What makes tomatoes go from green to red?

We checked several of our gardening and food science books to no avail, although we did learn from Lynn Coulter’s Gardening with Heirloom Seeds that tomatoes, native to South America and members of the nightshade family, took a while to catch on among Europeans.

However, Brian McMahon at MentalFloss, Mandy Kendrick at Scientific American, and the University of Cambridge’s IntoBiology website all had the answer to our question. Chlorophyll makes the tomatoes green and, as they ripen, the chlorophyll begins to dissolve. Lycopene, a chemical in the tomato that has a red color, shows through as the chlorophyll dissolves. As this happens, the tomato will also become sweeter, softer, less acidic, and ready to eat.

Fruits produce a chemical called ethylene in certain conditions, including as they ripen, and other fruit will respond to it. According to Jeremy Dore at GrowVeg and McMahon at Mental Floss, a green tomato in a paper bag with a ripe banana will respond to the ethylene given off by the banana, and it will begin to ripen itself.