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ISSN : 1229-1153(Print)
ISSN : 2465-9223(Online)
Journal of Food Hygiene and Safety Vol.34 No.1 pp.1-12
DOI : https://doi.org/10.13103/JFHS.2019.34.1.1

Potential Contamination Sources on Fresh Produce Associated with Food Safety

Jungmin Choi1, Sang In Lee1, Bryna Rackerby2, Ian Moppert1, Robert McGorrin1, Sang-Do Ha3, Si Hong Park1*
1Department of Food Science and Technology, Oregon State University, Corvallis, Oregon, USA
2Department of Microbiology, Oregon State University, Corvallis, Oregon, USA
3Department of Food Science and Technology, Advanced Food Safety Research Group, Brain Korea 21 Plus, Chung-Ang University, South Korea
*Correspondence to: Si Hong Park, Department of Food Science and Technology, Oregon State University, Corvallis, OR 97331
December 29, 2018 January 23, 2019 February 14, 2019

Abstract


The health benefits associated with consumption of fresh produce have been clearly demonstrated and encouraged by international nutrition and health authorities. However, since fresh produce is usually minimally processed, increased consumption of fresh fruits and vegetables has also led to a simultaneous escalation of foodborne illness cases. According to the report by the World Health Organization (WHO), 1 in 10 people suffer from foodborne diseases and 420,000 die every year globally. In comparison to other processed foods, fresh produce can be easily contaminated by various routes at different points in the supply chain from farm to fork. This review is focused on the identification and characterization of possible sources of foodborne illnesses from chemical, biological, and physical hazards and the applicable methodologies to detect potential contaminants. Agro-chemicals (pesticides, fungicides and herbicides), natural toxins (mycotoxins and plant toxins), and heavy metals (mercury and cadmium) are the main sources of chemical hazards, which can be detected by several methods including chromatography and nano-techniques based on nanostructured materials such as noble metal nanoparticles (NMPs), quantum dots (QDs) and magnetic nanoparticles or nanotube. However, the diversity of chemical structures complicates the establishment of one standard method to differentiate the variety of chemical compounds. In addition, fresh fruits and vegetables contain high nutrient contents and moisture, which promote the growth of unwanted microorganisms including bacterial pathogens (Salmonella, E. coli O157: H7, Shigella, Listeria monocytogenes, and Bacillus cereus) and non-bacterial pathogens (norovirus and parasites). In order to detect specific pathogens in fresh produce, methods based on molecular biology such as PCR and immunology are commonly used. Finally, physical hazards including contamination by glass, metal, and gravel in food can cause serious injuries to customers. In order to decrease physical hazards, vision systems such as X-ray inspection have been adopted to detect physical contaminants in food, while exceptional handling skills by food production employees are required to prevent additional contamination.



초록


    Oregon State University

    “Food safety” refers to the control of foods in the farm to fork continuum to prevent diverse foodborne diseases derived from chemical, microbiological, and physical hazards. Poor hygiene can lead to unsafe foods through contamination by microbes, resulting in a multitude of human health problems. The US Food and Drug Administration (FDA) reported more than 48 million cases of foodborne illnesses annually in the US associated with the consumption of contaminated foods. According to recent statistics, foodbornerelated sicknesses resulted in an estimated 128,000 hospitalizations and 3,000 deaths in the US, annually1). According to the World Health Organization (WHO), 1 in 10 people fall ill from consumption of contaminated foods every year, and an estimated 420,000 deaths occur2). During the last two decades, fruits and vegetables have been identified as one of the main causes of foodborne outbreaks3).

    Fresh produce includes raw and fresh fruits, vegetables, herbs, fungi, and nuts, which are essential components in the diet4). Fruits and vegetables are rich in a variety of nutrients, including vitamins, trace minerals, dietary fiber, and many other classes of biologically active compounds which inhibit or prevent chronic diseases such as heart disease, cancer, diabetes, and obesity5). Increased rates of fresh produce consumption reported over the past two decades can be attributed to a few factors. First, consumers are becoming more concerned about health through eating correctly, leading to increased demands for a larger variety of domestic and imported products during all seasons throughout the year6). Secondly, there have been increased efforts by the government to promote healthy foods. As the consumption of fresh produce has increased, the number of foodborne illnesses outbreaks associated with fruits and vegetables has risen7). Because fresh produce is mostly consumed raw or after minimal processing, pathogen contamination constitutes a potential health risk8). Fresh produce is easily contaminated by chemical, biological, and physical hazards during the transition from farm to fork phase. A recent report by the Center for Science in the Public Interest (CSPI) indicates that one of the highest numbers of outbreaks can be attributed to the fresh produce industry in the US between 2006 and 2016. Fresh produce-related outbreaks constitute not only one of the greatest numbers of total illnesses, but also the largest average number of illnesses per outbreak9).

