The difference between the sensation of heat and cold produced by certain spicy foods depends on the chemical compound they contain and the type of receptor they activate on the tongue and oral mucosa. Although the sensation resembles real heat or cold, in both cases it is a chemical response, not a thermal one.
The compound responsible for the heat-inducing spiciness: capsaicin
Capsaicin is the compound found in chili peppers and hot peppers. When it comes into contact with the mucous membrane of the mouth, it binds to a specific receptor called TRPV1 (transient receptor potential vanilloid 1). This receptor is normally activated by high temperatures, above 43 °C, and sends signals to the brain that are interpreted as a sensation of heat or burning. Capsaicin does not damage tissue, but it tricks the nervous system, which reacts as if there were an actual heat source.
The compounds responsible for the cold-inducing spiciness: menthol and related substances
Menthol, found in mint, and other substances such as eucalyptol activate a different receptor, TRPM8, which responds to low temperatures, around 25 °C or lower. By stimulating this receptor, the brain interprets that the area is exposed to cold, even though the actual temperature of the mouth has not changed. That is why mint candies, gum, or mint infusions produce a refreshing sensation.
Other substances that produce crossed sensory effects
In addition to capsaicin and menthol, there are other compounds that activate thermal receptors:
- Piperine, found in black pepper, also activates TRPV1 receptors, although with less intensity than capsaicin.
- Gingerol and shogaol, found in fresh and dried ginger, activate the same receptors as capsaicin, generating heat.
- Some synthetic compounds used in extreme candies, such as resiniferatoxin, are thousands of times more potent than capsaicin at activating TRPV1.
Why water does not always relieve these sensations
Capsaicin and similar compounds are poorly soluble in water, so drinking water barely relieves the burning. Dairy products, which contain casein, or foods rich in fats, on the other hand, help dissolve these compounds and reduce the sensation. In the case of menthol, the sensation of cold disappears once the compound is no longer in contact with the receptor, since it is not an actual change in temperature.
The key difference between the two sensations
In short, the sensation of heat comes from the activation of receptors associated with high temperatures (TRPV1), while the sensation of cold comes from receptors associated with low temperatures (TRPM8). The brain does not distinguish whether the stimulus is thermal or chemical: it interprets the receptor's signal as if the temperature had actually changed. That is why a chili pepper
