Behavior of Salmonella spp. on fresh-cut tropical fruits.
Ma Chen, Li JianGuo, Zhang Qun
Author Affiliation: Hainan Provincial Key Laboratory of Quality and Safety for Tropical Fruits and Vegetables, Laboratory of Quality & Safety Risk Assessment for Tropical Products (Haikou) Ministry of Agriculture, Analysis and Testing Center, Chinese Aca
Food Microbiology 54 : 133-141
Abstract : 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 (?)=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 (?max, 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.