Food poisoning is a potentially lethal condition and therefore a serious problem for the food industry. Each year, some 50 million people suffer food poisoning in the U.S. alone, including more than a million cases of potentially lethal salmonella poisoning.

So finding ways to prevent the spread of this and other kinds of bacteria is an important goal. But it is hard to detect bacteria in food products. The most common detection methods involve techniques such as microbiological culturing, polymerase chain reactions, high-performance liquid chromatography, and mass spectrometry, to name just a few.

These methods are complex, expensive, and time-consuming. And they require highly trained technicians to perform them. Consequently, few food companies and outlets have access to this kind of technology, and consumers have to take the hygiene of most foods they buy on trust.

Now that looks set to change thanks to the work of Jonghee Yoon and pals at the Korea Advanced Institutes of Science and Technology in South Korea. These guys have found a quick and cheap way to spot bacteria on the surface of foods in just a few seconds. They say their technique could be easily used in food processing lines and even fitted to standard home fridges.

The new technique is simple in principle. Bacteria such as salmonella have hair-like flagella that they use to propel themselves across surfaces. This movement turns the surface of contaminated food into an ocean of writhing microörganisms. It is this movement that Yoon and co have worked out how to spot.

Their method is straightforward. When a red, coherent laser beam hits biological tissue, it is scattered through the material. This scattering causes the light to interfere, creating a random pattern called laser speckle.