Wasabi is a green Japanese horseradish paste that is commonly served with sushi and sashimi. It adds a sharp, pungent kick to these dishes. But what exactly does wasabi do to your mouth to give it that intense burning sensation?
The Active Compounds in Wasabi
The main compounds responsible for wasabi’s pungency are isothiocyanates, specifically allyl isothiocyanate. Isothiocyanates are produced when the enzyme myrosinase breaks down glucosinolates, which are natural compounds found in wasabi root. When the wasabi root is grated, the myrosinase comes into contact with the glucosinolates, triggering this reaction.
Allyl isothiocyanate is volatile, meaning it can vaporize at room temperature. This allows the sensation from wasabi to spread rapidly once the root is grated. The vapor activates sensory neurons in the nasal cavity and oral cavity, which contain special receptor proteins called TRP channels. TRP channels get triggered by physical or chemical stimuli and transmit the signal of irritation to the brain.
How Wasabi Activates TRP Channels
The TRP channel primarily responsible for detecting wasabi’s pungency is called TRPA1. When allyl isothiocyanate interacts with TRPA1, it causes the channel to open, allowing positive ions like sodium and calcium to flow into the cell. This depolarizes the neuron and generates an action potential signaling pain, irritation, or warmth.
TRPA1 is found on sensory neurons that innervate the entire oral and nasal cavities. So wasabi can stimulate trigeminal receptors all over these areas to produce a widespread burning sensation. Interestingly, TRPA1 is also temperature sensitive, so the warming sensation from wasabi may also activate the channel.
Other Effects in the Mouth
In addition to binding TRPA1 channels, allyl isothiocyanate has other effects in the mouth that enhance the intensity of wasabi:
- It can inhibit certain enzymes like acetylcholinesterase, leading to increased levels of the neurotransmitter acetylcholine and enhanced sensitivity of neurons.
- It causes vasodilation of blood vessels in the oral mucosa, which may heighten sensory activation.
- It stimulates saliva, tear, and mucus production, which can help clear out the compound but also spread and prolong the sensation.
Adapting to Wasabi Over Time
Although wasabi produces an intense burning hit initially, the sensation fades relatively quickly. Within minutes, the TRPA1 channels may become desensitized to further stimulation from allyl isothiocyanate. Tolerance can also build up over time among frequent wasabi consumers.
However, mixing wasabi with soy sauce prevents rapid desensitization, prolonging the sensation. Soy sauce contains salts that help extract more allyl isothiocyanate from the wasabi, enabling it to keep activating TRPA1.
The Benefits of Wasabi’s Pungency
While wasabi’s burning sensation may seem like pure punishment for the mouth and nasal passages, it actually has some benefits:
- It may help kill potentially harmful oral bacteria and viruses.
- It promotes saliva flow, which can neutralize oral acid and prevent cavities.
- It may stimulate dilation of airway passages, temporarily relieving nasal congestion.
- The irritation triggers tears, mucus production, and coughing, which can help clear irritants or pathogens from the respiratory tract.
Conclusion
Wasabi creates a potent burning sensation by activating TRPA1 channels on sensory neurons in the mouth and nose. Its active ingredient, allyl isothiocyanate, interacts with TRPA1 to excite trigeminal receptors throughout the oral and nasal cavities. The sudden influx of ions generates action potentials that are perceived as irritation and heat. Wasabi also enhances neuron sensitivity through other mechanisms. The initial surge of burning fades within minutes due to receptor desensitization. But while the pain may be momentary, wasabi’s unique mouth-burning properties seem to offer some health-protective benefits.