Behavior of Salmonella spp. on fresh-cut tropical fruits

The behavior of Salmonella spp. on fresh-cut dragon fruit, banana, starfruit, mango, pineapple, guava and wax apple at 28 °C and 4 °C was studied. Growth of Salmonella on the fresh-cut starfruit was studied at 7, 10, 15, 20, 25 or 30 °C. Tropical fruits were cut into cubes and spot inoculated with three-strain cocktail of Salmonella spp. at four inoculum levels (0.1, 1.0, 2.0 and 3.0 log CFU/g). Results indicated that Salmonella grew well at 28 °C on all tested fruits at different inoculum levels [growth potential (δ) = 2.57–4.95] except for mango and pineapple, with the maximum populations ranging from 2.67 to 6.95 log CFU/g. Starfruit was the most suitable matrix for Salmonella growth. Salmonella exhibited a poor growth on mango and no growth on pineapple. At 4 °C for 6 days, no obvious Salmonella growth was observed on all the tested fruits. In addition, Salmonella growth was inhibited by different ratios of mango or pineapple ethanol extracts to Luria–Bertani (LB) broth. The inhibition percent of pure mango or pineapple ethanol extracts on Salmonella growth was 96.3% or 108.9%, respectively. Predicted growth parameters fitted by the Baranyi and Robert model indicated that on fresh-cut starfruit, Salmonella spp. grew immediately at 25 and 30 °C with no lag time and grew slowly at 7–20 °C with lag times of 74.74, 34.19, 9.32, 2.61 h. The predicted growth rate (μmax, log CFU/g/h) for Salmonella on starfruit was 0.0048 ± 0.00022, 0.011 ± 0.00067, 0.039 ± 0.0027, 0.088 ± 0.0022, 0.19 ± 0.0061, 0.29 ± 0.023 at 7, 10, 15, 20, 25 and 30 °C, respectively. At higher storage temperatures, the growth rate and maximum population of Salmonella were higher. This study suggests that Salmonella may grow and reach high populations on fresh-cut tropical fruits depending on storage conditions except for mango and pineapple and should be stored at low temperatures (<4 °C) to ensure the safety and extend the shelf life of fresh-cut tropical fruits.