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Development of validated seed disinfection strategies for the organic production of sprouted vegetables

Activity summary

Sprouted vegetables have been recognized as a significant source of foodborne disease in recent decades. Seed is the most likely source of contamination and early research to identify an effective sanitation procedure suggested that soaking in a 20,000 ppm chlorine solution can eliminate most, but not all, human pathogens from seed. The US FDA endorsed the treatment in 1999 (). In Canada, the CFIA formulated a code of practice which recommends soaking seed in a 2,000 ppm chlorine solution or 6-10 % hydrogen peroxide (). Unfortunately, there are serious occupational health and safety concerns associated with the handling of either solution, and organic production guides disallow the application of chlorine sanitizers to food products. In the absence of a reliable and acceptable seed disinfection treatment, the organic industry relies on expensive seed and end-product testing programs to reduce the risk associated with sprouted vegetables. Alternative chemical (organic acids, natural antimicrobials) or physical treatments (mild heat, disinfection with gases) have been investigated for the purpose of sprouted seed disinfection. To date, however, none has led to the development of an acceptable alternative, mainly because they do not provide the degree of disinfection afforded by chlorine-based treatments. And, unfortunately, the well-established limitations attributed to seed and end-product testing cannot guarantee pathogen-free sprouted products.

To address this food safety gap, we will explore the use of alternate strategies as single and combined treatments for their ability to eliminate relevant foodborne pathogens, such as Escherichia coli O157:H7 and Salmonella, in sprout seed. Specifically, using artificially inoculated seed, we will investigate the efficacy of organic acids (e.g., acetic acid, ascorbic acid, citric acid, and lactic acid), natural antimicrobials (e.g., thymol, and vanillin), or treatments involving heat and gas phase application in their ability to eliminate these pathogens in alfalfa, pea, and radish seeds. We anticipate that this systematic assessment and validation of combined treatments will lead to the development of more reliable sprouting seed disinfection protocols that avoid the use of occupationally hazardous chemicals or approaches that do not meet Canadian organic standards. Importantly, such treatments are expected to be valuable for the control of plant pathogens on food and non-food seed. In the end, this will afford organic growers scientifically validated options for the production of risk-reduced sprouted products that currently do not exist. In doing so, improvements in safety and grower confidence will lead to a stronger, more competitive organic sector on local, national, and international levels.Ìý

• Ga-Hee Ban, Yue Dai, Tao Huan, Alfred Ke, Pascal Delaquis, Siyun Wan. mSystems Feb 2021, 6 (1) e00898-20; DOI: 10.1128/mSystems.00898-20

• • Delaquis P, Wang S, Chen J, Wakeling C, Bach S, Orban S. 2020. doi: 10.4315/JFP-19-508
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• • Trzaskowska M, Dai Y, Delaquis P and Wang S*. 2018. Food Microbiology 76:62-68.

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