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13In the summer of 2010, one-half billion eggs distrib-uted by a number of Iowa farms were recalled due to Salmonella bacteria contamination. The tainted eggs sickened 2000 people and were found in 14 states. The outbreak lasted from April to August and was probably caused by rodents, contaminated hens, or contami-

nated feed. Luckily, unlike in a number of other earlier

contamination scares, no fatalities were associated with

the tainted eggs.

Eggs are now included in the list of foods that have

recently sickened or killed a number of Americans: E. coli bacteria in Nestlé Toll House cookie dough in 2009; Sal- monella-tainted jalapeño peppers and peanuts in 2008; Salmonella in ground beef and Banquet pot pies in 2007; and E. coli in spinach in 2006. Even our water is some- times threatened: In 2008, residents of a small Colorado

town were forced to subsist on bottled and trucked-in

water when Salmonella was found in the water supply.

How Safe Is Our Food Supply?

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465

Stimulate your interest by reading the introduction and looking at the visual.

Scan the Learning Objectives in each section:

p. 466 p. 470 p. 481 p. 489 p. 494

Read the text and study all figures and visuals. Answer any questions.

Analyze key features

Process Diagram, p. 467 p. 468 p. 473 p. 475 p. 494

Nutrition InSight, p. 471 p. 478 p. 495

Thinking it Through, p. 479

What a Scientist Sees, p. 480

Stop: Answer the Concept Checks before you go on:

p. 469 p. 480 p. 486 p. 493 p. 497

End of chapter

Review the Summary, Key Terms, and Online Resources.

Answer the Critical and Creative Thinking Questions.

Answer What is happening in this picture?

Complete the Self-Test and check your answers.

CHAPTER PLANNER

CHAPTER OUTLINE Keeping Food Safe 466

Pathogens in Food 470

Agricultural and Industrial Chemicals in Food 481

Technology for Keeping Food Safe 487

Biotechnology 494

Despite these frightening incidents, most foods

arrive in our homes safe and fit to eat, and they remain

that way if we handle them properly. The modern U.S.

food supply is perhaps the safest in human history, but

danger still lurks if adequate food-handling practices are

not in place from farm to table.

Keeping Food Safe LEARNING OBJECTIVES 1. Name the primary cause of food-borne illness.

2. Explain why a contaminated food does not cause illness in everyone who eats it.

3. Discuss the roles of the federal agencies re- sponsible for the safety of the U.S. food supply.

4. Explain how a HACCP system helps prevent food-borne illness.

ave you ever had food poisoning? Whether you know it or not, you probably have. Often- times what we call the 24-hour flu is actually food poisoning, also called food-borne illness.

Most food-borne illness is caused by consuming food that has been contaminated by microbes; occasionally it is caused by toxic chemicals or other contaminants that find their way into food.

Whether or not you get sick from eating a contaminated food depends on how potent the contaminant is, how much of it you consume, and how often you consume it, as well as on your age, size, and health. Some food contaminants cause

food-borne

illness An illness

caused by consump-

tion of contaminated

food.

microbes Micro-

scopic organisms,

or microorganisms,

including bacteria,

viruses, and fungi.

Agencies that monitor the food supply Table 13.1

International Organizations

Federal Organizations

State and Local Governments

harm even when minute amounts are consumed, and almost any substance can be toxic if a large enough amount of it is consumed. How well a substance is absorbed and how it is metabolized by the body affect toxicity. Dietary factors and nutritional status can affect ab- sorption. For example, mercury, which is extremely toxic, is not absorbed well if the diet is high in selenium, and lead absorption is decreased by the pres- ence of iron and calcium in the diet. Contaminants that are stored in the body after being absorbed are more likely to be toxic because they accumulate over time, eventu- ally causing symptoms of toxicity. Contaminants that are easily excreted from the body are less likely to cause toxicity.

An individual’s size, overall health and nutritional sta- tus, and immune function affect his or her risk of food- borne illness. Infants and children are at greater risk than adults because their immune systems are immature and their small size means that a given amount of contaminant represents a greater amount per unit of body weight than

it would in an adult. Elderly people, people with AIDS, and those receiving chemotherapy or other immunosuppres- sant drugs are at increased risk because their immune systems may be compromised. Pregnancy weakens the im- mune system, putting pregnant women and their unborn babies at risk. Poor nutritional status and chronic condi- tions such as diabetes and kidney disease may decrease the body’s ability to detoxify harmful substances.

The Role of Government Agencies at international, federal, state, and local levels monitor the safety of the food supply (Table 13.1). Federal agencies set standards and establish regulations for the safe handling of food and water and for the information included on food labels. They regulate the use of additives, packaging materials, and agricultural chemicals; inspect

food processing and storage facilities; monitor domestic and imported foods for contamination; and investigate outbreaks of food-borne illness.

Each year, 1 in 6 Americans, or about 48 million peo- ple, get sick, 128,000 are hospitalized, and 3000 die from food-borne illnesses.1 Media coverage of outbreaks of food-borne illness on cruise ships, of deaths from E. coli infection, and of cows infected with mad cow disease have heightened public concern and led to the development of the National Food Safety Initiative. The goal of this ini- tiative is to reduce the incidence of food-borne illness by improving food safety practices and policies throughout the United States. Because food can be contaminated any- where in the supply chain—from where it is grown to when it is served in your home—the program targets food safety from farm to table (Figure 13.1). In 2011, in response to

1 Farm Crops can be contaminated with bacteria

before they are even harvested.

Good agricultural practices help

minimize contamination during

growing, harvesting, sorting,

packing, and storage.

P R

O C

E S

S D

IA G

R A

THE PLANNER

Keeping food safe involves identifying possible points of contamination along a food’s

journey from the farm to the dinner table and implementing controls to prevent or contain

contamination.

2 Processing Contamination of processing equipment can transfer

microbes to food. To prevent

contamination, processors must

follow guidelines concerning

cleanliness and training of workers;

develop a protocol that anticipates

how biological, chemical, or physical

hazards are most likely to occur; and

establish appropriate measures to

prevent them from occurring.

3 Transportation During transport, poor sanitation and inadequate

refrigeration can contaminate

food and allow microbes to grow.

Clean containers and vehicles,

plus refrigeration can prevent the

growth of food-borne bacteria.

4 Retail Food can become contaminated during

handling or storage in

grocery stores or during

preparation in restaurants.

The FDA’s Food Code

provides recommendations

for the handling and service

of food in an effort to help

owners and employees

at retail establishments

prevent food-borne illness.

Local health inspections

ensure cleanliness and

proper procedures.

5 Table Even a safe food can be contaminated in

the home. Consumers

can prevent food-borne

illness at their table by

learning to handle, store,

and prepare food safely.

A s k Yo u r s e l f

control contamination. Then, by monitoring these criti- cal control points, contamination can be prevented or eliminated (Figure 13.2). Unlike traditional methods of protecting the food supply, which use visual spot checks and random testing to catch contamination after it occurs, HACCP systems are designed to prevent contamination.

The Role of the Consumer Although government agencies, manufacturers, and re- tailers are involved in creating a safe food supply, consum- ers also need to assume responsibility for their food. Even a food that has been manufactured, packaged, and trans- ported with great care can cause food-borne illness if it is not handled carefully at home. In fact, most cases of food-borne illness are caused by foods prepared at home.3

Consumers can prevent most food-borne illness through careful food handling, storage, and preparation (discussed in depth later in the chapter). They can also protect them- selves and others by reporting incidents involving unsani- tary, unsafe, deceptive, or mislabeled food to the appropriate agencies (Table 13.2).

the continued threat from our food supply, the FDA Food Safety Modernization Act was passed. This legislation fo- cuses on preventing food-borne illness, not just reacting to problems as they occur. It gives the FDA an inspection mandate and new legal powers to ensure that companies are doing their part and to stop potentially unsafe food from entering the marketplace.2

The Role of Food Manufacturers and Retailers The responsibility for providing safe food to the market- place falls on the shoulders of food manufacturers, pro- cessors, and distributors. To meet this responsibility, they

must establish and implement a Hazard Analysis Critical Control

Point (HACCP) system. A HACCP system analyzes food production, processing, and transport, with the goal of identifying potential sourc- es of contamination and points where measures can be taken to

Hazard Analysis

Critical Control

Point (HACCP) A

food safety system that

focuses on identifying

and preventing haz-

ards that could cause

food-borne illness.

