title: Behavior of Salmonella spp. and natural microbiota on fresh-cut dragon fruits at different storage temperatures.
abstract: 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°C for 48h and at 4°C and 12°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°C for 48h. Only unadapted and acid-adapted cells grew with 0.7 to 0.9log increase at the low inoculum level at 12°C for 96h. No significant growth was observed at both inoculum levels during storage at 4°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°C by 9.9 and 52.9h. Similar with Salmonella spp. there was no growth of natural microbiota at 4°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°C to ensure the safety as well as to extend the shelf life of fresh-cut dragon fruits.
authors.affiliation: Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore.
authors.forename: Hui Li
authors.initials: HL
authors.lastname: Sim
authors.forename: Yoon-Ki
authors.initials: YK
authors.lastname: Hong
authors.forename: Won Byong
authors.initials: WB
authors.lastname: Yoon
authors.forename: Hyun-Gyun
authors.initials: HG
authors.lastname: Yuk
mesh_terms: D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D005511:Food Handling / Q000379:methods* / Q000592:standards*; D005516:Food Microbiology; D005638:Fruit / Q000382:microbiology*; D054892:Metagenome / Q000502:physiology; D012475:Salmonella / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D013696:Temperature; D013997:Time Factors