Transfer and Survival of Salmonella Newport and Typhimurium on Fresh-Cut Tomato and Cucumber

摘要

The project aims to identify and characterize fruit attributes, bacterial determinants, storage periods, processing factors and material properties that collectively lead to the transfer and survival of Salmonella enterica including serotype Newport and Typhimurium on fresh-cut tomatoes and cucumbers. This study investigated the transfer pattern of Salmonella on fresh-cut tomato and cucumber by using a knife contaminated by cutting inoculated samples to cut four uninoculated samples successively. Each group of sliced samples was homogenized with 0.1% BPW (1:1 dilution) in sterile blender jars and filtered by Whirl-Pak filter bag. The population of transferred Salmonella was evaluated by plating on XLD agar plates with proper dilution. The transfer rate of Salmonella was determined by comparing each group of sliced samples (2 nd to 4th cut) with the first group of cut samples. The survival of Salmonella on contaminated fresh-cut or in blended juice samples was also monitored at 90% +/- 5% RH for up to 7 days at 4C. Negative control was included to eliminate the native flora background and each test was performed in triplicates. The distribution of Salmonella on the cut surface of tomato and cucumber halves were examined by placing the cut side down on the XLD agar plate for 10 seconds. The distribution of Salmonella was observed and photographed on XLD plates after incubating at 37C for 24h. As for results, produce type played a significant role (P < 0.05) in the transfer of Salmonella but no such trend was found either between one day and two days storage period or two Salmonella strains. The transfer rate of Salmonella decreased as the frequency of cutting increased. After seven-day storage period, Salmonella could survive well in both of tomatoes and cucumbers and no significant differences (P > 0.05) between fresh-cut and juice samples were observed in survival dynamic.