Gamma radiation effects on the survival and reduction of Listeria monocytogenes on carrot and tomato

Abstract

Assessment of pathogen survival is important for food safety. Listeria monocytogenes causes significant produce and food contamination worldwide. The objective of this research was to assess survival and reduction of L. monocytogenes on post-harvest carrot and tomato subjected to low-dose radiation at different storage temperatures and times. Radiation levels of 0, 0.25, 0.50, 0.75, and 1 kGy were applied on produce inoculated with L. monocytogenes. Gamma radiation reduced Listeria populations by 5.9 logs on carrot and 3.9 logs on tomato at 3 days of storage (5 °C), while reductions were 4.4 and 4.0 logs on carrot and tomato, respectively; at 7 storage days (5 °C). At 20 °C, Listeria reductions were 2.8 logs on carrot and 4.2 logs on tomato (3 storage days) and pathogen decreases were 2.2 logs on carrot and 2.9 logs on tomato (7 storage days). Although pathogen reductions by radiation treatment varied with storage temperatures and days, the linear decreases were significant as the dosage increased from 0.25 to 1.0 kGy, implying that treatments were efficacious for pathogen inactivation. As low dose gamma radiation (1 kGy) showed substantial reduction of Listeria monocytogenes on fresh carrot and tomato, thus, use of low dose low dose gamma radiation can improve the post-harvest safety of carrot and tomato.

Keywords:
Listeria monocytogenes; gamma radiation; inactivation; carrot; tomato; post-harvest