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R E T A I L FS-
FOOD (^) SAFETY
Foodborne Illness
The United States has the safest food supply in the world. However, an estimated 25-250 million illnesses and 10,000 estimated deaths occur because of eating contaminated foods each year (1995 Food Code). There are many areas within the food production chain, from the farm to the retail establish ment, where foods may be contami nated and/or mishandled. It is therefore important for all areas of food produc tion to be carefully monitored and controlled so that the risk of foodborne illness is decreased. Many foodborne illnesses occur because of mishandled foods in foodservice and food retail establishments. Since foods prepared in these establishments are the closest link to ingestion by the consumer, monitor ing, and control of foodborne hazards is most critical at the foodservice and food retail end of the food production.
Foods can be contaminated by biologi cal, chemical, or physical hazards. This publication will address each type of foodborne hazard and will focus primarily on biological hazards since they are the most common hazard in foodservice and food retail.
If you have ever had food poisoning, you know that it is an experience that you don’t ever want to have again. Symptoms of foodborne illness are not pleasant and usually include one or more of the following: diarrhea, vomiting, headache, nausea, and dehydration. Foodborne illness is
Food Safety
Hazards in
Foodservice and
Food Retail
Establishments
Dr. Richard Linton,
Extension Specialist
Department of
Food Science
Purdue University
This publication was reviewed by the following outside reviewers: Dr. Joseph Eifert, Ph.D. Manager of Microbiology, Nestle USA, Inc
Dr. Jeff Rhodehamel, Ph.D. Microbiologist U.S. Food and Drug Administration
Dr. Cameron Hackney, Ph.D. Professor of Food Microbiology Virginia Polytechnic Institute and State University
generally classified as an infection, an intoxication, or a toxico-infection (Figure 1).
Figure 1. Classification of foodborne illness. Infection - Ingestion of a harmful microorganism within a food. Intoxication - Ingestion of a harmful toxin produced within a food. Toxico-infection - Ingestion of a harmful microorganism within a food that produces a toxin in the human body.
An infection is caused when a living microorganism is ingested as part of a food. After ingestion, the microorgan ism can then attach to the gastro intestinal tract and begin to grow. This can lead to the common symptoms of foodborne illness like diarrhea. In some instances, the microorganisms may be carried in the blood stream from the gastro-intestinal tract to other parts of the body. Foodborne viruses and parasites are good examples of microor ganisms that can cause infection. An example of a bacterial infection is Salmonella spp.
An intoxication is caused when a living microorganism grows in or on a food and produces a toxin. The food containing the toxin is then ingested and the toxin itself causes illness. A good example of a food intoxication is bacteria like Clostridium botulinum and Staphylococcus aureus. An intoxication
Department of Food Science • Purdue Cooperative Extension Service
Figure 3. Common biological hazards in a food retail operation.
Bacteria Viruses Bacillus cereus Campylobacter jejuni Clostridium perfringens Clostridium botulinum Escherichia coli Listeria monocytogenes Salmonella spp. Shigella spp. Staphylococcus aureus Vibrio spp.
(From FDA Food Code, 1995)
Hepatitis A Norwalk virus group Rotavirus
Parasites Anisakis spp. Crytosporidium parvum Giardia lamblia Trichinella spiralis
may also occur due to the consumption of a toxic chemical such as a cleaning chemical.
An toxico-infection is caused when a living microorganism is consumed (like an infection) and then the microorgan ism produces a toxin in the body, as opposed to in the food, that leads to illness. It is different from an intoxica tion. A good example of a food toxico infection is from Clostridium perfringens.
It is important to understand that, under the right set of circumstances, anyone can become ill due to eating contaminated foods. A healthy adult may be without symptoms or may have gastro-intestinal symptoms. In most cases, the healthy adult host will recover in a few days. However, the risks and dangers associated with foodborne illness are much greater for the elderly, infants, pregnant women, and people who have a weakened immune system (Figure 2). For these groups of people, symptoms and length of foodborne illness can be much more severe, even life threatening.
Figure 2. People at greater risk of acquiring foodborne illness. Elderly Infants Pregnant Women Immuno-compromised/Weakened immune system
Foodborne illness not only affects the health of individuals who become ill, but it can also have a dramatic eco nomic impact to the eating establish ment. An estimated $7.7-23 billion dollars every year spent each year on foodborne illness in the food industry (1995 Food Code). The costs associ ated with foodborne disease and the damage to the reputation of the establishment can be a high price to pay.
