Seed Safety

Over the past decade, commercially produced sprouts have been implicated in health outbreaks involving thousands of consumers. In response to safety concerns across the industry, ISS has developed a method of screening seed for human pathogens that has been confirmed, referenced and/or recommended by the World Health Organization (WHO), the US Food & Drug Administration (FDA), the US Department of Agriculture (USDA) and other organizations.

Since 1988, seeds have been the likely source of contamination in nearly every outbreak in which the source was determined. The suspected scenario is that seed is contaminated in the field by manure used as fertilizer, by grazing animals, or in silos or bins by bird or mouse droppings and urine. The process of sprouting creates conditions (i.e. food, moisture, warmth) that allow a single pathogen cell to proliferate into over one hundred thousand pathogenic cells.

Unfortunately, chlorine is not enough to decontaminate seeds since pathogens do not remain on the seed coat. Instead, bacteria are trapped in cracks and crevices in the seed coat and appear to be protected from disinfectants. There is even evidence that some bacteria can be internalized within the seed itself. If a single pathogen cell is left alive in the seed, it will quickly multiply back to pre-sanitation levels.

To date no sanitation technique has been shown to completely eradicate pathogenic microorganisms from either the seed or the sprouts.

The best way to avoid outbreaks is to ensure that seed is not contaminated in the first place. Historically, sprout seed has been tested for plant pathogens and quality, but not for human pathogens. ISS has developed a seed screening process for ISS Screened Sprouting Seed that substantially reduces the risk of food-borne illnesses related to commercial sprout production. This multi-step process includes: Seed Sampling, Seed Inspection, Sprout Growing (Enrichment), Water Sampling & Testing, Sprout Testing, Documentation, and Pre-Screening.

  1. Seed Sampling. In order to detect a pathogen in a lot of seed, you first need to “capture” it in the seed sample you intend to test. The probability of picking up at least one contaminated seed in a 40 lb seed sample is very high at an average contamination level of 4 CS/kg (4 Contaminated Seeds per 2.2 pounds of seed), but very low with smaller samples and smaller contamination rates.
  2. Seed Inspection. After a representative sample is taken, the composite sample of seed is inspected for indicators of contamination. This includes inspecting the bags for mouse urine or dropping, holes in the bags, insect larva, bird droppings, etc. The seed is then carefully inspected with both a magnifying glass and microscope to determine its fitness for human consumption. Again, we look for traces of visitation by animals and insects. In the process we have also found glass, seed that was blended with seed that had been treated with a fungicide, and other things.
  3. Sprouting (Enrichment). The entire sample is sprouted. The seed is not sanitized prior to sprouting. In 48 hours the pathogens, if present, should have increased about 1,000,000 times, substantially increasing the probability of detection.
  4. Water Sampling & Testing. At about 48 hours, a sample of the runoff water is collected and enriched to make the pathogens multiply about 5 log (100,000 times) and the water is tested for salmonella, E.coli, and E.coli 0157:H7. These tests are run in duplicate.
  5. Sprout Testing New! Some of the sprouts produced from the composite sample are sent to a separate lab. The lab crushes the sprouts and tests for Salmonella, E.coli 0157:H7, Listeria monocytogenes, Shigella and generic E.coli. They are also tested in a separate lab for Enterotoxigenic E.coli (ETEC) if generic E.coli is found.
  6. Documentation. Every step is thoroughly documented and personally approved by the people who are responsible for each stage of the process. The entire ISS seed testing process closely conforms to the philosophy that if it isn’t documented, it wasn’t done.
  7. Pre-Screening. As an extra step, we inspect, sprout and test a sample before we receive a shipment of seed. If the seed doesn’t pass visual inspection, we reject it immediately, without taking the time to sprout it and test it for pathogens.