Purpose: The purpose of this study was to evaluate the efficacy of pulsed light for decontaminating sprout seeds in both dry and wet environments. Wet environment is expected to reduce the temperature buildup during pulsed light treatment and protect germination of seeds.
Methods: Alfalfa seeds were inoculated with 4-strain Salmonella cocktail (Tennesse, Cubana, Muenchen and St. Paul). For dry treatments, 1 g of alfalfa seeds forming a 1-mm thick monolayer was treated with pulsed light. For wet treatment, 1 g of seeds was immersed in 1 ml of water during pulsed light treatment. Temperature profile was recorded using an infrared camera for both dry and wet treatments.
Results: The microbial reduction increased with the increased treatment time (up to 80 s) and shorter distances from the pulsed light lamp (3.26 to 5.26 in). However, increased microbial reduction typically resulted in decreased germination rate. An 80 s pulsed light treatment at 4.26 in from the window face reduced the Salmonella level by 2.18 ± 0.70 log CFU/g. The corresponding seed germination rate was 28 ± 2%. In wet environment, temperature profile showed that 1:1 (volume to mass) water was able to reduce the surface temperature of seeds by >20°C. An 80 s pulsed light treatment in the wet environment at 4.26 in resulted in 1.44 ± 1.01 log CFU/g reduction of Salmonella on seeds while maintaining the germination rate at > 80%.
Significance: Pulsed light technology can potentially be used for decontamination of sprout seeds. There is a potential to combine the existing sanitizer treatment with pulsed light for increased efficacy.