Science News - May 5, 2012

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Genes matter
for truffle aroma

By Rachel Ehrenberg

Mon dieu! A truffle’s delectable aroma may be as much about genetics as it is about geography.

For years a truffle’s flavor has been attributed mostly to environmental factors, akin to how terroir — the soil, climate and geology of a region — bestows qualities to wine. But a new analysis, published in the May New Phytologist, finds that a truffle’s particular blend of chemical compounds is linked instead to its genetic background.

By casting light on what gives these elusive underground fungi their prized flavor, the study could help transform some truffles from species harvested in the wild to consistent crops.

“Truffles are a really valuable natural
resource, and it’s the aroma that really
gives them their value,” says Gregory
Bonito of Duke University, an expert in
truffle evolution.

Just as yeast strains affect the flavor of wine, fungal genetics affect the aroma of Burgundy truffles, a new study finds.

Smoking out clues from gun residue

Laser method identifies caliber of weapon without a bullet

By Rachel Ehrenberg

As forensic evidence goes, gunshot residue can be full of holes. But a new technique could provide a more definitive link bet ween suspect and gun. A tool that employs lasers may allow investigators to match residue alone to a specific caliber of firearm, scientists report in two recent papers in Analytical Chemistry.

“Anything that’s going to enhance or
expedite the detection of gunshot resi-
due and provide stronger evidentiary
value is a way forward,” says analytical
chemist Jason Birkett of Liverpool John
Moores University in England. “This
work is very good and very novel and will
do nothing but assist.”
Along with the bullet, a cartridge or
round also contains a propellant (such as
gunpowder) and a primer. When the fir-
ing pin strikes the primer cap, the primer
ignites, igniting the propellant and expel-
ling the bullet from the gun. These reac-
tions result in a spray of residue that can
land on clothing, skin or anything nearby.

microbes thought to contribute to the warty lumps’ flavor.

Although the genetic blueprint for the famed black Périgord truffle ( Tuber melanosporum) was published in 2010, the genetic particulars of other truffles aren’t well understood. “We wanted to add the genetic dimension into the picture,” says Richard Splivallo of the University of Göttingen in Germany, who led the new work.

So the researchers collected more than 200 Burgundy truffles from seven countries over four years. The scientists examined the profile of some of the 20 to 50 volatile chemicals that contribute to the truffle’s delicate, nutty flavor.

When the researchers grouped the truffles by their genetic relatedness, truffles that were more closely related had more similar volatile profiles than more distantly related truffles.

“This is the first study to show a clear link between volatiles and genetics,” says Claude Murat, who studies truffle genetics at the French National Institute for Agricultural Research in Nancy.

more distantly related truffles.

“This is the first study to show a clear link between volatiles and genetics,” says Claude Murat, Research in Nancy.

traveled, but the approach is often not specific enough to link the residue to a gun of a particular caliber.

Now two teams have tackled gunshot residue with Raman spectroscopy, in which laser light of a specific wavelength induces vibrations in some of the residue molecules. Researchers in Spain analyzed spectra of six kinds of ammunition and compared these spectra with residue from fired guns, revealing a particular signature for each type of ammunition. These findings suggest that Raman spectroscopy could be used in situations where the bullet was not recovered or was too mangled to match to a weapon.