Application of physical and chemical means to kill foodborne pathogens on alfalfa seeds
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Most foodborne illness outbreaks which alfalfa sprouts have been implicated have been associated with seeds contaminated with human pathogenic bacteria. efficacy of ultrasound treatment with combinations of heat and chemical antimicrobial solutions was investigated. Significant (P ¡Â 0.05) reductions of over 4.33 log CFU/g of Salmonella populations were reached with ultrasound in combination with 1% Ca(OH) The 2 at 55oC for 5 min, 1% Ca(OH)2 plus 1% Tween 80 at 23 or 55oC for 2 or 5 min, and 8% H2O2 at 23oC for 5 min, 55oC for either 2 min without inhibiting the germination percentage of seeds. However, none of these treatments can completely eliminated the populations of Salmonella on seeds. Treatment of seeds with with 331 ppm Tsunami¢ç 200 and 1200 ppm Sanova¢ç were less effective in killing Salmonella on alfalfa seeds. Dielectric heating alone also caused significant reductions of Escherichia coli O157:H7, Salmonella and Listeria monocytogenes on alfalfa seeds without inhibiting the germination rate. When the seed moisture content was ca. 6.5%, dielectric heating reduced E. coli O17:H7 populations by 1.14 log at 89oC for 20 sec; Salmonella populations by 1.06 log at 89oC for 20 sec; and L. monocytogenes by 0.89 log at 82oC for 12 sec. The overall appearance and color of sprouted seeds after treatment were not significantly different with untreated sprouted seeds.