The scrambled eggs served in your cafeteria at school or work most likely came out of

a carton rather than a shell. To produce this product, eggs are shelled, mixed together

in large vats, heated to kill microbial contaminants, packaged, and either refrigerated or

frozen. A contaminated batch could sicken hundreds of people. This example shows how a

HACCP system might be used to prevent contaminated eggs from reaching the consumer.

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1 Conduct a hazard analysis The manufacturer analyzes its processing steps for

potential hazards and determines what preventive

measures can be taken. In the case of eggs, there is a

large potential for contamination with the bacterium

Salmonella. Adequate heating is a preventive measure that can eliminate this hazard.

468 CHAPTER 13 How Safe Is Our Food Supply?

2 Identify the critical control points

Critical control points are the

steps in a food’s processing

at which the hazard can be

eliminated. In the case of egg

processing, the critical control

point is heating the shelled egg

mixture in a large chamber.

3 Establish critical limits Critical limits are the

parameters that will prevent

the hazard. In the case of

these eggs, the critical limits

are sufficient heating time and

temperature to ensure that Salmonella bacteria are killed.

THE PLANNER

Egg Pasteurization Record

Date Batch number

Time Temp.

Keeping Food Safe 469

4 Establish monitoring procedures Procedures need to be in place

to continually monitor the critical

control points. With egg processing,

each batch is tested for the presence

of Salmonella. If the temperature is not hot enough or the heating is not

continued long enough, Salmonella can survive, as shown here by the

growing bacterial colonies.

5 Establish corrective action If a critical limit is not

met, corrective action is

necessary. Batches of eggs

that are contaminated with

Salmonella are discarded, and the temperature of the

heat chamber is adjusted to

ensure that Salmonella in the next batch will be killed.

6 Keep records Extensive records are kept,

documenting the monitoring

of critical control points,

verification activities, and

corrective actions taken. This

enables the manufacturer

to trace the source of the

problem in the event of an

outbreak of food-borne illness.

7 Verify procedures Review of plans and

records helps ensure

that the HACCP plan

is working and only

safe eggs are reaching

consumers.

A s k Yo u r s e l f

Salmonella

3. Who is responsible for the safety of the food you eat?

4. How does HACCP differ from tradi- tional visual food inspection?

1. What causes food-borne illness?

2. Why might the same food make one person sick and not another person?

How to report food-related issues Table 13.2

Problems related to any food except meat and poultry, including adverse reactions:

Issues related to meat and poultry:

Restaurant food and sanitation problems:

Issues related to alcoholic beverages:

Pesticide, air, and water pollution:

Products purchased at the grocery store:

470 CHAPTER 13 How Safe Is Our Food Supply?

harmless, some are beneficial, and a few are pathogenic, causing food-borne infection or intoxication.4

Bacterial food-borne infection Salmonella is the most common cause of food-borne illness in the United States.4 Contaminated meat, dairy products, seafood, fresh produce, and cereal have caused outbreaks, but poultry and eggs are the foods most commonly contaminated with the bacterium (Figure 13.3a and b). Because Salmonella is killed by heat, foods that are likely to be contaminated should be cooked thoroughly.

Campylobacter jejuni is the leading cause of acute bacte- rial diarrhea in developed countries.5 Common sources are undercooked chicken, unpasteurized milk, and untreated water (Figure 13.3b and c). A sampling of raw chicken from supermarkets found that about 70% of samples were contaminated with Campylobacter.6 This organism grows slowly in cold temperatures and is killed by heat, so care- ful storage and thorough cooking help prevent infection.

Escherichia coli, commonly called E. coli, is a bacterium that inhabits the gastrointestinal tracts of humans and other animals. It comes into contact with food through fecal contamination of water or unsanitary handling of food. Some strains of E. coli are harmless, but others can cause serious food-borne infection. One strain of E. coli, found in water contaminated by human or animal feces, is the cause of “travelers’ diarrhea.” Another strain, E. coli O157:H7, produces a toxin in the body that causes abdominal pain, bloody diarrhea, and in severe cases a form of kidney failure called hemolytic-uremic syndrome, which can be fatal.

E. coli O157:H7 entered the public spotlight in 1993, when it led to the deaths of several children who had consumed undercooked, contaminated hamburgers from a fast-food restaurant (Figure 13.3d).7 Thorough cook- ing of the hamburgers would have killed the bacteria that caused these deaths. E. coli can also contaminate produce such as lettuce, spinach, and green onions and cause illness if the produce is eaten raw (Figure 13.3e). In 2010, E. coli contamination of lettuce sickened people in five states.8 In 2011, infected bologna, another food that we don’t typi- cally cook, sickened people in five different states.9 In ad- dition to concerns about E. coli O157:H7 in our meat and produce, a new, even more deadly strain of E. coli emerged in Europe in 2011, sickening thousands and killing dozens.

Pathogens in Food LEARNING OBJECTIVES

1. Distinguish food-borne infection from food- borne intoxication.

2. Discuss three types of bacteria that commonly cause food-borne illness.

3. Explain how viruses, molds, and parasites can make us sick.

4. Describe how careful food handling can prevent food-borne illness.

ost cases of food-borne illness in the United States are caused by food that has been con- taminated with pathogens. The pathogens that most commonly affect the food supply

include bacteria, viruses, molds, and parasites. A typical case of food-borne illness causes a short bout of flulike symptoms, including

abdominal pain, nausea, diarrhea, and vomiting. However, more severe symptoms, such as kidney failure, arthritis, paralysis, mis carriage, and even death, sometimes occur.

Any food-borne illness caused by pathogens that mul- tiply in the human body is called a food-borne infection. Contracting a food-borne infection usually involves con- sumption of a large number of pathogens that infect the body or produce toxins within the body. Any food-borne illness caused by consuming a food that contains toxins produced by pathogens is referred to as food-borne in- toxication. Even food that contains only a few pathogens can cause food-borne intoxication if the pathogens have produced enough toxin. Avoiding food-borne illness— both infection and intoxication—requires knowing how to handle and store food in ways that will prevent contami- nation and prevent or minimize the growth of pathogens that may already be present in the food. Even a food that is contaminated with pathogens can be safe if it is pre- pared in a manner that destroys any pathogens or toxins that are present.

Bacteria in Food Bacteria are present in the soil, on our skin, on most surfaces in our homes, and in the food we eat. Most are

M pathogen A biologi-

cal agent that causes

disease.

