Green-seeds.com:
publications & research: articles

Vegetarian 99-12

FDA Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables


The Centers for Disease Control recently released the following information: "To better quantify the impact of foodborne diseases on health in the United States, we compiled and analyzed information from multiple surveillance systems and other sources. We estimate that foodborne diseases cause approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States each year. Known pathogens account for an estimated 14 million illnesses, 60,000 hospitalizations, and 1,800 deaths. Three pathogens, Salmonella, Listeria, and Toxoplasma, are responsible for 1,500 deaths each year, more than 75% of those caused by known pathogens, while unknown agents account for the remaining 62 million illnesses, 265,000 hospitalizations, and 3,200 deaths. Overall, foodborne diseases appear to cause more illnesses but fewer deaths than previously estimated." (Source: Food-Related Illness and Death in the United States. Paul S. Mead, Laurence Slutsker, Vance Dietz, Linda F. McCaig, Joseph S. Bresee, Craig Shapiro, Patricia M. Griffin, and Robert V. Tauxe. Centers for Disease Control and Prevention, Atlanta, Georgia, USA.).

Significantly, the incidence of foodborne disease attributed to fruits and vegetables is very small compared to the total numbers. However, unpasteurized juices and fresh sprouts have been implicated in recent outbreaks. In October, 1999 the FDA released two guidance publications on safe sprout handling and testing of irrigation water in sprout production respectively). Ensuring that our fresh produce is as safe as possible involves close collaboration of everyone involved. Produce can become contaminated at any point, beginning in the field and continuing through packing, handling, shipping and retail.

The U.S. Department of Health and Human Services, Food and Drug Administration (FDA), Center for Food Safety and Applied Nutrition (CFSAN) published the very useful "Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables" for growers, packers, and shippers about one year ago as part of the Presidentís Food Safety Initiative. By identifying basic principles of microbial food safety within the realm of growing, harvesting, packing, and transporting fresh produce, users of this guide will be better prepared to recognize and address the principal elements known to give rise to microbial food safety concerns. Here are the highlights from the guide:

Water Quality

Wherever water comes into contact with fresh produce, its quality dictates the potential for pathogen contamination.

Water can be a carrier of many microorganisms including pathogenic strains of Escherichia coli, Salmonella spp., Vibrio cholerae, Shigella spp., Cryptosporidium parvum, Giardia lamblia, Cyclospora cayetanensis, Toxiplasma gondii, and the Norwalk and hepatitis A viruses. If pathogens survive on the produce, they may cause foodborne illness. Even small amounts of contamination with some of these organisms can result in foodborne illness.

In general, the quality of water in direct contact with the edible portion of produce may need to be better than the quality of water in which contact with the edible portion of the plant is minimal.

Agricultural water quality will vary, particularly surface waters that may be subject to intermittent, temporary contamination, such as waste water discharge or polluted runoff from upstream livestock operations. Ground water that is influenced by surface water, such as older wells with cracked casings, may also be vulnerable to contamination.

Water quality should be adequate for its intended use. Where water quality is unknown or cannot be controlled, growers should use other good agricultural practices to minimize the risk of contamination.

Practices to help ensure adequate water quality may include ensuring that wells are properly constructed and protected, treating water to reduce microbial loads, or using alternative application methods that reduce or avoid water-to-produce contact.

Processing water should be of such quality that it does not contaminate produce.

Practices to Ensure and Maintain Water Quality. Perform periodic water sampling and microbial testing; Change water as necessary to maintain sanitary conditions; Clean and sanitize water contact surfaces, such as dump tanks, flumes, wash tanks, and hydrocoolers, as often as necessary to ensure the safety of produce; Install backflow devices and legal air gaps, as needed, to prevent contamination of clean water with potentially contaminated water (such as between potable water fill lines and dump tank drain lines; Routinely inspect and maintain equipment designed to assist in maintaining water quality, such as chlorine injectors, filtration systems, and backflow devices, to ensure efficient operation.

Prevention of contamination is preferred over application of antimicrobial chemicals after contamination occurs.

However, antimicrobial chemicals in processing water are useful in reducing microbial build-up in water and may reduce microbial load on the surface of produce. Washing fresh produce can reduce the overall potential for microbial food safety hazards. This is an important step since most microbial contamination is on the surface of fruits and vegetables. If pathogens are not removed, inactivated, or otherwise controlled, they can spread to surrounding produce, potentially contaminating a greater proportion of the produce. A number of post-harvest processes, such as hydrocooling, use of dump tanks, and flume transport, involve a high degree of water-to-produce contact. Packers should follow good manufacturing practices to maximize the potential for these processes to assist in cleaning produce.

Manure and Municipal Biosolids

Growers should follow good agricultural practices for handling animal manure or biosolids to minimize microbial hazards.

Properly treated manure or biosolids can be an effective and safe fertilizer. Untreated, improperly treated, or recontaminated manure or biosolids used as a fertilizer, used to improve soil structure, or that enters surface or ground waters through runoff, may contain pathogens of public health significance that can contaminate produce.

Good agricultural practices for the use of animal manure or biosolids include treatments to reduce pathogens and maximizing the time between application to production areas and harvest of the crops.

Growers purchasing manure should obtain a specification sheet from the manure supplier for each shipment of manure containing information about the method of treatment.

Animal feces is a known source of pathogens that can cause foodborne illness.

A particularly dangerous pathogen, Escherichia coli O157:H7, is known to originate primarily from ruminants such as cattle, sheep and deer, which shed it through their feces. In addition, animal (and human) fecal matter are known to harbor Salmonella, Cryptosporidium, and other pathogens. Domestic animals should be excluded from fresh produce fields, vineyards, and orchards during the growing season. In addition, high concentrations of wildlife (such as deer or waterfowl in a field) may increase the potential for microbial contamination.

