Everyone loves a sweet slice of ripe melon or a luscious ripe peach. Every day of their lives, people eat ripened fruits and vegetables – but who ever asks himself, “What causes a hard peach to become soft and sweet?” or “What makes a green banana turn yellow and taste better?” Did you notice I mentioned three features of ripeness? One – what causes a hard fruit or vegetable to develop a pleasant, soft texture? Two – what chemical change occurs during the ripening process that makes ripe fruits sweeter than unripened fruits? Three – what in the ripening process produces color changes? We will consider, especially, the case of the banana.
Ripeness – a Matter of Biology and Chemistry
All fruits, vegetables – and in fact everything else living – consists of cells connected to one another. We learned this in highschool biology. The outer walls of cells of fruits and vegetables contain pectin. Pectin is a heteropolysaccharide,¹ used in the kitchen for making jams and jellies. The thickening property of pectin strengthens cell walls, but in addition, there is an additional layer of pectic compounds that connects adjacent cells to each other. This layer is called the middle lamella. For a beautiful technical discussion, refer to this article by Indiana University.
Texture – One Feature of Ripeness
As a piece of fruit or a vegetable matures, enzymes cause the lamella to break down, which loosens the attachment of the cells for one another, softening it. In other words, when a fruit or vegetable is harvested, one of its chemicals causes the food to soften.
Other Ripeness Features – Taste and Color
What about the banana’s improving sweetness levels with ripening? And what about the peel’s color change? Bananas are generally picked green. When they are picked, chemical changes begin to take place. First, ethene gas is given off by the banana. This in turn promotes the formation of enzymes. One of the enzymes produced breaks the starches in bananas down into sugars, making the fruit sweeter. Another enzyme breaks down the chlorophyll, removing the green color of the peel.
Such natural processes make ripe fruits and vegetables more appealing, easier to eat, and enjoyable.
If you have any questions concerning Kitchen Chemistry or suggested topics for future articles in the series, please feel free to comment in the section below this article.
¹ For further discussion, see Kitchen Chemistry: What is Pectin? How Does It Work? by the author.