Ninth-generation farmer Paul Moyer grows pick-your-own cherries, peaches, plums and apples in Ontario, Canada, not far from Niagara Falls. Several years ago, he started a side hustle: caramel apples.

It was a promising business until around early 2015, after listeria-contaminated caramel apples killed seven of 34 people hospitalized. Moyer’s apples weren’t implicated, but his caramel apple sales dropped by half.

Caramel apples are just one source of the food-borne disease outbreaks linked to fresh produce — from spinach to melons to romaine lettuce — that have sickened and even killed consumers over the past decade or so. Although the stick inserted into the caramel apples provided a conduit for contamination, listeria microbes were found on California apples identified in the outbreak. Other outbreaks have been linked to whole or juiced apples.

In the wake of the tragedy, Moyer decided that there had to be a way to prevent more outbreaks. He approached the Ontario Centers of Excellence, a Canadian government organization that supports industry-academic partnerships, which connected him to Keith Warriner, a food scientist at the University of Guelph in Ontario.

Warriner first published a process using ultraviolet light and hydrogen peroxide in 2006, but the technology, which featured a design similar to a washing machine, was largely ignored. Together, he and Moyer developed the idea further. Their “advanced oxidative process” combines ultraviolet light with ozone and hydrogen peroxide to form an antimicrobial mist. Moyer suggested a conveyer-belt system — and turned the idea into a company, Clean Works.

Warriner’s tests have shown that, in less that 30 seconds, the mist can zap 99.9 percent of pathogens, molds and mildews. With those spoilage microorganisms gone, fruit shelf life increases by 25 percent. Next month, Moyer and Warriner will receive the International Association for Food Protection’s innovation award.

Behind the scenes, the fresh produce industry is in the midst of a transformation. From the field to the grocery store, outbreak prevention is a priority. The Center for Produce Safety, created in 2006 in response to a spinach outbreak, has funded dozens of projects to, for example, document how pathogens move in soil, improve agricultural water quality and even optimize the welding on lettuce-harvesting knives to prevent tiny pockets where microbes can hide.

“The big change in thinking is that what we’re putting into boxes is ready-to-eat food,” said Tim York, president of Markon Cooperative, a collective of seven independent food service companies in the United States and Canada. “Consumer confidence is a big driver. We don’t want to make people sick, and we want them to feel good about eating more fruits and vegetables.”

Look no further than the health-conscious “raw movement” — featuring products such as pressed juices, fruit and vegetable smoothies and packaged salads — to find motivation for increased food safety.

Perhaps the most significant shift is greater interest in a “kill step,” a process that could reduce the number of live microbes by 99.9 percent, or 100,000-fold. Water washes are inconsistent and, at best, reduce microbes tenfold.

“You can roast almonds or pasteurize milk to kill bacteria, but spinach washes aren’t necessarily enough to eliminate every pathogen coming out of the field,” said Michele Jay-Russell, a research microbiologist and the program manager of the Western Center for Food Safety at the University of California at Davis. “If people want convenient, raw produce, we need a safe kill step as an option at the processing level.”

York agrees that a kill step could be an industry standard in a decade or so. He is unfamiliar with the advanced oxidative process, but there are many strategies being researched and techniques that probably will be combined, he said. Other sanitation techniques that have been explored over the past few years include various forms of irradiation, ultraviolet light, radio frequencies, chlorine dioxide and cold plasma, the latter being a process that turns gas molecules into charged ions able to kill microbes.

Consumers have been reluctant to embrace irradiation, which exposes food products to ionizing radiation, and organic standards don’t allow its use. Although chlorine and acids are used in produce washes to prevent cross-contamination, they don’t kill every microbe, and chlorine dioxide gas treatments can leave unwanted residues on fruit. Warriner, who said he is familiar with all of the technologies, suggests that the advanced oxidative process is the most effective and the least expensive to implement — though it’s an area ripe for additional study.

“There is more emphasis coming from distributors and buyers saying food safety is important,” said Kalmia Kniel, a food microbiologist at the University of Delaware and the president-elect of the International Association for Food Protection.

Though the industry is more receptive to kill-step sanitation technologies, she said, “we’re in the early adoption phase.”

In the past two years, Moyer’s caramel apple sales have quadrupled. More than 2,000 stores carry his apples. “Retailers are very excited about this [process] because it gives them a firewall between the field and the dinner plate,” Moyer said. “Until now, it’s been literally wishy-washy.” Warriner estimates that 99 percent of post-harvest produce treatment is a water wash. The 2016 Food Safety Modernization Act crafted the first science-based standards for post-harvest water quality, meant to reduce the potential for cross-contamination of the wash water.

Although water washes are routine for bagged salad mix, it’s not standard on other products, such as cut heads of iceberg, romaine, celery or broccoli, which are packed in the field and unpacked in the final grocery store destination, said York.

“Produce is a very complex industry,” hundreds of industries in one, said Bonnie Fernandez-Fenaroli, the executive director of the Center for Produce Safety based in Woodlands, Calif. Put simply, there is no one-size-fits-all sanitation solution. “Tender products, like berries and lettuce, don’t hold up under a lot of treatments,” she added.

Farms are bigger, produce travels farther from the source than it used to and is touched by more hands than in the past. “All of those moving parts are added complexities and opportunities for failure. A final kill step before the consumer actually consumes makes a lot of sense,” said Anthony Green, chief executive of fresh-pressed juice company Greenhouse in Ontario.

The Clean Works equipment recently arrived at his facility. He plans to use it as the final step before produce is juiced to make his products. Previously, he struggled to find a sanitation step that didn’t degrade the nutrients. “We want to make the healthiest types of plant-based beverages, including cold-pressed juices, so our raw materials have to be as fresh as possible,” he said. He gets as much fruit as possible locally, but after the summer, it comes mostly from California. “I think the industry has learned, sometimes the hard way, you can never have enough fail-safes in your system,” Green said.

California citrus cooperative Sunkist Growers is also testing the advanced oxidative process, first on lemons. “While Sunkist has a strong post-harvest processes in place, this could add one more food safety solution to the mix,” said Sunkist communications director Christina Ward.

Moyer said interest in the advanced oxidative process spans the food production system — from retailers to processors to growers. The industry has always been concerned about safety, but there is more emphasis now on exploring more tools and with more scientific rigor, said Steve Kenfield, vice president of sales and marketing at HMC Group Marketing, a California-based farm operation that grows and sells, for example, single-service table grapes to food services and schools to boost the consumption of fresh fruit. “It’s no longer optional” to focus on food safety, said Kenfield. “Unless you are willing and able to meet a higher level of standards, you are going to exit the business one way or another.”

York said that’s a good thing. “I hope days are numbered of people not following best practices, and that comes down to buyers reinforcing that message,” he said.

Warriner’s food safety career is long enough to be littered with heartbreaking stories. He still thinks about the 2-year-old boy in Ontario who died as a result of last year’s E. coli outbreak affecting romaine lettuce. If there is a driving force that bolsters his ongoing efforts to research new methods, he said, it is preventing further tragedies.

Gewin is a science journalist based in Portland, Ore.

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