SAIC High Power Microwaves
Microwaves turn kitchen cloths into germ killers
Last updated at 09:54am on 24th January 2007
Two minutes in the microwave can kill 99 per cent of the germs harboured by kitchen sponges, scientists have found.
Dishcloths and sponges are known to breed microbes such as E. coli and salmonella, that can cause potentially lethal food poisoning.
But researchers in the U.S. have found that the microwave is an effective weapon against them.
Gabriel Bitton, professor of environmental engineering at the University of Florida, said: 'Basically what we find is that we can knock out most bacteria in two minutes.
'People often put their sponges and scrubbers in the dishwasher but if they really want to decontaminate them and not just clean them, they should use the microwave.'
The scientists soaked sponges and scrubbing pads in untreated wastewater containing 'a witch's brew of faecal bacteria, viruses, protozoan parasites and bacterial spores including Bacillus cereus spores which are quite resistant to radiation, heat and toxic chemicals, and are notoriously difficult to kill'.
They also used bacterial viruses as substitutes for disease-causing viruses, such as hepatitis A.
Then they used a microwave oven to zap the sponges and scrub pads for varying lengths of time, wringing them out and checking for microbes after each test.
The results were unambiguous. Two minutes of microwaving on full power mode killed or inactivated more than 99 per cent of all the living pathogens in the sponges and pads.
The Bacillus cereus spores required four minutes for total inactivation.
Professor Bitton said the heat, rather than the microwave radiation, was the most likely cause of death for the pathogens. As the microwave works by exciting water molecules, it is better to put wet rather than dry sponges or scrub pads into the oven.
He added: 'The microwave is a very powerful and an inexpensive tool for sterilisation.'
Cooks should microwave their sponges every other day, he suggested.
The warm, damp environment of kitchen cloths is the ideal breeding ground for microbes.
In the right conditions one bacterium can multiply to more than four million in just eight hours. This can make them up to 200 times more infested that a lavatory seat.
The Food Standards Agency estimates that up to 5.5million people in the UK are struck down with food poisoning each year.
The U.S. researchers also found that microwaves were effective in decontaminating syringes, but that it generally took up to 12 minutes to kill Bacillus cereus spores.
Professor Bitton, co-author of the report, published in the Journal of Environmental Health, said preliminary research also shows that microwaves might be effective against bioterrorism pathogens such as anthrax, although more study was needed.
Informant: Iris Atzmon