Freshly ground coffee has a strong aroma, but now a Tel Aviv University expert on odors says that a coffee extract can actually inhibit the growth of bacteria that lead to bad breath. Prof. Mel Rosenberg, a TAU biochemist who is renowned for his expertise on odors - including bad breath - presented his team's research last month at a meeting in Germany of the International Society for Breath Odor Research. The research was led by Yael Gov, a researcher in Rosenberg's lab. "Everybody thinks that coffee causes bad breath," says Rosenberg, "and it's often true, because coffee, which has a dehydrating effect in the mouth, becomes potent when mixed with milk and can ferment into smelly substances." But not always. "Contrary to our expectations, we found some components in coffee that actually inhibit bad breath," he said. In the laboratory, the team monitored the bacterial odor production of coffee in saliva. In the study, three different brands of coffee were tested - Israel's Elite brand, Landwer Turkish coffee, and America's Taster's Choice. Rosenberg expected to demonstrate the malodor-causing effect of coffee in an in vitro saliva test developed by Dr. Sarit Levitan in his laboratory. To his surprise, the extracts had the opposite effect. "The lesson we learned here is one of humility," says Rosenberg, who has developed a mouthwash sold in Europe, a pocket-based breath test and a deodorizing chewing gum. "We expected that coffee would cause bad breath, but there is something inside this magic brew that has the opposite effect." The team now aim to isolate the bacterial-inhibiting molecule so they could discover the antibacterial substance in coffee. "It;s not the raw extract we will use," he says, "but an active material within it." His latest discovery could be the foundation for an entirely new class of mouthwash, breath mints and gum. Purified coffee extract can be added to a breath mint to stop bacteria from forming - stopping bad breath at its source, instead of masking the smell with a mint flavor.