Maria Grudén (SLU, Swedish University of Agricultural Sciences, Dep. of Biosystems and Technology, Microbial horticulture)Lars Mogren (SLU, Swedish University of Agricultural Sciences, Dep. of Biosystems and Technology, Microbial horticulture)Beatrix W. Alsanius (SLU, Swedish University of Agricultural Sciences, Dep. of Biosystems and Technology, Microbial horticulture)
The bacterial colonization of rocket leaves was studied before processing and after bagging. At the same time the raw and process water quality at different stages during processing under commercial conditions was studied. Both leave and water was analyzed with respect to microorganisms at 22 degrees C, slow growing bacteria, total coliform bacteria, E. coli, intestinal enterococci, as well as Listeria monocytogenes, Salmonella spp., and Campylobacter spp.. Samples were collected at four occasions with 3 replicates per event. The bacterial load in the process water increased substantially after produce came in contact with the raw water. Microorganisms at 22 degrees C and slow growing bacteria exceeded 300 000 CFU ml-1 and 50 000 ml-1. Also intestinal enterococci were very frequent, in contrast to total coliform bacteria and E. coli. Microbial reduction rate before and after washing was log 0.5. Microbial communities inhabiting the produce before and after washing as well as the raw and process water were collected and analyzed using DGGE. From these specimens, microorganisms were grown on semi-selective media (0.1 TSA, King Agar B, Enterococci agar, and VRBD). Five randomly selected colonies were identified using Biolog GenIII panels. Various Pseudomonas species and Pantoea agglomerans were frequent in the process water. Also the phyllosphere flora before washing was dominated by Pantoea agglomerans. After washing, Pantoea agglomerans, Rahnella aquatilis and Pseudomonas were abundant. Pseudomonas fluorescens as well as Enterobacter cloaceae resisted washing procedures in the washing line and under laboratory conditions.