Foodborne Hazards
Foodborne hazards are generally classified as either biological, chemical, or physical. Among these, there are over 200 foodborne hazards known that cause foodborne illness. Biological hazards are dangers from disease-causing microorganisms and from poisonous toxins that they may produce. Biologi cal hazards are by far the most impor tant foodborne hazard in foodservice and food retail. They are the cause for most foodborne illnesses, and include bacteria, viruses, and parasites (Figure 3). Chemical hazards include un wanted substances such as cleaning solutions and pesticides. Chemicals, as well as other non-food substances, should never be placed near food items. Physical hazards are dangers posed by the presence of particles that are not supposed to be a part of the food, such as glass, metal, or bone.
Bacterial Growth in Foods
Bacteria are the most troublesome and important biological foodborne hazard for the foodservice and food retail establishment. Bacteria are living microorganisms that are a single cell. Bacterial cells can exist in two different states: the vegetative state and the spore state (Figure 4). All bacteria live in a vegetative state which can grow and reproduce. Few bacteria are able to
change into a special state called the spore state. Spores are produced when the bacterial cell is in an environment where it cannot grow (frozen foods, dried foods). Spores are not able to grow or reproduce. Instead, spores are a means of protection when bacteria are in an environmental that they cannot grow.
Bacteria are usually classified by their requirements needed for growth and as a spoilage or pathogenic microorganism. Spoilage bacteria break down foods so that they look, taste, and smell bad. They affect quality. Pathogenic bacteria are disease-causing microor ganisms and, if ingested in a food, can make people ill. Both spoilage and pathogenic bacteria are important to those preparing and serving foods. Since pathogens affect food safety, they will be emphasized. Keep in mind, however, that the more effort taken to ensure that foods are safe will generally lead to a better quality food as well.
Bacteria have different required temperatures for growth (Figure 5). Psychrophiles (cold-loving) bacteria grow within a temperature range of 6 70 °F. These microorganisms are particularly important since they can grow at room temperature and at refrigerated temperatures. Most psychrophilic bacteria are spoilage microorganisms, but some are patho-
Figure 7. Bacterial growth.
of cells 1 2 4 16 >1000 >1million
Time 0 15min 30min 60min 3hr 5hr
Figure 8. Bacterial growth needs.
Food - High protein
Acid - Foods with pH 4.6 or higher
Temperature - 41°-140°F
Time - 4 hours Oxygen - Aerobic, Anaerobic, Facultative anaerobic, Microaerophilic
Moisture - Water activity (A ) greater than 0.85w
Figure 9. Foods that support the growth of bacteria.
Acidity
Disease-causing bacteria grow at a pH of more than 4.6. The term pH is used as a symbol to designate the degree of acidity of a food. The scale for measur ing pH is from 0 to 14 (Figure 10). A pH of a food that is 7.0 is neither acidic or basic and is considered “neutral”. A pH less than 7.0 indicates that a food is “acidic.” A pH range greater than 7. refers to a food that is “basic”. Most foods are in the acidic range, or less than 7.0 pH.
Bacteria tend to prefer conditions that are near pH 7.0 but are capable of growing in a pH range of 4.6-7.0. There are many retail foods that fall
within this range (Figure 11). Foods that are at a pH less than 4.6 will not support growth of disease-causing bacteria.
Temperature Temperature is probably the most critical factor affecting growth of bacteria in foods. Most disease causing bacteria grow within a temperature range of 41°-140°F. This is commonly referred to as the “Temperature Danger Zone” (Figure 12).
Careful monitoring of temperature is the best way for a food retail manager to prevent bacteria from growing on foods. There is an old saying “Keep cold foods cold and hot foods hot.” This means that all cold foods should be stored at
less than 41°F and all hot foods held at more than 140°F (after proper cooking).
Time Because bacteria grow in such a fast manner, it doesn’t take long before many cells are produced. A rule of thumb in the food industry is that bacteria need about 4 hours to grow to high enough numbers to cause illness. This includes total time that a food is between 41°-140°F. Remember, a single bacterial cell can produce over 1 million cells in just 5 hours under ideal conditions.
Oxygen As discussed earlier, different bacteria require different amounts of oxygen to grow. Some require a lot of oxygen (aerobic), others cannot tolerate oxygen (anaerobic), some only grow within a narrow oxygen range (microaerophilic), while others can grow with or without oxygen (faculta tive anaerobes).
Moisture Just like most other forms of life, moisture is an important factor affecting bacterial growth. That’s why humans have been preserving foods for thou sands of years by drying them. Scien tists have determined that it isn’t how much moisture is in a food that most affects bacterial growth. Growth is influenced most by the amount of “available water” which is designated with the symbol A .w
A (^) wis water that is not bound to the food and is available for bacterial growth. A (^) wis measured on a scale from 0-1.0. Disease causing bacteria can only grow in foods with Aw greater than .85 (Figure 13). There are many preservation processes that can be done to reduce the Aw of foods including sun drying and freeze drying. The addition of salt or sugar can also be used as a means to reduce available water, however, very high amounts need to be used making this method impractical.
