GC–MS Probes Acidity and Heat in Wasabi, Mustard

The sharp, nose-tingling heat of wasabi and mustard comes from a natural compound called allyl isothiocyanate (AITC). It works by switching on a sensor in our nerve cells that detects irritants, which is what causes that burning sensation. Across many different foods and condiments, this compound is almost always found in a sour, acidic setting. Yet very little research has looked at whether that acidity changes how hot the compound feels.

To find out more, researchers examined eight store-bought wasabi and mustard products, using gas chromatography–mass spectrometry (GC–MS), to separate and identify the compounds in a sample, and ion chromatography, to measures acid and other charged substances. A paper based on their research was published in the journal Food Research International.¹

How Does Allyl Isothiocyanate in Wasabi and Mustard Create Its Burning Sensation?

As mentioned earlier, AITC causes the familiar burning or stinging feeling in the nose and mouth. This is a classic example of chemesthesis, the way chemicals can trigger sensations like heat, cooling, or tingling rather than taste or smell.²Scientists have a good understanding of how this works. The compound strongly switches on a sensor found on nerve cells in the face, the same nerves that carry feelings of touch and pain from the nose and mouth.³ The compound latches onto specific spots on this sensor, causing it to change shape and open like a gate. Calcium then rushes into the nerve cell, which fires off signals to the brain that we feel as pain and irritation.⁴

While the research team believes acidity and AITC might work together on the same nerve sensor, and this interaction could change how hot the compound feels, there have been few studies which explored how this plays out in what people actually experience when they eat, and there is little hard evidence connecting this molecular interaction to the heat of mustard and similar condiments.¹

What Did the Study Find About How Acidity Affects the Heat of Wasabi and Mustard?

The researchers found that allyl isothiocyanate was the main source of heat in the wasabi products, but in the mustard products it was present only in small amounts or could not be detected at all. All the products were fairly acidic, with pH levels ranging from 3.0 to 5.0.¹

In taste tests with 13 volunteers, mustard oil mixtures that had been made more acidic (pH 4) tasted noticeably less hot than the same mixtures at a neutral pH. On a scale of 1 to 9, the acidic version scored about 4.9 on average, compared with about 6.8 for the neutral one.¹

Laboratory experiments backed this up. In human cells engineered to carry large numbers of the nerve sensor that detects the compound, making the surroundings more acidic sharply weakened the cells’ reaction to it. The same thing happened in human nerve cells grown from stem cells: in acidic conditions, the compound triggered less nerve activity.¹

The researchers also used computer modeling, including an artificial intelligence (AI) tool that predicts protein structures, to explore what might be happening at the molecular level. These early simulations suggest that acidity may make the connection between the compound and the nerve sensor less stable, with the sensor’s shape shifting and loosening over time. A less stable connection would mean the sensor switches on less strongly, which fits with the reduced heat people tasted.¹

“Overall,” write the authors of the paper,¹ “these findings provide preliminary insights into a potential mechanism by which food matrix acidity may modulate TRPA1 activity, offering a tentative scientific basis for the formulation of pungent foods with reduced irritancy.”

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References

1. Wang, S.; Xie, J.; Ma, F. et al. TRPA1-associated Attenuation of AITC-evoked Pungency in Acidic Wasabi Sauces: Sensory, Cellular and in silico Insights. Food Res Int. 2026, 245 (Pt 2), 120795. DOI: 10.1016/j.foodres.2026.120795
2. Xie, J.; Shi, Q.; Chai, G. et al. Crossmodal Integration of Chemesthesis, Taste and Olfaction in Flavor: A Perspective from TRP Channel Agonists. Food Rev. Int.2026, 42 (8), 1-13. DOI: 10.1080/87559129.2026.2664054
3. Hinman, A.; Chuang, H. H.; Bautista, D. M. et al. TRP Channel Activation by Reversible Covalent Modification. Proc Natl Acad Sci U S A 2006, 103 (51), 19564-19568. DOI: 10.1073/pnas.0609598103
4. Laursen, W. J.; Bagriantsev, S. N.; Gracheva, E. O. TRPA1 Channels: Chemical and Temperature Sensitivity. Curr Top Membr. 2014, 74, 89-112. DOI: 10.1016/B978-0-12-800181-3.00004-X