Effects of pulsed light and aerosolized organic acid treatments on inactivation of Salmonella enterica on cherry tomato, reduction of microbial loads, and preservation of quality.

Authors: Mukhopadhyay, Sudarsan; Ukuku, Dike; Olanya, Modesto; Sokorai, Kimberly; Fan, Xuetong

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2021
Publication Date: 11/9/2021
Citation: Mukhopadhyay, S., Ukuku, D.O., Olanya, O.M., Sokorai, K.J., Fan, X. 2021. Effects of pulsed light and aerosolized organic acid treatments on inactivation of Salmonella enterica on cherry tomato, reduction of microbial loads, and preservation of quality. Food Control. https://doi.org/10.1016/j.foodcont.2021.108667.
DOI: https://doi.org/10.1016/j.foodcont.2021.108667

Interpretive Summary: Produce safety continues to be the major source of food borne illness outbreaks. Pathogens like Salmonella, Escherichia coli, Listeria monocytogenes have been implicated in outbreaks linked with leafy greens, tomatoes, and cantaloupes. As a result, there is a serious need for effective intervention technology that can eliminate field-acquired contamination, especially given fresh produce is eaten raw. We developed a small, laboratory scale, high-intensity-short-time light based cold technology, which when combined with tiny antimicrobial drops, kills pathogens like Salmonella on the surface of tomatoes used here as a model food. This technology requires no heating yet can eliminate or at least minimize field-acquired contamination. This low-cost clean technology holds great promise for market implementation.

Technical Abstract: Fresh produce remains the leading cause of foodborne illness outbreaks. Novel nonthermal technologies are needed to reduce the risk of pathogen contamination. The objective of this study was to develop a novel intervention technology exploiting synergistic integration of high intensity short time (10 s) pulsed light (PL) and aerosolized formic acid (AFA) for inactivation of Salmonella and maintenance of quality of the cherry tomato. Smooth surfaces of tomatoes, inoculated with a cocktail containing three serotypes of Salmonella enterica, were treated with PL for 10 s followed by 2 min treatment with 1 % AFA. Un-inoculated treated tomatoes were used to study the treatment effects on native microflora and quality. PL delivered significant inactivation at low doses. An optimal 10 s PL treatment equivalent to a dose of 10.5 Joule/square cm, provided a 2.2 log reduction of Salmonella while a 2 min exposure in 1% AFA antimicrobial yielded comparatively low, 1.7 log CFU/g reduction of Salmonella on tomato. The combination treatments of PL (10 s) followed by 1 % AFA (2 min) provided significant synergistic inactivation yielding a 4.2 log reduction of the pathogen. During cold storage (10 degree Celsius ) the survivor population declined further providing a 4.8 log reduction on day 21. The combination PL-AFA treatment not only significantly reduced the native microbiota of tomato but also hindered their growth while in storage for three weeks. Mold and yeast spoilage organism populations were declined to below the detection level. Furthermore, the apparent quality factors as firmness and color of tomatoes were not significantly affected by the combination treatment. The treatment boosts the redness appearance of tomatoes indicating favorable consumer acceptability. Overall, our results demonstrate that combination of PL and AFA treatment could potentially be used as a novel approach to enhance microbial safety and quality of tomatoes.