Behavior of Salmonella spp. on Fresh-cut Dragon Fruits at Different Storage Temperatures

Introduction: Dragon fruit is one of the popular tropical fruits in Southeast Asia. Although there has been no outbreak associated with dragon fruits, the likelihood of foodborne outbreak still exists since Salmonella spp. have been isolated from the fruits in Malaysia. Thus, it is important to understand the behavior of Salmonella spp. on fresh-cut dragon fruits during storage at various temperatures in order to minimize the risk of salmonellosis.

Purpose: The aim of this study was to determine the survival or growth of unadapted, acid-adapted and cold-stressed Salmonella spp. on fresh-cut dragon fruits at different storage temperatures.

Methods: The dragon fruits were sliced and spot inoculated with a five-strain cocktail of Salmonella spp. at two inoculum levels (2.5 log CFU/g and 5.5 log CFU/g). Inoculated fruits were air dried and stored at 28 °C for 48 h and at 4 °C and 12 °C for 96 h.

Results: Salmonella populations significantly (P < 0.05) increased by 2.5 to 3 log CFU/g at low inoculum level, whereas the numbers increased by 0.3 to 0.7 log CFU/g at high inoculum level on fresh-cut dragon fruits held at 28 °C for 48 h. Only unadapted control and acid-adapted cells grew with 0.7 to 0.9 log increase at low inoculum level at 12 °C for 96 h. No significant growth was observed at both inoculum levels during the storage at 4 °C. Overall, acid or cold adaptation of Salmonella spp. did not show better survival or growth on fresh-cut dragon fruits during storage compared with unadapted control cells.

Significance: 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 °C to inhibit the proliferation of Salmonella spp.