INTELLIGENT PACKAGING- PART- III

GAS INDICATORS

Oxygen indicator

       The integrity of a gas package is one of its most essential properties. If the package leaks, the optimized atmosphere surrounding the food will deteriorate as the head space gas merges with the normal atmosphere surrounding the package and the beneficial effects will be lost. It is essential to detect a leakage in order to avoid the serious effects of contaminated food on the consumer’s health, especially if the sensory quality does not correlate with the microbial quality. Package integrity testing taking place in the food processing plant is not sufficient for the detection of leakage created after the product has left the processing plant. Therefore a leak indicator attached to the package would advantageously ensure the package integrity throughout the whole distribution chain from the manufacturer to the consumer.

       Most of the commercial internal O2 indicators are either colour labels or tablets. O2 indicators react with O2 coming from the outside of the package  through leakages (leakage indicator) or they are intended to be used with O2 absorbers to verify that all O2 has been absorbed from the package head-space(e.g. Yoshikawa et al., 1979; Perlman and Linschitz, 1985; Krumhar and Karel,1992). O2 indicators can be used successfully to confirm that the product has been properly packaged. The most famous O2 indicator is Ageless-Eye the indicator is pink when there is no O2 in the environment (0.1% or less) and blue if O2 does exist (0.5 % or more) (Abe, 1990).

       A typical visual O2 indicator consists of a redox dye, a reducing compound and an alkaline compound. In addition to these main components, compounds such as a solvent (typically water and/or an alcohol) and bulking agent (e.g. zeolite, silica gel, cellulose materials, polymers) are added to the indicator (Yoshikawa et al., 1979). The indicator can be formulated as a tablet (Goto, 1987; Yoshikawa et al., 1979) or a printed layer (Davies and Garner, 1996; Krumhar and Karel, 1992; Yoshikawa et al., 1979) or it can also be laminated in a polymer film (Nakamura et al., 1987).

       The O2 indicators are too sensitive to O2 from the gas packaging point of view and they are also reversible in colour change reaction. So, in the first case, the indicators may react to the residual O2 entrapped in the gas packaging process or, in the second case, they may indicate that there is no O2 in a package (i.e. a package should be intact) even though the product is spoiled by microbial growth which has consumed O2 entrapped through leakage (Ahvenainen et al.,1995b). The colour change of the indicators should therefore be irreversible.

Ageless Eye O₂ indicator

Ageless Eye sachets (Mitsubishi Gas Chemical Company, Japan) contain an oxygen indicator tablet in order to confirm the normal functioning of Ageless absorbers. When oxygen is absent in the headspace (>0.1%), the indicator displays a pink color. When oxygen is present

REFERENCES

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·      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.).

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·      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.

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