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Comparison of the Efficacy of Three Organic Sanitizers with 20,000 ppm Calcium Hypochlorite for Inactivation of Salmonella on Artificially Contaminated Alfalfa Seeds

Food Science and Nutrition Project
Qing Li
Graduate Student Seminar Days
Spring 2014

Although treatment of seeds with 20,000 ppm calcium hypochlorite, Ca(OCl)2, is considered the gold standard, the high level of chlorine is potentially hazardous. Sprout growers are in need of alternative sanitizers. Many organic sanitizers have been approved for disinfection of produce; whether they perform equally well in disinfection of seeds for sprouting needs to be determined. Evaluate the efficacy of three organic sanitizers: acidified sodium chlorite (ASC, also known as Sanova), stabilized oxychloro-based sanitizer (SOC, also known as Germin-8-or), and the organic CHICO wash, in comparison with 20,000 ppm Ca(OCl)2 for disinfection of alfalfa seeds artificially inoculated with Salmonella. Small-scale experiments were conducted to determine the best treatment conditions. Large-scale studies were performed to evaluate the commercial applicability of these sanitizers. Ten g of seeds inoculated with 3-4 log cfu/g of S. Typhimurium expressing green fluorescent protein was treated with different concentrations of ASC, SOC, and the CHICO wash for different periods of time. For large-scale runs, 1 kg of seeds spiked with 1% (w/w) of inoculated seeds was treated with each sanitizer under optimal treatment conditions. As a comparison, seeds were also treated with 20,000 ppm Ca(OCl)2 for 15 minutes. After treatments, seeds were rinsed twice with sterile tap water and analyzed for Salmonella by plate counts or the 3-tube MPN method. The efficacy of ASC and SOC increased with increasing concentrations (up to 1500 ppm) and treatment time (up to 3 h hours); however, the germination rates for seeds treated with > 1200 ppm of either sanitizer were < 80%. Treatment with 800 ppm of ASC or SOC for 3 h hours reduced the Salmonella level, respectively, by 2.3 logs or > 2 logs to an undetectable level, compared with the ~1 log decrease observed in seeds treated with 20,000 pm Ca(OCl)2. Treatment with 15% (v/v) CHICO wash for 10 minutes lowered the germination rate to 73% but only reduced the Salmonella count by 0.9 log. For the large-scale runs, the Salmonella level in seeds treated with 800 ppm SOC for 3 h hours decreased by > 1.9 log to an undetectable level (< -2.52 log MPN/g) compared with a 1.5 log reduction in seeds treated with 20,000 ppm Ca(OCl)2. The stabilized oxychloro-based sanitizer may provide an alternative seed treatment method for organic sprout growers.

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