Evaluation of pulsed light treatment for inactivation of Salmonella in packaged cherry tomato and impact on background microbiota and quality

Authors: Mukhopadhyay, Sudarsan; Ukuku, Dike; Jin, Zhonglin; Olanya, Modesto; Fan, Xuetong

Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2022
Publication Date: 1/13/2023
Citation: Mukhopadhyay, S., Ukuku, D.O., Jin, Z.T., Olanya, O.M., Fan, X. 2023. Evaluation of pulsed light treatment for inactivation of Salmonella in packaged cherry tomato and impact on background microbiota and quality. Journal of Food Safety. https://doi.org/10.1111/jfs.13035.
DOI: https://doi.org/10.1111/jfs.13035

Interpretive Summary: Fresh produce has been increasingly implicated as the leading cause of foodborne illnesses, which costs the US economy enormously in terms of loss in productivity and medical expenses. There is a serious need for safe and effective methods that can eliminate field-acquired contamination threats. We developed a small laboratory scale, high-intensity-short-time light based technology that can penetrate plastic packing enclosures and kill harmful agents like Salmonella on produce such as tomato which was used as a model commodity. This is a sustainable green technology that requires no heat, water or chemicals. The technology can be used either directly or after packaging of food items and hence can eliminate undesirable post-treatment recontamination in the supply chain. This low cost clean technology holds a great promise for market implementation.

Technical Abstract: Incidences of foodborne illness outbreaks associated with fresh fruits and vegetables continues to be a major concern. Safe and effective nonthermal technologies are needed to lessen the risk of pathogen contamination. The objective of this study was to investigate the efficacy of high intensity short time pulsed light (PL) application against populations of Salmonella and native microorganisms in packaged cherry tomatoes, and to evaluate the changes in quality during storage. Stem scars of tomatoes, inoculated with a three serotype cocktail of Salmonella enterica were treated with PL for up to 60 s. Polyethylene (PE) films of 25.4, 50.8 and 76.2 micrometer thickness were used for packaging treatment. Both packaged and direct PL treatment provided greater than 1 log reduction of the pathogen in 10 s (10.5 Joule per square cm). Direct treatment for 10 s resulted in 1.9±0.57 log CFU/g reduction of Salmonella, whereas log reductions were 1.6±0.29, 1.4±0.39 and 1.1±0.42 log CFU/g for tomatoes packaged in 25.4, 50.8 and 76.2 micrometer thick packaging enclosures respectively. However, this decrease in log reductions was not significantly (P > 0.05) affected by the film thicknesses tested. Also, no significant difference in PL decontamination efficacy between packaged and unpackaged tomatoes was observed. Treatment significantly reduced the initial populations of aerobic mesophilic bacteria, and molds and yeast by >1 log. Packaged tomatoes were softer, but not significantly, after treatment. Storage time did not affect fruit firmness. No significant change in the visual appearance of fruits was observed after treatment and during the entire 14 days of storage. Overall, the results of this study demonstrate that high intensity short time PL treatment of packaged cherry tomato may enhance microbial safety without affecting quality and reduce post processing recontamination in the supply chain.