Burger bugs busted
7 October 2005
Bacteria experts have devised a speedier way to spot spoiled meat. Their new bug-busting test takes seconds, not hours, so it could stop badly contaminated products from reaching shop shelves. Antenna investigates...
Image: Stephen Ausmus/USDA
The new test doesn't count the contamination culprits themselves - bacteria. Instead it measures meat's changing biochemical 'fingerprint' as bacteria break it down. The test is chemical-free and quick: it takes just 60 seconds to complete, say its developers at the University of Manchester.
Pseudomonas bacteria like these can spoil meat before it even reaches the shops.
Image: David Ellis
Ground-up meat samples are loaded into the spectrometer for testing.
Image: David Broadhurst
The test uses a piece of kit called a spectrometer, which shines infrared light onto samples of the meat and records which wavelengths of light bounce back. The result is a light absorbance spectrum, a distinctive pattern that depends on the chemicals present in the sample. |
The spectrometer (in the background here) sends readings to a computer, which food researchers use to calculate their results.
Image: David Broadhurst
Meat's spectrometer readings change as bacteria grow because the bugs release biochemicals with characteristic light absorbance patterns. With the help of some clever computer software, the Manchester scientists used these patterns to calculate how many bacteria their meat samples contained. |
'We've shown that our test will work on both chicken and beef. Chicken begins to go off and becomes just about detectable by the human nose when there are about 10 million bacteria per square centimetre on the surface of the meat. When that number reaches about 100 million it really is quite smelly.
'Our technique can detect bacteria numbers as low as hundreds of thousands in poultry and tens of thousands in beef.'
David Ellis, bacteria expert, University of Manchester
David Ellis, bacteria expert, University of Manchester
David Ellis, bacteria expert, University of Manchester.
Image: Roger Jarvis
Image: Keith Weller/USDA
David and his team hope their new test could be on production lines soon. Because it's so quick it could stop meat that's going off from even leaving the factory. Today's testing techniques take a few hours, so meat is already on its way to the supermarket by the time the results are in. |
Rod-shaped E. coli bacteria like these can cause food poisoning.
Image: Eric Erbe/Christopher Pooley/USDA
At the moment the test just looks for meat-spoiling bacteria, but David told Antenna he and his team want to develop their technique further: 'We are about to investigate its possible use as a detection system for food-poisoning bacteria, like E. coli and Salmonella.' |
Will the new bug detector do the business?
The people who inspect the UK's meat factories told Antenna that the new test sounds promising. 'The Food Standards Agency welcomes advances in technology that could contribute to reducing foodborne disease and food spoilage through the rapid detection of micro-organisms. Although the test is still in development, it is potentially very exciting.'