Submitted to: Meeting Abstract
Publication Type: Other
Publication Acceptance Date: 11/29/2002
Publication Date: 4/14/2003
Citation: Niemira, B.A., Fan, X., Sommers, C.H. 2003. Radiation sensitivity of a pathogen (listeria monocytogenes) and a surrogate (l. innocua) on inoculated endive (cichorium endiva). Report of 2nd FAO/IAE Research Co-ordination Meeting (RCM), April 14-18, 2003, Belfast, Ireland. p. 94-96.
Technical Abstract: Ionizing radiation inactivates the pathogenic bacteria that can contaminate leafy green vegetables. Leaf pieces and leaf homogenate of endive (Cichorium endiva) were inoculated with the pathogen Listeria monocytogenes or Listeria innocua, a non-pathogenic surrogate bacterium. The radiation sensitivity of the two strains were found to be similar, although L. innocua was more sensitive to the type of suspending leaf preparation. During refrigerated storage following irradiation, the population of L. monocytogenes on inoculated endive was briefly suppressed by 0.42 kGy, a dose calibrated to achieve a 99% reduction. However, the pathogen regrew after 5 days until it exceeded the bacterial levels on the control after 19 days in storage. Treatment with 0.84 kGy, equivalent to 99.99% reduction, suppressed L. monocytogenes throughout the course of refrigerated storage. Doses up to 1.0 kGy had no significant effect on color of endive leaf material, whether taken from the leaf edge or the leaf midrib. The texture of leaf edge material was unaffected by doses up to 1.0 kGy, while the maximum dose tolerated by leaf midrib material was 0.8 kGy. These results show that endive leaves may be treated with doses sufficient to achieve at least a 99.99% reduction of L. monocytogenes with little or no impact on the product's texture or color.