    In this review, the chemical, biological, and physical hazards associated with food safety in fresh produce will be described, as well as transmission routes, symptoms of contamination, and detection methods.

    Chemical contaminants on fresh produce

    Chemical contaminations involve the presence of chemicals in a food matrix where their concentration exceeds safe level. Chemical hazards are one of the main causes for foodborne disease outbreaks10) derived from a variety of sources from harvest to processing. Contamination of fresh produce can occur from soil, sewage, external surfaces, and live animals11). Chemical hazards have been considered one of the most serious consumer concerns because of long-term carcinogenic potential from chemical contaminants12). The chemical hazards on fresh produce are classified as agro-chemical, natural toxins, and heavy metals (Table 113)). Symptoms caused by chemical contaminants span from mild gastroenteritis to fatal cases of hepatic, renal, and neurological syndromes14). In recent years, with industrial development and subsequent environmental pollution, foods contaminated by chemicals have become more serious issues15). In Nigeria, 400 to 500 children have died annually due to lead poisoning caused by ingestion of foods contaminated with lead-containing soil and dust16). According to the Foodborne Disease Surveillance System of the US and Puerto Rico, 257 chemical hazard outbreaks were reported between 2009 and 2015 including 1,024 illnesses and 5 deaths17).

    Agro-chemical hazards

    Pesticides

    Agricultural pesticides are commonly utilized in farming operations for fruits and vegetables to increase the viability and quality of fresh produce. However, if pesticides are not degraded, these chemical hazards will penetrate plant tissues and can persist into processed products like juices and jams18). Another important aspect of pesticides is their transmission to animals or water sources in different ways. Pesticides in fresh foods may result in a number of different health problems such as kidney damage, congenital disabilities, reproductive problems and cancer. In addition, the accumulations of pesticides in the human body may contribute to metabolic degradation19). Moreover, pesticides can produce a variety of transformational products (TPs), which can be much more toxic than the parent compounds20).

    Fungicides

    Fungicides are widely used chemical agents that provide protection to crops and seedlings in the field and during the storage of foods. Fungicides are unlikely to cause frequent or severe systemic poisoning since a large number of fungicides have low bioavailability and toxicity in mammals 21). However, the possibilities of chronic health problems and environmental effects have been identified and recently brought to public concern. Dichloran (nitro derivative), flutriafol (triazole), O-phenylphenol (biphenyl), prochloraz (imidazole) and tolclofos methyl (thiophosphate) are representative chemical structures available commercially for different crops which have already been proven to have carcinogenic effects in animal and human22). To minimize potential hazards, the European Union Commission and the US Environmental Protection Agency (US EPA) established maximum residue limits (MRLs) in fruits and vegetables to ensure that fungicides are not present at certain levels that may influence health threats to the public23).

    Herbicides

    In order to control weeds in crops and increase the yield and quality of produce, modern agricultural production systems rely on the use of herbicides24). In general, most herbicides are soil-applied agro-chemicals and their toxicity to mammals is low. Despite the low toxicity, herbicides which are widely used in agriculture, have found their way into public concern due to the presence of their residues identified in foods25).

    Natural toxins

    Mycotoxins

    Mycotoxins are secondary metabolites produced by fungi. Despite efforts to control fungal contamination, fungi are ubiquitous in the environment and found in most fresh produce26). Penicillium, Fusarium and Aspergillus are representative fungi that produce mycotoxin compounds which have a toxigenic impact on food safety. There are more than 1,000 varieties of mycotoxins already reported as causes of several health issues27,28) from milder symptoms including diarrhea, abdominal pain, or other gastrointestinal problems to more severe complications like cancer27). Among varieties of mycotoxins, most of the toxins occur as aflatoxins, ochratoxin A, and patulin28). Mycotoxins can contaminate fresh produce via many different routes from pre-harvest to storage since fungi easily colonize crops and contaminate them during harvest or post-harvest stages29). Mycotoxins in foods may be partially degraded by physical and chemical methods, as well as irradiation. For example, 54% of patulin can be removed from vegetables or fruits through washing steps. Furthermore, washing rotten or damaged apples results in a 10-fold decrease of the concentration of patulin30).

