Introduction
HACCP is a systematic approach to be used in food production as a means to ensure food safety. The first step requires a hazard analysis, an assessment of risks associated with all aspects of food production from growing to consumption. However, before one can assess the risk, a working knowledge of potential hazard must be obtained. A hazard is defined by the National Advisory Committee on Microbiological Criteria for Foods (NACMCF) as any biological, chemical or physical property that may cause an unacceptable consumer health risk. Thus, by definition one must be concerned with three classes of hazard, biological, chemical, and physical.
This article provides a generalized background of the potential hazard associated with foods. Appropriate reference materials on food hazards have been included. A number of textbooks are available on the subject of hazards in foods.
Biological Hazards
The first hazards category, biological or microbiological, can be further divided into three types: bacterial, viral, and parasitic (protozoa and worms). Many HACCP programs are designed specifically around the microbiological hazards. HACCP programs address this food safety problem by assisting in the production of safe wholesome foods.
When developing a HACCP programs, the food grower or processor should have three basic aims with regard to biological hazards: (1) destroy, eliminate, or reduce the hazard; (2) prevent recontamination (3) inhibit growth and toxin production. Preventive measures should be taken to achieve these goals.
Microorganisms can be destroyed or eliminate by thermal processing, freezing and drying. After the microorganism has been eliminated, measures to prevent recontamination should be taken. Finally, if hazard cannot be totally eliminated from the food, microbial growth and toxin production must be inhibited. Growth can be inhibited through the intrinsic of the food, such as pH and water activity (aw), or by the addition of salt or other preservatives. Condition under which the food is packaged (aerobic or anaerobic) and storage temperatures (refrigeration or freezing) can also used to inhibit growth.
Bacterial Hazards
Bacterial hazards can result either in foodborne infections or intoxications. A foodborne infection is caused by ingesting a number of pathogenic microorganisms sufficient to cause infection, and the reaction of tissues to their presence, multiplication, or elaboration of toxins. A foodborne intoxication is caused by the ingestion of preformed toxins produced and excreted by certain bacteria when they multiply in foods.
The following summary discusses the notable characteristics of the various foodborne bacterial pathogens of concern to the food industry and their relationship to the developing of a HACCP program. The natural incidence and the severity of disease caused by these bacteria, along with the general conditions required for their control represent a cross-section of challenges for HACCP programs. If these organisms are controlled, numerous other pathogens may be similarly controlled.
Clostridium botulinum
Clostridium botulinum, the causative agent of botulism (foodborne intoxication), is an anaerobic, spore-forming rod that produces a potent neurotoxin. Its notable characteristics are its heat-resistant spores and their widespread distribution. Some strains of C. botulinum are psychotropic. The spores survive most thermal processes except those specially designed to eliminate them. If such a process is not used, one must assume that spores are present in the food. If the food is to be packaged in an anaerobic or reduce oxygen atmosphere, measures to inhibit the growth and toxin production by the organism are necessary. C. botulinum growth can be controlled by one or a combination of the following conditions : pH < 4.6; aw <= 0.94; 5-10% salt concentration; nitrite and salt combination (e.g. cured meats); other preservatives, temperature control (freezing/refrigeration) and biocontrol (e.g. inoculation of product with lactic acid bacteria). Sole reliance on refrigeration to ensure safety is risky. Botulinum toxin produced is one of the most potent substances known but is relatively heat labile (destroyed by boiling for 10 minutes). Reliance on final cooking the consumer to destroy the toxin is extremely risky.
Listeria monocytogenes
Listeria monocytogenes is a hazardous foodborne microorganism of relatively recent concern. It is ubiquitous in nature and is commonly found in food processing environments. It causes listerosis, a severe and often fatal illness, to which certain populations (e.g. pregnant mother, newborn, immunocomprised individuals, transplant recipients) may be susceptible. Fatality rates with the more severe forms of listerosis can be as high as 70% for those untreated, but generally are between 25 and 35%. The organism is psychotropic and can grow at refrigeration temperatures. Its widespread distribution and its ability to multiply at refrigeration temperatures and cause severe illness makes it a hazard of particular concern to the food industry and regulatory agencies. HACCP programs should attempt to destroy, eliminate or reduce this hazard and prevent the opportunity for subsequent recontamination.
