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Polymers - Active Packaging - Intelligent Packaging - Thermochromic.

Polymers are used to make different types of packaging for food.

Active packaging contains something that will interact with the contents.
Examples are cans that have something to make the contents hot,
cold or release gas (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 which 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 used in poly(ethene) film wrapping for cheese.

Intelligent packaging can detect changes in the contents
and give people useful information. Some substances change colour
 when they are heated or cooled. They are called thermochromic
 and 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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