INTELLIGENT PACKAGING -PART -IV

CO2 INDICATORS

These indicators provide fast colour reaction, demonstrating that the correct CO2 level has been put in every package. The indicators display the desired concentrations of carbon dioxide inside the package (Ahvenainen, Hurme, 1997). This allows incorrectly packaged product to be immediately repacked

       The chemistry that is usually employed to sense CO2 is based on its ability to acidify water.

       The detection of the protons released by carbonic acid, H₂CO₃, is easily achieved using a pH-indicating dye, such as meta-cresol purple, which is blue when deprotonated (MCP^-) and yellow when acidified (MCPH). Thus, an aqueous solution containing MCP^- is blue in the absence of CO₂, but yellow when saturated with CO2. ideally, a solvent-based (i.e., largely hydrophobic), intelligent ink for CO2 is desired. This is achieved by coupling the anion of the pH-indicating dye with a phase transfer cation, Q+, such as the tetraoctyl ammonium cation, to create a solvent-soluble ion pair, MCP_Q+xH2O, which, as indicated by its molecular formula, usually retains a few molecules of water. As a consequence, when incorporated into an ink, the following reversible colorimetric process can be effected.

       The Trufflex GS carbon dioxide SPD, which has been promoted by Cryovac-Sealed Air Ltd., is an example of this technology.

       CO2 indicators can be used in package leakage control. However, reversible colour change of the CO2 indicators may in the worst case result in false information for the consumer: if the packed product is microbiologically spoiled, e.g. due to leakage, the CO2 produced by microbial metabolism may still keep the head-space CO2 at a level that indicates good product quality. The colour change of the CO2 indicators used as leak indicators should therefore be irreversible (Hurme and Ahvenainen, 1996).

REFERENCES

·      AHVENAINEN, R., 2003: Novel Food Packaging Techniques. Cambridge UK: Wood head Publishing, 400 p. ISBN 978-1-85573-675-7.

·      COLES, R., MCDOWELL, D. and KIRWAN, M. J., 2003: Food Packaging Technology. Oxford, UK: Blackwell Publishing, 346 p. ISBN 978- 0849397882.

·      C. Suzuki, J. Chem. Ed. 68, 588–589 (1991).

·      FQSI International, FreshQt smart sensor label web information. Available at http://www.fqsinternational.com/products.htm. Accessed March 2008.

·      International published Patent WO 2006/032025 A1, J. R. Williams, K. E. Myers, M. M. Owens, and M. A. Bonne (to Food Quality Sensor International, Inc.).

·      R. Want, ‘‘Enabling Ubiquitous Sensing with RFID,’’ Computer 37, 84–86 (2004).

·      S. Nambi, S. Nyalamadugu, S. M.Wentworth, and B. A. Chin, ‘‘Radio Frequency Identification Sensors,’’ 7th World Multiconference on Systemics, Cybernetics and Informatics, Dubna, Russia, July 30–August 2, 2003.

·      SUMMERS, L., 1992: Intelligent packaging for quality. So_ Drinks Management International, Vol. 36, p. 32–33. ISSN 0953–4776.

·      RODRIGUES, E. T. and HAN, J. H., 2003: Intelligent packaging. In: Heldman, D. R. and Moraru, C. I. (ed.). Encyclopaedia of Agricultural, Food and Biological  Engineering. 2nd edition, New York: Marcel Dekker, pp. 528–535. ISBN 978-1439811115

·     HAN, J. H., HO, C. H. L. and RODRIGUE, E. T., 2005: Intelligent packaging. In: Han, J. H. Innovation in food packaging. UK, London: Elsevier Academic  Press, p. 138–155. ISBN 978-0123116321.

·      Gontard, N. Active packaging for food processing and preservation. In: International Congress on Engineering and Food: ICEF 9, 7e11 March 2004, Montpellier, France.

To be continued...............