ACID ALKALINE
(3.5-4.0)jams^ (5.7-6.0)celery^ (6.3-6.8)milk lemons strawberries mayonaise^ chicken^ butter^ shrimp 7.0egg white (2.2-2.4) (3.0-4.2) (3.8-4.0)^ (5.5-6.4)^ (6.1-6.4)^ (6.8-8.2) (7.6-9.5) pork & beef(5.3-6.4) (6.0-6.3)lettuce
0 1.0^ limes 2.0 (^) apples tomatoes4.0 carrots (^) (5.6-6.8)peas 6.0 8.0 9.0 10.0 11.0 12.0 13.0 14. (1.8-2.0) (2.8-4.6) (3.7-4.9) (4.9-6.3)bread^ (5.9-6.5)corn apple sauce(3.4-3.5) (5.0-6.0) canteloupe(6.2-6.5)
(5.0-6.1)cheese
0.5 0.75 eggs(0.97) vegetablesdried (0.54-0.75)honey^ (0.95-0.96)breads^ 0.981. crackers
0 0.1 0.2 0.3 0.4 0.6 0.7 (^) (0.8-0.87)rice^ 0. (0.91-1.00)cheese jams & jellies(0.75-0.80) meatsfresh (0.97-1.00) fresh fruits& vegetables (0.97-1.00) freshpoultry (0.98-1.00)& fish POTENTIALLY distilledwater HAZARDOUSFOODS minimum requiredfor bacteria to grow
Figure 10. The pH scale.
ACID ALKALINE
0 1.0^ 2.0 3.0 4.0^ 6.0^ 8.0 9.0^ 10.0^ 11.0^ 12.0^ 13.0^ 14.
Range Where Disease-causing Foodborne Microorganisms Grow
Figure 11. Acidity range of common foods prepared in food retail establishments.
Figure 12. The Temperature Danger Zone.
40-140 1 °F range 140 60 130
where (^) disease causing micro 120 organisms 110 100 grow. 90 80 70 60 (^50) 4. 40
Figure 13. Water activity (Aw) of common foods prepared in food retail establishments.
Common foods: Foods with a pH greater than 4.6, that are not properly heat processed and then packaged anaerobically (can or vacuum pouch), and held at above 41°F. A good example would be improperly home- canned foods.
Transmission in foods: Illness due to Clostridium botulinum is almost always attributed to ingestion of foods that were not heat processed correctly and packaged anaerobically.
Prevention: Discard damaged cans. Do not can or vacuum package foods in a food retail establishment.
Nonspore-Forming Foodborne Bacteria
The following group of bacteria are not capable of producing a spore structure; they are always in the vegetative state. Compared to spore-forming bacteria that are in the spore state, vegetative cells are easily destroyed by proper cooking. There are numerous examples of nonspore-forming foodborne bacteria that are important in the food retail industry.
Campylobacter jejuni
Description: Campylobacter jejuni is considered by many food scientists as the number one agent that causes foodborne illness. The microorganism, which causes infection, is unique compared to most other foodborne pathogens because it has a very strict gaseous requirement for growth. It is classified as a microaerophile because it can tolerate only 3-6% oxygen for growth. The infective dose for Campylobacter jejuni is foods is low.
Common foods: This microorganism is commonly found in raw milk and in raw chicken. Some scientists estimate that Campylobacter jejuni may be present in nearly 100% of retail chickens.
Transmission in foods: Campylobacter jejuni is often transferred from raw meats to other foods by cross-contami nation. This is typically done by transfer from a food contact surface
(such as a cutting board) or from food worker’s hands.
Prevention: Cook raw meats properly. Do not use raw (unpasteurized) milk. Thoroughly clean food contact surfaces (cutting boards) and hands after handling raw foods. Escherichia coli Description: The Escherichia coli (or E. coli) group of bacteria includes four strains of foodborne pathogens; enterotoxigenic E. coli , enteropath ogenic E. coli , enterohemorragic E. coli , and enteroinvasive E. coli. The most important of the group is a particular type of enterohemorrhagic E. coli called E. coli 0157:H7. This is a facultative anaerobic bacterium that can be found in the intestines of warm blooded animals. Illness can be due to an infection and a toxico-infection. Illness due to E. coli 0157:H7 is particularly serious in infants because it can cause kidney failure and bloody diarrhea. Common foods: This microorganism has been isolated from raw milk and raw ground beef.
