Sensor May Detect Spoiled Milk
Posted on March 21st, 2008 at 7:10 am by admin under Unusual
A plastic widget that floats around in milk, soup or fruit juice cartons could tell you if it contains food poisoning bacteria - without you having to open them. A scanner at the supermarket checkout would simply sound an alarm if the pathogens are present.
The idea is the brainchild of Craig Grimes at Pennsylvania State University and Qingyun Cai at Hunan University in Changsha, China. The technology uses a novel mechanism to detect the food bug Staphylococcus aureus in milk which has not been properly refrigerated.
The key component of the widget is a strip of iron, nickel, molybdenum and boron alloy that has an unusual property: it vibrates in a magnetic field. The strip’s vibrations in turn generate its own magnetic field which can be picked up using a nearby detector coil.
Fresh milk is relatively thick and so the sensor strip is only able to vibrate slowly when exposed to a magnetic field. But S. aureus causes milk to decompose, which lowers its viscosity and allows the sensor to vibrate at a telltale higher frequency, the team found.
Grimes envisages the strip being built into a spherical plastic widget - large enough to avoid becoming a choking hazard - that floats inside the cartons. The strips could be tuned to work with soups and juices, too.
A very cheap detector could be placed at supermarket checkouts to identify contaminated cartons, Grimes says, needing only an electromagnet to induce vibrations in the strip and a coil to detect the widget’s response.