Pathogens in Food 471

THE PLANNERNutrition InSight How bacteria contaminate our food

a. Because poultry farms house

large numbers of chickens in close

proximity, one infected chicken can infect

thousands of others. Salmonella can infect the ovaries of hens and contaminate the

eggs before the shells are formed, so that

the bacteria are present inside the shell

when the eggs are laid. Therefore, eggs

should never be eaten raw.

b. In processing plants, Salmonella and Campylobacter from infected birds can be transferred to the meat of

healthy birds. Consumers should always handle raw chicken

as if it contains pathogens.

c. Campylobacter are often carried by healthy cattle and by flies on farms. As a result, the bacteria are commonly

present in unpasteurized (raw) milk. Unpasteurized milk is also a

common source of Listeria. During pasteurization, milk is heated to a temperature that is high enough to kill both Campylobacter and Listeria. Avoiding products made with unpasteurized milk will reduce the risk of Campylobacter and Listeria infection.

d. E. coli O157:H7 can live in the intestines of healthy cattle and contaminate the meat after slaughter. E. coli–contaminated meat that comes into contact with a grinder may contaminate hundreds

of pounds of ground beef. Ground beef contaminated with E. coli O157:H7 is a particular concern because the pathogens are mixed

throughout during grinding rather than remaining on the surface,

as they do on steaks and chops. The E. coli on the outside of the meat are quickly killed during cooking, but those in the interior

survive if the meat is not cooked thoroughly.

e. E. coli and other bacteria can also contaminate fruits and

vegetables if they are fertilized with

raw or improperly composted manure

or irrigated with water containing

untreated sewage or manure.

Produce may also be contaminated

by wash water or through direct or

indirect contact with cattle, deer, or

sheep. Thoroughly washing fruits and

vegetables can reduce the number

of pathogens but does not make

contaminated produce risk free.

Why should hamburger be cooked more thoroughly than steak to prevent E coli infection?

T h i n k C r i t i c a l l y

Video

472 CHAPTER 13 How Safe Is Our Food Supply?

Each year in the United States, an estimated 1600 persons become seriously ill due to infection with Listeria monocytogenes, and of these, 260 die.10 In most people, Listeria infection just causes flulike symptoms, but in high-risk groups, such as pregnant women, children, elderly people, and people with compromised immune systems, it can be more serious. Pregnant women are at particular risk; Listeria infection is 18 times more common in pregnant women than in the general population. Infection during pregnancy is associated with an increased risk of spontane- ous abortion and stillbirth, and it can be transmitted to the fetus, causing meningitis and serious blood infections.11 Listeria is ubiquitous in the environment and can survive and grow at refrigerator temperatures. Because it can grow at cool temperatures, this bacterium can infect ready- to-eat foods such as hot dogs and lunch meats, even if they have been kept properly refrigerated. To prevent infection, ready-to-eat meats should be heated to the steaming point, and unpasteurized dairy products should be avoided.

The food-borne infection caused by the bacterium Vibrio vulnificus usually causes gastrointestinal upset but can be deadly in people with compromised immune systems. The most common way in which people become infected is by eating raw or undercooked shellfish, particularly oysters. Vibrio bacteria grow in warm seawater. The incidence of Vibrio infection is higher during the summer months, when warm water favors growth.

Bacterial food-borne intoxication Staphylococcus aureus is a common cause of bacterial food-borne intoxication. These bacteria live in human nasal passages and can be transferred to food through coughing or sneezing. They can then grow on the food, producing a toxin that causes vomiting soon after ingestion.

Another cause of food-borne intoxication is the bacterium Clostridium perfringens. It is often called the cafeteria

Because acid prevents the germination of Clostridium botulinum spores, foods that are low in acid, such as green beans, corn, peppers,

asparagus, and mushrooms, are more likely to cause botulism than are

acidic foods. To avoid botulism, discard bulging cans, as the bulge could

indicate the presence of gas produced by the bacteria as they grow.

Once it has formed, botulism toxin can be destroyed by boiling for at

least 10 minutes, but if the safety of a food is in question, it should be

thrown away; even a taste of a food contaminated with botulism toxin

can be deadly.

germ because it grows in foods that are stored in large con- tainers like those used in cafeterias. Little oxygen gets to the food at the center of a large container, thus providing an excellent growth environment for bacteria such as these, which thrive in low-oxygen environments. C. perfringens are difficult to kill because they form heat-resistant spores. Spores are a stage of bacterial life that remains dormant un- til environmental conditions favor their growth. C. perfringens may cause illness through both infection and intoxication.

The deadliest of all bacterial food toxins is produced by Clostridium botulinum. Heat-resistant spores of C. botulinum are found in soil, water, and the intestinal tracts of ani- mals. The toxin is produced when the spores begin to grow and develop. When consumed, the toxin blocks nerve func- tion, resulting in vomiting, abdominal pain, double vision, and paralysis that leads to respiratory failure. If untreated, botulism is often fatal, but modern detection methods and rapid administration of antitoxin have reduced mor- tality rates. C. botulinum grows in low-oxygen, low-acid conditions, so improperly canned foods and foods such as potatoes or stew that are held in large containers where there is little exposure to oxygen provide optimal condi- tions for botulism spores to germinate ( ).

Infant botulism is a type of botulism that is seen only in infants. Though rare, it occurs worldwide and is the most common form of botulism in the United States.12 It is caused by ingestion of botulism spores. When ingested, the spores germinate in the infant’s gastrointestinal tract, producing toxin. Some of the toxin is absorbed into the bloodstream, causing weakness, paralysis, and respiratory problems. In the absence of complications, infants gener- ally recover. Only infants are affected, because in adults, competing intestinal microflora prevent spores from ger- minating. Because honey can be contaminated with botu- lism spores, it should never be fed to infants under 1 year of age.

Pathogens in Food 473

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Viruses make us sick by reproducing inside our cells. Viruses that cause food-borne illness

enter the body through the gastrointestinal (GI) tract. Other types of viruses may enter the

body through open cuts, the respiratory tract, or the genital tract.

Viruses in Food Unlike bacteria, the viruses that cause human diseases can- not grow and reproduce in foods. Human viruses can repro- duce only inside human cells. They make us sick by turning our cells into virus-producing factories ( ).

Noroviruses are a group of viruses that cause gastro- enteritis, or what we commonly call “stomach flu.” These viruses are believed to be responsible for about 50% of all food-borne gastroenteritis outbreaks in the United States.13 Norovirus illness is contracted either by eating food that is contaminated with the virus or by touching a contaminated surface and then putting your fingers in

your mouth. Shellfish can be contaminated with norovi- rus if the water in which they live is polluted with human or animal feces. Cooking destroys noroviruses, so un- cooked foods and water are the most common causes of norovirus food-borne illness. Norovirus infection can be spread from one infected person to another, so it spreads swiftly where many people congregate in a small area. You may have heard of it as a cause of food-borne ill- ness aboard cruise ships. These outbreaks make head- lines, but norovirus outbreaks are just as likely in nursing homes, restaurants, hotels, and dormitories as they are aboard cruise ships.

The virus travels through the GI tract and attaches itself to cells lining the intestines.

A food such as a raw oyster that is contaminated with virus particles is consumed.

Viral genetic material

Nucleus

The virus transfers its genetic material into the intestinal mucosal cells.

The virus uses the cells’ metabolic machinery to make new virus particles.

The infected intestinal cells are damaged or killed and release copies of the virus, which infect more cells of the intestine’s lining.

2 3 4 5

Mucosal cells

474 CHAPTER 13 How Safe Is Our Food Supply?

identified. Cooking and freezing stop mold growth but do not destroy toxins that have already been produced. If a food is moldy, it should be discarded, the area where it was stored should be cleaned, and neighboring foods should be checked to see if they have also become contaminated.

Parasites in Food Some parasites are microscopic single-celled animals, and others are worms large enough to be seen with the naked eye. Parasites that can be transmitted through consumption of contami- nated food and water cause food-borne illness. Giardia lam- blia is a single-celled parasite that is often contracted by hikers who drink untreated water from streams contami- nated with animal feces. Giardia infection is also becoming a problem in day-care centers where diapers are changed

Hepatitis A is another viral infection that can be con- tracted from food or water that is contaminated with fecal matter. Hepatitis A infection causes liver inflammation, jaundice, fever, nausea, fatigue, and abdominal pain. The infection can require a recovery period of several months, but it does not require treatment and does not cause permanent liver damage. Hepatitis in drinking water is destroyed by chlorination. Cooking destroys the virus in food, and good sanitation can prevent its spread. A vaccine that protects against hepatitis A infection is available.