Salmonella
Salmonella species can be found on most raw foods of animal origin. Salmonellosis is one of the most frequently reported foodborne diseases. Symptoms of salmonellosis are most severe in susceptible populations (the elderly, infants, and the infirm). Salmonella species are destroyed by normal pasteurization processes and are most commonly spread through contamination of processed materials with raw products or with the juices of raw products via hands, utensils, or food-contact surfaces. HACCP plans for processed foods should include controls to destroy and eliminate this organism and to prevent recontamination.
Staphylococcus aureus
Staphylococcus aureus may produce a very heat-stable enterotoxin when permitted to grow to an elevated level (>105 organisms/g). The foodborne intoxication is caused by ingestion enterotoxins produced in food by some strains of S. aureus, usually because the food has not been kept hot enough or cold enough. The organism is commonly isolated from hands and nasal passages of humans. Thus, foods which are handled or require preparation are at risk. The organism can grow at an aw of 0.86, and in high salt concentrations. Proper processing handling of raw materials is essential. If conditions allow the organism to grow and produce enterotoxins, subsequent thermal processing will destroy the vegetative organisms while the head-stable toxin persists. There is evidence that the enterotoxins may not be completely inactivated at retort temperatures (1210C or 2500F). HACCP plans should provide for proper handling of raw materials, steps to destroy, eliminate, or reduce the hazard and controls to prevent recontamination. If organisms can reasonably be expected in the final product, conditions to inhibit growth and toxin production should be controlled.
Clostridium perfringens
Clostridium perfringens is another anaerobic, spore-forming, rod-shaped bacterium. Perfringens food poisoning is caused by consuming foods that contain large numbers of those Clostridium perfringens that are capable of producing the food poisoning toxin, which is usually formed in the digestive tract and is associated with sporulation. Limited evidence exists that preformed toxin can be found in food. Perfringens food poisoning is frequently associated with food service operations; temperature abuse of prepared foods, such as large poultry or cooked cuts of meat and gravies and sauces prepared in large containers, can provide anaerobic conditions. Because spores are heat resistant, small numbers of organisms may be present after cooking (or large numbers after improper cooking). Subsequent temperature abuse (not keeping cooked foods above 600C; 1400F or not providing rapid, even cooling to refrigeration temperatures) may permit the organisms to multiply to food poisoning levels. HACCP plans should control proper cooking conditions and subsequent handling temperatures to inhibit growth of this organism.
Viral hazards
Viruses are very small particles that cannot be seen with a light microscope. They are obligate intracellular parasites that are unable to reproduce outside the host cell. Thus, they are inert in foods and do not multiply in them. However, viruses may be transmitted to foods via the fecal-oral route, either directly or indirectly. Some viruses may be inactivated in foods by thorough cooking and some by drying. However, contamination of foods with viruses should be avoided. Direct contamination can occur when an infected food handler contaminates food. Indirect contamination can occur when foods such as bivalve mollusks become contaminated in waters infected by untreated sewage. The viruses most commonly recognized as foodborne disease agents are summarized below.
Hepatitis A virus
Hepatitis A virus (HAV) is classified with the enterovirus group of Picornaviridae family. The terms hepatitis A or type A viral hepatitis have replaced all previous names for the illness. Hepatitis A is usually mild illness characterized by onset of fever, malaise, nausea, anorexia, and abdominal discomfort, followed in several days by jaundice. Occasionally, the symptoms are severe and convalescence can take several months. The incubation period for hepatitis A varies from 10 to 50 days (mean 30 days). The period of virus shedding or communicability extends from early in tile incubation period to about a week after the development of jaundice. The greatest danger of spreading the disease to others occurs 10-14 days before the first presentation of symptoms. The infectious dose is unknown but presumably is 10-100 virus particles.
