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United States Department of Agriculture

Agricultural Research Service

Title: Irradiation D-Value for Escherichia Coli O157:h7 Sp and Salmonella Sp. on Inoculated Broccoli Seeds and Effect of Irradiaton on Broccoli Sprout Keeping Quality and Seed Viability

item Rajkowski, Kathleen
item Boyd, Glenn
item Thayer, Donald

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 13, 2002
Publication Date: September 13, 2002
Citation: VOL. 66, NO. 5, 2003, PAGES 760-766

Interpretive Summary: Broccoli seeds when sprouted are consumed for health benefits. In order to control pathogenic bacteria on both the broccoli sprouts and seeds the irradiation process can be used. There are no reports on the effect of irradiation on commercially raised broccoli sprouts, broccoli seed viability, or the amount of irradiation needed to destroy bacterial pathogens on the seeds. After irradiating the broccoli sprouts at a low level, the shelf life of the sprouts was increased by 10 days because there was a decrease in the native microflora. Broccoli seeds had a decreased germination rate after irradiation at low levels. The broccoli sprouts raised from these irradiated seeds were smaller and weighed less than sprouts from the non-irradiated seeds. Irradiation conditions to maintain seed viability were only capable of reducing the bacterial pathogens by 90%. However, a safer fresh broccoli sprout can be provided to the consumer rby irradiating the sprout rather than the seeds at a low level of irradiation approved by the FDA. This study provides information important to seed distributors, sprout producers and government agencies.

Technical Abstract: Broccoli sprouts contain beneficial health compounds. Like alfalfa sprouts, broccoli sprouts can be the vehicle of bacterial pathogens, which when consumed can cause illness. To reduce the bacterial pathogens the gamma irradiation process was used to study the effect on broccoli sprouts keeping quality and seed viability, and to determine the radiation D-value of Salmonella spp. and strains of Escherichia coli O157:H7 on broccoli seeds. After irradiating the broccoli sprout to a dose of 2 kGy, the total background and coliform counts decreased, increasing the shelf life by 10 days. Broccoli seeds were irradiated at various dose levels from 1 to 5 kGy to determine the effect of radiation on % germination, yield ratio (w/w), sprout length and thickness. The yield ratio (w/w), sprout length and thickness decreased at a dose level greater or equal to 2 kGy, whereas % germination decreased at a dose level greater than 3 kGy. The radiation D- value of 1.10 kGy for the Salmonella spp. isolated from vegetables was significantly higher than the D-value of 0.74 kGy for the non-vegetable isolates. The D-value for the non-vegetable strains of Escherichia coli O157:H7 was 1.43 kGy, which was significantly higher than the D-value of 1.11 kGy for the vegetable isolates. The radiation D-values of Salmonella spp. and strains of Escherichia coli O157:H7 on dried inoculated broccoli seeds were higher than previous reported values for inoculated sprouts. Irradiation to a dose level of 2 kGy extended the shelf life of broccoli sprouts, but had an adverse effect on sprout production by the irradiated seed.

Last Modified: 4/18/2015