Behavior of Salmonella spp. and natural microbiota on fresh-cut dragon fruits at different storage temperatures

초록

The aim of this study was to determine survival or growth of unadapted, acid-adapted and cold-stressed Salmonella spp., and natural microbiota on fresh-cut dragon fruits at different storage temperatures. Dragon fruits were sliced and spot inoculated with five-strain cocktail of Salmonella spp. at two inoculum levels (2.5 or 5.5 log CFU/g). Inoculated fruits were stored at 28 degrees C for 48 h and at 4 degrees C and 12 degrees C for 96 h. Salmonella population significantly increased by 2.4 to 3.0 log CFU/g at low inoculum level, whereas the numbers increased by 0.4 to 0.7 log CFU/g at the high inoculum level on fruits held at 28 degrees C for 48 h. Only unadapted and acid-adapted cells grew with 0.7 to 0.9 log increase at the low inoculum level at 12 degrees C for 96 h. No significant growth was observed at both inoculum levels during storage at 4 degrees C. Overall, acid, starved and cold adaptation of Salmonella spp. did not show significant difference in survival or growth on fresh-cut dragon fruits during storage compared to unadapted control cells. For natural microbiota on the fruit, mesophilic bacterial counts reached to 5-log CFU/g at 28 and 12 degrees C by 9.9 and 52.9 h. Similar with Salmonella spp. there was no growth of natural microbiota at 4 degrees C. These results showed that Salmonella spp. could grow on fresh-cut dragon fruits under inappropriate storage conditions, indicating that fresh-cut dragon fruits could be a potential vehicle for salmonellosis. Thus, this study suggests that fresh-cut dragon fruits should be stored at 4 degrees C to ensure the safety as well as to extend the shelf life of fresh-cut dragon fruits. (c) 2012 Elsevier B.V. All rights reserved.

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