Survival of listeria, staphylococcus, and salmonella on sliced cantaloupe and tomatoes treated with 1.0 and 3.0 kGy using a 5 MeV electron beam accelerator

This research was conducted to determine microorganism survival and shelf life extension for sliced cantaloupe and tomatoes treated with electron beam irradiation. In the first study, the survival of Listeria and Staphylococcus in sliced cantaloupe held at 4 °C and treated with 1.0 and 3.0 kGy was examined along with the shelf life extension of irradiated cantaloupe slices. Serial dilutions were plated on standard methods agar (SMA) for aerobic plate count, RoseBengal agar with supplement C (RBA-C) for yeast and mold, violet red bile agar (VRB-MUG) for conforms, Baird Parker agar with egg yolk telurite (BRA) for S. aureus, and PALCAM with Ceftazidmine for Listeria: Samples (25 g) were enriched in Listeria enrichment broth and streaked onto PALCAM agar. The shelf life study involved two experienced panelists using a visual rating scale. Listeria and Staphylococcus survival was significantly (P<0.05) inhabited by 3.0 kGy. Additionally, 3.0 kGy increased the shelf life of cantaloupe slices while not effecting texture quality.

In the second study, the survival of Listeria and Salmonella on tomato slices stored at 4 °C and treated with 1.0 and 3.0 kGy electron beam irradiation was examined. Additionally, the shelf life extension of irradiated tomato slices was also examined utilizing two experience panelist using a visual rating scale. Samples (25 g) were enumerated on six different media. Samples were also enriched for Listeria on PALCAM agar and Salmonella on Hektoen Enteric and Bismuth Sulfite agar. The survival of Listeria and Salmonella was significantly (P<0.05) inhibited by 3.0 kGy. Positive confirmation of Listeria and Salmonella at the 3.0 kGy treatment during enrichment indicate that enrichment procedures must also be used to ensure the destruction of microorganisms. Additionally, 1.0 and 3.0 kGy irradiation can extend the shelf life of tomatoes.