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P3-59 The Efficacy of Chlorine and Acidified Sodium Chlorite for Disinfection of Seeds Artificially Inoculated with Salmonella as Affected by Treatment Time, Concentration, and Seed Type

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Zijing Zhang , Illinois Institute of Technology, Institute for Food Safety and Health , Bedford Park , IL
Yingqun Lei , Illinois Institute of Technology, Institute for Food Safety and Health , Bedford Park , IL
Mengqi Li , Illinois Institute of Technology, Institute for Food Safety and Health , Bedford Park , IL
Tong-Jen Fu , U.S. Food and Drug Administration, Division of Food Processing Science and Technology , Bedford Park , IL
Introduction: Treatment of seeds with 20,000 ppm calcium hypochlorite, Ca(OCl)2, is considered the gold standard; however, the high level of chlorine is potentially hazardous. There is a need to determine whether prolonged treatment with lower levels of chlorine would achieve similar degrees of pathogen reduction. Certain organic sanitizers (e.g., acidified sodium chlorite) exhibited equivalent or better efficacy in treating alfalfa seeds. Whether similar performance will be observed in other types of seeds remains to be determined.

Purpose: The efficacy of chlorine (prepared as Ca(OCl)2) and acidified sodium chlorite (ASC) for treatment of six types of seeds/beans (alfalfa, clover, broccoli, onion, radish, and mung beans) artificially inoculated with Salmonella and the impact on germination rates, as affected by treatment time, concentration, and seed type was evaluated.

Methods: Ten grams seeds inoculated with four to six log cfu/g of Salmonella Typhimurium expressing green fluorescent protein were treated with different concentrations of Ca(OCl)2 or ASC (200 to 20,000 ppm or 200 to 1,500 ppm, respectively) for different times (0.25, 0.5, 1, 3, 6, 16, or 24 h). After treatment, seeds were rinsed twice with sterile water and analyzed for Salmonella by plate counts and culture enrichment.

Results: Treatment with 20,000 ppm Ca(OCl)2 for 15 min resulted in a greater log kill for clover, onion, and mung beans (reductions of 2.8, 3.1, and 3.8 log units, respectively) than for alfalfa seeds (1.3 log units). Free chlorine was rapidly consumed during treatment (from 2,000 ppm to < 0.02 ppm after 3 h). The efficacy of ASC increased with increasing concentration and treatment time. Treatment of clover, broccoli, and mung beans with 1,500 ppm of ASC for 3 h reduced Salmonella levels by 2.6, 4.2, and 3.6 log units, respectively, to undetectable (<1 log cfu/g).

Significance: Longer treatment with lower concentrations of chlorine was not effective due to the rapid disappearance of free chlorine. Acidified sodium chlorite provided an effective seed treatment option.

Back to: Poster Session 3 – Low-water Activity Foods, Packaging, Produce, Microbial Food Spoilage, Antimicrobials, Laboratory and Detection Methods, Water
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