Transmission in foods: E. coli is usually transferred to foods like beef by contact with the intestines of animals. Trans mission can also occur if employees are carriers and do not wash their hands properly after going to the bathroom. Prevention: Cook hamburger patties until well done or until all the juices run clear. Do not use raw milk prod ucts. Make sure that employees practice good personal hygiene.
Listeria monocytogenes Description: Listeria monocytogenes is a facultative anaerobic bacterium that causes foodborne infection. It is important to food retail operations because it can survive under many conditions such as high salt foods. Unlike many other foodborne patho gens, it can grow at refrigerated temperatures below 41°F. Listeriosis,
the illness caused by Listeria monoc ytogenes, usually causes gastro-intestinal symptoms for the healthy adult. However, disease complications can be life threatening (septicemia, meningitis, encephalitis) for people with weakened immune systems.
Common foods: This microorganism has been isolated from many foods and is most common in raw meats, raw poultry, dairy products (cheeses, ice cream, raw milk), raw vegetables, and seafood.
Transmission in foods: Transmission to foods can occur by cross-contamina tion. Also, foods that are not cooked properly can contain live cells.
Prevention: Cook foods thoroughly. Practice good personal hygiene.
Salmonella spp. Description: Salmonella is a facultative anaerobic bacterium that frequently causes a foodborne infection. Like E. coli, the source for Salmonella is the intestinal tracts of warm blooded animals.
Common foods: This microorganism exists in many foods, especially raw meat and poultry products, eggs, milk, dairy products, pork, milk chocolate, and cream- filled desserts. Transmission in foods: Transmission to foods is very common by cross contamination from raw foods (espe cially poultry), from food contact surfaces (cutting boards), or from food handlers.
Prevention: Cook foods thoroughly. Practice good personal hygiene, and clean and sanitize food contact surfaces after use with raw foods. Shigella spp. Description: Shigella is a facultative anaerobic bacterium that causes about 10% of foodborne illnesses in the U.S. The microorganism is frequently found in the intestines of humans and warm blooded animals. The microorganisms can cause an infection or toxico
infection. A common illness caused by Shigella is bacillary dysentery.
Common foods: This microorganism is common in ready-to-eat salads (i.e. potato, chicken), milk and dairy products, poultry, and raw vegetables.
Transmission in foods: Water that is contaminated by fecal material and unsanitary handling by food workers are common transmission routes.
Prevention: Practice good personal hygiene and wash foods with potable water supply (suitable for drinking).
Staphylococcus aureus
Description: Staphylococcus aureus is a facultative anaerobic bacterium that produces a very heat-stable toxin as it grows on foods. It is therefore an example of an intoxication. The microorganism is normally present on human skin, hands, and nasal passages, and can be transferred to foods easily. It also survives in high salt conditions.
Common foods: This microorganism is common to cooked ready-to-eat foods, salads, meats and poultry products, custards, and high salt foods (like ham), and milk and dairy products.
Transmission in foods: Since humans are the primary source, cross-contami nation from the worker’s hands is the most common way the microorganism is introduced into foods. Foods requiring large amounts of food preparation and handling are especially susceptible.
Prevention: Practice good personal hygiene. Keep ready-to-eat foods out of the temperature danger zone.
Vibrio spp.
Description: There are three species within the Vibrio group of bacteria that cause been implicated in foodborne infections. They include Vibrio cholera, Vibrio parahaemolyticus, and Vibrio vulnificus. All are important since they are very resistant to salt and are common in seafood.
Common foods: Vibrio spp. are commonly found in raw, under-
processed, improperly handled, con taminated fish and shellfish. These bacteria are generally found more in the summer months and from warmer waters.
Transmission in foods: Since the microorganism exists in many raw seafood, transmission to other foods by cross contamination is a concern. Most illnesses are caused due to eating raw or undercooked seafood, especially oysters. Prevention: Cook seafood properly. Avoid consumption of raw seafood. Practice good personal hygiene.
Foodborne Viruses
Foodborne viruses differ from foodborne bacteria. They are the smallest and simplest form of life known. Viruses require a living host (animal, plant, or human) to grow and reproduce. Unlike bacteria, they do not reproduce or grow in foods. They are usually transferred from one food to another, from a food handler to a food, or from a water supply to a food. There are three viruses that are important in food retail preparation; Hepatitis A, Norwalk virus, and rotavirus.
