Why Some Wines Smell Like Tropical Fruits

If you’ve ever smelled a New Zealand Sauvignon Blanc, you’ve smelled thiols (“thigh-all”, rhymes with “style”). These are the aroma compounds that smell like grapefruit, guava, passion fruit, and yes, sometimes cat pee.

(Shown are guava, passionfruit, & grapefruit aromas) Drawing by Anna Sprenger

What are thiols?

Thiols are odorous compounds that contain sulfur. Our understanding of thiols is a recent development in the wine world. In 1995, some researchers in Bordeaux identified a volatile thiol, called 4MMP for short, which is a dominant aroma in Sauvignon Blanc. They found this compound after they realized that adding copper to the wine removed tropical fruit smells. Since they knew that copper reacts with sulfur to form an odorless compound, they worked backward and concluded that the tropical fruit aromas must be coming from a sulfur-containing volatile thiol.

Since then, many different volatile thiols have been found. The most common include:

4MMP (4‐mercapto‐4‐methylpentan‐2‐one): Boxtree, passion fruit, broom, black current

3MH (3-Mercaptohexan-1-ol): Passion fruit, grapefruit, gooseberry, guava

3MHA (3-Mercaptohexyl acetate): Passion fruit, grapefruit, box tree, gooseberry, guava

You can see that one aroma compound can produce a range of different smells depending on its…