The Norwalk virus family
Norwalk virus is the prototype of a family of unclassified small round structured viruses (SRSVs), which may be related to the caliciviruses. Common names of the illness caused by the Norwalk and Norwalk-like viruses are viral gastroenteritis and acute nonbacterial gastroenteritis. The disease is self-limiting, mild, and characterized by nausea, vomiting, diarrhea, and abdominal pain. Headache and low-grade fever may occur. The infectious dose is unknown but presumed to be low. Norwalk gastroenteritis is transmitted by the fecal-oral route via contaminated water and foods. Secondary person-to-person transmission has also been documented. Water is the most common source of outbreaks and may include water from municipal supplies, well, recreational lakes, swimming pools, and water stored aboard cruise ships. Salad ingredients and shellfish are the foods most often implicated in Norwalk outbreaks. Ingestion of raw or insufficiently steamed clams and oysters poses a high risk for infection with Norwalk virus. A variety of foods other than shellfish are contaminated by ill food handlers and include salads, fruits, eggs, clams, and bakery items.
Rotavirus
Rotaviruses are classified with the Reofiridae family. Rotaviruses cause acute gastroenteritis. Infantile diarrhea, winter diarrhea, acute nonbacterial infectious gastroenteritis, and acute viral gastroenteritis are names applied to the infection caused by the most common and widespread group A rotavirus. Rotavirus gastroenteritis is a self-limiting, mild-to-severe disease characterized by vomiting, watery diarrhea, and low-grade fever. The infective dose is presumed to be 10-100 infectious viral particles. Rotaviruses are transmitted by the fecal-oral route. Infected food handlers may contaminate foods that require handling and no further cooking, such as salads, and fruits.
Other viruses associated with gastroenteritis
Although the rotaviruses and the Norwalk family of viruses are the leading causes of viral gastroenteritis, a number of other viruses have been implicated in outbreaks, including astroviruses, caliciviruses, enteric adenoviruses, and parvoviruses. Astroviruses, caliciviruses, and the Norwalk family of viruses possess well-defined surface structures and are sometimes identified as “small round structured viruses” or SRSVs. Viruses with a smooth edge and no discernible surface structure are designated “featureless viruses” or “small round viruses” (SRVs). These agents resemble enterovirus or parvovirus, and may be related to them.
Parasitic protozoa and worm hazards
Parasites are organisms that derive their sustenance on or within their host. A variety of parasitic animals are of concern to the food microbiologist. They include protozoa, nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes). Some foodborne parasites may be transmitted through food and water contaminated by fecal material that contains parasites shed by infected hosts. Other parasites spend a portion of their life cycle in food animals and are thus ingested along with the food. Method for preventing transmission of parasites to foods via the fecal contamination route include good personal hygiene practices by food handlers, proper disposal of human feces, eliminating the use of insufficiency treated sewage to fertilize crops, and proper sewage treatment. Thorough cooking of foods will eliminate all foodborne parasites. Freezing, and in specific instances brining, may be used to destroy various parasites in foods.
Giardia Lamblia
Giardia Lamblia (intestinalis) is a single-celled protozoa that causes giardiasis in human. G.lamblia exists in two separate stages: the active feeding (trophozoite) stage and the infective environmental (cyst) stage in which the organism survives outside the host. Human giardiasis may involve diarrhea within a week after the cyst is ingested. Other symptoms include abdominal cramps, fatigue, nausea, flatulence, and weigh loss. The illness may loss for one to two weeks, but chronic infections may last months to years. Colonization and pathogenesis generally occur in the lumen of the small intestine, but the disease mechanism is unknown. Giardiasis is most frequently associated with the consumption of contaminated water. Outbreaks have been traced to food contamination by infected food handlers, and the possibility of infection from contaminated vegetables that are eaten raw cannot be excluded. Cool contamination by infected food workers can be prevented by proper personal hygiene. Thorough cooking of foods destroys G. lamblia.
