Fate of Salmonella montevideo on and in raw tomatoes as affected by temperature and treatment with chlorine

Abstract

A study was undertaken to determine the survival patterns of Salmonella montevideo G4639 on and in tomatoes during storage and the efficacy of chlorine treatment on inactivation of the pathogen. The population of S. montevideo on the surfaces of inoculated tomatoes stored at 10°C did not change significantly (P < 0.05) throughout an 18-day storage period. Significant increases in population occurred within 7 days and within 1 day when tomatoes were stored at 20 and 30°C, respectively. A significantly higher number of cells was taken up by the core tissue of tomatoes tempered at 25°C when the tomatoes were dipped in a suspension at 10°C compared with the number taken up when the tomatoes were dipped in cell suspensions tempered at 25 or 37°C. Populations remained constant throughout subsequent storage for 8 days at 10°C, regardless of the temperature differential between tomatoes and the dip suspension. Storage of tomatoes at 20°C, however, resulted in significant increases in populations of S. montevideo. Populations of the pathogen on the surfaces and in the core tissues of tomatoes were significantly reduced by dipping for 2 min in a solution containing 60 or 110 ppm (60 or 110 μg/ml) chlorine, respectively; however, treatment in solution containing 320 ppm chlorine did not result in complete inactivation. Populations of S. montevideo remained unchanged in chopped tomatoes stored at 5°C for 216 h (9 days) but increased significantly after storage for 96 or 22 h at 20 or 30°C, respectively. We recommend that tomato packinghouses maintain their dip tanks at a temperature higher than the temperature of the tomatoes and at a free chlorine concentration of 200 ppm. The temperature of tomatoes should be reduced to 10°C as rapidly as possible after harvesting and should be held at 10°C until they are ripened immediately before consumption.