Inactivating Salmonella Typhimurium on Contaminated Alfalfa Seeds for Sprouting without Detrimental Effect on Viability of Seeds

Abstract

The purpose of this study was to inactivate Salmonella Typhimurium loaded on alfalfa seeds without having negative effect on seed germination. Inoculated alfalfa seeds were treated with dry heat at 60, 70 or 80°C for 0, 12, 18 or 24 h followed by 2% hydrogen peroxide solution (10 min). Also, the effect of sequential treatment of hydrogen peroxide, drying, vacuum packaging, and dry heat was verified. Populations of Salmonella on alfalfa seeds treated with dry heat alone (60, 70 or 80°C) for up to 24 h were reduced by 0.26 to 2.76 log CFU/g, and sequential treatment with dry heat and H2O2 reduced populations by 1.66 to 3.60 log CFU/g. The germination percentage of seeds subjected to sequential treatments was significantly enhanced to up to 97%, whereas that of untreated seeds was only 79.5%. This result suggests that sequential treatment with dry heat and hydrogen peroxide is applicable for reducing levels of Salmonella on seeds while simultaneously enhancing seeds germinability. Also, Populations of Salmonella on alfalfa seeds after sequential treatment were not detected after 8 or 3 h of dry heat treatment at 70 or 73 °C. Salmonella populations including injured cells were also reduced to below the detection limit after 8 or 4 h of dry heat treatment. The germination rate of alfalfa seeds subjected to the harshest treatment was not significantly different (P＞0.05) from that of untreated seeds. Vacuum packaging is conducive to preserving the moisture content of alfalfa seed and improving the efficiency of dry heat treatment. This study suggests that sequential treatment is recommended and applicable for decontaminating alfalfa seeds for sprout production.