    Plant toxins

    Plant toxins, or phytotoxins, are secondary metabolic compounds produced from plants that play a role in defense mechanisms against insects and fungi. Plant toxins induce a range of negative health effects in humans, from inhibiting an uptake of specific nutrients to carcinogenic properties31). Represented plant toxins include potato glycoalkaloids and toxins produced from herbs, such as pyrrolizidine alkaloids and anisatin in certain varieties of star anise25). Pyrrolizidine alkaloids are one of the most common phytotoxins having carcinogenic, hepatotoxic, genotoxic and teratogenic properties 32). Despite the serious health impact of phytotoxins, regulations are not well established in comparison with other chemical hazards such as mycotoxins or herbicides25). Until now, there have been a lack of routine methods for the determination of plant toxins due to over 200,000 varieties of secondary plant metabolites reported33).

    Heavy metals

    Certain metals (e.g., iron, zinc, manganese and copper) are required micronutrients to maintain proper health. Despite the health benefits of metals, excessive accumulation in animals may induce serious health problems due to the low biodegradability and concentration through the food chain34). Industrial processing, pesticides or chemical fertilizers, mining, and automobile exhaust are the main sources of heavy metals in the environment and these compounds are easily transmitted to fresh produce35). Heavy metals can seriously deplete specific nutrients in the body, which can lower the natural immunological defenses, impair psychosocial facilities, and cause intrauterine growth retardation. Heavy metal consumption is also associated with malnutrition, and reports have claimed that heavy metals increase the rates of gastrointestinal diseases and cancer36). Among various heavy metals, lead (Pb), cadmium (Cd), and mercury (Hg) are the most probable causes of the heavy metal-related diseases37).

    Detection of chemical hazards on fresh produce

    US and European governments attempt to define one standard technique to detect chemical hazards from foods, however establishing one standard method to analyze a variety of chemical contaminants is very difficult since all chemical hazards have diverse structures and characteristics 24,38). Chemical hazard detection methods vary based on the target compounds (Table 2). Classical chemical contamination detection procedures use solvents to extract target analytes. The solvent extraction method is a reliable test, however it is time-consuming, requires a trained technician and large volumes of solvent which produce a large amount of waste18,24). In order to reduce chemical waste and analysis time, a chromatography method has been developed to identify chemical compounds. In the past few years, nanostructured materials such as NMPs, QDs and magnetic nanoparticles or nanotubes have been invented for simple, highly sensitive and selective assessment compared with conventional protocols34).

    Biological contaminants on fresh produce

    Fresh produce such as whole or fresh-cut fruits and vegetables are important dietary constituents, as they contain high levels of vitamins and minerals51). Due to these health benefits, most fresh vegetables and fruits receive minimal processing and are usually consumed as raw. Pathogens can easily contaminate fresh produce, leading to serious health problems52). In spite of considerable protection from microbial contamination by low pH, skins, and waxy coatings on fresh produce, the high levels of nutrients and moisture present in fresh produce can create a suitable environment for pathogens27,29). Rupturing plant tissues through peeling or cutting releases nutrients and encourages growth of unwanted microorganisms52). Microbial contaminations easily occur during the different stages from farm to consumer including production, harvest, processing, storage, transportation and can be introduced from environmental, animal or human sources53). Symptoms of foodborne illness range from mild complications as abdominal pain, diarrhea, fever, headaches, vomiting and muscle aches11), to severe health issues such as autoimmune complications, bloody diarrhea, enterotoxin poisoning, meningitis, septicemia, hemorrhagic colitis, hemolytic uremic syndrome (HUS) and miscarriage in pregnant women27). Foodborne pathogens frequently associated with a consumption of fresh produce include viruses (norovirus), parasites, and bacteria (Salmonella, Escherichia coli O157: H7, Shigella, Listeria monocytogenes, Bacillus, Campylobacter, and Clostridium)9). Fig. 1 indicates the number of bacterial outbreaks, illnesses and deaths attributed to fresh produce from 2006 to 2016 according to the National Outbreak Reporting System (NORS) from the CDC web database9). There are a diverse number of pathogens in existence, however this review focuses on the most common illnesses caused by the bacterial foodborne pathogens Salmonella, E. coli O157:H7, Shigella, Listeria and Bacillus cereus as well as norovirus and parasites. The possible routes and sources of contamination in fresh fruits and vegetables are diverse, and the exact mechanisms for introduction of pathogens into fresh produce are still unclear54). Despite intensive efforts to prove accurate pathways of contamination by biological hazards, the routes to fresh produce contamination in the wild are varied from livestock and other sources such as surface water, soil, and ground water (Fig. 2)52).

