Microbial Contamination of Fresh Fruits and Vegetables

Abstract

Investigation Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.5 Potential Sources of Produce Contamination byHuman Pathogens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 1.5.1 Food Safety Risk Factors Associated with Productionof Fresh Produce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 1.5.1.1 Land Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.5.1.2 Soil Amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.5.1.3 Wild and Domestic Animal Control . . . . . . . . . . . . . . . . 14 1.5.1.4 Irrigation Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.5.1.5 Harvest Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151.5.2 Food Safety Risk Factors Associated with Postharvest Handling of Produce. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 1.5.2.1 Employee Hygiene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 1.5.2.2 Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 1.5.2.3 Wash and Hydrocooling Water . . . . . . . . . . . . . . . . . . . . 17 1.5.2.4 Cold Storage Facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1.5.2.5 Packaging Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1.5.2.6 Modified Atmosphere Packaging ofFresh Produce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181.5.2.7 Refrigerated Transport, Distribution, and Cold Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191.5.3 Food Safety Risk Factors Associated with Foodservice, Restaurant, and Retail Food Stores Handling of Produce. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201.5.4 Consumer Handling of Produce from Purchase to Plate . . . . . . 21 1.6 Effective Management Strategies: Contamination Preventionand Intervention. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 1.6.1 Good Agricultural Practices (GAPs) . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.6.2 Current Good Manufacturing Practices (cGMPs). . . . . . . . . . . . . 23 1.6.3 Hazard Analysis Critical Control Point (HACCP) . . . . . . . . . . . . 241.7 Research Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1.7.1 Microbial Ecology of Human Pathogens in the AgriculturalProduction Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.7.2 Agricultural Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.7.3 Soil Amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.7.4 Proximity Risk of Potential Contaminant Sources . . . . . . . . . . . . 27 1.7.5 Intervention Strategies to Reduce the Risk ofHuman Pathogen Contamination of Fresh Produce . . . . . . . . . . 27 1.8 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Fresh fruits and vegetables are perceived by consumers to be healthful andnutritious foods because of the plethora of scientifically substantiated anddocumented health benefits derived from consuming fresh fruits and vegetables[1]. However, recent foodborne illness outbreaks in the U.S. and throughoutthe world have been increasingly linked epidemiologically to consumption offresh fruits, vegetables, and unpasteurized juices. These incidents have causedgrowers, shippers, fresh-cut produce processors, distributors, retailers, import-ers, and government public health officials to re-evaluate the risk of con-tracting foodborne illness from consumption of fresh fruits and vegetablesand to re-evaluate current production and handling practices. While the probability of contracting a foodborne illness via consumptionof fresh fruits or vegetables is very low, a small probability does exist. Becausefresh fruits and vegetables are often consumed uncooked so that there isno ‘‘kill’’ step, prevention of produce contamination with human pathogensis the only practical and effective means of ensuring that these food pro-ducts are wholesome and safe for human consumption. This means that acomplete supply chain approach to prevent contamination at any point in theproduce continuum is essential to ensuring public health by minimizing theincidence of foodborne illness associated with produce consumption. Ensuringof andthe integrity of produce from field to fork is the responsibility of everyone inthe produce continuum, including growers, shippers, processors, distributors,retailers, and consumers. It must also be remembered that the health benefitsderived from eating at least five servings of fresh fruits and vegetables dailyfar outweigh the very small probability of contracting a foodborne illness. A meaningful assessment of the risk associated with contracting afoodborne illness from consumption of fresh fruits and vegetables involvesunderstanding the microbiology of fresh fruits and vegetables as well as fieldproduction, processing, and handling practices. As such, the fresh produceindustry is extraordinarily diverse and complex in the number of productsproduced, how the products are grown and handled, and the geographicareas from which these products are sourced. A typical retail grocer in NorthAmerica will have available on a daily basis upwards of 300 differentproduce items for sale. The morphological characteristics of a produce itemmay also contribute to its propensity for contamination, since produceitems may be derived from the leaves, stems, stalks, roots, fruits, and flowersof plants. Because the produce continuum represents such diversity, it isonly possible to describe broad generalities about current practices of theproduce continuum and the food safety risk associated with them, as anin-depth analysis of this plethora of products would be encyclopedic in volume.Contamination of fruits and vegetables by human pathogens can occuranywhere in the farm to table continuum including contamination of seedstocks and during production, harvesting, postharvest handling, storage,processing, transport distribution, retail display, and/or preparation (food-service or home). Produce contaminated with human pathogens cannot becompletely disinfected by washing or rinsing the product in an aqueoussolution, and low sporadic levels of human pathogens can be found on pro-duce [2,3]. In 2004 the Alliance for Food and Farming [4] analyzed Centersfor Disease Control and Prevention (CDC) data sets [5,6] and summa-rized information regarding foodborne illness outbreaks that have beenassociated with produce consumption. The study’s objective was to analyzelikely sources of produce contamination and categorize the most likely placethat the contamination occurred, that being either during production/growing or during postproduction handling. The ‘‘postproduction’’ categoryincluded produce-associated foodborne illnesses that were most likely due toimproper handling at the foodservice, retail, or consumer level, while the‘‘grower’’ category included foodborne illnesses associated with produce thatwere most likely attributable to the farm, packing, shipping, or otheragricultural postharvest handling. Analysis of CDC data indicated thatimproper handling of fruits and vegetables at foodservice establishments orby consumers caused 83% of produce-associated foodborne illness outbreaks,while ‘‘grower’’-implicated cases comprised 17% of produce-associatedfoodborne illness outbreaks. Data from this report presented in Figure 1.1 show that the percentage of ‘‘grower’’-related contamination incidents as a percent of all produce related outbreaks has been declining since 1996, and this trend is most likely due to implementation of good agricultural practices (GAPs) by grower/shipper/packers.