Do Bananas Need Sunlight to Ripen?"

http://homeguides.sfgate.com/bananas-need-sunlight-ripen-75153.html

chiquitabananas.com "Frequently Asked Questions about Bananas"

http://www.chiquitabananas.com/worlds-favorite-fruit/banana-answers-information-faqs.aspx