    Bacterial contaminants on fresh produce

    Salmonella

    Salmonella is a Gram-negative, non-spore forming bacterium, and is included in the family Enterobacteriaceae. The Salmonella genus is composed of two species; S. enterica and S. bongori55). S. enterica, which are a main cause of gastroenteritis, is subdivided into hundreds of serovars. Salmonella can be easily found in the gastrointestinal tract of animals, from livestock to humans56). Previously, most people suspected salmonellosis was attributed to consuming contaminated poultry products, however an increasing number of outbreaks are associated with fresh produce in the US that can be traced back to bacterial contamination by Salmonella57). In addition, S. enterica has been found to easily colonize seeds, leaves, and fruits including watermelon, sprouts, tomatoes, mangoes and lettuce9,54). For example, from 2006 to 2016, 131 incidents of foodborne illness outbreaks of Salmonella related to vegetables and fruits were reported (Fig. 1)9). Approximately 60% of human salmonellosis cases reported by CDC were caused by four serotypes of Salmonella: S. Typhimurium, Enteritidis, Newport and Heidelberg58).

    Escherichia coli O157

    Escherichia coli (E. coli) is a Gram-negative, facultative anaerobe that commonly inhabits the gastrointestinal tract of mammals and belongs to the family of Enterobacteriaceae59). Though most strains of E. coli are harmless, several pathogenic strains have been identified that cause serious clinical problems in humans. Enterotoxigenic Escherichia coli (ETEC) is a group of pathogens that have the ability to colonize the small intestine in humans, where heat-stable (ST) or plasmid-encoded heat-labile (LT) enterotoxins are produced. Collectively, these organisms cause hundreds of millions of cases of diarrheal diseases each year, particularly in developing countries, with 300,000 to 500,000 estimated deaths of children annually60).

    Six primary pathogenic groups of E. coli (enterotoxigenic, enteropathogenic, entero-invasive, enterohemorrhagic, enteroaggregative and adherent-invasive E. coli) have been documented. Of these six main pathogen groups, E. coli O157 is one of the most common causes of foodborne outbreaks. Pathogenic E. coli strains that belong to the Enterohemorrhagic group of E. coli (EHEC) are known for verocytotoxin-producing or Shiga-toxin-producing strains61). Outbreaks of E. coli O157 have been associated with lettuce, unpasteurized apple cider, cantaloupes, and sprouts9,62). According to a CDC report, an E. coli O157 outbreak linked to romaine lettuce in June 2018 infected 210 people in 36 different states and resulted in 5 deaths63).

    Shigella

    Shigella is a Gram-negative, facultative aerobic intracellular pathogen64). Species of Shigella are most frequently isolated from patients experiencing diarrhea. Between five to fifteen percent of all diarrheal patients worldwide are Shigella related65). Shigella is a member of the Enterobacteriaceae family which closely related to E. coli. Though Shigella and E. coli share very similar DNA sequences, they have remained separate species for clinical reasons66). The infective dose for Shigella is very low: only 10 cells of S. dysenteriae and 500 cells of S. sonnei can be infectious67). According to CDC reports (Fig. 1), a total of 7 outbreaks, 495 illnesses, and 1 death related to Shigella have occurred from 2006 to 2016. In addition, Shigella is easily transmissible through person-to-person contact68).

    Listeria monocytogenes

    The genus Listeria consists of Gram-positive, facultative, non-spore forming bacteria. Listeria is represented by seven species: Listeria monocytogenes, innocua, welshimeri, grayi, seeligeri, ivanovii and marthii. Among the seven species, L. monocytogenes is the primary human pathogen and causes a life-threatening disease known as listeriosis69). L. monocytogenes represents a serious threat to the food industry because it can survive conventional food processing conditions, such as high salinity, acidity, refrigeration temperatures and low water activity. Though Listeria is unable to survive pasteurization temperatures70), most fresh produce are provided without heat treatment, leading to serious listeriosis outbreaks. In 2015, listeriosis outbreaks occurred in multiple states in the US. All of the patients were over 19, and one of them died9).

