Bitterness is a difficult modality to define. Sweet molecules roughly correspond to molecules which have a defined chemical structure, salt and acidity as well. Even umami is (so far) strictly related to the detection of glutamate. But bitterness escapes any chemical definition as there are thousand of molecules of different structures which are detected as "bitter".
What make molecules "bitter" is our sensory system: detecting bitter molecules triggers an aversive reaction, interrupting feeding activities and even triggering active aversive reactions such as rinsing the mouth, throwing up and displaying a specific face of disgust. Similar reactions are observed in insects. It is generally believed that bitterness is a taste modality which helps organisms to avoid ingesting potentially toxic molecules.
Many plants synthesize secondary compounds which are aversive (bitter) or toxic to herbivores. Since bitter chemicals are mostly detected by contact, we study how insects use their contact chemoreceptor sensilla to evaluate food quality and how they use this information combined with previous experience or internal sensations to adapt their feeding. We believe that the sensory equipment of insects is shaped by evolution and as such, that it should reflect the selection pressures present in their environment.
One application of these studies is to find aversive molecules that are innocuous to the environment and to humans, and which deter insects from feeding on plants or animals that we want to protect. Another possibility is to induce insects to feed on traps spiked with specific insecticides, thus avoiding dispersing pesticides within the environment. Lastly, if entomophagy develops into a real industry, we will need to find insects which eat what we give them as food: the only insect which is really domesticated is the silkworm. After 4000 years of domestication, it is still only eating mulberry leaves and nothing else!
last edited: septembre 10, 2015