this rate, your question may wind up as someone’s doctoral thesis. We have contacted various experts on fruits and vegetables and have been met by a collective shrug of the shoulders.
One, however, a postharvest specialist at the University of California, Davis, offers a few clues. Exposure to ethylene gas can cause bitterness in carrots (was anyone welding in your kitchen the day you prepared your carrots, or administering an anesthetic, perhaps?). No matter, the UC Davis folks don’t think that is the most likely cause.
There is a chemical compound, terpenes, that plants may produce that can cause “harshness (often confused with bitterness) in carrots.” Insect bites, for instance, can stimulate plants to produce these defense terpenes. “Perhaps,” our UC Davis source says, “the physical damage associated with blending is leading to a transformation in some specific terpenes causing rapid formation of a bitter element.”
So add a little brown sugar or honey, and we’ll let you know when the thesis comes out.