When you eat chillies, you feel a burning sensation, you also start feeling very hot and begin to sweat. This happens because of ‘Capsaicin’, the active compound in chilli peppers that them hot.
The chemical name for ‘Capsaicin’ is ‘8-methyl-N-vanillyl-6-nonenamide’. It belongs to the ‘vanilloid’ group of compounds, the same family that also gives us the vanilla flavour. It is interesting to note how just a few changes in chemical structure can result in such vast differences in taste.
Capsaicin brings about its effects by binding to the receptor called TRPV1 (Transient Receptor Potential V1). The TRPV1 receptor generally gets activated when the temperature increases beyond 42̊C. However, this receptor also gets activated when it binds to the compound Capsaicin. This explains why you experience the same symptoms when you eat chillies, as when you touch something hot: you feel a burning sensation, feel hot and begin to sweat to cool down your body. Then the TRPV1 receptor gets activated, either by heat or by capsaicin, it sends signals to the brain, where this information is processed. Once this information is processed, specific instructions are sent back down, which make you sweat etc.
Capsaicin Receptor Locations
There are receptors for tastes such as sweet, salty, sour, bitter, umami, etc on the tongue. However, TRPV1 receptors for heat and Capsaicin are present in various other regions of the body too. These receptors are present in the anterior region of the face, including the oral cavity, skin over the cheeks, eyes etc. That is why you feel the spicy chilly when you rub your eyes with your hand after touching chillies. TRPV1 receptors are also present in other regions such as the internal lining of our digestive organs.
Pathway to Brain
When the information has to be sent from the receptor to the brain, it has to go through certain steps of the pathway. In the Central Nervous System or CNS, after TRPV1 receptors are activated, endorphins, specifically Beta endorphins are released. These beta endorphins then bind to mu opioid receptors. These mu opioid receptors are the same receptors that get activated when individuals consume opioid drugs. The binding of endorphins to mu opioid receptors then inhibits the release of a neurotransmitter called GABA. When GABA is inhibited, it ensures excess release of the excitatory neurotransmitter Dopamine, which gives us pleasure. This is why we experience pleasure when we eat spicy food and keep eating it though we experience the discomforting burning sensation.
Capsaicin and Pain
Not everyone likes eating spicy food, rather spiciness is an acquired taste. When TRPV1 receptors are activated, substance P is released. Substance P is thought to be very important in the transmission of pain signals to the brain. People who regularly eat spicy food have depleted levels of Substance P. Hence, Capsaicin is also used in pain relieving creams as they reduce the levels of Substance P that is involved in Pain Transmission.
The Capsaicin molecule is not hydrophilic, which means that it does not dissolve in water. It is a bad idea to drink water if you want the spicy taste to go away from your mouth. Instead, drinking liquids like milk will help to carry the molecule away.
How hot is spicy? The level of spiciness or the measurement of pungency carried out on the Scoville Scale in the form of Scoville heat Units (SHU).
Pure Capsaicin has a score of 16000000 SHUs, Jalapeno has a score of about 5000 SHUs and Kashmiri Chillies have a score of about 1000 to 2000 SHUs.
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Saunri Dhodi Lobo is pursuing M.Sc in Life Sciences with specialization in Neurobiology. Her interests include writing poetry, going for nature walks and swimming. Currently she is involved in research on Alzheimer’s Disease in fruit flies.
Read all Articles by Saunri Dhodi Lobo
Photos, Vector Graphics & Illustrations Credits
“Some Like It Hot” by Jim, the Photographer