Watching Garlic Slay Bacteria

Vampires aren't the only villains vulnerable to garlic: Harmful bacteria also fall victim to the bulb's pungent mixture of compounds. Garlic could find use as a natural food preservative, but just how it destroys bacteria has been unclear. Now, researchers report that infrared and Raman spectroscopies provide a detailed account of garlic's war on bacteria (Anal. Chem., DOI: 10.1021/ac2001498).

Previous studies suggested that a sulfurous component, called diallyl sulfide, is key to garlic's antimicrobial properties. "We know these compounds are getting into the bacterial cell and doing damage," says Barbara Rasco at Washington State University, Pullman. She and her team wanted to know how.

So they watched key biomolecules in bacteria as garlic attacked them. The researchers used infrared and Raman spectroscopies to monitor the proteins, lipids, nucleic acids, and carbohydrates in two strains of bacteria that cause foodborne illness: Escherichia coli O157:H7 and Listeria monocytogenes. When the researchers mixed the bacteria with either diallyl sulfide or a crude garlic extract, the DNA, proteins, and particularly the membranes of the bacteria became chemically dismantled, the researchers found.

Garlic and diallyl sulfide showed more-potent antibacterial activity at room temperature than when refrigerated, Rasco says. She suggests that adding garlic to processed food could help keep perishable food safe if, for instance, it is left in the trunk of a car for too long. She adds that these garlicky weapons work at concentrations that wouldn't overwhelm the taste of foods that they're trying to protect. No word on the risk of garlic breath.