Report Addresses Safety of Fresh Fruits and Vegetables

As part of its five-year contract with the Food and Drug Administration, IFT has completed a third report, “Analysis and Evaluation of Preventive Control Measures for the Control and Reduction/Elimination of Microbial Hazards on Fresh and Fresh-Cut Produce.” The main objectives of the project were to assess the safety of fresh produce, identify production points with high contamination risks, and assess the efficiency of control methods. Here are some highlights:
• There are many points at which produce can become contaminated with pathogens, either directly, e.g., through manure in fertilizer, or indirectly, e.g., through wild animal and insect vectors. The potential for contamination from manure depends on such factors as pathogen population in feces, processing methods, soil stability, and relative timing and location of manure. Data suggest that the level of some pathogens in manure is higher than previously thought. Properly composted manure, however, should result in negligible risk of contamination. Overall, the effectiveness of preventive measures in place has not been established.

The report also reviews the potential for contamination of produce through irrigation methods. Currently, there are no standard procedures being followed to ensure the microbiological quality of irrigation water. The persistence of pathogens in produce due to irrigation water is not clear and depends on some-what uncontrollable factors. Microbiological standards for agricultural water based on risk assessments for pathogens of concern are needed.

Numerous research data demonstrate that the use of reclaimed water with strict microbiological specifications and process controls (in effect in some states) present minimal food safety risks, even if used for overhead irrigation. Unless the microbiological quality of irrigation water is controlled, growers should follow responsible irrigation practices, such as the use of reclaimed water or water from properly designed, maintained, and inspected wells.

• Postharvest operations, such as packing, also present potential risk factors for contamination, mostly related to water quality and manufacturing practices. Water quality is especially important during cooling of produce, particularly if icing, hydrocooling, or vacuum cooling is used, because of the potential for pathogen contamination and/or internalization. After harvest, some pathogens will survive but not grow on the surface of most produce, unless the protective barrier is broken, either by damage or by processing (e.g., fresh-cut produce), especially at nonrefrigerated temperatures.

There are no known mitigation strategies that will completely remove pathogens without compromising the sensory qualities of produce. The effectiveness of washing and sanitizing methods depends on several factors, including water quality and characteristics of the produce surface. Some of the most promising methods are physical removal, chlorine dioxide, acidified sodium chlorite, acidic compounds, and ozone. The use of irradiation is limited, due in part to the loss of sensory attributes. Strict adherence to Good Agricultural Practices, Good Manufacturing Practices, and HACCP programs continues to be the primary pathogen control strategy.

Indicators and surrogate microorganisms may be used for evaluating safety of fresh or fresh-cut fruit and vegetable products by assessing or validating the effectiveness of microbial control measures. Although frequently used on an informal basis within a specific company, use of indicators is highly dependent upon microbiological criteria that are in place for the specific produce item or category. All of the considerations that must be addressed in establishing microbiological criteria must also be in place if indicators are to be utilized in process verification.

• Many new packaging materials are being studied for preserving fresh fruits and vegetables for shelf life extension through modified atmosphere packaging. MAP, however, may enhance the potential for pathogens which may be resistant to carbon dioxide to outgrow spoilage microorganisms. MAP of produce should always incorporate packaging materials that will not lead to an anoxic environment. Also, spoilage microorganisms should not be eliminated, as their interaction with pathogens may play a role in product safety.

• The gains in public health safety need to be carefully weighed against any intervention strategies developed to reduce contamination in fresh produce. These strategies must be flexible to serve small and large farming and processing operations, while assuring that they are affordable, efficient, and safe controls.

The report will be released on FDA’s Web site at the end of the year and published as a Journal of Food Science supplement in 2002. Through projects such as these, IFT is harnessing the power of food science and technology to contribute to federal decision making on food safety regulations and policies.

by MARIA ORIA
Staff Scientist
IFT Dept. of Science and Technology Projects