Comparison of chemical treatments to kill Salmonella on alfalfa seeds destined for sprout production

Outbreaks of salmonellosis in the US, Canada and Finland linked to alfalfa sprouts have been attributed to Salmonella stanley in 1995 and Salmonella newport in 1996. This study was undertaken to compare the efficacy of chemical treatments in killing a mixture of five Salmonella serovars inoculated onto alfalfa seeds. Solutions containing calcium hypochlorite or sodium hypochlorite at concentrations of 1800 and 2000 μg/ml active (available) chlorine, respectively, as well as 6% hydrogen peroxide or 80% ethanol were effective in reducing Salmonella populations by more than 1000 fold. However, viable Salmonella cells were detected in seeds treated for 10 min in these solutions. The inaccessibility of Salmonella cells in crevices and between the cotyledon and testa of seeds to lethal concentrations of these chemicals are thought to be the reason for the lack of effectiveness.