Question: Fruit tastes very different when it is ripe compared to when it is not ripe. What chemical changes occur in fruit during the ripening process?
Answer: Unripe fruit is hard, bitter, and usually green. When fruit ripens it is soft, sweet, juicy, aromatic, and usually changes color. Fruits are either climacteric or nonclimacteric.
Climacteric fruits increase respiration and ethylene production upon ripening; nonclimacteric fruits do not(3). Plants have receptors that bind Ethylene, a hormone that causes ripening(1, 2). Binding of Ethylene turns off transcription of ETR1 and CTR1 genes(2). When ETR1 and CTR1 genes are off, genes that code for amylase, hydrolases, pectinase, and kinases are transcribed(1, 2). Amylase converts starch into glucose; adding sweetness and reducing mealiness(1). Pectinase breaks down pectin; giving fruit a soft texture(1). Kinases neutralizenutralize acids; decreasing bitterness. Hydrolases break down chlorophyll and other large organics; allowing fruit to change color and release aromatics(1).
Climacteric fruit can be picked before it is ripe and upon exogenous exposure to ethylene will ripen. This method is currently used in agriculture to ship fruit with less bruising, and increase the time fruit can remain in the market before spoiling(3).
- Tiffany E.
- Koning, Ross E. 1994. Fruit Ripening. Plant Physiology Information Website.
- Kendrick, Mandy. “The Origin of Fruit Ripening.” Scientific American. Scientific American, a Division of Nature America, Inc., 17 Aug. 2009. Web. 30 June 2016.
- Mattoo, Autar K., and Jean Claude Pech. Fruit Ripening, Physiology, Signaling, and Genomics. Ed. Pravendra Nath and Mondher Bouzayen. Boston: CABI, 2014. Print.