Inactivation of Salmonella in cherry tomato stems cars and quality preservation by pulsed light treatment and antimicrobial wash

Authors: LENG, JUNCAI - Tianjin University Of Science And Technology; Mukhopadhyay, Sudarsan; SOKORAI, KIMBERLY - US Department Of Agriculture (USDA); Ukuku, Dike; Fan, Xuetong; Olanya, Modesto; Juneja, Vijay

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2019
Publication Date: 11/16/2019
Citation: Leng, J., Mukhopadhyay, S., Sokorai, K., Ukuku, D.O., Fan, X., Olanya, O.M., Juneja, V.K. 2019. Inactivation of Salmonella in cherry tomato stems cars and quality preservation by pulsed light treatment and antimicrobial wash. Food Control. 110:107005. https://doi.org/10.1016/j.foodcont.2019.107005.
DOI: https://doi.org/10.1016/j.foodcont.2019.107005

Interpretive Summary: Tomato provides a good ecological niche for the proliferation of numerous microorganisms including Salmonella. Produce industry uses chlorine-based sanitizer wash to control cross-contamination which has only limited efficacy and produce organochlorine carcinogens. New methods are needed. Pulsed light (PL) is a safe and effective non-thermal technology. However, prolonged exposure to PL to achieve a pasteurization level intensity causes quality deterioration. Therefore, a low dose PL treatment in combination with active sanitizer wash may prove appropriate to enhance safety and quality of fresh produce.

Technical Abstract: The objective of this study was to investigate the efficacy of pulsed light (PL) treatment, a new formula antimicrobial (LAPEN) wash and the combinations thereof in inactivating Salmonella on stem scars of cherry tomato. The treatment effects on background microbiota and sensory quality during storage at 10 °C for 21 days was also determined. A bacterial cocktail containing three serotypes of Salmonella enterica was used for this study based on their association with tomato-related outbreaks. Tomatoes were spot inoculated on stem scars before being treated with PL (1- 63 J/cm2), LAPEN sanitizer (2 min) or combinations of PL with LAPEN Sanitizer. PL inactivation was in'uenced signi'cantly at low doses. Treatment time of 30 s, equivalent to PL dose of 31.5 J/cm2, was found optimal. The optimal PL dose resulted 2.3 log CFU/g reduction of Salmonella while a 2 min wash in LAPEN sanitizer provided 2.1 log CFU/g reduction of the pathogen on stem scars location. Two possible sequences of PL and LAPEN combinations were explored. For PL-LAPEN combination treatment, inoculated tomatoes were initially treated with optimal PL dose (31.5 J/cm2) followed by 2 min immersion in LAPEN sanitizer whereas in LAPEN-PL treatment, tomatoes were first washed in LAPEN prior to PL exposure. Treatment of PL-LAPEN indicated a strong synergistic inactivation as no Salmonella survivor were detectable after treatment indicating greater than 5 log reduction, while LAPEN-PL treatment indicated a compound inactivation activity providing 4.5 logs reduction of the pathogen. The PL-LAPEN treatment not only reduced native spoilage microbiota of tomato but also hindered their growth while in storage for three weeks. The visual and firmness quality of tomato were not significantly affected by the PL-LAPEN treatment. Overall, our results demonstrate that PL-LAPEN intervention technology can be used as novel method to enhance microbial safety and quality of cherry tomato.