Effects of seed decontamination treatments on germination of red radish seeds during presoaking

The antibacterial effects of seed decontamination during presoaking before sprouting as an intervention step for eliminating foodborne pathogens on red radish seeds were evaluated. The effect of seed decontamination on seed germination rate was also evaluated. Red radish seeds were inoculated (at a level of 3 to 4 log CFU/g) with Listeria monocytogenes ATCC 19111 and decontaminated with 20,000 ppm calcium hypochlorite, 50 and 100 ppm chlorinated water, acidic electrolyzed water, low-alkaline electrolyzed water, and ozonated water for 6 hours. The control seeds were immersed in distilled water. The germination rate was measured on each treatment for 48 hours. Treatments with 20,000 ppm calcium hypochlorite, acidic and low-alkaline electrolyzed water were more effective than treatments with chlorinated water and ozonated water. Immersion in 20,000 ppm calcium hypochlorite resulted in the largest microbial reduction (more than 3 logs). Treatments with acidic and low-alkaline electrolyzed water reduced APC by 3 logs and L. monocytogenes counts by 2 logs. After sprouting, APC and L. monocytogenes counts on seeds treated with 20,000 ppm calcium hypochlorite, acidic and low-alkaline electrolyzed water were significantly lower than the control. The germination rate ranged from 93.5% to 97.7% except for 20,000 ppm calcium hypochlorite (from 82.3% to 84.8%) after 48 hours. Although the treatments tested in this study will not eliminate L. monocytogenes on inoculated red radish seeds, the results show that rapid growth of surviving cells during sprouting could be prevented if red radish seeds are given a presoak treatment used in combination with a disinfectant treatment of irrigation water.