Survival of Listeria innocua, Salmonella salford and Escherichia coli on the surface of fruit with inedible skins

Abstract

The survival and growth of Salmonella salford, Escherichia coli and Listeria innocua on the surface of fruit with inedible skins was investigated. Passionfruit, banana, cantaloupe (rock melon) and honeydew melon were inoculated by immersion in solutions containing two inoculum levels and then stored under normal storage and distribution temperature regimes. A low (ca. 103 cfu ml−1) and high (105–106 cfu ml−1) inoculum concentration was used for each organism. Bananas were stored for 13 days at 18 °C, passionfruit for 6 days at 10 °C, cantaloupes for 7 days at 8 °C and honeydew melons for 1 day at 12 °C then 5 days at 8 °C. Generally, the fruit did not support growth under the conditions employed, although test organisms could usually be recovered either directly or after an enrichment step. The exception was the growth of L. innocua on the skin of cantaloupe. Significant growth was observed for both the low and high inoculum levels during storage at 8 °C. Cantaloupes inoculated with 2.4×106 cfu ml−1 had an initial level of 3.4×103 cfu cm−2 and this increased to 2.9×105 cfu cm−2 during 7 days storage. For the low inoculum (1.3×103 cfu ml−1), levels that could only be detected by enrichment initially increased to 1.4×102 cfu cm−2.