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2,4-Dithiapentane, aka bis(methylthio)methane, is the simplest alkyl dithioether. Horst Böhme and Robert Marx at the University of Berlin reported its synthesis in 1941. A quarter century later, A. Fiecchi and colleagues at the University of Milan and San Giorgio Essences (Turin, both in Italy) isolated it from white truffles (Tuber magnatum) and demonstrated that it is the odor principle of the highly valued fungus.

The odor of 2,4-dithiapentane in white truffles is mild; but in pure form it smells strongly like freshly prepared mustard. It would be nice to think that commercial products such as truffle oil, butter, and puree contain the natural substance; but most such products contain synthetic 2,4-dithiapentane.

That’s OK so long as these foodstuffs are labeled correctly. Counterfeit white-truffle products have been around for several years, but fakes would be more easily detected if there were a rapid analytical method for doing so.

Up stepped Luigi Mondello and collaborators at several Italian universities and private companies. They hypothesized that the ¹²C/¹³C isotope ratio would be different in natural and synthetic 2,4-dithiapentane because the compound would have dissimilar origins (fungus environment versus petroleum-based feedstock).

Sure enough, a gas chromatography–mass spectrometry technique showed that   than the manufactured kind. The authors verified their findings by examining the isotope ratios of 2,4-dithiapentane extracted from a wide variety of truffle-flavored foods.