The improvement to food quality comes about by actively supplying substances to the product or the open area inside the pack - antioxidants, CO2, aroma, ethanol or other antimicrobial substances. Active packaging can also involve actively absorbing undesirable substances, such as oxygen or ethylene.
Among the so-called intelligent packaging methods we find indicators that provide relevant information about the food product and its life cycle, for example quality and maturation indicators or time and temperature indicators.
Packaging with built in temperature sensors that "blab" to the consumer when the chill chain is broken can be found on the market. This works as a flexible indicator of shelf life. For example the indicator might change from green to yellow if the food product is exposed to higher temperatures than it has been produced and packed to accept. The actual distribution temperature decides the shelf life of the product. The shelf life is currently decided by simulating distribution temperature. If the food product is stored at a temperature far higher than that recommended by the producer and the authorities, the product may in the worst case become both spoiled and actually hazardous to health before the "use by" date. This could give producer and consumer a false sense of safety.
How the sensors work
The indicators are based on a temperature-dependent physical, chemical or enzymatic reaction that can only go one way (irreversible). The change can be shown as a colour change for example. If the temperature increases, so does the speed of the reaction, which again reduces the time before the change is indicated. The indicators can be pre-programmed for a time and temperature to suit the food in the pack.
