Microbes’ role in truffle scents not trifling

Truffles, the homely fungal celebrities of the culinary world, have unseen help concocting their prized — and pricey — aromas.

Microbes that inhabit the subterranean mushrooms probably produce key chemicals that make truffles smell like truffles, according to a new analysis appearing online July 17 in Applied and Environmental Microbiology.

Certain microbes may help brew the signature scents that distinguish one truffle species from another, the authors suggest.The pleasant-smelling partners may also explain fluctuating fragrance within individual truffle species.

“There is big variability from season to season, from place to place,” says study coauthor Richard Splivallo, a chemist at Goethe University Frankfurt. A truffle species’ scent can change in both character and intensity, swaying prices that can reach thousands of dollars per kilogram.

The mushrooms generally emit chemicals with an earthy, garlicky and sulfuric bouquet — making gourmands swoon worldwide. But some species also have nuanced notes, such as whiffs of rose. (Splivallo says comparing truffle aromas is like comparing Bordeaux and Burgundy wines.)

Truffle scent production and variability have long been a mystery (SN: 5/5/12, p. 16). Splivallo and colleagues had earlier data showing that microbes can be involved, but the researchers didn’t know to what extent.

Unable to grow truffles in the lab, the team dug up published data on odorous microbial compounds and four culinary truffles. The truffle data included the mushrooms’ genetic blueprints, volatile chemicals and microbial tenants. The researchers then linked truffle scents to individual microbes and to mushrooms that have the biochemical wherewithal to make those scents.

The general truffle smell is probably a collaborative effort between microbes and mushrooms, the researchers found. And microbes may help make signature truffle scents. The famed sulfuric aroma of a white Italian truffle, for instance, probably comes from a bacterial compound.  

Splivallo and colleagues are now comparing microbes of fragrant and faint-smelling truffles to see if potentially fickle residents make the difference.

For fungal ecologists, including Antonietta Mello of the Italian National Research Council in Turin, the study could change the way people see truffles: not as gourmet fungi but microbe-mushroom mash-ups.