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

Authors: BERRIOS-RODRIGUEZ, AMARYNETTE - University Of Puerto Rico; Olanya, Modesto; Ukuku, Dike; Niemira, Brendan; Mukhopadhyay, Sudarsan; ORELLANA, LYNETTE - University Of Puerto Rico

Submitted to: Food Science and Technology (Sociedade Brasileira de Food Sci. and Tech) -SBCTA
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2022
Publication Date: 9/2/2022
Citation: Berrios-Rodriguez, A., Olanya, O.M., Ukuku, D.O., Niemira, B.A., Mukhopadhyay, S., Orellana, L.E. 2022. Gamma radiation effects on the survival and reduction of Listeria monocytogenes on carrot and tomato. Food Science and Technology (Sociedade Brasileira de Food Sci. and Tech) -SBCTA. https://doi.org/10.1590/fst.17622.
DOI: https://doi.org/10.1590/fst.17622

Interpretive Summary: Produce such as carrot and tomato is quite popular with consumers and accounts for 16.8 metric tons of total world production. In the US, the annual consumption of both produce is approximated at 6.2 metric tons. Despite the relative abundance and consumption, carrot and tomato have been prone to pathogen contamination and associated illnesses. Listeria is one such a pathogen that has been implicated in produce associated illnesses. In this research, we determined the 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 to 1 kGy were applied on produce inoculated with Listeria. Gamma radiation reduced Listeria populations by 5.9 logs on carrot and 3.9 logs on tomato (3 days, 5C), while reductions were 4.4 and 4.0 logs on carrot and tomato (7 days, 5C), respectively. The mean Listeria decreases on carrot and tomato by low-dose radiation at 20C were less than at 5C, and ranged from 2.2-4.2 logs. Although inactivation of Listeria by radiation treatment varied with storage temperatures and days, the reductions were significant, implying that this established technology is efficacious and applicable for Listeria control. As a 1 kGy of gamma radiation application has shown substantial Listeria reductions, its potential application could eliminate this harmful microbe and improve the post-harvest safety and utilization of carrot and tomato.

Technical Abstract: Assessment of pathogen survival is important for food safety. Listeria monocytogenes is a substantial problem on produce and food contamination. As a non-thermal process, low-dose gamma radiation may be a useful tool for pathogen inactivation, since it is rapid and has little toxic by-products. Therefore, the objective of this research was to assess the 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 (3 days of storage, 5°C), while reductions were 4.4 and 4.0 logs on carrot and tomato (7 storage days, 5C); respectively. At 20C, Listeria reductions by low-dose radiation were 2.8 logs on carrot and 4.2 logs on tomato (3 day storage) and pathogen decreases were 2.2 logs on carrot and 2.9 logs on tomato (7 storage days). Although the reductions of the pathogen by radiation treatment varied with storage temperatures and days, the linear decreases were significant (P<0.05) as the dosage increased from 0.25 to 1.0 kGy, implying that treatments were efficacious for Listeria control. As a 1 kGy of gamma radiation application has shown substantial Listeria reductions on produce, its potential utilization could improve the post-harvest safety of carrot and tomato.