Application Of High-Hydrostatic Pressure to Inactivate Escherichia Coli O157:h7 On Alfalfa Sprout Seeds – Sprout Food Safety Research

Application of high-hydrostatic pressure to inactivate Escherichia coli O157:H7 on alfalfa sprout seeds.

Institute of Food Technologists Annual Meeting, New Orleans, Jun 29, 2008,Hudaa S. Neetoo, University of Delaware, Newark, DE; Mu Ye, University of Delaware, Newark, DE; Haiqiang Chen, University of Delaware, Newark, DE

Alfalfa sprouts are among the most widely consumed sprouts in the United States due to their nutritional and health-promoting benefits. Sprouts eaten raw are increasingly being perceived as hazardous foods as they have been implicated inEscherichia coli O157:H7 outbreaks. Seeds usually are already contaminated at the time of sprouting and although initial pathogen contamination levels are very low, the conditions used in the sprouting process are congenial for the growth of E. coliO157:H7. The objective of our study was to evaluate the potential of using high hydrostatic pressure (HHP) technology for alfalfa seed decontamination. Alfalfa seeds (2g) inoculated with a cocktail of five strains of E. coli O157:H7 to a final level of ~ 8 log10CFU/g were subjected to pressures of 500 and 600 MPa for 2 min at 20°C in a dry or wet (immersed in 3 mL water) state. Immersing seeds in water during pressurization considerably enhanced pressure inactivation of E. coli O157:H7 achieving reductions of 3.5 log and 5.7 log at 500 and 600 MPa, respectively. When dry seeds were pressurized, both pressure levels reduced the counts by < 0.7 log. No significant difference (P > 0.05) in germination rate was observed between un-treated alfalfa seeds (control) and pressure-treated wet seeds at either 500 or 600 MPa.Seeds that were pressure-treated at 600 MPa in the dry state had a significantly (P < 0.05) lower germination potential after 3 days’ germination compared to water-immersed pressurized seeds. Dry seeds pressure-treated at 500 MPa had lower germination rates than water-immersed ones although the difference was not significant. These results therefore demonstrate the potential application of HHP at 600 MPa as a highly effective (> 5 log reduction) intervention technique for decontamination of alfalfa seeds.