Survival of Salmonella Transformed To Express Green Fluorescent Protein on Italian Parsley as Affected by Processing and Storage

To study the effect of processing and storage parameters on the survival of Salmonella on fresh Italian parsley, parsley bunches were dipped for 3 or 15 min in suspensions that were preequilibrated to 5, 25, or 358C and inoculated with Salmonella transformed to express enhanced green fluorescent protein. Loosely attached and/or associated, strongly attached and/or as-sociated, and internalized and/or entrapped Salmonella cells were enumerated over 0, 1, and 7 days of storage at 258C and over 0, 1, 7, 14, and 30 days of storage at 48C using surface-plating procedures. Leaf sections obtained from samples after 0, 1, and 7 days of storage were examined using confocal scanning laser microscopy. Temperature of the dip suspension had little effect on the attachment and survival of Salmonella cells on parsley. Regardless of the temperature or duration of dip, Salmonella was internalized. Immersion for longer times resulted in higher numbers of attached and internalized cells. Micro-scopic observations supported these results and revealed Salmonella cells near the stomata and within cracks in the cuticle. Storage temperature had the greatest impact on the survival of Salmonella cells on parsley. When stored at 258C, parsley had a shelf life of 7 days, and Salmonella populations significantly increased over the 7 days of storage. For parsley stored at 48C, numbers of Salmonella cells decreased over days 0, 1, and 7. After 7 days of storage, there were no viable internalized Salmonella cells detected. Storage temperature represents an important control point for the safety of fresh parsley. Fresh produce is an important source of enteric path