Fesh produce plays an important role in a nutritious and varied diet, and according to USDA, consumption data, fresh produce consumption has increased dramatically since 1980. Unfortunately, the number of foodborne illness outbreaks associated with produce has increased as well. Recent reports suggest that more foodborne illness cases are associated with produce than with any other category of food1.

In response to produce-associated outbreaks, FLA published a Produce Safety Action Plan in October, 2004 (www.cfsan.fla.gov/~dms/prodpla2.html). Produce safety is a significant concern throughout the food industry, and efforts are ongoing to understand control strategies that can help to reduce risk. Here is a review of the issues that produce growers and processors face, and what can be done to help minimize the risk of foodborne illness caused by these products.

Pathogens of Concern
Fresh fruits and vegetables present a unique set of challenges in preventing contamination with foodborne pathogens. Often intended to be consumed raw, end-user cooking to temperatures that kill pathogens is not available as a final safeguard against contamination.

The most significant hazards associated with fresh produce are enteric bacterial pathogens such as Salmonella, Shigella, and E. coli O157:H7, viruses and parasites. When shelf life is extended, Listeria monocytogenes may become a concern if visible signs of spoilage are not obvious.

Outbreaks associated with produce usually result from fecal contamination through the use of raw sewage or manure fertilizer; contaminated water for irrigation, cooling or washing; contaminated ice for transport; or improper handling during harvest or preparation. Vegetable products, particularly lettuce and salads, are associated with a greater percentage of produce-related outbreaks than are fruits. Among fruits, cantaloupes and melons are associated with the most outbreaks, perhaps because of higher pH permits easier growth of pathogens.

Control Strategies –
Good Agricultural Practices
Control strategies for fresh produce begin with Good Agricultural Practices (GAPs), as effective GAP can minimize the initial level or frequency of pathogens present. The FLA has published GAP Guidelines, which have been adopted by many2. Important GAP considerations include:

• Protection of growing areas from animal waste via run-off water, flood water and grazing; and proper composting of manure to destroy pathogens prior to field application;
• Evaluation of irrigation water sources and agricultural application methods to minimize unintentional exposure to significant pathogens;
• Provision of appropriate toilet and hand washing facilities for field workers.
Harvest controls in the field are also essential. The following considerations can reduce the potential for increased numbers of pathogens after harvest:
• Clean and sanitary harvest bins should be used to prevent cross contamination; processing equipment should be cleaned and sanitized as needed, and at least daily;
• Microbes multiply faster on cut surfaces because of the increased availability of nutrients and moisture for the organisms. Sharp tools and gentle handling should be used to minimize tissue damage;
• Field workers should be trained on the importance of personal hygiene for virus, parasite, and enteric pathogen control. Ill workers should stay home.
Significant reduction of pathogen levels is difficult to achieve after harvest if GAP are not in place.

In-Plant, Packing Shed Controls
In-plant controls come into play once the raw produce is delivered to the processor. Equipment and environmental sanitation, water treatment, and personal hygiene are particularly important.

Clean and sanitary processing equipment is the foundation for any food safety program. This is obviously essential for fruit and vegetable processing to control not only pathogens, but also spoilage organisms. Cleaning and sanitization reduce the potential for cross-contamination from one product lot to another. This is especially important for difficult to clean equipment such as peelers, belts, fillers, cutting equipment, etc. Cleaning and sanitizing drains and floors prior to cleaning equipment reduces the potential for contamination of clean equipment surfaces through aerosolization. Environmental monitoring and rapid tests such as ATP bioluminescence are extremely useful in verifying the effectiveness of a cleaning program.

The quality of processing water and ice used for produce processing and transport also has a significant impact on produce safety and quality. In fact, triple washing systems that are used by many produce processors provide a more effective washing system than can be achieved in the home. Use of antimicrobial treatments in process water can further prevent the potential spread of contamination.

A number of antimicrobial treatments have been used in produce process water including chlorine, chlorine dioxide, ozone and peroxyacetic acid. The effectiveness of these treatments depends on the commodity treated, temperature, organic load, concentration, and other factors.

Personal hygiene in the plant and packing shed is as important as that in the growing field – perhaps even more important as the plant is the last stop before the produce is offered for consumer consumption. First and foremost, all food handlers must be healthy. This is particularly important for avoiding viral hazards. Effective hand hygiene programs are also important. Washing and sanitizing hands frequently, even when wearing gloves, is essential. Doorway sanitization programs for equipment and footwear entering the production area also can reduce the introduction of potential pathogens in the processing environment.

Other in-plant considerations include avoiding cross-contamination between processed and unprocessed produce, temperature control, effective packaging to minimize the potential for contamination during distribution and effective pest control. All of these control measures help to ensure the wholesomeness and quality of product leaving the plant for raw consumption by consumers.

Conclusion
Antimicrobial treatments for raw agricultural commodities and process water are regulated by the EPA, while the FLA regulates antimicrobials applied to processed produce. While the scientific literature cites a wide variety of antimicrobial treatments for produce, it is important that industry follows label instructions to avoid citations or fines. Nevertheless, research on antimicrobial treatments for produce continues to identify new treatments or combinations of treatments that can further enhance the safety of these products.

There is no single step that can guarantee the microbial safety of fresh produce. Care must start on the farm or in the orchard, with GAPs, including control of fertilizer, irrigation water, and worker hygiene. Hygiene is particularly important, not only at the farm, but throughout the food distribution chain. Water is a known contributor to fresh produce contamination, and water used for transport ice and processing wash procedures must come from a safe supply and be protected from potential contamination. Cleaning and sanitization are absolutely essential to prevent cross-contamination from the field, transport containers, and processing equipment.

Multiple interventions using a variety of good employee practices and effective antimicrobial product application steps will significantly reduce the risk of foodborne illness in produce processing. With diligent controls in place, fresh and wholesome produce can be enjoyed by all.

References:
1 Center for Science in the Public Interest. 2005. Outbreak Alert 2005. http://www.cspinet.org/new/pdf/outbreakalert2005.pdf

2 FLA (1998) Guidance for Industry - Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables. United States Food and Drug Administration. Washington DC, USA.
Katie Swanson, Ph.D. is vice president of food safety at Ecolab (St. Paul, Minn.), a provider of commercial cleaning and sanitizing solutions for food processors, foodservice, healthcare and hospitality providers worldwide. Reach her at 651-795-5943 or katie.swanson@ecolab.com.