Cooked garlic still kills bacteria.

Researchers have long known that chemicals isolated from raw garlic can kill a wide variety of bacteria, but the cooked herb hadn't been tested. A new study suggests that cooked garlic can still kill bacteria, though less efficiently than does a raw bulb.

Microbiologist Chitra Wendakoon of New Mexico State University in Las Cruces worked with several common types offood-borne bacteria, such as strains of salmonella, listeria, and shigella. She created extracts of raw garlic and garlic and then boiled them for 15 minutes. Wendakoon added the boiled extracts to lab dishes in which the bacteria were growing.

Within a day, bacteria-free zones surrounded the spots where either the raw- or cooked-garlic extracts had been placed. However, the dead zone for the raw extract was about twice as large as that for the cooked one.

Wendakoon obtained similar results when she tested the extracts on bacteria growing in a nutrient broth. In that experiment, cooked garlic killed hundreds of millions of bacteria, but raw garlic killed about 10 times as many.

The finding suggests that some of garlie's antibacterial components "are probably heat stable," says Wendakoon. The next step, she adds, will be to isolate these hardy antibacterial compounds.--C.B.