    Bacillus cereus

    Bacillus cereus is a Gram-positive, spore-forming, motile, aerobic rod that can also grow in anaerobic conditions. B. cereus easily grows within a temperature range of 10 to 50°C with an optimum between 28 and 35°C, however members of Bacillus survive in a wide variety of environmental conditions due to their ability to form endospores, which are resistant to dehydration, heat, and other physical stresses71). B. cereus also has the ability to form biofilms on stainless steel72), demonstrating an increased level of resistance against environmental factors that typically prevent bacterial growth. It also has the ability to contaminate nearly any agricultural product due to its abundance in soil and the ability to form spores and biofilms73). B. cereus is readily found on a variety of food products, including vegetables, fruits and grains71).

    Non-bacterial contaminants on fresh produce

    Norovirus

    Foodborne viruses are present in high numbers in human feces. The two types of viruses most frequently implicated in foodborne outbreaks are noroviruses (NoVs) and hepatitis A viruses (HAVs)74). Human NoVs are one of the primary sources of viral gastroenteritis around the world, and are the main cause of foodborne illness in Europe75) and the US76). Fresh produce has been identified as a common vehicle for the transmission of foodborne viruses74). According to a comprehensive survey of outbreaks identified with fresh produce sources in the US from 2006 to 2016 (Fig. 1), NoVs are the second largest cause of outbreaks (32.8%). Aside from murine strains, NoVs cannot be cultivated in vitro, which prevents classification into distinct serotypes and screening from plating77).

    Parasites

    Various fruits and vegetables have been identified as vehicles for the transmission of parasites. Parasites associated with vegetable- or fruit-borne outbreaks include helminths such as Fasciola hepatica78), Ascaris lumbricoides and Ascaris suum79). Over 1.5 billion people worldwide have been diagnosed with parasitic infection by at least one species of soil transmitted helminth (STH)80). In many developing countries, the use of inappropriate treated wastewater to irrigate vegetables has contributed to contamination with pathogenic parasites. Poor hygienic practices during production by food handlers also contributes to the number of cases of parasitic infeciton81). The lack of a globally acceptable methods for the detection and quantification of STH eggs in environmental samples poses a challenge for comparative assessments of egg concentrations in different sample matrices82).

    Symptoms of biological hazards on fresh produce

    Biological contaminations of fresh produce induce a variety of symptoms to consumers from mild diarrhea to life-threatening health issues depending on the type of pathogens (Table 3). For instance, the symptoms of salmonellosis, including abdominal cramps, diarrhea, fever, headache, nausea, and vomiting83), usually develop 8 to 72 h after consumption of contaminated food, and may last from four to seven days. Arthritis-like symptoms may follow three to four weeks after onset of acute symptoms84). The typical symptoms of shigellosis are also similar with salmonellosis which include bloody diarrhea, abdominal pain, fever, and malaise87). When it comes to E. coli O157, the most common etiological problem is hemolytic uremic syndrome (HUS). The virulence level of E. coli O157 strains ranges from asymptomatic colonization within the body to potentially lethal HUS disease. Diarrhea-associated HUS is often attributable to Shiga toxin (Stx) produced by pathogenic E. coli85). Stx-producing E. coli (STEC) was named because of the similarity of the toxin generated by the stx1 gene to the Stx produced by Shigella dysenteriae. STEC have an eae gene that translates for intimin, which adheres to the outer membrane protein and enables the bacterium to enter the intestinal wall of a host. After the invasion, Stxs which come from STEC can cause life-threatening health complications, especially to infants and the elderly86). Additionally, L. monocytogenes leads to two types of listeriosis: non-invasive gastrointestinal listeriosis and invasive listeriosis. Both invasive and non-invasive listeriosis are dangerous for elderly and immunocompromised adults, as Listeria can manifest as septicemia or meningoencephalitis88). Invasive listeriosis is especially dangerous to pregnant women, since perinatal listeriosis is a serious threat to the unborn child and can lead to miscarriage89). Additionally, B. cereus causes two types of food poisoning that result from different types of toxins, emetic- and entero-toxins, which lead to vomiting and diarrhea, respectively73). Emetic toxin syndrome is defined by nausea, vomiting, and abdominal cramping, which occur 1 to 5 h after ingestion of the contaminated food. The illnesses are self-limiting, and recovery usually occurs within 6 to 24 h. Hospitalization is occasionally required due to excessive vomiting, and fatality is rare. The onset of the diarrheal syndrome generally ranges from 8 to 16 h after exposure, and the symptoms resolve themselves in 12 to 14 h71). Enterotoxins are proteins causing cytotoxicity marked by fluid accumulation in the ligated ileal loop, dermonecrosis, and lethality in mice90). Lastly, the most common acute symptoms of NoVs infection are diarrhea and nausea, followed by vomiting, abdominal pain, fever and fecal incontinence. Various non-specific symptoms are also reported, such as anorexia, thirst and lethargy, headache and vertigo, listed in order of decreasing prevalence. Acute symptoms typically subside after three to four days of illness, whereas nonspecific symptoms can persist for up to 19 days91).

