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A plastic food wrap developed in Canada changes color
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.
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 colored
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 colored complex latches onto
it. The captured -- and now colorful -- 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 coli O157 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. The new wrap would
cost about 25 per cent more than plain wrap.
New
Scientist April 7, 1999
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