Bananas are harvested prior to ripening and between the time they are harvested and the time they arrive on the grocery display, they are placed into ripening rooms and exposed to ethylene gas, which acts as a catalyst for ripening. By the time you purchase them at the grocery store, they have already started their ripening process and have reached a certain ripeness stage, which is why the banana display will normally have a range of bananas from more green to more yellow. Then when you take them home and set them on the counter, the ripening process continues.
The picture above is a demonstration I recreated with iodine and bananas, where I cut sections from bananas that were at different ripeness stages and dipped them into an iodine solution (just a generic bottle purchased from the pharmacy) so that you can see what is happening internally with the bananas as they ripen. You can see that as you go from left to right, the colorant from the iodine increases as the bananas go from spotty (riper) to green (less ripe). The amount of colorant is demonstrating the level of starch contained in the banana because as the banana ripens, there is an internal process that is converting starch to sugar. That is why the spotty bananas are sweeter, because they contain a greater amount of sugar!
This same type of study can be done with apples and pears to demonstrate their starch versus sugar contents (Blankenship et al., 1993). If you have any iodine laying around, I encourage you to try it out for yourselves! Please comment and share your results, as well as which banana is right for you!
Blankenship, Sylvia M., Ellsworth, Donna D., and Ronald L. Powell. “A Ripening Index for Banana Fruit Based on Starch Content.” HortTechnology 3.3 1993: 338-339. Web. 29 May 2016.
Food and Agriculture Organization of the United Nations. Banana Market Review 2013 – 2014.FAO, Oct. 2015. Web. 20 May 2016.
About The Produce Nerd
Megan Crivelli is a produce industry professional, with a background in postharvest and food safety. She founded The Produce Nerd (www.theproducenerd.com), which is a produce blog that educates its followers on where their produce comes from, and all of the work that goes into bringing a piece of produce to the grocery display. Her goal is to share the side of the produce industry that is not commonly seen by consumers to encourage and excite them to consume more produce and live happier, healthier lives.