Purpose: The purpose of this study was to investigate the ability of Salmonella Agona and Typhimurium to grow on alfalfa sprouts after CFIA-recommended seed treatments and a treatment compliant with organic production principles.
Methods: Alfalfa seeds inoculated with Salmonella Agona PARC 5 isolated from alfalfa sprouts or Salmonella Typhimurium PARC 64 (4.67±0.26 log CFU/g) were subjected to three types of sanitizing treatments: 5,000 ppm chlorine, 8% hydrogen peroxide, and an organic treatment (50°C hot water, 2% hydrogen peroxide, and 0.1% acetic acid). The sanitized seeds were sprouted and Salmonella were recovered on xylose lysine deoxycholate agar during germination. Survival curves were plotted and compared using one-way ANOVA.
Results: The density of both Salmonella serovars increased from <10 CFU/g immediately after treatment to 5.5 to 7.5 log CFU/g after six days of germination. The lag phase of both serovars, after the chlorine treatment, were significantly shorter (P<0.05) compared to those after the other two treatments. The maximum growth rate of Salmonella Agona was greater (P<0.05) than Typhimurium. For instance, the cell density of Salmonella Agona reached 7.34±0.27 log CFU/g 24 hours after the chlorine treatment versus 5.77±0.51 and 6.87±0.14 log CFU/g after the hydrogen peroxide and the organic treatments, respectively.
Significance: These data show that Salmonella cells were able to recover and grow on sprouting alfalfa seeds. More lethal treatments need to be devised for production of pathogen-free sprouted vegetables.