Hepatitis A Description: Hepatitis A is a foodborne virus that is associated with many foodborne infections. It is a particularly important hazard to retail food establishments because it has an incubation period of 10-45 days. This means that a food worker can harbor the microorganism for up to 6 weeks and not show symptoms of illness. However, during this time, the food worker can contaminate foods and other workers in the food retail estab lishment. Common foods: Ready-to-eat foods that are washed with a non-potable water supply or foods that are handled excessively can be contaminated with Hepatitis A. Examples include raw vegetables and raw seafood. Due to the long incubation period, it is very
difficult to identify the food source of a Hepatitis A infection.
Transmission in foods: The virus is primarily transmitted from person-to person contact, by cross contamination, and by fecal contamination. Prevention: Handle and cook foods properly. Avoid consumption of raw seafood. Practice good personal hygiene.
Norwalk virus group, Rotavirus Description: The Norwalk virus and rotavirus are other common foodborne viruses that are associated with many foodborne infections, with some outbreaks involving up to 3000 people. Common foods: Raw seafood. Raw fruits and vegetables that are washed with a contaminated water supply. Non-heated foods that are handled by people who are shedding the virus.
Transmission in foods: The virus is transmitted from person-to-person contact and by fecal contamination.
Prevention: Handle and cook foods properly. Avoid consumption of raw seafood. Practice good personal hygiene.
Foodborne Parasites
Foodborne parasites are another important foodborne biological hazard. Parasites are small or microscopic creatures that need to live on or inside a host to survive. There are many examples of parasites that can enter the food system and cause foodborne illness. Included here are a list of a few of the most troublesome ones that may appear in food retail establishments. Parasitic infection is far less common than bacterial or viral foodborne illness.
Anisakis spp****. Description: Anisakis spp. are nematodes (or roundworms) that have been associated with foodborne infection. Common foods: They generally cause foodborne disease through consumption
more common with mussels. NSP is common for Gulf Coast marine animals.
Transmission in foods: Inherent to marine shellfish.
Prevention: Purchasing food from a reputable supplier.
Mycotoxins
Another group of foodborne microor ganisms that can cause disease include fungi. Fungi include both molds and yeasts. They differ from bacteria in that they are larger in size and usually prefer foods that are high in sugar or starches. They can often withstand more extreme conditions (highly acidic foods, lower Aw foods) compared to bacteria.
Foodborne molds are important because they can produce chemical compounds called mycotoxins. Mycotoxins have been linked to cancer. Yeasts do not cause foodborne illness.
There are several molds that produce mycotoxins. An important and common foodborne mycotoxin, called aflatoxin, is produced by Aspergillus spp. Mycotoxins are commonly found in dry and/or acidic foods. Common foods containing mycotoxins include corn, nuts, and grains. Many mycotoxins are not destroyed by cooking.
Added Chemicals
There is a long list of chemicals that are added to foods which can pose a health risk. Intentionally added chemicals may include food additives, food preservatives, and pesticides. Pesticides leave residues on fruits and vegetables, and can usually be removed by a vigorous washing procedure or by peeling off the skin. Use of intended food additives is regulated by the Food and Drug Administration and Environ mental Protection Agency to assure that they are safe. Non-intentionally added chemicals may include contami nation by chemicals such as cleaning compounds.
Physical Hazards Physical hazards can enter the food system and cause foodborne illness (Figure 15). Animal bones are a good example of a particle that can easily be part of a food such as ground beef. Stones, rocks or wood particles can be associated with raw fruits and veg etables. For physical hazards, it is important to wash all raw fruits and vegetables thoroughly and visually inspect foods that cannot be washed (such as ground beef).
Figure 15. Common physical hazards in a food retail operation. Bone particles Glass Metal Stone Wood
(From 1995 Food Code)
Conclusion
There are many foodborne hazards that a food retail establishment may encounter. Food retail operations are typically toward the end of the food production chain because foods are prepared and eaten there. It is very important to control activities in these operations and prevent foodborne hazards that could lead to foodborne illness. Control and prevention of foodborne hazards in a food retail establishment starts with understanding the different types of foodborne hazards. The next step is to understand how to control foodborne hazards with good personal hygiene, prevention of cross contamination, as well as proper storage, cooking, cooling, and reheating of foods.
References
Food and Drug Administration. 1992. Foodborne Pathogenic Microorganisms and Toxins. Center for Food Safety and Applied Nutrition. Washington, D.C.
Pierson, M. D. and D. A. Corlett.
- HACCP Principles and Applications. Van Nostrand Reinhold:New York.
U.S. Department of Health and Human Services, Public Health Services, Food and Drug Administration. 1995. Food Code (1995). U.S. Department of Commerce. Springfield, Va.
