Constant Watch: The fight against listeria in the cold chain

The country is dealing with a widespread recall of romaine lettuce linked to E. coli contamination. However, the Shigatoxin-producing bacteria is not the only threat to the U.S. food supply and fresh produce is not the only product category that has to be vigilant on the food safety front.

Frozen produce has its unique challenges. For example, in 2016 a supplier with locations in the southern and western U.S. recalled 47,112,256 pounds of Asian-inspired meal kits due to Listeria monocytogenes. Though dozens of brands and flavors were affected, what the products had in common was that they were frozen vegetables from the same supplier.

The supplier in question, CRF Foods out of Pasco, Washington, issued a voluntary recall once an outbreak of listeriosis was identified.

The American Frozen Food Institute (AFFI) is helping facilities prevent future problems. The group is putting out guidance to help processors follow best practices in frozen food safety that includes resources such as its guide for processors to validate the effectiveness of their blanching procedures.

“This is really a commitment our members have made to double down on listeria prevention,” said Adrienne Seiling, vice president of communications with AFFI.

Specifically, the document outlines a template to be used by frozen food processors for the application of blanching equipment as a preventive control to address risks associated particularly with listeria, but with other pathogens as well. It highlights key information such as the appropriate equipment and process, achieving desired lethality, and verification to establish blanching as a process preventive control.

AFFI has convened a member group of 70 food safety professionals to develop best practices, as well as guidance on equipment maintenance and upgrades. These resources are intended both for AFFI members and non-members.

Donna Garren, executive vice president for science and policy at AFFI, said that as someone who has worked for a family-owned business, she believes the group is well aware of the challenges and costs associated with improving listeria safety.

“I can appreciate the sensitivity to limited resources in a company and there should be some return on that investment. That’s actually why we’re going down this path to make these tools, (so) that when they invest in new equipment they know their investment is well made,” she said.

For example, she said many companies can’t invest in a new spiral freezer, but for those who can, selecting the right freezer is key. Processors want to avoid investing money in a new freezer only to discover they can’t clean it to their safety standards.

“I think we’re hoping we can provide them with those internal resources at their disposal to make wiser, better investments in continually upgrading food safety in their operation,” Garren said.

Many smaller companies may have no in-house food s afety e xpert a nd AFFI is aiming its resources at assisting those processors.

“A key component of AFFI’s goal to advance food safety includes providing AFFI members and the entire frozen food industry with educational resources that represent the industry’s best thinking,” said AFFI President and CEO Alison Bodor, regarding the new resources. “Especially in the area of developing and implementing most effective food safety practices, the entire industry must work together.”

One of the most important parts of protecting against listeria is having an effective kill step. Blanching is one method. Lyco’s rotary drum blancher, Thermal-Flow two-zone blancher and Vapor-Flow steam blanchers can provide a kill step for frozen produce. Photo: Lyco

When validating the effectiveness of the blanching process, one of the key considerations is verifying the effectiveness of the blanching step.

“Time and temperature are the two most important parameters that dictate the use of blanching as a process preventive control,” according to the AFFI guide. “Thus, measurements related to time and temperature are essential to validating a blancher.”

Wireless temperature probes can be an invaluable tool when making those measurements.

Best practices for using these wireless continuous temperature recording devices include: 

  • Type of probe: use certifiable and calibrated probes designed for heating, capable of measuring the internal temperature of product
  • Frequency of data capture: seconds, minutes
  • Frequency of lethality verification: A minimum of annual verification after initial validation

One of the other specific areas of concern in the frozen chain is the post-lethality step. Once produce has passed through the kill step it’s vital to maintain high standards as not to re-introduce pathogens.

“It’s difficult to be in a QA’s (quality assurance person’s) shoes. With the different facility types and products they might have, and when you grow in fields and soil, you’re potentially bringing in listeria from the fields and there’s that constant control to mitigate that risk,” Garren said. “It’s difficult to (concentrate on) one particular area of focus but definitely if you have a lethality step, looking at that post-lethality step is a good use of resources.”

Proof of the high stakes for these efforts can be found in the scope of the problems caused by the contamination at CRF’s Washington facility. The FDA’s recall ultimately affected 358 consumer products sold under 42 separate brands, which included over two dozen types of products such as organic and non-organic broccoli, carrots, corn, edamame, blueberries, peaches, raspberries and strawberries. Also, though the recall happened in 2016, because it involved frozen products, the sell-by dates of the last of the affected products passed this April.

AFFI did not comment on the CRF case but said that, in general, consumer education and proper handling of foods is also important in ensuring the safety of the entire frozen food chain.

Aside from its reach, the 2016 incident had serious effects for the public and for CRF. Nine people were hospitalized and one death was linked to the outbreak. The facility closed because of the recall but is slated to open sometime this year. That reopening only comes after CRF’s parent company R.D. Offutt and J.R. Simplot agreed to a joint venture, according to a local newspaper.

“We’re also having ongoing consultation with the (Food and Drug Administration) to ensure the facility meets or exceeds the highest levels of their food safety requirements,” Josh Jordan, J.R. Simplot spokesman told the Tri-Cities Area Journal of Business.

Scott Stuntz, managing editor

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