15D-17

 

 

            For the past decade, numerous foodborne outbreaks have been linked to the consumption of sprouts produced from seeds contaminated with pathogens. The Food and Drug Administration has recommended producers to treat seeds with sanitizers prior to sprouting. The effectiveness of this treatment, however, varied widely between seed lots.

            Hence, alternative methods need to be developed to insure the safety of sprout consumption. This study assesses the use of high hydrostatic pressure (HPP) technology as an alternative method to eliminate pathogens in seeds.

            Following inoculation with Escherichia coli O157 and Listeria monocytogenes, alfalfa seeds were subjected to HPP treatment at 275, 375, 475 and 575 Mpa, respectively for 2 minutes at 40–45°C. Another set of sample was treated at a constant pressure of 475 MPa for 2, 4, 6 and 8 minutes, respectively at 40-45°C.

            A significant reduction in population of E. coli O157 occurred with increasing pressure and exposure to HPP. At 575 Mpa, a 2-log reduction of E. coli O157 was achieved and with the 8-minute exposure, the kill rate doubled. L. monocytogenes, however, showed resistance to the bactericidal effect of HPP, obtaining a 1-log reduction at 575 Mpa (2 minutes) and 475 Mpa (8 minutes). HPP was also observed to negatively affect the germination rate of seeds, with treated seeds achieving only 58-70% germination capability, compared to 97% in control seeds. Treated seeds also took a longer time to germinate.

            These results suggest that L. monocytogenes is more resistant to HPP than E. coli O157. Past studies have reported similar results, attributing the resistance of L. monocytogenes to its Gram-positive characteristics.  Although HPP may be effective in reducing the population of E. coli O157 in alfalfa seeds, this was achieved at the expense of germination and as such, may not be an economical treatment for sprout producers.