Page Banner

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 and Regrowth of Indigenous Microflora on Vegetable Sprouts and on Warm/cold Water-Washed Cut Iceberg Lettuce

item Rajkowski, Kathleen
item Fan, Xuetong
item Sommers, Christopher
item Niemira, Brendan

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: January 27, 2005
Publication Date: July 11, 2006
Citation: Rajkowski, K.T., Fan, X., Sommers, C.H., Niemira, B.A. 2006. Irradiation destruct values of shigella sonnie, salmonella or escherichia coli o157:h7 and post irradiation survival and regrowth of indigenous microflora on vegetable sprouts and on warm/cold water-washed cut iceberg lettuce. IAEA, July 25-29, 2005, Vienna, Austria. p. 317-324.

Technical Abstract: Consumption of contaminated fresh produce with Salmonella spp., Escherichia coli O157:H7 or Shigella sonnie resulted in confirmed food-borne outbreaks in the United States and elsewhere. Irradiation destruct values of the produce related isolates 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, 0.30, and 0.24 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 sprouts and cut lettuce washed in 5 and 47 C water. Microbiological profiles were monitored during refrigerated (4 C) storage and analyzed each week for up to three weeks to determine the keeping quality. Regardless of the initial background, after irradiating to 2 kGy, a two log reduction was observed for the total aerobic and coliform counts on the sprouts or lettuce samples. During storage the bacterial counts of the irradiated samples 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, inhibited microbial spoilage and achieved a 5 log reduction for both the E. coli O157:H7 and Shigella sonnie. The reduced bacterial counts would also provide a margin of safety by also reducing food-borne pathogen levels.

Last Modified: 4/22/2015