Effect of sequential presoaking and chlorine dioxide treatment on the inactivation of pathogenicEscherichia coliandSalmonellaspp. on sprout seeds

Abstract

This study was conducted to evaluate the effect of sequential presoaking and chlorine dioxide (ClO2) on the reduction of pathogenicEscherichia coliandSalmonellaspp. in alfalfa. When unsoaked and presoaked alfalfa were exposed to 200 ppm ClO(2)for 15 min, the population ofE. coliandSalmonellaspp. on presoaked seeds reduced more than those on unsoaked seeds by 2.07 and 1.43 log CFU g(-1)(p < 0.05), respectively. To determine the optimal concentration and treatment time to reduce pathogenicE. coliandSalmonellaspp. in alfalfa seeds immersed in water for 5 h, presoaked seeds were exposed to four different concentrations of ClO2(50, 100, 150, and 200 ppm) for 15, 30, 45, and 60 min. The most effective condition to eliminateE. coliandSalmonellaspp. from alfalfa seeds was sequential immersion in water for 5 h and 200 ppm ClO(2)treatment for 1 h. After the optimal condition was applied to eight kinds of sprout seeds, the pathogens were completely inactivated in all seeds, except radish seeds. Growth of pathogenicE. coliandSalmonellaspp. during sprouting after ClO(2)treatment of alfalfa seeds was also completely inactivated. However, the germination rate of seeds did not significantly decrease after ClO(2)treatment. In addition, ClO(2)residues were not present in any sprout during 3 days of cultivation. These results demonstrated that sequential presoaking and 200 ppm ClO(2)treatment is the optimal seed disinfection treatment to prevent foodborne diseases associated with sprout consumption.