FATE OF SALMONELLA-MONTEVIDEO ON AND IN RAW TOMATOES AS AFFECTED BY TEMPERATURE AND TREATMENT WITH CHLORINE

A study was undertaken to determine the survival patterns of Salmonell a montevideo G4639 on and in tomatoes during storage and the efficacy of chlorine treat:ment on inactivation of the pathogen. The population of S. montevideo on the surfaces of inoculated tomatoes stored at 10 degrees C did not change significantly (P < 0.05) throughout an 18-day storage period. Significant increas;es in population occurred within 7 days and within 1 day when tomatoes were stored at 20 and 30 degrees C, respectively. A significantly higher number of cells was taken up by the core tissue of tomatoes tempered at 25 degrees C when the tomat oes were dipped in a suspension at 10 degrees C compared with the numb er taken up when the tomatoes were dipped in cell suspensions tempered at 25 or 37 degrees C. Populations remained constant throughout subse quent storage for 8 days at 10 degrees C, regardless of the temperatur e differential between tomatoes and the dip suspension. Storage of tom atoes at 20 degrees C, however, resulted in significant increases in p opulations of S. montevideo. Populations of the pathogen on the surfac es and in the core tissues of tomatoes were:significantly reduced by d ipping for 2 min in a solution containing 60 or 110 ppm (60 or 110 mu g/ml) chlorine, respectively; however, treatment in solution containin g 320 ppm chlorine did not result in complete inactivation. Population s of S. montevideo remained unchanged in chopped tomatoes stored at 5 degrees C for 216 h (9 days) but increased significantly after storage for 96 or 22 h at 20 or 30 degrees 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 concentra tion of 200 ppm. The temperature of tomatoes should be reduced to 10 d egrees C as rapidly as possible after harvesting and should be held at 10 degrees C until they are ripened immediately before consumption.