Moldy Foods Many types of mold grow on foods such as bread, cheese, and fruit. Under certain condi- tions, these molds produce toxins (Figure 13.6). More than 250 different mold toxins have been

mold Multicellular

fungi that form fila-

mentous branching

growths.

parasite An organ-

ism that lives at the

expense of another.

I n t e r p r e t i n g D a t a Which continents have the highest inci- dence of liver cancer? Are these areas also at risk for aflatoxin exposure?

b. Exposure to aflatoxin can lead to

liver cancer. Many regions with high

rates of liver cancer also have high

exposure to aflatoxin.14

Incidence of liver cancer per 100,000 males

Areas at high risk for aflatoxin

exposure

<99

<15

<10

<5.6

<3.3

a. The filamentous growths

seen in this electron micrograph

belong to the mold Aspergillus flavus. It produces aflatoxin, which is among the most potent

carcinogens and mutagens

known. This mold commonly

grows on corn, rice, wheat,

peanuts, almonds, walnuts,

sunflower seeds, and spices

such as black pepper and

coriander. The level of aflatoxin

that may be present in foods in

the United States is regulated to

prevent toxicity.

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The abnormal prions that cause BSE differ from normal proteins

in the way they are folded—that is, in their three-dimensional

structure. When the improperly folded form of a prion is

introduced into the brain after a person has eaten contaminated

tissue, it can reproduce by corrupting neighboring proteins,

essentially changing their shape so that they, too, become

abnormal prions. Because the abnormal prions are not degraded

normally, they accumulate and form clumps called plaques.

These plaques cause deadly nervous tissue damage.

Prions in Food

The strangest and scariest yet rarest food-borne illness is caused not by a microbe but by a protein, called a prion, that has folded improperly. Abnormal prions are believed to be the cause of mad cow disease, or bovine spongiform encephalop- athy (BSE), a deadly degenerative neurological disease that affects cattle. The human form of this dis- ease is variant Creutzfeldt-Jakob Disease (vCJD). People are be- lieved to contract it by eating tissue from a cow infected with BSE ( ).16 Symptoms of vCJD begin as mood swings and numbness and within about 14 months progress to dementia and death.

and hands and surfaces are not thoroughly washed.4 Cryp- tosporidium parvum is another single-celled parasite that is commonly spread by contaminated water, but cases have also been reported in patients who have eaten contami- nated raw fruits and vegetables.15

Trichinella spiralis is a parasite that is found in raw and un- dercooked pork and game meats. Once ingested, these small, wormlike organisms find their way to the muscles, where they grow, causing flulike symptoms. Fish are another com- mon source of parasitic infections because they carry the lar- vae of parasites such as roundworms, flatworms, flukes, and tapeworms (Figure 13.7). As the popularity of eating raw fish has increased, so has the incidence of parasitic infections from fish. Parasites, including those in fish, are killed by thor- ough cooking. When consuming raw fish, parasitic infections can be avoided by eating fish that has been frozen.

The body cavity of this herring contains the larval form of the small

roundworm Anisakis simplex, also called herring worm. When consumed in raw fish, these parasites invade the stomach and

intestinal tract, causing Anisakis disease, which is characterized by severe abdominal pain. The fresher the fish when it is eviscerated,

the less likely it is to cause this disease because the larvae move

from the fish’s stomach to its flesh only after the fish dies.

prion A pathogenic

protein that is the

cause of degenerative

brain diseases called

spongiform encepha-

lopathies. Prion is short for proteinaceous infectious particle.

Pathogens in Food 475

Normal prion proteins are present in the brain.

Abnormal prion proteins arise spontaneously or enter from the diet.

Abnormal prion proteins accumulate in the brain, leading to the formation of plaques that damage brain tissue.

Normal and abnormal prion proteins come into contact with each other.

Normal prions are converted into abnormal prions.

2 3 4 5

476 CHAPTER 13 How Safe Is Our Food Supply?

Summary of bacterial, viral, and parasitic food-borne illnesses Table 13.3

Onset

(time after

Microbe Sources Symptoms consumption) Duration

Bacteria

Salmonella

Campylobacter jejuni

Listeria monocytogenes

Vibrio vulnificus

Staphylococcus aureus

Escherichia coli

Clostridium perfringens

Clostridium botulinum

Shigella

Yersinia enterocolitica

Viruses

Parasites

Giardia lamblia

Cryptosporidium parvum

Trichinella spiralis

Anisakis simplex

Toxoplasma gondii

Pathogens in Food 477

even more cases of food-borne illness than was possible a few years ago. Given this and the extensive media coverage of outbreaks of food-borne illness and recalls of contaminated foods, one would expect that the incidence of food-borne illness has been rising. In fact, there has been no increase over the past four years.18

Public awareness of the problem and education on how to handle food safely should make food-borne illness even less frequent in the future.

Preventing Microbial Food-Borne Illness Microbes in food multiply when they are presented with the right conditions for growth. The first step in prevent- ing microbial food-borne illness is to minimize the pres- ence of microbes by choosing food carefully ( ). Preparing food in a clean kitchen reduces cross-contam- ination. Storing food at refrigera- tor or freezer temperatures either limits or stops microbial growth. Heating foods to the recommend- ed temperature kills microbes and

vCJD is believed to be transmitted by consumption of the brain and nervous tissue, intestines, eyes, or tonsils of contaminated animals, but thus far meat (if free of central nervous system tissue) and milk have not been found to transmit either BSE or vCJD.4 Even though cooking does not destroy prions, the risk of acquiring vCJD is extremely small. Safeguards are in place to prevent cattle in the United States from contracting BSE. These include restrictions on the import of animals and animal products from coun- tries where BSE has occurred, restrictions on what can be included in cattle feed, and testing for BSE before meat is released into the food supply.17 Several cows with BSE have been identified in the United States, but meat from these animals did not enter the food supply. Thus far there has been no known instance of U.S. beef causing a case of vCJD.

What Bug Has You Down? There are certainly a wide variety of food-borne pathogens that can make you sick (Table 13.3). Recent improvements in governmental outbreak surveillance, attentiveness by health-care professionals, and testing frequency and accuracy have made it possible to identify

cross-contamina-

tion The transfer of contaminants from

one food or object to

another.

Safe grocery choices Table 13.4

Sell-by or pull-by date:

Best if used by, use-by, quality assurance, or freshness date:

Expiration date: A s k Yo u r s e l f

478 CHAPTER 13 How Safe Is Our Food Supply?

THE PLANNER

Nutrition InSight Safe food handling, storage, and preparation

478 CHAPTER 13 How Safe Is Our Food Supply?

Clean Wash hands and surfaces often.

Chill Refrigerate promptly

Separate Don’t cross- contaminate.

Cook Cook to proper temperatures.

K e

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te r

IG H T B A C !

BA C!

Hands, countertops, cutting boards, and utensils should be washed with warm, soapy water before each step in food preparation.

Foods that are going to be cooked should not be prepared on the same surfaces as foods that are eaten raw.

250°F

212°F

165°F

135°F 125°F

60°F

40°F 32°F

0°F

Minimum temperature for reheating foods. Warming temperatures control growth but allow survival of some bacteria.

Some growth may occur: Many bacteria survive.

Range of cooking temperatures to kill most bacteria. The amount of time needed decreases as the temperature increases.

Canning temperature for low-acid foods in pressure cooker

Some bacterial growth may occur in this zone.

Cold temperatures allow slow growth for a few cold-tolerant organisms but stop the growth of most.

Freezing temperatures prevent bacterial growth but some bacteria are able to survive.

