Looking at the merits of preharvest testing

The “optics” and the science behind product testing were evaluated in a June 10 session at the United Fresh Produce Association’s Reimagine Conversations web seminar.

Panelist Tim York, CEO of the California Leafy Greens Marketing Agreement, said preharvest testing is a soon-coming requirement for LGMA leafy greens and lettuce growers in California and Arizona.

California alone accounts for about 30 billion servings of lettuce and leafy greens, and combined, Arizona and California account for 95% of the lettuce and leafy greens consumed in the U.S., he said.

LGMA works with handlers and growers by verifying food safety practices, enforced through government audits that are conducted by USDA trained auditors.

“If you’re a member of the LGMA, it requires that you follow our metrics and our standards and accept those as the way that you’re going to farm, and so it does require that farmers commit to that continuous improvement,” York said.

From Tim York: Pathogen testing: A positive test can be a positive thing

On April 16, about 10 days after the Food and Drug Administration released a report that addressed animals, primarily cattle, as an area of concern relating to pathogens spread to leafy greens, the LGMA declared its path toward preharvest testing.

The FDA talked about the incidence of animal feeding operations within Southern Monterey County in the Santa Maria area. 

“We had been working on preharvest testing prior to the FDA report, but we accelerated our work in pre harvest testing as a response to the FDA report,” York said.  

As a response to the FDA report, in mid-April the LGMA board endorsed pre-harvest testing to reduce outbreaks. 

Dan Sutton, chairman of the California LGMA, said at the time, “We are endorsing preharvest testing in direct response to the U.S. Food and Drug Administration’s recent report on outbreaks associated with lettuce in 2020, which identified the recurring E. coli strain implicated to be a reasonably foreseeable hazard.”

York said the way the LGMA is addressing the “reasonably foreseeable hazards” is through preharvest testing.

“We wanted to send a clear message to FDA that our industry is in fact taking additional measures to reduce outbreaks,” he said. 

LGMA guidance now calls for preharvest testing of leafy greens and lettuces when risk assessments deem it necessary.

“The methodology is currently under development,” he said. “This fall will have pre-harvest testing uniformly used across the California lettuce and leafy greens industry.”

Read more: California LGMA endorses pre-harvest testing to reduce outbreaks 

York said the LGMA realizes that pre-harvest testing is not a “silver bullet.”

“It’s one indication we can use to see the efficacy of our programs,” he said. 

The guidance on preharvest testing applies to lettuce and leafy greens grown in proximity to animals, whether those animals are in large, concentrated animal feeding operations, medium-sized feeding operations, on grazing land, or on hobby farms.

“We’ve identified all those as elevated risk factors and we’ve given farmers guidance around that,” York said. 

Factors considered include distance of the animals from the crop, the opportunity for water runoff from the irrigation or water sources, prevailing wind or weather events, and other factors.

“All of these are potential risk factors we’ve guided farmers to be assessing if they’re in proximity to these animal operations,” York said. 

“Our methodology is currently under development, and we’re working with Dr. Trevor Suslow, recently out of UC Davis, on all variables such as target organisms, a timeline, lot size and sampling, the sampling design, sample collection and measurement criteria and importantly, remedial actions.” 

Read more: Produce safety professionals weigh in on biggest needs

In May, LGMA conducted a survey of handlers that had a 55% response rate, York said. 

Nearly 90% of the handlers that responded said they conducted preharvest testing in an average month.

Most of them, York said, do testing within four to seven days before harvest, with sampling done by third-party or outside companies. 

Sampling is typically done using the Z pattern, and sampling blocks are typically of one to five acres.

Testing done is in lots of 60 samples, with testing for E. coli O157:H7 and salmonella.

York said the majority of those respondents have not had preharvest test results come back positive within the past 12 months, though they all have established procedures in place for dealing with positive test results. 

The main procedures in place are product destruction, root cause analysis for implicated lots, equipment cleaning and sanitation, buffering and verification of prior results. 

“The LGMA will have preharvest testing uniformly across California and Arizona leafy greens industry this fall,” he said. “It is critical we get this right.”

York said that Drew McDonald, head of the technical committee at the Center for Produce Safety, and vice president of quality and safety for Taylor Farms, said preharvest testing, whether positive or negative, is always a learning opportunity.

“If you have a positive or if you have a negative, what does that tell you? If you have a negative does that tell you that you don’t have potential contamination, or does it tell you maybe the pattern that you’re using, the sample size, those may be not as effective as you wish? Or if we have a positive, what does that tell us about where that potential contamination came from, how it got into our crop? So as Drew says, every, every test is an opportunity to learn.”

York said LGMA realizes that pre-harvest testing is not the silver bullet, but it allows the industry to gain valuable information and data.

“It does require that farmers (take) remedial actions,” York said. “LGMA members will be required to conduct a root cause analysis for any positive tests.”