A PLASTIC food wrap developed in Canada changes colour if food is
contaminated with food-poisoning bugs. The new wrap, being developed by the
Toronto company Toxin Alert, uses standard antibody tests to warn of four
pathogens.
The antibodies, which have been modified to stick on the inside of plastic
wrapping, are activated when the wrap touches contaminated food. But some food
scientists are concerned that the wrapper might not be sensitive enough to
detect low levels of these organisms, even though slight contamination may make
people ill.
“This should be affordable for everyone. If you can afford a sandwich bag,
you should be able to afford one of our sandwich bags,” says Gord Furzer,
vice-president of operations for Toxin Alert.
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The packaging uses separate layers to capture the pathogen and detect it.
Toxin Alert coats the inside surface of standard polyethylene plastic food wrap
with antibodies specific to one of four food-poisoning organisms. This coating
can be applied to form a pattern which could, for example, be the shape of a
large X—though to start with it is invisible.
On top of this is a layer made up of a nutrient gel that holds another set of
antibodies, which are attached to a coloured chemical complex. Finally, there is
a porous layer that makes contact with the food, and allows disease-causing
organisms to pass through to the nutrient gel beneath.
When a pathogen passes through the porous layer and reaches the gel, an
antibody carrying the coloured complex latches onto it. The captured—and
now colourful—organisms diffuse towards the antibodies stuck to the inner
surface of the plastic wrap, where they accumulate, making the X pattern
visible.
The wrap will be made to detect Salmonella, Campylobacter,
Escherichia coliO157 and Listeria bacteria. Toxin Alert says
the wrap could be adapted to detect pesticides or even proteins characteristic
of genetically modified foods.
The wrap could be used by food packagers and retailers, and to wrap left-over
food in the home. Furzer says the new wrap would cost about 25 per cent more
than plain wrap.
But some researchers fear that the wrap won’t be sensitive enough to be
useful. Mike Doyle, a microbiologist and director of the Center for Food Safety
and Quality Enhancement at the University of Georgia, points out that laboratory
tests for food poisoning work by culturing enough organisms from a sample to
show up on the test. He thinks it’s unlikely the food wrap will be sensitive
enough to detect the very low levels of organisms that can cause disease.
“They’re going to give people a false sense of security. There are a lot of
disease-positive products out there that aren’t going to get picked up,” he
says. Furzer admits the product won’t detect low levels of bacteria. “What we’re
looking at is stopping gross contamination that causes mass illness and death,”
he says.