Application of Physical and Chemical Means to Kill Foodborne Pathogens On Alfalfa Seeds

Application of Physical and Chemical Means to Kill Foodborne Pathogens on Alfalfa Seeds (2001)

C. Lu, S. O. Nelson, L. R. Beuchat, and M. A. Harrison

Most foodborne illness outbreaks where alfalfa sprouts have been implicated have been associated with seeds contaminated with human pathogenic bacteria. The efficacy of ultrasound treatment in combination with heat and chemical antimicrobial solutions was investigated. Significant (P < 0.05) reductions of over 4.33 log10 cfu/g of Salmonella populations were reached with ultrasound in combination with 1% Ca(OH)2 at 55°C for 5 min, 1% Ca(OH)2 plus 1% Tween 80 at 23 or 55°C for 2 or 5 min, and 8% H2O2 at either 23°C for 5 min, or 55°C for 2 min without inhibiting the germination percentage of seeds. However, none of these treatments completely eliminated the populations of Salmonella on seeds. Treatment of seeds with 330 ppm Tsunami® 200 and 1200 ppm Sanova® 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 O157:H7 populations by 1.14 log10 for 20 sec at 89°C; Salmonella populations by 1.06 log10 for 20 sec at 89°C; and L. monocytogenes by 0.89 log10 for 12 sec at 82°C. The overall appearance and color of sprouted seeds after treatment were not significantly different than untreated sprouted seeds.