Acidified sodium chlorite as an alternative to chlorine for elimination of Salmonella on alfalfa seeds

Authors: Liao, Ching Hsing

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2009
Publication Date: 4/1/2009
Citation: Liao, C. 2009. Acidified sodium chlorite as an alternative to chlorine for elimination of Salmonella on alfalfa seeds. Journal of Food Science. 74(4):M159-164.

Interpretive Summary: Consumption of tainted alfalfa sprouts has been implicated in numerous food-borne illness outbreaks in the last two decades. Pathogens (or disease-causing bacteria) associated with these outbreaks were believed to originate from seeds used in sprouting. Chlorine has been recommended by the U.S. Food and Drug Administration (FDA) to disinfect alfalfa seeds before sprouting. In spite of its effectiveness, there is an increasing concern about the health hazard and environmental impact associated with the use of chlorine as a disinfecting or bleaching agent. The objective of this study was to evaluate the potential of using another antimicrobial agent, acidified sodium chlorite (ASC), as a replacement of chlorine for seed treatment. Results presented here show that the efficacy of ASC for seed treatment can be greatly improved by extending the treatment time from traditional 15 to 45 min. Soaking seeds in ASC at the concentration of 800 ppm for 45 minutes could eliminate 99.9 to 99.99 % of pathogens (e.g. Salmonella) on seeds. By comparison, soaking seeds in chlorine for 45 min at the concentration recommended by FDA only removed 90 to 99 % of pathogens. Furthermore, treatment of seeds with ASC for 45 minutes did not significantly affect seed germination and sprout quality. However, treatment of seeds with chlorine for 30 min reduced seed germination by more than 20%. This study suggests that ASC is a possible alternative to chlorine for disinfection of alfalfa seeds destined for sprout production.

Technical Abstract: The disadvantage associated with the use of chlorine for food processing and water treatment had been documented previously. This study was conducted to determine if acidified sodium chlorite (ASC) could be used to replace calcium hypochlorite [Ca(OCl)2] for disinfection of alfalfa seeds. Seeds containing approximately 5 × 10**7 cfu/g of Salmonella were treated with ASC or Ca(OCl)2 at different concentrations and for different periods of time. Results showed that the efficacy of ASC or Ca(OCl)2 for elimination of Salmonella on alfalfa seeds could be greatly improved by extending the treatment time from the traditional 15 to 45 minutes. Treatment of contaminated seeds with 800 ppm of ASC for 45 minutes reduced the number of Salmonella on alfalfa seeds by 3.5 log units, approximately 1.2 logs higher than that treated with 20,000 ppm of Ca(OCl)2. Treatment of seeds with ASC at a lower concentration (less than or equal to 200 ppm) for 45 minutes reduced the number of Salmonella by only 0.8 to 1.9 log units. ASC was in general more effective as a disinfectant than Ca(OCl)2. Treatment of seeds with 800 ppm of ASC for 45 minutes did not significantly affect seed germination and sprout quality. However, treatment of seeds with 20,000 ppm of Ca(OCl)2 for 45 minutes reduced seed germination by 20 %. Unlike Ca(OCl)2, antimicrobial activity of ASC was not significantly affected by pre-exposure to alfalfa seeds. Data presented also revealed that Salmonella on newly-inoculated seeds were more sensitive to sanitizer treatments than those on seeds that had been stored for 4 weeks or longer.