Vicky Boyd, Staff Writer
Vicky Boyd, Staff Writer

Pathogen-contaminated wash water has been linked to a handful of foodborne illness outbreaks over the years, including last year’s listeria outbreak at a Colorado cantaloupe grower-packer-shipper.

But reducing the risks isn’t as simple as dumping in an appropriate amount of disinfectant and walking away.

Wash water and its interaction with produce, organic matter associated with produce and even other micro-organisms found on produce is a complex subject with no single answer.

This was evident as a handful of researchers presented updates on their projects at the Center for Produce Safety’s third annual Produce Research Symposium June 27 in Davis, Calif.

“The researchers don’t always agree,” said Bob Whitaker, chief science and technology officer with the Produce Marketing Association, Newark, Del., as he reviewed the projects at the PMA’s Gold Circle Breakfast the next morning.

“One size doesn’t fit all.”

Because of potential risks and complexities, Whitaker said PMA will focus on wash water in educational sessions during the next five months.

The subject also is a research priority for the Davis-based Center for Produce Safety, said Bonnie Fernandez-Fenaroli, executive director.

One thing researchers did agree upon was that wash water shouldn’t be viewed as a kill step.

Instead, growers should start with GAPS, or good agricultural practices, in the field to minimize the risk of foodborne pathogens. Similar food-safety steps should be followed throughout the food chain.

“The take-home message is it’s quality in, quality out,” said Keith Warriner, a food science professor at the University of Guelph in Ontario.

“If you get bad quality going in, you get bad quality going out.”

At best, wash water should not be a source of cross-contamination.

As its name implies, wash water is intended to remove dirt and other impurities from produce including tomatoes, peppers, cantaloupe and leafy greens.

If unsafe water is used, it can contaminate everything it contacts.

Even if you start with safe water, cross-contamination may occur should one piece of produce carry pathogens that are washed off.

“Typically 90% of the microbial load is shed. Therefore, we need to come up with means to decrease levels to prevent cross-contamination,” said Elliot Ryser, a food science professor at Michigan State University, East Lansing.

That’s where a disinfectant comes in, frequently some form of chlorine.

But it’s not simply dumping in a jug of chlorine.

Even produce operations that carefully monitor levels of chlorine, pH and other components find it’s a daunting task to keep disinfectants at appropriate levels.

They may sample every hour, but the results only give you a picture of what happened at that moment in time.

It doesn’t show what happened the other 59 minutes.

Chlorine is very sensitive to organic matter, so when you dump in a load of chopped lettuce, for example, the organic matter in the lettuce juice can greatly reduce the disinfectant’s effectiveness.

Whitaker said the industry has made great strides from just 10 years ago, when he witnessed packinghouse workers using swimming pool chlorine and pH paper to test the water.

Although he said most of the larger packers have since installed much more sophisticated systems, some of the smaller packers no doubt still use the old system.

“And if those guys have a problem, we all have a problem,” he said, referring to how a foodborne illness outbreak can taint the entire industry.

Like all the research CPS funds, the wash water projects are designed to yield applicable results in only a couple of years.

Let’s hope it’s sooner, rather than later.

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