Entamoeba histolytica
Entamoeba histolytica is a single-celled protozoa that predominantly infects humans and other primates. Like G. lamblia, E. histolytica can exist as two separate stage: a trophozoite or a cyst. Cysts survive outside in water, in soils, and on foods, especially under moist conditions. When swallowed, they cause infections by excysting (to the trophozoite stage) in the digestive tract. Infections can be accompanied by a mild gastrointestinal distress or dysentery (with blood and mucus). E. histolytica may penetrate the intestinal wall, and if it enters the blood, may gain access to other organs. Large numbers of cysts can be shed in the feces of infected individuals. Infection can result from the fecal contamination of drinking water and foods, and by direct contact with dirty hands or objects. Preventive measures are similar to those describes for G. lamblia.
Ascaris lumbriciodes
Humans worldwide are infected with Ascaris lumbriciodes. The eggs of this roundworm (nematode) are “sticky” and may be carried to the mouths by hands, other body parts, omits (inanimate objects), or foods. Asacariasis, the scientific name for this infection, is also commonly known as the “large roundworm” infection. Ingested eggs hatch in the intestine, and larvae begin to migrate, reaching the lungs through the blood and lymph systems. In the lungs, the larvae break out of the pulmonary capillaries into the air sacs, ascend into the throat, and descend again to the small intestine where they grow to sexual maturity. On occasion, larvae will crawl up into the throat and try to exit through the mouth or nose. Vague digestive tract discomfort sometimes accompanies the intestinal infection, but intestinal blockage may occur in small children who have more than a few worms because of the large size of the worms. Large numbers of eggs maybe voided in feces.
Chemical Hazards
Webster defines a chemical as any substance used in or obtained by a chemical process or processes. All food products are made up of chemicals, and all chemicals can be toxic at some dosage level. However, a number of chemicals are not allowed in food and others have established allowable limits.
Naturally occurring chemicals
The naturally occurring toxicants include a variety of chemicals of plant, animal, or microbiological origin. Although many naturally occurring toxicants are biological in origin, they have traditionally been categorized as chemical hazards. However, for individual HACCP programs, their inclusion in the biological hazard category would be equally appropriate. The following overview discusses several naturally occurring toxicants.
Mycotoxins
A number of fungi produce compounds (mycotoxins) toxic to man. Mycotoxins are secondary metabolites of certain fungi. Among some of the better known and studied groups of mycotoxins are the aflatoxins, which include a group of structurally related toxic compounds, produced by certain strains of the fungi Aspergillus flavus and A. parasiticus. Under favorable conditions of temperature and humanity, these fungi grow and produce aflatoxins on certain foods, grains, nuts, and feeds. The most pronounced contamination has been encountered in tree nuts, peanuts, and other oilseeds including corn and cottonseed.
Scombrotoxin (Histamine)
Scombroid poisoning or histamine poisoning occurs when foods that contain high levels of histamine (or possibly other vasoactive amines and compounds) are ingested. Histamine is produced by the microbial of histidine, a free amino acid found in abundance in dark-fleshed fish, including members of the Scombridae family from temperate and tropical regions. Fish that have been temperature abused are the most commonly implicated foods such as Swiss cheese have been reported to cause illness most often implicated are tuna, mackerel, bluefish, and amberjack.
Ciguatera
Ciguatera is a form of human poisoning caused by the consumption of tropical marine finfish, which have accumulated naturally occurring toxins through their diet. The toxins originate from several dinoflagellate (algae) species common to ciguatera endemic regions and accumulate through the food chain. Manifestations of ciguatera in humans usually involve gastrointestinal, neurological, and cardiovascular disorders.
Marine finfish most commonly implicated in ciguatera fish poisoning are predators and include the groupers, barracudas, snappers, jacks, mackerel, and triggerfish. Other species of warm-water fishes have been reported to harbor ciguatera toxins. The presence of toxic fish is sporadic; not all fish from a given locality or species will be toxic.
