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New UC-Davis study backs up earlier Canadian findings that RPC process could harbor contaminants

While the produce industry and the federal government have made great strides in protecting the nation's food supply with steps like the Produce Traceability Initiative and the Food Safety Modernization Act, a new study from the University of California-Davis suggests reusable plastic containers may represent a backdoor for contamination.

Research led by Trevor V. Suslow of the UC-Davis Department of Plant Sciences shows that in some cases the sanitation cycle for RPCs is ineffective. Samples from a single, unnamed provider taken on six non-consecutive days over a 16-day period show that bacteria, fungus and even particulate matter can sometimes survive the cleaning process, representing possible sources of contamination.

"That has been a long-standing concern with RPCs," Suslow said. "I've been involved with it on and off ever since they were brought from the European model over to the U.S. 15 years or so ago. One sort of accepted and had confidence in the fact that [RPCs] would go to a depot, they would be cleaned and they would be sanitized properly. Both from a visual standpoint - things you can see [like] excess water, residues of previous product, stickers and labeling - just the visual standpoint started raising questions, along with what you can't see. With the food-safety expectations facing growers and shippers, we said, 'OK, let's take a look and see whether the process we believe should be working, is working.'

"I think the outcome is that it's just not uniform," Suslow continued. "There are some concerns for how that process control actually functions. It should be manageable, it should be controllable, it shouldn't be something growers and shippers have to think about or consider within their own program. It's identifying a need that's not being adequately addressed."

A 2013 study from Canada's University of Guelph found visible organic residue, bacteria, mold and yeast in some recycled RPCs. A follow-up last month showed the same results; researchers from Guelph and the UC-Davis examined 160 randomly selected crates from different lots of trays that had been delivered on pallets wrapped in plastic over a period of up to 10 weeks in Ontario and Quebec.

"The fact that Guelph had similar outcomes and we had a similar outcome in a very different region says that there's a general issue to be brought to the forefront," Suslow said.

The microbiological survey by Suslow's team, which included researchers from the University of Florida Institute of Food & Agricultural Sciences and PrimusLabs, was designed only to test for indicator bacteria and did not include methods to detect or recover any pathogen or pathogen virulence_markers. The goal, according to the research summary, "was to indirectly assess the general sufficiency of cleaning and sanitizing procedures used by RPC providers without raising unreasonable or unnecessary fears regarding the potential for unintended adulteration on produce packed and shipped interstate."

While Suslow notes there have been no foodborne illness outbreaks traced to RPCs, the study summary reads, "Although there is no direct evidence, at this time, for the transfer of microbiological hazards from RPC surfaces to their product or any direct role in documented foodborne illness, this confidence has been somewhat eroded by recent studies."

The Guelph studies and Suslow's research led to another question: Is there something inherently flawed in RPC technology or is it the process involved in sanitizing those containers that creates avenues for contamination?

"There are some inherent issues with any multiple use container, it doesn't matter what it's made of, and we certainly highlight and try to bring visibility to that in terms of potential for cross-contamination," Suslow said.

With RPCs, having "access to the process, to the validation data, how those studies were done as to base time and temperature of washing cycles and the chemistries used to deal with the actual challenges that RPCs may be exposed to in their multiple uses, that's one part," Suslow continued. "My own personal experience working in and around any kind of packing facility or operation where you have repetitive work, you may have a well-designed process and validated process controls, but making that work day in day out, every day, with the labor force you can assign to something like that, is tough."

Suslow continued, "The other part, from having worked with RPCs in a variety of ways and having been around them a lot, because they're folded, unfolded, they've got hinges, contact points, and the way they're used, the way they're handled, there are many opportunities for things to get entrapped and adhere and be exposed to a variety of things that would make cleaning very difficult if it's not adequately done. There are numerous challenges to make the process work the way it should."

According to the summary, the aim of the UC-Davis research "is to develop for produce suppliers, which choose to or are required by customer specifications to pack produce into RPCs, a science_based and data_based informed view of the microbiological status of their multiple_use packing supplies."

"As the FDA's preventive controls rules get established and become regulation and become enforceable, [we are] trying to help the industry figure out for themselves what sort of cleaning and sanitizers will work best for their own internal cycle and close those loopholes," Suslow said.