Fresh tomatoes have been implicated in multiple Salmonella foodborne outbreaks in recent years. Many intervention technologies have limited effectiveness against Salmonella, likely due to the presence of pathogens in protective sites such as stem scar areas. The study was conducted to evaluate the effects of washing tomato fruit with combinations of organic acids and post-treatment rinsing with water on populations of Salmonella inoculated onto stem scar areas of two types of tomatoes. In addition, impact on fruit quality was investigated during 21 days post-treatment storage at 10°C. A four-strain cocktail of Salmonella enterica (S. Montevideo, S. Newport, S. Saintpaul, and S. Typhimurium) was inoculated onto stem scar areas of grape and large round tomatoes. The inoculated fruits were then treated for 2 min with the following solutions: water, 2% lactic acid + 2% acetic acid + 2% levulinic acid, 1.7% lactic acid + 1.7% acetic acid + 1.7% levulinic acid, and 3% lactic acid + 3% acetic acid. After treatments, half of the fruits were washed with water while another half were not rinsed. Non-inoculated grape tomatoes, used for quality analysis, were treated with the same solutions with and without subsequent water rinse. Results showed that the acid combinations reduced populations of Salmonella enterica on the stem scar area of grape tomatoes by 1.52-1.90 log CFU/fruit, compared with the non-treated control while water wash and rinse removed the bacterium by only 0.23-0.30 log CFU/fruit. On the stem scar of large round tomatoes, the same acid treatments achieved 3.54 log CFU/fruit reduction of the pathogen. Rinsing with water after acid combination treatments did not significantly affect the efficacy of the treatments in either grape or large round tomatoes. Acidic off-odor was detected on fruits treated with acid combinations without water rinse 1 day after treatment while the water rinse eliminated off-odors. The acid treatments with and without water rinse did not consistently affect appearance, color, firmness, or lycopene or ascorbic acid contents of tomatoes during 21-days storage at 10°C. Therefore, washing tomato fruit with organic acids followed by rinsing with water can be used to reduce populations of Salmonella without damage to fruit quality.

Washing tomato fruit with organic acids to reduce populations of Salmonella and preserve fruit quality

255th National Meeting (2018)

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