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Antimicrobial packaging targets listeria

By Joe Whitworth , 04-Oct-2012
Last updated the 04-Oct-2012 at 15:25 GMT

Researchers have found packaging with an oxygen scavenger or carbon dioxide generator can inhibit the growth of listeria on ready-to-eat (RTE) meat.

Jinru Chen and Aaron Brody also found packaging structures with an allyl isothiocyanate (AIT) generator only had a limited antimicrobial effect.

Cooked ham samples (25g) inoculated with a five-strain mixture of Listeria monocytogenes (2 or 4 log CFU g−1) were packaged into three different     antimicrobial packaging structures and samples in the non-antimicrobial packaging structure served as controls.

Control spoilage

The purpose of incorporating antimicrobials into food packaging structures is to control spoilage as well as contamination with pathogens.

The structures evaluated have not previously been used for bacterial growth control on food products but modified atmosphere packaging (MAP) has been used to assure product safety and quality.

The samples were stored at 4, 10, or 22 °C, and populations of total aerobic bacteria, Enterobacteriaceae, and inoculated L.monocytogenes were     determined twice a week over a four week storage period.

In three out of four occasions the carbon dioxide generator and oxygen scavenger more effectively controlled L.monocytogenes growth at 10 °C than at 22 and 4 °C.  

The researchers said the reasons are not precisely known but speculated it may be associated with different rates of carbon dioxide generation and     migration within the antimicrobial films at different storage temperatures.

Study findings

Packaging structures with the carbon dioxide generator and oxygen scavenger evaluated in the present study effectively controlled the growth of L. monocytogenes artificially inoculated on cooked ham samples.

In the non-antimicrobial, control packaging structure, the average populations of L. monocytgenes increased from the initial 2 log CFU g−1 inoculation level to 2.84, 5.21 and 6.42 log CFU g−1 at 4, 10, and 22, respectively over the 4 w storage period.

“Significant inhibitions on total aerobic bacteria and Enterobacteriaceae counts were also observed in packaging structures with the CO2 generator and O2 scavenger. However, packaging structures with the AIT generator only significantly inhibited L. monocytogenes, total aerobic bacteria, and Enterobacteriaceae in some samples, mainly those stored at 22 °C,” said the researchers.

“Packaging structures with the CO2 generator or O2 generator significantly inhibited the growth of artificially inoculated L. monocytogenes on cooked ham. The same structures also inhibited the growth of naturally contaminated total aerobic bacteria and Enterobacteriaceae.

“In comparison, packaging structures with the AIT generator only had limited antimicrobial effects.”

The researchers suggested that some of the evaluated packaging structures can effectively control bacterial populations, particularly Listeria populations on RTE meat products.

They concluded that the antimicrobial packaging structures evaluated could have potential uses in improving the safety of processed, ready-to-eat meat products.

Source: Science Direct - Food Control, Volume 30 Issue 1, March 2013, pages 306-310

Published online ahead of print, doi: 10.1016/j.foodcont.2012.07.002

"Use of active packaging structures to control the microbial quality of a ready-to-eat meat product" 

Authors: Jinru Chen and Aaron L. Brody