Antimicrobial packaging targets listeria

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