Few people would ever think of eating raw garlic, and likewise, few people will try wasabi after hearing stories about its sharp taste. However, even fewer people understand the chemistry behind the extremely pungent taste and smell of garlic and wasabi. Although garlic and wasabi certainly look nothing alike on the outside, they share various similarities in their chemical composition and chemical properties.
Garlic belongs to a genus of plants called Allicin. Many plants of this genus, such as garlic, produce sulfur compounds, which are often associated with foul odors. One of these organic compounds is allicin, which is only released when garlic is crushed or eaten raw, but not after the garlic has been cooked. Wasabi, and other mustard plants, produces another organosulfur compound called allyl isothiocyanate (AITC) that is responsible for its pungent taste.
Allicin and AITC are not only both organosulfur compounds, but also share structural similarities. AITC has been known to activate TRPA1 ion channels, which are found on sensory neurons that release pain signals. A study in 2005 found that allicin also activates a subset of these AITC-sensitive neurons due to a few structural similarities with AITC. Because both chemicals induce activation of the primary pain-pathway, it is not surprising that many people are deterred from eating garlic or wasabi.
Author: Jonathan Yu
Food Composition and Taste 