UAlbany scientists help solve garlic riddle

Authors: Steve Barnes
TimesUnion 2010, Mar, 22, ,

 

A head of garlic in its papery skin is relatively odorless. But crushing or slicing a clove ”” or, egad, chewing on one ”” produces that distinctive, pungent aroma.

What happens to garlic at the precise moment you cut it? The seemingly simple question has challenged food scientists and chemists for more than 50 years.

A research team led by University Albany chemistry professor Eric Block, using instrumentation at the JEOL USA laboratories in Peabody, Mass., solved the mystery by detecting the key compound involved. They measured its fraction-of-a-second lifetime using a new type of instrument called a DART® (Direct Analysis in Real Time) mass spectrometer, or DART®-MS.

Intact garlic contains the odorless sulfoxide alliin. Cutting garlic releases the enzyme alliinase, which breaks down the alliin, rapidly forming the garlicky-smelling allicin. Scientists had long believed 2- propenesulfenic acid, thought to be a powerful antioxidant formed from garlic, intervened between the alliin and allicin, but its existence had never been proved ”” until now.

Through use of the DART®-MS, Block and his JEOL coworkers observed what happens when a garlic clove is poked with a glass tube. Using fast data collection, 2-propenesulfenic acid was observed forming and then disappearing within a fraction of a second.

Other breakdown products of alliin and allicin were observed at the same time, consistent with their formation upon crushing garlic.

Block’s National Science Foundation-sponsored work is reported in the latest edition of Journal of Agricultural and Food Chemistry, as well as, in part, in his just-published “Garlic and Other Alliums: The Lore and the Science”쳌 (Royal Society of Chemistry/Springer, 2010).

“I was amazed at how fast these processes occur. Our direct detection of 2-propenesulfenic acid is significant because many of the beneficial antioxidant properties of allicin are in fact attributed to 2-propenesulfenic acid,”쳌 Block said in a news release. “The stinky compounds from garlic are defensive compounds, since allicin is a repellent for nematodes (crop-destroying microscopic worms) as well as birds.”쳌

Block also found using DART®-MS that elephant garlic, a larger and milder relative of garlic, formed both allicin and propanethial S-oxide, the tear-producing compound from onion (onion lachrymatory factor, or LF).

Block said, “I was surprised to find that elephant garlic is not just a milder form of garlic as previously thought, but in fact is a unique plant, combining garlic- and onion-type compounds, and it therefore should have a somewhat different taste than garlic. Holding up crushed elephant garlic to our eyes caused tearing, which does not occur with crushed garlic itself.”쳌

Paper co-authors and researchers included JEOL Scientists Dr. Robert B. Cody and Dr. A. John Dane, and Postdoctoral Fellow Siji Thomas, of the Department of Chemistry at the University at Albany.