Gamma radiation treatment of post-harvest produce for Salmonella enterica reduction on baby carrot and grape tomato

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

Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2021
Publication Date: 2/8/2022
Citation: Berrios-Rodriguez, A., Olanya, O.M., Niemira, B.A., Ukuku, D.O., Mukhopadhyay, S., Orellana, L. 2022. Gamma radiation treatment of post-harvest produce for Salmonella enterica reduction on baby carrot and grape tomato. Journal of Food Safety. 42(1)e12951:1-10.

Interpretive Summary: Contamination of produce by Salmonella bacteria is a significant food safety issue, due to health effects on consumers. Therefore, mitigation of Salmonella contamination of produce is paramount. In this research, we evaluated the effects of low-dose gamma radiation on survival and reductions of Salmonella on post-harvest carrot and tomato. Irradiation treatments of 0 to 1 kGy were applied on produce subsequent to pathogen inoculations. The effects of storage temperatures (5 and 20C) and times (0, 3 and 7-days) on Salmonella reductions were determined. Gamma radiation treatment resulted in significant pathogen reductions at both temperatures and days. Radiation treatment reduced Salmonella populations on carrot (5C, 3-day) from 7.55 (0 kGy-control) to 2.57 log CFU/g (1 kGy); and on tomato (5C, 3-day) from 7.15 log CFU/g (0 kGy) to non-detectable level (1 kGy). Pathogen reductions at 20C and 0 and 7 storage days were similar. Although injury to Salmonella cells were quantified due to radiation treatment, injured cells recovery from produce were low, implying that pathogen re-growth from injured bacteria may be minimum at these treatments. These results indicate that low-dose irradiation treatments as an established technology may provide sufficient pathogen reductions, and serve as a valuable mitigation tool for enhanced post-harvest pathogen control on produce.

Technical Abstract: Occurrences and contamination of Salmonella enterica on produce is a significant food safety issue. The objective of this research was to evaluate the effects of low-dose gamma radiation on survival and reductions of S. enterica on post-harvest carrot and tomato. Irradiation treatments of 0 to 1 kGy was applied on produce, following pathogen inoculations in replicated experiments. The effects of temperatures (5 and 20C) and produce storage times (0, 3 and 7-days) on pathogen reductions were determined. The average Salmonella populations in untreated control varied from 7.12±0.05 to 7.54±0.12 log CFU/g of produce. Pathogen reductions were recorded at 5 and 20C immediately after treatment but differed between temperatures and storage days. At 3-day storage, Salmonella populations on carrot (5C) were reduced by radiation treatments from 7.55±0.16 (0 kGy) to 2.57±0.33 log CFU/g (1 kGy); and on tomato (5C) from 7.15±0.11 log CFU/g (0 kGy) to non-detectable level (1 kGy). Similar trends of pathogen reductions at 20C at 0 and 7-day storage were recorded. Injury to Salmonella cells by radiation treatment varied, however; recovery of injured bacterial cells did not differ significantly (P>0.05) on produce at 20C, implying resuscitation of injured cells was similar at that temperature. Low-dose irradiation treatment could provide sufficient pathogen reductions on produce as a post-harvest mitigation technology with numerous avenues for its applications.