Effect of Chlorine Dioxide Treatment Followed by Storage in a Modified Atmosphere on Inactivating Cronobacter spp. on Radish Seeds

Introduction: Seed sprouts are often contaminated with foodborne microorganisms, since they are frequently consumed raw. Cronobacter spp. have been detected on various types of food including fresh produce.

Purpose: This study evaluated the inactivation of Cronobacter spp. on radish seeds using ClO₂ treatment followed by storage in a modified atmosphere for up to 4 days.

Methods: Radish seeds were inoculated with Cronobacter spp. (5 log CFU/g) adapted to nalidixic acid and treated with ClO₂ solution (0, 50, or 100 ppm). Then, the seeds were stored in a modified atmosphere (MA) (air; O₂ 10%/CO₂ 10%/N₂ 80%; O₂ 5%/CO₂ 10%/N₂ 85%; or O₂ 10%/CO₂ 0%/N₂ 90%) for up to 4 days.

Results: The Cronobacter spp. (4.8 log CFU/g) population on the radish seeds was reduced to 3.1, 2.8, and 2.5 log CFU/g after treatment with 0, 50, and 100 ppm ClO₂, respectively, and to 2.7, 1.8, and 0.8 log CFU/g after 2 hours of drying. After 4 days of storage under a MA, no Cronobacter spp. were detected on the seeds treated with 100 ppm ClO₂ solution. On the seeds treated with sterile water, the population began to decrease after 2 days of storage in a MA, but was not significantly different from that on seeds stored in air for 4 days. More than 90% of the radish seeds germinated after ClO₂ treatment, regardless of the ClO₂ concentration.

Significance: These results indicate that seeds should be treated with sanitizers at an appropriate concentration. In addition, the treatment of the seeds is more critical than the storage conditions for enhancing microbial safety.