260°

220°

240°

200°

180°

160°

140°

120°

100°

80°

60°

40°

20°

0°

Danger Zone Temperatures in this zone allow rapid bacterial growth and production of bacterial toxins. Foods should only be allowed to remain in this temperature range for minimal amounts of time.

Safe Cooking Temperatures19

Food item

Beef roasts and steaks

Ground meat

Pork

Poultry

Fish

Eggs

Leftovers and casseroles

Internal temperature (°F) or description

145 or until the flesh is opaque and separates easily with a fork

145 (allow meat to rest 3 min before carving or consuming)

160

165

Until the yolk and white are firm, not runny (egg dishes 160)

165

Why is a tempera- ture between 41 and 135°F consid- ered to be the danger zone?

T h i n k C r i t i c a l l y

Fight Bac! is an educational campaign conducted by the

Partnership for Food Safety Education. It is designed to teach

food-handling practices that will keep food safe from bacteria

and prevent food-borne illness. Fight Bac! recommends that

consumers follow four steps—clean, separate, cook, and

chill—to prevent food-borne illness (see www.fightbac.

org).19

Meats and casseroles should be cooked, and leftovers

reheated, until they reach the internal temperatures

shown here, which will ensure that microbes have been

killed. Use a food thermometer to make sure that the

food is cooked to a safe internal temperature;

color is not a good indicator of safety.

Fresh and frozen foods

brought from the store

should be refrigerated or frozen

immediately. Fresh meat, poultry,

and fish should be frozen if it will

not be used within a day or two.

Processed meats such as hot dogs

and bologna should be refrigerated

but can be kept longer than fresh

meat. Freezers should be set to 0°F

and refrigerators to less than 40°F.

Temperature is one of the best

weapons consumers have for

preventing food-borne illness. Low

temperatures slow or stop microbial growth,

and high temperatures kill microorganisms.

Ecological Niches 479

be used as sauces on cooked food. Leftover cooked food should be refrigerated as soon as possible after it has been served. The temperature range that is most favorable for microbial growth is the range at which food usually sits between service and storage. Large portions of food should be divided before refrigeration so they will cool quickly. Most leftovers should be kept for only a few days.

Although most food-borne illness in the United States is caused by food prepared in homes, an outbreak in a commercial or institutional establishment usually involves more people and is more likely to be reported (see Thinking It Through). Food in retail establishments

destroys toxins ( ). Foods that are served cold should be kept cold until they are served. Frozen foods should be kept frozen and then thawed in the refrigerator or microwave before cooking, not thawed at room temper- ature, which favors microbial growth. Cooked food should be handled with care and kept hot until it is served. When in doubt about the safety of a food, throw it out.

Cross-contamination can occur when uncooked foods containing live microbes come into contact with foods that have already been cooked. Therefore, cooked meat should never be returned to the same dish that held the raw meat, and sauces used to marinate uncooked foods should never

THINKING IT THROUGH A Case Study on Tracking Food-Borne Illness

On Friday, more than half of the 200 children enrolled at the local elementary school were either absent or went home sick

sometime during the school day. Symptoms included nausea and

vomiting, diarrhea, abdominal pain, and fever. Food-borne illness

was suspected, and the local health department was notified.

Inspectors were able to trace the source of the outbreak to the

Spring Celebration held at the school on Thursday. For this event,

the first-graders made cupcakes, the second-graders, cookies;

the third-graders, fruit salad, and the fourth-graders, frozen

custard. All the children were interviewed about which of these

foods they had eaten that day, and the information was used to

compile the following graph:

Based on the graph, which food is the most likely cause of the illness? Why?

Your answer:

Physicians saw many of the sick children, and the bacterium

Salmonella enteritidis was isolated from their stool samples. The

health inspectors determined that the fourth-graders had used

six grade-A raw eggs to make the frozen custard.

How can eggs become contaminated with Salmonella?

Your answer:

The cookie and cupcake recipes also called for eggs. Why are these unlikely to be the cause of the problem?

Your answer:

Suggest a reason why 20 children who consumed the frozen custard did not get ill.

Your answer:

What could the fourth-graders have done to avoid the risk of Salmonella in their frozen custard?

Your answer:

(Check your answers in Appendix J.)

100

150

200

N u

m b e r

o f ch

ild re

Cupcakes Cookies Fruit salad Frozen custard

Became ill

Stayed healthy

Foods eaten

THE PLANNER

480 CHAPTER 13 How Safe Is Our Food Supply?

WHAT A SCIENTIST SEES A Picnic for Bacteria

20,000

N u m

b e r

o f b a ct

e ri a l c

e lls

25,000

30,000

35,000

40,000

45,000

15,000

10,000

5,000

0 10 2 3 4

Time (hours)

L ooks great—lots of food and people together on a warm,

sunny day. Most people see lunch, but those concerned with

food-borne illness see trouble. If a food is contaminated with

pathogenic bacteria, it won’t take long before enough bacteria

are present to cause food-borne illness. The number of bacterial

cells doubles each time the cells divide, resulting in an exponen-

tial growth curve like the one shown here. If 10 bacterial cells

contaminate the egg salad during preparation and then it sits

in the warm sun for 4 hours, during which time the cells divide

every 20 minutes, there will be 40,960 bacterial cells in the salad

when you scoop a portion of it onto your plate.

What foods would be the safest to include in lunch boxes and serve at picnics? Why?

T h i n k C r i t i c a l l y

has many opportunities to be contaminated because of the large volume of food handled and the large number of peo- ple involved in its preparation. Consumers should choose restaurants with safety in mind. Restaurants should be clean, and cooked foods should be served hot. Cafeteria steam tables should be kept hot enough that the water is steaming and food is kept above 135°F. Cold foods, such as salad bar items, should be kept either refrigerated or on ice to keep the food at 41°F or colder.

Picnics, potluck suppers, and other large events where food is served provide a prime opportunity for bacteria to flourish because food is often left at room temperature or in the sun for long periods before it is consumed. When diners serve themselves, cross-con- tamination from dirty hands or used plates and utensils is possible. Unlike the food in salad bars at restaurants,

the food at a family picnic is not placed under a sneeze guard to prevent contamination from coughs and sneez- es. All food that is served outdoors at a picnic or county fair should be approached with food safety in mind (see What a Scientist Sees).

1. How does Clostridium botulinum cause food- borne illness?

2. What pathogenic bacteria commonly contami- nate chicken and eggs?

3. How do viruses make us sick?

4. How does refrigeration help prevent food- borne illness?

THE PLANNER

Limiting bacterial growth is a consideration any time food

must be carried out of the home. Any food that is transported

should be kept cold. Lunches should be transported to and

from work or school in a cooler or an insulated bag and refriger-

ated upon arrival. Perishable foods that are brought home from

work or school uneaten should be thrown out and not saved for

another day.

Agricultural and Industrial Chemicals in Food 481

Agricultural and Industrial Chemicals in Food LEARNING OBJECTIVES

environment quickly because they are broken down by microorganisms or chemical reactions. Others remain in the environment for very long periods, and when taken up by plants and small animals, they are not metabolized or excreted. When these plants or small animals are consumed by larger animals that are in turn eaten by still larger animals, the contaminants accumulate, reach- ing higher concentrations at each level of the food chain (Figure 13.10). This process is called bio- accumulation. Because the toxins are not eliminated from the body, the greater the amount consumed, the greater the amount present in the body.

1. Illustrate how contaminants move through the food chain and into our foods.

2. Compare the risks and benefits of using pesti- cides with those of growing food organically.

3. Describe how to minimize the risks of exposure to chemical contaminants.

hemicals used in agricultural production and industrial wastes contaminate the en- vironment and can find their way into the food supply. How harmful these chemicals

are depends on whether they persist in the environment and whether they accumulate in the organisms that con- sume them or can be broken down and excreted by those organisms. Some contaminants are eliminated from the

C bioaccumula-

tion The process by

which compounds

accumulate or build

up in an organism

faster than they can

be broken down or

excreted.

