Q&A: Food Safety in the Produce Aisle (Part I)

In Part I of this two-part series, Peyman Fatemi, Ph.D., the professional services specialist in the food safety group at 3M, discusses the unique challenges fruit and vegetable processors face, as well as special food safety concerns which apply to these products.

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This is an expanded version of a feature that first appeared in the July/August 2013 issue of Food Manufacturing.

Interview with Peyman Fatemi, Professional Services Specialist, 3M

In Part I of this two-part series, Peyman Fatemi, Ph.D., the professional services specialist in the food safety group at 3M, discusses the unique challenges fruit and vegetable processors face, as well as special food safety concerns which apply to these products.

Q: What unique challenges do fruit and vegetable processors face?

A: Challenges within the Supply Chain

Fruits and vegetable processors face some unique challenges that other food sectors either do not face or have means to overcome. One challenge for these processors is maintaining quality and safety of their product due to its short shelf life and minimal processing. Product degradation begins as soon as it is harvested and is accelerated if it is not cooled immediately. This could impact the microbiological safety of the product, especially with vegetables. To avoid this issue, there must be strong coordination between all players within the product supply chain. This starts in the field with the following:

  • Grower, that must meet the good agricultural practices criteria,
  • Inspector that verifies this criteria is met and may test product before harvest,
  • Harvesting personnel and equipment to ensure proper efficiency and hygiene, and the
  • Shipper that take the harvested product to the processor or packing house.

At the processing facility, the processor must:

  • receive and cool the product immediately,
  • inspect for quality,
  • test for safety,
  • process and pack while avoiding compromising the quality and safety of the product,
  • test the finished product, and
  • ship the product to market within a few short days of harvest.

Fruit growers and packers face similar challenges, but most can better control the issue of degradation by harvesting an unripe product and controlling the ripening process through controlled atmosphere storage. This could impact the microbiological safety of the product and it changes if the product is fresh-cut and packaged. The consumer also plays a very significant role in maintaining the quality and safety of the product within the farm to table chain.

Over the last 30 years, the challenges within the supply chain have increased, for several reasons:

  • Significant increase in consumption of raw or minimally processed fruits and vegetables.
  • Demand for year round availability of fruits and vegetables has forced processors to source their products from outside their region or country.
  • Demand for packaged salads and fruits exposes the product to different production practices.

Foodborne Outbreaks Associated with Fruits and Vegetables

One potential consequence of this globalization of the food supply is that the quality and microbiological safety of produce may not be as strictly controlled in other countries or regions of the world. These factors, along with the increased consumption, and perhaps others have undoubtedly contributed to the increase in reported foodborne outbreaks associated with fruits and vegetables produced both inside and outside of the United States.

  • There were 131 outbreaks associated with contaminated produce between 1996 and 2010, causing more than 14,000 illnesses and 34 deaths, according to the FDA. 
  • There is now increased surveillance of fruits and vegetables for the presence of pathogens by the government and the industry.
  • The development of more sensitive detection and identification methods is allowing us to gather and share unique information about microorganisms in question and their sources.
  • The food industry has identified biological hazards such as Salmonella, E. coli O157:H7, Shigella, Listeria, Hepatitis A, and Cyclospora as leading causative agents associated with fruits and vegetables.
  • There is increased funding for better understanding the routes of contamination of fruits and vegetables and strategies to decontaminate them.

This has challenged the produce industry as well as the federal and state governments to work more closely together to come up with a method, based on science, to better safeguard against contamination. One such example is the Leafy Greens Marketing Agreement (LGMA), which is a public-private partnership in California and Arizona. LGMA requires government oversight to ensure safe produce production practices are being followed in leafy green farms. According to the LGMA, mandatory government audits are conducted for each member 6 to 8 times per year. To achieve certification, members are required to achieve 100 percent compliance with all required food safety practices. The learning from this unique partnership undoubtedly influenced the FDA when it proposed the produce safety rule, as part of Food Safety Modernization Act (FSMA) focused on setting enforceable standards as part of the requirement for the food safety modernization act that will be discussed in more detail.

Q: Why are fruits and vegetables so prone to dangerous microorganisms like E. coli and Listeria?

A: Fresh produce can become microbiologically contaminated at any point along the farm-to-table food chain. This is because:

  • Contamination of fruits and vegetables, unlike cattle that are known reservoirs of E. coli O157:H7, is a consequence of association with human or animal feces.
  • The source and quality of the water that comes in contact with produce dictates the potential for contamination. Moisture, warm temperatures, sufficient time and environmental factors can create conditions where pathogens, if present, can survive and potentially multiply.
  • A study by UC Davis Center for Produce Safety recently showed higher levels of contamination of produce associated with elevated temperatures after a rain event.

As a consequence, harvesting and processing equipment, human handlers and shipping containers that come in contact with the contaminated produce, can further disseminate the organisms if they are not cleaned properly and regularly.

Washing Produce

Because the majority of fruits and vegetables are eaten raw or are minimally processed, they are not subject to processes that would destroy these pathogens. Produce are often washed in the processing facility, but research has shown that the waxy, hydrophobic surfaces of fruits and vegetables that guard them against desiccation, may also protect the pathogen attached to it from the action of chemical solutions. Therefore, most produce washes are only effective in removing dirt, debris, field heat and only some of the pathogen. Furthermore, most wash water chemicals are inactivated in the presence of organic matter and if the chemical concentration falls below effective levels, the wash water can become a possible source of contamination. Therefore, processors must constantly filter the water to remove organic matter and are always on the lookout for more effective produce wash systems.

Packaging Produce

Other factors, such as packaging with oxygen barriers to extend product shelf life may also make the environment more suitable for pathogen survival. Some pathogens such as E. coli and Listeria have been shown to survive in reduced oxygen conditions whereas the normal flora is reduced. Reduction of natural plant bacteria may also reduce competition for food source, allowing for survival of the pathogen.

Transport and Storage of Produce

Produce may also be subjected to temperature abuse and unsanitary conditions during storage and transport. Economic conditions such as the gas price increase of 2008-2009 can further exacerbate the problem. For example, it was found that some truck drivers, in an effort to save gas, were turning off their refrigerated containers during transit resulting in elevated temperatures. That not only resulted in reduced product shelf life, but may have led to increases in pathogenic organism as well.

Handling of Produce at Food Service Establishments and at Home

There have been a number of documented foodborne outbreaks associated with contamination during handling at retail, restaurants and at home by the consumer. In fact, a significant portion of foodborne illnesses have been attributed to mishandling of produce at home or at a foodservice environment. They are often limited in scope and many go unreported, but government and outreach programs are continually educating the public about how to prevent contaminating the food.

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