Worker Health and Hygiene

Infected employees who work with fresh produce increase the risk of transmitting foodborne illnesses.

Be aware of existing state and Federal regulations regarding standards for worker health, hygiene and sanitation practices during the growing, packing, holding, and transport of human food. Train all employees to follow good hygienic practices.

Sanitary Facilities

Operations with poor management of human and other wastes in the field or packing facility can significantly increase the risk of contaminating produce.

Toilet facilities should be accessible. Toilet facilities should be properly located. Toilet facilities and handwashing stations should be well supplied. All facilities should be kept clean.

Field Sanitation

Poor management of human and other wastes in the field can significantly increase the risk of contaminating produce.

Microbial contamination or cross-contamination of fresh produce during pre-harvest and harvest activities may result from contact with soils, fertilizers, water, workers, and harvesting equipment. Any of these may be a source of pathogenic microorganisms. Clean harvest storage facilities prior to use. Discard damaged containers that are no longer cleanable. Clean containers or bins before using to transport fresh produce. Ensure that produce that is washed, cooled, or packaged in the field is not contaminated in the process. Remove as much dirt and mud as practicable from the produce before it leaves the field. Use harvesting and packing equipment appropriately and keep it as clean as practicable. Any equipment used to haul garbage, manure, or other debris should not be used to haul fresh produce. Keep harvest containers clean to prevent cross-contamination of fresh produce

Packing Facility Sanitation

It is important to maintain buildings, fixtures, and other physical facilities, and their grounds, in good condition to reduce the potential for microbial contamination of produce.

Operations with poor sanitation in the packing environment can significantly increase the risk of contaminating fresh produce and water used on produce. Pathogenic microorganisms may be found on the floors and in the drains in the packing facility and on the surfaces of sorting, grading, and packing equipment. Without good sanitary practices, any of these surfaces that come in contact with fresh produce could be a potential source of microbial contamination. Packers should employ good sanitation practices as a standard operating procedure to maintain control throughout the packing operation.

Transportation

The proper transport of fresh produce from farm to market will help reduce the potential for microbial contamination.

Transportation operations include transportation from the field to the cooler, packing facility, and on to distribution and wholesale terminal markets or retail centers. Microbial cross-contamination from other foods and nonfood sources and contaminated surfaces may occur during loading, unloading, storage, and transportation operations. Wherever produce is transported and handled, the sanitation conditions should be evaluated. Transporters should separate fresh produce from other food and nonfood sources of pathogens in order to prevent contamination of the produce during transport operations.

Workers involved in the loading and unloading of fresh produce during transport should practice good hygiene and sanitation practices. Product inspectors, buyers, and other visitors should comply with established hygienic practices, such as thoroughly washing their hands before inspecting produce. Inspect trucks or transport cartons for cleanliness, odors, obvious dirt or debris before beginning the loading process. Keep transportation vehicles clean to help reduce the risk of microbial contamination of fresh produce. Maintain proper temperatures to help ensure both the quality and safety of fresh produce. Load produce in trucks or transport cartons in a manner that will minimize damage.

Traceback

The ability to identify the source of a product can serve as an important complement to good agricultural and management practices intended to minimize liability and prevent the occurrence of food safety problems.

(Brecht, Ritenour, and Sargent, Vegetarian 99-12)

1998-1999 Oriental Vegetable Introduction in South Florida


Mr. Ping Qiao, a scientist with the Division of Plant Industry, Florida Department of Agriculture and Consumer Services, initiated several field trails during October 1998-September 1999 to conduct preliminary performance tests of 33 oriental vegetable cultivars on a calcareous gravelly soil at the Tropical Research and Education Center, Homestead. The seeds of most cultivars were sowed in seedling plates and transplanted into field beds under plastic mulch when the seedlings had 3-5 true leaves. Some of them, like radish and amaranth, were sowed directly into the field beds. The bed height was about 8 inches and each bed was provided with 1 or 2 irrigation drip lines. The distance between beds was 6 feet. Some insecticides and nematicides were applied when making beds to control the pests in the soil. The Centerís farm manager was in charge of irrigation, fertilization and pest management. In spite of diligent pest control interventions some cultivars were damaged by thrips, mites or pickleworms. Doubtless these losses could be minimized though additional experience.

The experimental results are summarized in the table. The following preliminary conclusions were reached:

1. Regardless of the season many cultivars of oriental vegetables can be produced successfully in south Florida. In fall and winter, all hardy and semihardy vegetables and some warm season vegetables grow very well. In particular the various species of Brassica and Raphanus sativus, Lactuca sativa var. angustana can be relay planted many times and supplied for 4-5 months. Crowndaisy, chrysanthemum and mustard green can be harvested many times from the same planting provided that the plant root systems are protected from damage during harvest. Even napa was harvested more than one time from the same planting. During spring and summer, all warm season oriental vegetables and some hardy and semihardy oriental vegetables grow well. These include beans, cucurbits, solanaceous crops, amaranth, etc. Of course, the control of diseases and insects is very important for all crops, especially during the warm wet summer period.
   
   
2. Some cultivars of radish and asparagus lettuce were judged to be sufficiently promising for testing farm scale production. These include Qiatouqing, Xinlinmei, Yuanyiewosun, and Amaranth.
   
   
3. Experimental results showed that some varieties of napa and pak choi developed flower stalks prior to harvest. Both bolting varieties of napa and pak choi ­ Early #5 and Aijiaoqing, respectively, originated from a low latitude region of China. To avoid the problem of bolting, varieties form higher latitudes need to be evaluated.