Mushroom toxins
Mushroom poisoning is caused by the consumption of raw or cooked fruiting bodies of certain higher fungi. Unlike the previously mentioned aflatoxins, which are secondary metabolites produced when a contaminating mold grows on a food product, the mushroom itself is the toxic food product. Many species of mushrooms are toxic and there is no general rule to distinguish between edible and toxic species. Mushroom poisonings are usually caused by ingestion of toxic wild mushrooms that have been confused with edible species.
Shellfish toxins
Shellfish poisoning is caused by a group of toxins elaborated by planktonic algae (dinoflagellates, in most cases) upon which the shellfish feed. Under the appropriate condition toxic dinoflagellate populations may increase to high levels and persist for several weeks. The shellfish may accumulate and metabolize these toxins during their filter feeding.
The food processor may control some of these naturally occurring chemical hazards by learning in which foods (i.e., sensitive ingredient) they are most likely to occur. Proper raw material specification, vendor certification, and guarantees along with inspection and spot checks will help to prevent introduction of natural chemical hazards into plant facilities. Likewise, proper handling and storage of sensitive ingredients will prevent conditions conducive to the production of other natural toxicants (e.g., proper storage of grains and feeds to prevent aflatoxin production and avoidance of temperature abuse of fish susceptible to scombroid poisoning).
Added Chemicals
The second groups of chemicals, which may be potential hazards, are those that are added to foods at some point between growing, harvesting, processing, storage, and distribution. These chemicals are generally not considered hazardous if proper conditions of use are followed. Only when these chemicals are misapplied or when their permitted levels are exceeded is there a potential hazard.
Toxic elements (e.g., lead, mercury, arsenic) and other toxic compounds (e.g., some chemicals used in the food processing plant) are either not allowed in food at all or have established maximum tolerances. In some cases, these chemicals are present naturally and have not been added to the food. Other added chemicals in the food additive group, including direct, secondary direct, and indirect food and color additives, are permitted to be used in actual food processing to preserve the food (e.g., preservatives), enhance flavor, impart color, or nutritionally fortify (e.g., vitamins and minerals). Secondary direct and indirect chemicals used in food processing plants include chemicals such as lubricants, cleaners, sanitizers, paint, and coatings, which may become incorporated into food via migration from packaging materials, or microorganisms and enzyme preparations used in food processing. Allowable limits for all of these food additives have been set in accordance with Good Manufacturing Practices (GMPs). At established limits, these chemicals are not hazardous and a large safety factor is incorporated into the regulatory limits; however, if tolerances are exceeded, potential health risks to consumers may occur.
Physical Hazards
Physical hazards are often described as extraneous matter or foreign objects and include any physical matter not normally found in food, which may cause illness (including psychological trauma) or injury to an individual.
The main physical hazards of concern include glass, wood, stones, metal, insects and other filth, insulation, bone, plastic, and personal effects. Other items include hair, dirt, paint and paint chips, rust, grease, dust, and paper. The sources of physical hazards include raw materials, water, facility grounds, equipment, building materials, and employee personal effects. Physical hazards may be added inadvertently during distribution and storage, or intentionally introduced (sabotage).
Methods involved in controlling physical hazards include raw material specifications and inspections along with vendor certification and guarantees. Various preventive measures are available to find and remove certain physical hazards. Metal detectors can be used to locate ferrous and nonferrous metals in foods; various foreign objects, especially bone fragments can be found through X-ray technology. Effective pest control and foreign object removal from plant environments are also essential. Preventive maintenance and sanitation programs for plants and equipments are necessary. Proper shipping, receiving, distribution and storage procedures as well as packaging material handling practices (particularly those involving glass) must be evaluated for their potential to introduce hazards. Packaging should be tamper-proof and at least tamper-evident. Finally, employee education and practices must involve knowledge and prevention of physical hazard introduction.
