Decontamination of sprouting seeds using high hydrostatic pressure

Escherichia coli O157:H7 and Salmonella spp. have been associated with foodborne outbreaks of gastrointestinal illness caused by seed sprouts. Decontaminating sprouting seeds presents a unique challenge in that even a low residual pathogen population remaining on contaminated seed after treatments appears capable of growing to very high levels during sprouting. The objective of our study was to evaluate the potential of using high hydrostatic pressure (HHP) technology alone or in combination with other hurdles to decontaminate sprouting seeds from Escherichia coli O157:H7 and/or Salmonella spp.;In our first study, alfalfa seeds were inoculated with a cocktail of five strains of E. coli O157:H7 and subjected to various combinations of pressure levels and exposure times. When a pressure level of 650 MPa at 20°C was applied, the time required to achieve complete elimination was 15 min, achieving a germination rate identical to those of untreated seeds after eight days of sprouting. The second study demonstrated that soaking seeds prior to pressure treatment enhanced the pressure inactivation of E. coli O157:H7. The third and fourth study highlighted the effectiveness of high-pressure treatment in combination with mild heat to eliminate E. coli O157:H7 and Salmonella on seeds. The applicability of HHP to decontaminate other types of sprouting seeds (crimson clover, red clover, radish and broccoli seeds) was examined in our fifth study. Our final study comparatively assessed the efficacy of treatments of dry heating alone or in conjunction with high hydrostatic pressure (HHP) to eliminate a ∼5 log CFU/g load of Salmonella and E. coli O157:H7 on alfalfa seeds. Dry heating at 60 and 65°C for 24 and 12 h respectively followed by HHP at 600 MPa and 35°C for 2 min also eliminated both pathogens at a variable expense in the sprouting yield. Taken together, we can ascertain that high pressure processing is an intervention strategy that can potentially deliver > 5 log reduction and elimination of enterohemorrhagic E. coli O157:H7 and Salmonella spp. on sprouting seeds with a variable impact on the seed viability indices.