Freshness Indicators

Freshness Indicators belong to the group of intelligent packagings. Intelligent packaging systems are systems which monitor the condition of a product, detect changes in it and show its actual condition. They are usually applied in the form of labels on the packaging and thereby act as an indicator. These indicators are able to detect and display certain influences on the package and thus on the packaged product. Product information and information about the product history can thus be transmitted in a simple and fast way. Intelligent packaging is applied in the food sector as well as for the transport of valuable art objects, pharmaceuticals and other fragile and sensitive products.

A freshness indicator is a indicator that monitors and gives information about the quality of the packed food.

During food spoilage, two principal changes take place:

  • Microbiological growth and metabolism resulting in pH changes, formation of toxic compounds, off – odours, gas and slime formation.
  • Oxidation of lipids and pigments resulting in undesirable flavours, formation of compounds with adverse biological reaction or discoloration.


A freshness indicator indicates directly the quality of the product. Normally, these indicators are focused in detecting the first class of changes. These changes in pH, gas composition, etc. are detected by indicators and are transformed in a response, usually a colour response, that can be measured easily and that is correlated with the food freshness.

An essential prerequisite in the development of freshness indicators is knowledge about the quality indicating metabolites. The formation of the different metabolites depends on the nature of the packaged food product, spoilage flora and the type of packaging.

It is well known that high levels of basic volatile nitrogen compounds like ammonia, dimethylamine and trimethylamine give an indication about microbiological spoilage of fish . On the other hand, biogenic amines (e. g. tyramine, cadaverine, putrescine, histamine) and sulphur compounds are considered as indicators of hygienic quality of meat products. But there is also some others compounds that are not specific of one kind of product. For example, organic acids like lactic acid and acetic acid or ethanol are the major compounds having a role in glucose fermentation by lactic acid bacteria, carbon dioxide (CO2) is generally known to be produced during microbial growth and ATP – related compounds as hypoxanthine and inosine correlates with the sensory quality of a many of foodstuffs.

The aim of this platform is to explain the different freshness indicator available / patented at the moment. Most of the indicators available respond to a pH change and are not specific for a determinate product but there is also some specific indicator that detects a specific microorganism or metabolite.

Sources:

ÓLAFSDOTTER G., LUTEN J., DALGAARD P., CARECHE M., VERREZ – BAGNIS V., MARTINSDÓTTIR E AND HEIA K. Suitability of ammonia – n. dimethylamine – n,trimethylamine – n, trimethylamine oxide – n and total volatile basec nitrogen as freshness indicators in seafoods. Methods to determine the freshness of fish in research and industry EU – FAIR project AIR3CT94 2283, Paris, International Institute of Refrigeration, 92 - 99