Humans

Small marine animals

Water plants and microscopic animals

Grasses, grains, and other crops

Agricultural chemicals

Grazing animals

Industrial wastes

Small fish (sardines and herring)

Large fish (tuna)

Ground water, irrigation water, waterways, lakes, oceans

Contaminants are found in greater concentrations in the meat and milk from cattle than in the grasses they consume.

Concentrations are greater in large fish such as tuna than in algae (tiny marine organisms) or in small fish such as sardines and herring.

Industrial pollutants and

agricultural chemicals that

contaminate the water

supply enter the food

chain and accumulate as

they are passed through

the chain. Fat-soluble

contaminants concentrate

in body fat and cannot be

excreted. An animal that

occupies a higher level in

the food chain has higher

concentrations of these

contaminants because

it consumes all the

contaminants that have

been eaten by organisms

at lower feeding levels.

Why are you more likely to consume harmful amounts of toxins by eating tuna than by eating shrimp?

T h i n k C r i t i c a l l y

482 CHAPTER 13 How Safe Is Our Food Supply?

below federally permitted limits (Figure 13.11).22 Al- though repeated consumption of large doses of any one pesticide could be harmful, such a situation is unlikely be- cause most people consume a variety of foods that have been produced in many different locations.

Integrated pest management One way to limit pesticide use is through integrated pest management (IPM). IPM is a method of agricultural pest control that combines chemical and nonchemical methods and emphasizes the use of natural toxins and more effective pesticide application. For example, increasing the use of naturally pest-resistant crop varieties that thrive without the use of pesticides can reduce costs and do less environmental damage. IPM programs use information about the life cycles of pests and their interaction with the environment to manage pest damage economically and with the least possible hazard to people, property, and the environment.

Organic food production Organic food is produced using methods that emphasize a reduction in the use of chemical pesticides and fertilizers, the recycling of resources, and the conservation of soil and water to protect the environment (see Debate: Should You Go Organic?). The USDA sets standards for substances that can be used in or are prohibited from use in organic food production. Most conventional pesticides, fertilizers made with synthetic

Pesticides: Risks and Benefits Pesticides are used to prevent plant diseases and insect in- festations. They are applied both to crops in the fields and to harvested produce in order to prevent spoilage and ex- tend shelf life. Crops that are grown using pesticides gen- erally produce higher yields and look more appealing be- cause they have less insect damage. Once they have been applied, however, pesticides can travel into water supplies, soil, and other parts of the environment. Because pesti- cides enter the environment, pesticide residues are found not only on the treated plants but also in meat, poultry, fish, and dairy products (see Figure 13.10).

The potential risks of pesticides to consumers de- pend on the size, age, and health of the person who con- sumes the pesticides and on the type and amount con- sumed.20 To protect public health and the environment, the types of pesticides that may be used on food crops, how often they may be used, and the amount of residue that may remain when foods reach consumers are regu- lated. The EPA approves and registers pesticides that are used in food production and establishes tolerances. Pes- ticide tolerances are the maximum amounts of pesticide residues that may remain in or on a food.21 To establish tolerances that are safe for both children and adults, the EPA considers tests done in experimental animals and on cells growing in the laboratory, as well as the amount of the pesticide to which consumers are likely to be ex- posed. Tolerances are then set at least 100 times lower than the highest dose that has no harmful effects in test animals.

The FDA and the USDA monitor pesticide residues in foods. In general, pesticide residue levels in both do- mestic and imported foods have been found to be well

As shown in these pie charts from an analysis of samples of

domestically produced food and imported food from 100

countries, only a small percentage of foods exceed tolerances.22

To further reduce pesticide risks and exposure in the United

States, more effective, less-toxic chemical pesticides are being

developed; the use of older, more toxic products is decreasing;

and production methods that result in low-pesticide and

pesticide-free produce are being implemented.

No residue found

Residue found but levels are below tolerances

Residue found that exceeds tolerance or for which no tolerance has been established in the sampled food.

Domestic samples Imported samples

34.9%

0.9%

64.2%

23%

4.7%

72.3%I n t e r p r e t i n g D a t a

integrated pest

management

(IPM) A method of agricultural pest

control that integrates

nonchemical and

chemical techniques.

organic food Food

that is produced, pro-

cessed, and handled

in accordance with

the standards of

the USDA National

Organic Program.

Agricultural and Industrial Chemicals in Food 483

Debate Should You Go Organic?

The Issue: As people become more and more concerned about food safety, nutritional health, and the environment, they are turning to organic food. Is organic food safer, more nutritious, and more environmentally friendly than conventionally produced food?

The sale of organic foods is on the rise. Most of this increase has been from organic fruits and vegetables, which now represent 11.4% of all U.S. fruit and vegetable sales.24 Do organic production methods make these fruits and vegetables safer than traditional products? If safer is defined as containing fewer pesticides, the answer is clear. Organic foods are significantly lower in nitrates and pesticide residues than traditionally grown foods.25 But, it can be argued that there is little evidence that the current levels of pesticide exposure from conventional produce present risks to human health (see Figure 13.11). And, there are other contamina- tion risks associated with organic foods. Manure is often used for fertilizer. When the manure is not treated properly, it can contain pathogenic bacteria.26

Many consumers believe that organically produced food is not only safer but also more nutritious. Nutritious can mean that it is more effective at preventing nutrition-related diseases.27 When consumption of organic food is compared with consumption of conventionally produced foods, the majority of studies do not show organic foods to be beneficial in terms of preventing nutri- tion-related diseases. Research data on the nutrient content of organically produced food are ambivalent. Some studies report that organically produced foods contain more nutrients than con- ventionally produced food, and others have found no consistent differences in nutrient content.28 This confusion is not surprising

because many factors—including growing conditions, season, the fertilizer regime, and the methods used for crop protec- tion (for example, use of pesticides and herbicides)—affect the nutritional composition of fruits and vegetables. Nutrient content is also affected by how the food is stored, transported, and pro- cessed prior to consumption.

What about the environment? It is hard to argue that organic farming is not better for the environment. Instead of chemical pesticides and fertilizer, it relies on crop rotation, compost, and cover crops to maintain the soil. The result is preservation of the soil, so crops can be grown far into the future, and reduction in the amounts of chemicals released into the environment. But organic growing still impacts the environment because manure runoff can pollute waterways and because organic food is often shipped long distances. This shipping uses energy and pollutes the environment.

Is a diet based on organic foods safer, more nutritious, and bet- ter for the environment? We can assume that both conventional and organic foods sold in the United States are generally safe. Whether organic is more nutritious depends not only on individual foods but on the diet as a whole. If your choices of organic foods are limited by availability or cost, then choosing only organic may limit nutrient intake. Are organic foods better for the environment? They reduce pesticide and fertilizer use, but if organic foods are not available locally the environmental cost of transporting them may outweigh those savings.

Think critically: Are these organic onions that were shipped across the country a better environmental choice than conven- tionally grown onions from the farm across town?

THE PLANNER

484 CHAPTER 13 How Safe Is Our Food Supply?

move through the food chain into meat and milk (see Figure 13.10).

One group of carcinogenic compounds that pollutes the environment is polychlorinated biphenyls (PCBs). Prior to the 1970s, these chemicals were used in the manufacture of electrical capacitors and transformers, plasticizers, wax- es, and paper. PCBs in runoff from manufacturing plants contaminated water, particularly near the Great Lakes. PCBs are no longer produced, but because they do not de- grade, they are still in the environment and accumulate in fish caught in contaminated waters. PCBs are a particular problem for pregnant and lactating women because pre- natal exposure to PCBs and consumption of contaminated breast milk can damage the fetal and infant nervous system and cause learning deficits. Pregnant and breastfeeding women should check with their local health department for recommendations regarding fish consumption.

