We all know why Starbucks puts boxes of breath mints close to the cash register. Your morning latte can create a startling aroma in your mouth, strong enough to startle your co-workers too.

But intriguing new research from Tel Aviv University by renowned breath specialist Prof. Mel Rosenberg of TAU's Sackler Faculty of Medicine finds that a coffee extract can inhibit the bacteria that lead to bad breath. New laboratory tests have shown that the extract prevents malodorous bacteria from making their presence felt - or smelt.

"Everybody thinks that coffee causes bad breath," says Prof. 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," explains Prof. Rosenberg. The findings were presented last month to members of the International Society for Breath Odour Research in Germany by Yael Gov, a researcher in Prof. Rosenberg's laboratory.

A "taster's choice" for stopping bad bacteria

In the laboratory, the team monitored the bacterial odour production of coffee in saliva. In the study, three different brands of coffee were tested: the Israeli brand Elite coffee, Landwer Turkish coffee, and Taster's Choice. Prof. Rosenberg expected to demonstrate the malodor-causing effect of coffee in an in vitro saliva assay 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 Prof. Rosenberg. "We expected coffee would cause bad breath, but there is something inside this magic brew that has the opposite effect."

Prof. Rosenberg would love to isolate the bacterial-inhibiting molecule in order to reap the biggest anti-bacterial benefits from 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.

Prof. Rosenberg is a successful scientist and inventor who has already developed a popular mouthwash sold widely in Europe, a pocket-based breath test, and an anti-odour chewing gum.