Inactivation of Escherichia coli O157:H7 on inoculated alfalfa seeds with pulsed ultraviolet light and response surface modeling

Escherichia coli O157:H7-inoculated alfalfa seeds with seed layer thicknesses of 1.02 to 6.25 mm were subjected to pulsed UV light for up to 90 s at a 8-cm distance from the UV strobe. Population reductions higher than 4 log₁₀ colony-forming units (CFU)/g were achieved. For effect of distance from the UV strobe, seeds with 6.25-mm layer thickness were treated 3 to 13 cm from the strobe. Reductions at shorter distances, such as 60 s at 5 cm (1.93 log₁₀ CFU/g) and 60 to 90 s at 8 cm (4.89 log₁₀ CFU/g), were significantly higher (P ≤ 0.05). Data from the treatments were used to develop empirical models as a function of distance or layer thickness and treatment time for predicting the population of E. coli O157:H7 during pulsed UV-light treatment. This study demonstrates that pulsed UV light holds promise for eliminating pathogens from alfalfa seeds, and the models developed can be useful predictive tools.