Other contaminants from manufacturing, such as chlor- dane (used to control termites); radioactive substances such as strontium-90; and toxic metals such as cadmium, lead, arsenic, and mercury, have found their way into fish and shellfish. Cadmium and lead can interfere with the absorp- tion of other minerals. Cadmium can cause kidney damage, and lead can impair brain development. Arsenic is believed to increase the risk of cancer. Mercury, which has been found in large fish, particularly swordfish, king mackerel, tilefish,

ingredients, sewage sludge, genetically modified ingredients, irradiation, antibiotics, and growth hormones are prohibited from use in organic food production. Before a food can be labeled “organic,” the USDA must certify the farming and processing operations that produce and handle the food (Figure 13.12).

Organic farming techniques reduce farm workers’ ex- posure to pesticides and decrease the quantity of pesticides introduced into the food supply and the environment. Or- ganic foods, however, are not completely free of synthetic pesticides and other agricultural chemicals not approved for organic use because irrigation water, rain, and a variety of other sources can introduce trace amounts into organi- cally grown foods. The threshold for pesticide residues in organic foods is set at 5% of the EPA’s pesticide-residue tolerance.23 Choosing organic food will reduce pesticide exposure, but it will not make your food risk free.

Industrial Contaminants Industrial chemicals that contaminate the environment find their way into the food supply. Fish accumulate substances from the water in which they live and feed. Shellfish accumulate contaminants because they feed by passing large volumes of water through their bodies. Pollutants in the water can also contaminate crops and

Products that meet the definition of “100% organic” or “organic” may display the USDA

“organic” seal shown here.

USDA ORGANIC

Labeling term Meaning

100% organic

Organic

Made with organic ingredients

Contains 100% organically produced raw or processed ingredients.

Contains at least 95% organically produced raw or processed ingredients.

Contains at least 70% organically produced ingredients.

Agricultural and Industrial Chemicals in Food 485

that antibiotic. Because nearly half the antibiotics pro- duced in the United States are used to prevent disease in animals, this use is suspected of being a major contribu- tor to the development of antibiotic-resistant strains of bacteria. 31

Hormones are used to increase weight gain in sheep and cattle and milk production in dairy cows. Some hor- mones, such as estrogen and testosterone, occur naturally. Generally, these are administered in slow-release form, and their levels are no higher in treated animals than in untreated animals. Before a synthetic hormone can be used, it must be demonstrated that hormone residues in meat from treated animals are within safe limits.

A synthetic hormone that has created public concern is genetically engineered bovine somatotropin (bST). Cows naturally produce bST, which stimulates milk pro- duction. Genetically engineered bST is produced by bacteria and injected into cows to further increase milk production ( ). Milk from cows that have been treated with genetically engineered bST is indistin- guishable from other milk.

and shark, damages nerve cells (Figure 13.13).29 Because mercury is especially damaging during prenatal develop- ment, pregnant women are advised to avoid certain types of fish and limit their consumption of others (see Chapter 11).

Antibiotics and Hormones Antibiotics and hormones are administered to animals to improve health, increase growth, or otherwise enhance food production. To prevent these chemicals from being passed on to consumers, both the types of drugs used and when they can be administered are regulated, and animal tissues are monitored for drug residues. 30

Animals are treated with antibiotics when they are sick, and some animals are also given antibiotics to pre- vent disease and promote growth. This treatment increas- es the amount of meat produced and reduces costs, but if it is used improperly, antibiotic residues can remain in the meat. Another concern is the creation of antibiotic- resistant bacteria. When exposed to an antibiotic, bacteria that are resistant to it survive and produce offspring that are also resistant. If these antibiotic-resistant bacteria in- fect humans, the resulting illness cannot be treated with

This Japanese boy has Minamata disease, a neurological

syndrome caused by mercury poisoning. The disease first

appeared in Minamata, Japan, in 1956 and was caused by the

release of mercury into the water by a local chemical factory. The

mercury accumulated in the fat of fish and shellfish that were

eaten by the local population.

Consumer groups are concerned that the injection of cows with

bST may cause health problems for humans who consume the

milk. The FDA has concluded that bST causes no serious long-

term health effects, and it does not require milk from bST-treated

cows to be specially labeled. Some dairies voluntarily label their

products as bST free.

486 CHAPTER 13 How Safe Is Our Food Supply?

and other toxins that are ingested by animals concentrate in fat, so intake can be reduced by trimming all fat from meat and removing the skin from poultry.

Intake of pesticides and other chemical pollutants from fish and seafood products can also be minimized by choosing wisely and consuming a variety of fish (Figure

). To minimize consumption of contaminants, re- move the skin, fatty material, and dark meat from fish. Use cooking methods such as broiling, poaching, boiling, and baking, which allow contaminants from the fatty portions of fish to drain out. Do not eat the “tomale” in lobster. The tomale, a green paste inside the abdominal cavity of a cooked lobster, serves as the liver and pancreas and is the organ in which toxins accumulate. The analo- gous organ in blue crabs, called the “mustard” because of its yellow color, should also be avoided (see What Should I Eat?).

Choosing Wisely to Minimize Agricultural and Industrial Contaminants

Even though individual consumers cannot detect chemi- cal contaminants in food, care in selection and prepara- tion can reduce the amounts consumed. One of the easiest ways to reduce risk is to choose a wide variety of foods, thus avoiding excessive consumption of contaminants that may be present in any one food. To reduce exposure to pesticide residues in fruits and vegetables, consumers can choose organic foods or locally grown produce. Locally grown pro- duce contains fewer pesticides because the pesticides used to prevent spoilage and extend the shelf life of shipped produce are not needed. Exposure to pesticide residues on conventionally grown produce can be minimized by wash- ing and in some cases peeling ( ). Pesticides

a. Pesticide residues on fruits and vegetables can be

removed or reduced by peeling or washing with tap water

and scrubbing with a brush, if appropriate. In the case of

leafy vegetables such as lettuce and cabbage, the outer

leaves can be removed and discarded. Washing apples,

cucumbers, eggplant, squash, and tomatoes may not remove

all the pesticides because these fruits and vegetables are

coated with wax in order to maintain freshness by sealing

in moisture, but wax also seals in pesticides. The wax and

pesticides can be removed by peeling, but removing the peel

also eliminates fiber and some micronutrients.

b. Exposure to chemical contaminants can be minimized by

choosing saltwater fish caught well offshore, away from polluted

coastal waters. Fish that live near the shore or spend part of their

life cycle in fresh water are more likely to contain contaminants.

Smaller species of fish are safer because they are earlier in the food

chain, and smaller fish within a species are safer because they are

younger and hence have had less time to accumulate contaminants

(see Figure 13.10).

WHAT SHOULD I EAT? Food Safety Avoid ingesting pathogenic microbes

Reduce pesticides and pollutants in your food

Use iProfile to compare the Calories and grams of fat in a chicken breast with and without skin.

