Are Dirt Grown Sprouts a Health Hazard?

Are Dirt Grown Sprouts a Health Hazard?

Bob Rust


October 20, 2002

Dear Bob,
"Is there any way we can separate the growers who sprout in dirt from the rest of the industry?  They are an accident waiting to happen."

Dear Grower,
I'm not so sure that they are an "accident waiting to happen".  I have a theory (a bobism) that an unsafe soil grower is far less of a danger than an unsafe sprout grower.  Consider this:

For the sake of discussion let's say there is a seed lot (sunflower, green pea, whatever) that is 1% contaminated, which is a high level of contamination.  Now, let's say this seed is given to two sprout growers, one who grows in soil and the other who grows hydroponically.  Neither grower takes any safety precautions. 

The hydroponic grower places his seed in water and soaks it for four hours.  The water distributes the pathogens throughout the seed and the sprouts are placed on a rack in a warm, humid room where they receive water every couple hours.  The irrigation water runs throughout the sprouting seed and drips onto the trays below.  The pathogens proliferate about 100,000 times and are nearly perfectly distributed throughout the crop. 

The soil grower plants his seed in the ground and waters it.  There is little if any homogenizing of pathogens.  The water hits each seed and drains through the soil.  The pathogens proliferate, but nothing like those that are given the ideal growing conditions of a sprouting facility.  It may be possible that the majority of pathogens remain below the soil when the sprouts are cut.

This doesn't mean that people should switch to growing in soil.  Soil grown produce is nowhere near as safe as properly grown hydroponic sprouts.  Let's look at this same scenario involving a safe hydroponic sprout grower:

The safe hydroponic sprout grower take at least a 3 kg sample of the seed he received and inspects.  Bingo, he finds mouse droppings in the seed.  Ok, ok, there were no mouse droppings in the seed.  He grows out the seed and tests it for salmonella and E. coli 0157:H7.  When the seed is contaminated at the rate of 100 cfu/kg, the odds of him capturing a contaminated seed for testing is far in excess of 99.9999% .  Quite simply, he would have found the seed was contaminated and never used it in the first place. 

But let's suppose that he happened to be the one in a million to have not captured a contaminated seed when it is that heavily contaminated.  He then sanitizes his seed, further reducing the odds of having an outbreak. 

Now let's go to the absurd and say that a pathogen still got by the inspection, sampling, testing, and sanitizing.  The safe grower tests the runoff water from all his sprouts and holds his sprouts until the results are back. 

Kind of unfair wouldn't you say?  The contaminated seed never had a chance.

Just to be clear, a soil sprout grower can produce safe sprouts also.  They can buy ISS Screened Sprouting Seed which is pre-tested and they have the ability to re-sample and test their seed before planting it.  Soil growers can also sanitize their seed, and they could wash their sprouts and test the wash water before shipping.  Certainly the easiest and safest thing for any of these growers is to start with seed that is not contaminated in the first place.