Monitoring the Pulse

March 11/Food Weekly News -- "The risk of listeriosis associated with ready-to-eat foods is a major concern in the U.S.," explain researchers from Cornell Universty. "Pulsed light (PL) treatment has been effective for killing Listeria." The possibility of enhancing the antilisterial capability of PL treatment by combining PL with an additional hurdle, the natural antimicrobial nisin, was explored in this study," they opine in the Journal of Food Protection.

"First, the ability of Listeria innocua to mimic the response of Listeria monocytogenes to PL treatment was demonstrated. Subsequently, a series of inoculation studies was performed in which canned sausages were surface inoculated with L. innocua as a surrogate for L monocytogenes and then treated with a commercial preparation of nisin (Nisaplin), PL, or a combination of the two treatments. The application of a Nisaplin dip alone resulted in an immediate reduction of L. innocua by 2.35 +/- 0.09 log CFU. PL reduced L. innocua by 1.37 +/- 0.30 log CFU after exposure to 9.4 J/cm(2). A total reduction of 4.03 +/- 0.15 log CFU was recorded after the combined treatment of Nisaplin and PL for 48 h at 4 degrees C. The long-term survival of L. innocua was evaluated on sausages stored at 4 degrees C. Treatment with Nisaplin and PL resulted in a 4- to 5-log reduction for two replicate studies. The combination treatment resulted in no significant microbial growth during 28 and 48 days of refrigerated storage in the first and second replicates, respectively," wrote A.R. Uesugi and colleagues, Cornell University.

The researchers concluded, "These results suggest that this combination treatment can be used as an effective antilisterial step in the production of ready-to-eat foods."

Uesugi and colleagues published their study in the Journal of Food Protection ("Reduction of Listeria on Ready-to-Eat Sausages after Exposure to a Combination of Pulsed Light and Nisin." Journal of Food Protection, 2009;72(2):347-353).

Additional information can be obtained by contacting C.I. Moraru, Cornell University, Dept. of Food Science, Stocking Hall, Ithaca, NY 14853.

From the March 16, 2009, Prepared Foods E-dition