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United States Department of Agriculture

Agricultural Research Service

Title: Irradiation Destruct Values of Shigella Sonnie, Salmonella Or Escherichia Coli O157:h7 and Post Irradiation Survival An Regrowth of Indigenous Microflora on Vegetable Sprouts and on Warm Or Cold Water-Washed Cut Iceberg Lettu

item Rajkowski, Kathleen

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: May 5, 2005
Publication Date: July 25, 2005
Citation: Rajkowski, K.T. 2005. Irradiation destruct values of shigella sonnie, salmonella or escherichia coli o157:h7 and post irradiation survival an regrowth of indigenous microflora on vegetable sprouts and on warm or cold water-washed cut iceberg lettu. IAEA Research Co-Ordination Meeting. Islambad, Pakistan. July 25-29, 2005. U.S.A. Report.

Technical Abstract: Confirmed food-borne outbreaks have occurred in the United States and elsewhere caused by the ingestion of contaminated fresh produce with Salmonella spp., Escherichia coli O157:H7 or Shigella sonnie. The irradiation destruct values of the isolates from the fresh produce are not known and were determined after being inoculated on fresh lettuce or sprouts using a gamma source. The resulting destruct values for Salmonella, E. coli O157:H7 and Shigella sonnie were 0.46 ± 0.02, 0.30 ± 0.02, and 0.24 ± 0.03 kGy, respectively. These values are comparable with the published values for the meat-related food-borne isolates. Ionizing irradiation was used as an intervention to reduce the indigenous microbial populations on fresh cut lettuce washed in 5 and 47 C water or sprouts. The microbiological profiles were monitored during refrigerated (4 C) storage and analyzed each week for up to three weeks. Regardless of the initial background, a two log reduction was observed for the total aerobic and coliform counts on the lettuce or sprout samples. During storage the bacterial counts increased but not to the level of the non-irradiated samples. The results indicate that a 2 kGy dose improved the microbial keeping quality of the fresh produce and inhibited microbial spoilage. The reduced bacterial counts would also provide a margin of safety by also reducing food-borne pathogen levels.

Last Modified: 4/19/2015
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