Links Polymers Revision Questions 
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Polymers - Active Packaging - Intelligent Packaging.
Polymers are used to make different types of packaging for food.
What is Active Packaging?
Active packaging
contains something that will interact with the
contents.
Examples are cans that have something
to make the
contents hot (for example coffee) or
cold or release
gas (for example to form a foamy head on beer).
Some packaging contains substances which remove oxygen
or
water from the contents. Both of these are
needed for
the growth
of microorganisms (bacteria and fungi)
which cause
food to decay.
Removing oxygen and water limits the growth
of microorganisms
and makes the food stay fresh for
longer.
Packaging may also contain a substance that chemically
resists
the growth of microorganisms. One commonly
used
substance is
potassium sorbate (E202) which
resists the
growth of mould and
yeast.
Potassium sorbate is
present in some poly(ethene) film used for wrapping
cheese.
What are Intelligent Packaging and Thermochromic Packaging?
Intelligent
packaging can detect changes in
the contents
and give people useful information. Some substances
change colour
when they are heated or cooled. These
substances are called thermochromic
and they let people
know when the contents is at the correct temperature
to be
used. For example, thermochromic ink is used to let
people know
when the contents has been cooked for long
enough to reach the
correct temperature, or when the
contents has
been
chilled for long enough in a refrigerator.
Some beer is sold in white cans with thermochromic ink
which turns from white to blue when the beer is
cold
enough. The
blue pattern seems to magically
appear
at the correct temperature.
A different type of packaging
can use the same type of ink
to give an indication
if the contents have been warm for too
long and
microorganisms
have started to grow and cause decay.
Intelligent
packaging will increasingly be used
in the future
for medical and health care products.
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