Survival of Aeromonas hydrophila in fresh tomatoes (Lycopersicum esculentum Mill) stored at different temperatures and treated with chlorine.

This study examines the survival of two Aeromonas hydrophila strains (A. hydrophila ATCC 7965 [strain A] and A. hydrophila isolated from food [strain B] on the surface and core tissue of fresh tomatoes stored at different temperatures and the efficacy of chlorine treatment on their survival. Counts of A. hydrophila on the surface of tomatoes stored at 25 and 35 degrees C were significantly higher between days 1 and 4 for both strains as compared to results obtained at 6 degrees C. Core tissue counts of A. hydrophila cells on tomatoes dipped in a cellular suspension at 25 degrees C and stored at 25 degrees C were significantly higher (P < 0.05) than counts obtained with dip suspensions at 6 or 35 degrees C. In chopped tomatoes stored at 25 and 35 degrees C, populations of aerobic mesophiles showed significant increases after 96 and 70 h, respectively. The populations of both A. hydrophila strains in chopped tomatoes stored at 6 degrees C increased significantly after 96 h, while at 25 and 35 degrees C the counts increased in the first hours of incubation. Viable counts of A. hydrophila on the surface and central tissue of tomatoes significantly decreased (P < 0.05) when the samples were dipped for 2 min in chlorine at a concentration of 50 ppm (50 microgram/ml). The results suggest that tomatoes should be kept at low temperatures during storage, shipping, and retail stocking and that chlorine at a concentration of 50 ppm should be used to reduce the levels of A. hydrophila.