Inactivation of Salmonella Typhimurium and quality preservation of cherry tomatoes by in-package aerosolization of antimicrobials

Authors: JIANG, YUNBIN - Tianjin University Of Science And Technology; Fan, Xuetong; LI, XIHONG - Tianjin University Of Science And Technology; Gurtler, Joshua; Mukhopadhyay, Sudarsan; Jin, Zhonglin

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2016
Publication Date: 8/22/2016
Citation: Jiang, Y., Fan, X., Li, X., Gurtler, J., Mukhopadhyay, S., Jin, Z.T. 2016. Inactivation of Salmonella Typhimurium and quality preservation of cherry tomatoes by in-package aerosolization of antimicrobials. Food Control. doi: 10.1016/j.foodcont.2016.08.031.

Interpretive Summary: Multiple outbreaks of foodborne illnesses have attributed to Salmonella contamination of raw tomatoes in recent years. The conventional method of fresh produce washing is not effective to alleviate the problem of contamination. In this study, we applied common sanitizers as aerosols inside a package to inactivate attenuated Salmonella on tomatoes while maintaining fruit quality. Results demonstrated that the in-package treatment could reduce 99.999% of Salmonella on tomatoes without detrimental effects on sensory or nutritional quality attributes. Therefore, the in-package aerosolization technology may be used by the fresh produce industry as a novel method to minimize the presence of Salmonella on tomatoes.

Technical Abstract: The purpose of the present study was to investigate the efficacy of in-package aerosolized aqueous sanitizers in reducing populations of attenuated Salmonella enterica serovar Typhimurium inoculated on tomato fruit and in maintaining fruit quality. Cherry tomatoes were inoculated with a cocktail of attenuated S. Typhimurium ATCC 53467 and 53468 strains on the smooth skin surface and stem scar area. Next, 200 ppm free chlorine, and peroxyacetic acid (PAA) and aqueous ClO(2) at different concentrations, 2% lactic acid + 2% acetic acid +2% levulinic acid, and 3% acetic acid + 3% lactic acid were aerosolized into a clamshell container containing either the inoculated cherry tomatoes for the antimicrobial study or un-inoculated fruit for quality analyses. Treated fruit were stored at 10 degrees C for 3 weeks. Initial results demonstrated that a cocktail of S. Typhimurium ATCC 53467 and 53468 responded similarly to the antimicrobials as a cocktail of 4 outbreak-associated Salmonella spp., suggesting that the attenuated S. Typhimurium cocktail could be used as a surrogate. S. Typhimurium populations on smooth tomato surfaces were reduced by more than 5 log CFU/fruit with 400 ppm PAA, 2% lactic acid + 2% acetic acid +2% levulinic acid, 3% acetic acid + 3% lactic acid, and aqueous ClO(2) (100 and 400 ppm). PAA at 80 ppm and chlorine at 200 ppm achieved only 0.85 and 1.50 log CFU/fruit reductions, respectively. On the stem scar area, 400 ppm aqueous ClO(2) was more effective in reducing S. Typhimurium populations than other treatments, achieving 4.89 log CFU/fruit reduction, followed by 400 ppm PAA (2.62 log CFU/fruit). The efficacy of ClO(2) and acid combination treatments increased during storage, achieving >3 log CFU/fruit inactivation with the acid combination and ca. 6 log with for 400 ppm with ClO(2). None of the treatments significantly (p>0.05) affected color, appearance, firmness, vitamin C, lycopene or antioxidant values of tomatoes during 3 weeks of storage; although, an off-odor was detected for samples treated with the organic acids in the earlier period of the storage. These results suggest that in-package aerosolized sanitizers can be used as a novel method for the inactivation of Salmonella on tomato fruit.