"Long before it's in the papers"
January 28, 2015


Mouth microbes helping the chef make magic?

Nov. 11, 2008
Courtesy American Chemical Society
and World Science staff

Bac­te­ria in the mouth play a role in cre­at­ing the dis­tinc­tive fla­vors of cer­tain foods, sci­en­tists in Switz­er­land re­port.

The ex­pe­ri­menters found that these bac­te­ria ac­tu­ally pro­duce food odors from odor­less com­po­nents of food, al­low­ing peo­ple to fully sa­vor fruits and veg­eta­bles. 

Sci­en­tists re­port that mouth bac­te­ria are re­spon­si­ble for cre­at­ing the dis­tinc­tive fla­vors of cer­tain foods, in­clud­ing some fruits and veg­eta­bles. (Im­age cred­it: Wikipedia)

“The mouth acts as a re­ac­tor, adding an­oth­er di­men­sion to odor per­cep­tions,” the re­search­ers wrote in the stu­dy, to ap­pear in the No­vem­ber 12 is­sue of The Jour­nal of Ag­ri­cul­tur­al and Food Chem­is­try.

In the stu­dy, Chris­tian Starken­mann of Geneva-based fra­grance-and-fla­vor pro­ducer Fir­me­n­ich SA and col­leagues note that some fruits and veg­eta­bles re­lease char­ac­ter­is­tic odors only af­ter be­ing swal­lowed. 

Sci­en­tists had pre­vi­ously re­ported that this so-called re­tro­aro­matic ef­fect arises from chem­i­cals pro­duced from pre­cur­sors found in these foods. But the de­tails of this how this oc­curs weren’t un­der­stood. 

To help clear up the pic­ture, the sci­en­tists asked 30 trained pan­elists to eval­u­ate the odor in­tens­ity of chem­i­cals known as thi­ols re­leased from odor­less sul­fur com­pounds found nat­u­rally in grapes, on­ions, and bell pep­pers. 

When giv­en sam­ples of the odor­less com­pounds, it took par­ti­ci­pants 20 to 30 sec­onds to per­ceive the aro­ma of the thi­ols, the study found; this per­cep­tion per­sisted for three min­utes.

The re­search­ers al­so found that the odor­less com­pounds are trans­formed in­to the thi­ols by an­aer­o­bic (oxygen-avoiding) bac­te­ria liv­ing in the mouth, caus­ing the char­ac­ter­is­tic “retro­aro­matic” ef­fect. How­ev­er, the au­thors con­clud­ed, sali­va’s abil­ity to trap these free thi­ols is what helps mod­u­late the long-lasting fla­vors.

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Bacteria in the mouth play a role in creating the distinctive flavors of certain foods, scientists in Switzerland report. The experimenters found that these bacteria actually produce food odors from odorless components of food, allowing people to fully savor fruits and vegetables. “The mouth acts as a reactor, adding another dimension to odor perceptions,” the researchers wrote in the study, to appear in the November 12 issue of the Journal of Agricultural and Food Chemistry. In the study, Christian Starkenmann of Geneva-based fragrance-and-flavor producer Firmenich SA and colleagues note that some fruits and vegetables release characteristic odors only after being swallowed. Scientists had previously reported that this so-called retroaromatic effect arises from chemicals produced from precursors found in these foods. But the details of this transformation were not understood. To help clear up the picture, the scientists asked 30 trained panelists to evaluate the odor intensity of chemicals known as thiols released from odorless sulfur compounds found naturally in grapes, onions, and bell peppers. When given samples of the odorless compounds, it took participants 20 to 30 seconds to perceive the aroma of the thiols, and this perception persisted for three minutes. The researchers also found that the odorless compounds are transformed into the thiols by anaerobic (oxygen-avoiding) bacteria living in the mouth, causing the characteristic “retroaromatic” effect. However, the authors concluded, saliva’s ability to trap these free thiols is what helps modulate the long-lasting flavors.