Effect of wet steam on the survival of Salmonella and Listeria monocytogenes cells attached to Hass whole avocado

Abstract

The effect of wet steam treatment on the attached cells of Salmonella and Listeria monocytogenes on Hass avocados surface, according to the nozzle position of the steam generator and application time, was evaluated. Furthermore, the transfer of pathogenic bacteria from the wet steam-treated avocado epicarp to the pulp was investigated. Avocado epicarp was inoculated with Salmonella or L. monocytogenes and stored at 25 °C for 72 h. Later, avocados were washed with water and steamed from the top, upper front, and bottom front parts for 30, 45, and 60s. Both pathogens' loosely (LA) and strongly (SA) attached cells on the avocado surface were enumerated. Pulp samples treated avocados with steam from the top for 60 s were extracted to enumerate both pathogens. Salmonella was more susceptible than L. monocytogenes at steam treatments, whose efficacy varied according to the nozzle position and exposure time. For both pathogens, the maximum effectiveness of steam was obtained from the top for 60 s. Pathogens count in the pulp of avocados steamed from the top for 60 s was lower than in the pulp obtained from untreated avocados. These results indicate that steaming Hass avocados enhances the safety of rind and pulp.