    Detection methods for biological hazards on fresh produce

    In order to prevent foodborne illnesses, detection and identification of the specific foodborne pathogen is important and numerous methods have been previously published (Table 4). Conventionally, bacterial pathogens such as Salmonella, E. coli, Shigella, Listeria monocytogenes and B. cereus can be identified with culture-dependent methods92,93,97). Detection of a specific microbial species from a mixed culture using selective media can be accurate however, it usually requires pre-enrichment steps and culturing methods may take more than 1 to 2 days to obtain results93). Furthermore, NoVs are impossible to culture on the media77). In recent years, molecular microbiological methods such as PCR, rep-PCR and microarray have also been developed. In theory, DNA from a single bacterial cell can be amplified through PCR within 2 h, which is rapid compared to previously described methods94). Immunobased assays have also been created to detect pathogens through specificity of the antigen-antibody reaction, though immunological methods are less sensitive compared to the nucleic acid amplification and cross reactivity with other closely-related species is also a concern68,98).

    With regards to parasites, microscopic methods are traditionally used to identify and quantify eggs of parasites, however newer techniques have been developed. The advent of genomic sequencing and the wealth of data generated by it have markedly increased the feasibility of developing polymerase chain reaction (PCR)-based methods as diagnostic tools for parasites100). Another option for detection is analysis of metabolite compounds emitted by pathogencontaminated food with GC, GC-MS or GT-TOF-MS96). Despite the range of detection methods, current protocols are neither fast nor reliable enough to be used in emergency situations92).

    Physical hazards on fresh produce

    Physical hazards result from the introduction of unwanted foreign materials into food which cause physical damage to consumers6). Physical hazards may involve a wide range of objects, as are listed in Table 5101). The primary sources of physical hazards may include the manufacturing environment, raw materials and ingredients, plant equipment, contractors, and employees. In order to detect any contaminants in-line, automated vision systems, X-ray technology, filters and sieves are required101). Employee training programs and Good Manufacturing Practices (GMPs) are also included in a physical hazard control program. More effective control programs to prevent physical hazard contamination can be achieved by support from vendors and suppliers, as the magnitude of the potential threat will dictate the appropriate control strategies. A vision system or X-ray inspection may be necessary for the control of glass contamination, while a properly calibrated metal detector may be effective against both ferrous and nonferrous metal contaminants. Human inspection may be required for the detection and removal of dangerous pits and stems102).

    Summary

    Fresh produce is easily contaminated from farm to table by chemical, biological and physical hazards. Among three different type of contaminants, agrochemical, natural toxins and heavy metal contaminants are representative of chemical hazards, which can be detected using solvents, chromatography and nano-techniques. The wide range of chemical structures makes it difficult to establish a single and standardized method to detect target compounds.

    Furthermore, fruits and vegetables are a common source of foodborne pathogens, including bacterial pathogens (E. coli O157, Shigella, Salmonella, Listeria monocytogenes and Bacillus cereus) and non-bacterial pathogens (norovirus and parasites). In order to detect food pathogens and prevent foodborne illnesses, conventional culture dependent methods have been utilized. However, culturing methods require significant time and effort, and some pathogens, such as noroviruses, are unculturable. To detect foodborne pathogens derived from fresh produce more efficiently, immunological and nucleic acid-based methods should be applied. Finally, physical hazards including glass, plastics and stone contamination of fresh produce result in serious injuries such as choking, broken teeth and bleeding. To avoid serious injuries from physical hazards, vision systems or X-ray inspections are recommended in-line for use by well-trained employees.

    Acknowledgment

    This comprehensive review was supported by Oregon State University start-up funds provided to Dr. Si Hong Park.

    Figure

    JFHS-34-1-1_F1.gif

    Incidence of biological foodborne (a) outbreaks, (b) illnesses and (c) death associated with fresh produce reported by the CDC in the US from 2006 to 2016.

    JFHS-34-1-1_F2.gif

    Environmental risk factors associated with the pre-harvest fresh produce contamination.

    Table

    Example of chemical hazards in food

    Detection methods for chemical hazards on fresh produce

    Symptoms of biological hazards on fresh produce

    Detection methods for biological hazards on fresh produce

    Potential physical hazards in the food industry

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