As mentioned previously, I am interested in how food ingredients alter our taste responses and affects our perception of what we eat. Capsaicin, the “hot” ingredient of chili peppers, and piperine, from black pepper, trigger temperature and pain receptors in the mouth. Another chemical causing irritation is menthol. For sensory scientists, “irritation” and “sensitization” are not associated with causing harm, but relates to the responses including numbness, heat, cooling, burning and prickling.
These chemesthetic irritants stimulate receptors in the trigeminal (fifth (V) cranial nerve) nervous system. In particular, these sensory responses are part of the mandibular (V3) branch of the trigeminal nerve, which also serves the teeth, gums, lower lip and lower part of the face. The trigeminal receptors are exhaustive neurotransmitters so their depletion can have a significant impact the taste of further food and is a serious problem for sensory panels testing these foods [reference 1].
There is much information available on the action of “heat” producing compounds such as capsaicin. It is well known that hot spicy foods trigger both pain and temperature receptors is well known. In fact, capsaicin binds to the same receptors that would respond to heat and physical abrasion. The degree of “hotness” can also be predicted by determining its place on the Scoville scale.
The cold response is less well understood. In addition to the cold response, menthol has minor local anesthetic properties and also reducing itching and local irritations (this is known as antipruritic). Researchers studying the mechanisms have used pharmacological agents, such as menthol to learn which receptor is responsible for the cold response [reference 2]. It seems unlikely that this is the only receptor that responds to cold or cooling and it is also possible that menthol triggers other receptors due to its anesthetic properties.
Menthol has an accentuating effect; eat something containing menthol followed by a cold food; the cold food will taste even colder. Ever tried drinking orange juice after cleaning your teeth? Menthol’s behavior makes it a good ingredient in toothpaste; menthol acts as an appetite suppressant by making food less desirable. Next time you are feeling hungry; try cleaning your teeth.
It’s cool that food compounds can have this influence on our tastes. So cool that I asked YellowIbis to make a complimentary shirt to their hot like…with the structure of capsaicin and to design me a t-shirt stating: “cool as…” with the structure of menthol.
I’m so excited as you too can buy this t-shirt and be cool about menthol's influences on our taste buds too.
1) Allison, A-M. & Work, T (2004) Fiery and Frosty Foods Pose Challenges in Sensory Evaluation Food Technology 58(5) 32-37.
2) McKemy, D.D. Neuhausser, W.M. & Julius, D. (2002). Identification of a cold receptor reveals a general role for TRP channels in thermosensation. Nature 416, 52-58.