THE PLANNER

1. How can a pesticide used on broccoli plants end up in milk?

2. How can organic food cause food-borne illness?

3. What can you do to minimize PCBs in your diet?

Technology for Keeping Food Safe LEARNING OBJECTIVES

1. Describe how temperature is used to prevent food spoilage.

2. Discuss how irradiation preserves food.

ood spoils when its taste, texture, or nutrition- al value is changed either by enzymes that are naturally present in the food or by microbes that grow on the food. For thousands of years,

3. Explain how packaging protects food.

4. Discuss the risks and benefits of food additives.

humans have treated food in order to prevent spoilage. Techniques that preserve food work by destroying enzymes present in the food, by killing microbes, or by slowing mi- crobial growth ( ).F

FAT TOM Table 13.5

Food

Acidity

Time

Temperature

Oxygen

Moisture

488 CHAPTER 13 How Safe Is Our Food Supply?

Most of the oldest methods of food preservation— heating, cooling, drying, smoking, and adding substances such as sugar or salt—are still used today. In addition, new- er methods, such as irradiation and specialized packaging, have been developed. While all these technologies offer benefits, they can also create risks. Some risk arises when

substances find their way into food, either accidentally or as a normal part of the production process. The FDA considers any substance that can be expected to become part of a food a food additive and regulates the types and amounts of food additives that may be present in a particular food. Unexpected substances that enter food are con- sidered accidental contaminants and are not regulated.

High and Low Temperature Cooking food is one of the oldest methods of ensuring that food is safe. Cooking kills disease- causing organisms and destroys most toxins. Other preserva- tion techniques that rely on high temperature to kill microbes in- clude pasteurization, sterilization, and aseptic processing (Figure 13.16). Lowering the tempera- ture of food by means of refrig- eration or freezing does not kill

microbes but preserves the food and protects consumers because it slows or stops microbial growth.

Preservation techniques that rely on temperature ben- efit consumers by providing appealing, safe foods, but these foods are not risk free, particularly if they are handled in- correctly. If foods are not heated long enough or to a high enough temperature, or if they are not kept cold enough, they could pose a risk of food-borne illness. In addition, some types of cooking can generate hazardous chemicals. Carci- nogenic chemicals produced during the cooking of meats include polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs). PAHs are formed when fat drips on a grill and burns. They rise with the smoke and are deposited on the surface of the food. PAH formation can be minimized by selecting lower-fat meat and using a layer of aluminum foil to prevent fat from dripping on the coals. HCAs are produced by the burning of amino acids and other substances in meats and are formed during any type of high-temperature cooking. HCA formation can be reduced by precooking meat, marinating meat before cook- ing, cooking at lower temperatures, and reducing cooking time by using smaller pieces of meat and avoiding over- cooking. The cooking temperatures recommended by the FDA are designed to prevent microbial food-borne illness and minimize the production of PAHs and HCAs. Because PAHs and HCAs are considered accidental contaminants, their amounts in food are not regulated by the FDA.

Another contaminant formed during food prepara- tion is acrylamide. It is formed as a result of chemical reactions that occur during high-temperature baking or frying, particularly in carbohydrate-rich foods. The highest levels of acryl amide are found in French fries

The juice boxes that fit so conveniently into school lunch bags are

produced by aseptic processing. This technique heats foods to

temperatures that result in sterilization. The sterilized foods are then

placed in sterilized packages, using sterilized packaging equipment.

If the package remains unopened, juice or milk packaged aseptically

can remain free of microbial growth at room temperature for years.

food additive A substance that is

intentionally added to

or can reasonably be

expected to become a

component of a food

during processing.

accidental con-

taminant A

substance not regu-

lated by the FDA that

unexpectedly enters

the food supply.

pasteuriza-

tion The process of

heating food products

in order to kill disease-

causing organisms.

aseptic process-

ing The placement

of sterilized food in a

sterilized package us-

ing a sterile process.

Technology for Keeping Food Safe 489

and snack chips. Smaller amounts are found in coffee and in foods made from grains, such as breakfast cereal and cookies. High doses can cause cancer and reproductive problems in experimental animals and act as neurotoxins in humans. Thus far, dietary exposure to acryl amide has not been associated with cancer in humans, and more research is needed to determine whether long-term, low- level exposure has any cumulative effects.32 Methods for reducing the amounts and potential toxicity of acrylamide in foods are being investigated.33

Food Irradiation Food irradiation, also called cold pasteurization, is used in more than 40 countries to treat everything from frog legs to rice. Irradiation exposes food to high doses of X-rays,

gamma radiation, or high-energy electrons in order to kill microbes and insects and inactivate en- zymes that cause germination and ripening of fruits and vegetables (Figure 13.17).34 Because irra- diation produces compounds that are not present in the original

foods, it is treated as a food additive, and the level of radia- tion that may be used is regulated. At the allowed levels of radiation, the amounts of these compounds produced are almost negligible and have not been found to pose a risk to consumers.35

Food irradiation is used relatively infrequently in the United States because of a lack of irradiation facilities and because of public suspicion of the technology. The word irradiation fosters the belief that the food becomes radioac- tive. Opponents of food irradiation claim that it introduc- es carcinogens, depletes the nutritional value of food, and is used to allow the sale of previously contaminated foods. In fact, irradiated food is not radioactive, and scientific studies conducted over the past 50 years have found that the benefits of irradiation outweigh the potential risks.36

Irradiation can decrease the amounts of certain nutrients in foods, but these nutrient losses are similar to those that occur with canning or refrigerated storage.35

Because irradiation can be used in place of chemical treatments, it reduces consumers’ exposure to chemical pesticides and preservatives. It is one of the technologies promoted by the National Food Safety Initiative because of its potential for improving the safety of food and reducing the incidence of food-borne illness.

a. Irradiated foods must be labeled with the radura

symbol shown here and the statement “treated

with radiation” or “treated by irradiation.” This

symbol is not required on the labels of foods

that contain irradiated spices or other irradiated

ingredients.

b. Irradiation increases the safety and shelf life of foods and does not compromise nutritional quality or noticeably change food texture, taste,

or appearance, as long as it is properly applied to a suitable product. After

two weeks in cold storage, the strawberries on the right, which were treated

by irradiation, remain free of mold, whereas the untreated strawberries on the

left, which were picked at the same time, are covered with mold.

irradiation A

process that exposes

foods to radiation in

order to kill contami-

nating organisms and

retard the ripening

and spoilage of fruits

and vegetables.

TREATED BY IRRADIATION

NON - IRRADIATED IRRADIATED

490 CHAPTER 13 How Safe Is Our Food Supply?

MAP is often used to package cooked entrées such as pasta primavera or beef teriyaki. The raw ingredients are sealed in a plastic pouch, the air is vacuumed out, and the pouch and its contents are partially precooked and imme- diately refrigerated. This processing eliminates the need for the extreme cold of freezing or the extreme heat of canning, so flavor and nutrients are better preserved. Be- cause these products are not heated to temperatures high enough to kill all bacteria and are not stored at temper- atures low enough to prevent all bacteria from growing, they could pose a food safety risk. To ensure safety, fresh refrigerated foods should be purchased only from repu- table vendors, used before the expiration date printed on the package, refrigerated until use, and heated according to the time and temperature directions on the package.

Packaging can protect food from spoilage, but even the best packaging can introduce risk if it becomes part of the food. A variety of substances found in paper and plas- tic containers and packaging, and even dishes, can leach into food ( ). Substances that are known to contaminate food are regulated by the EPA and the FDA. However, these regulations apply only to the intended use of the product. When a product is used improperly, sub- stances from its packaging can migrate into food. For in- stance, some plastics migrate into food when heated in a microwave oven. Thus, only containers designed for micro- wave cooking should be used for microwaving food.

modified atmo-

sphere packaging

(MAP) A preserva- tion technique used to

prolong the shelf life

of processed or fresh

food by changing the

gases surrounding the

food in the package.

Bisphenol A is a chemical found in

polycarbonate plastic used to manufacture

hard, transparent water bottles, baby bottles,

and food containers as well as the coating

inside cans. The transfer of bisphenol A into

food and water is a concern for pregnant

women and infants. A review by the U.S.

National Toxicology Program found that

although there is negligible risk of adverse

effects in most adults, exposure of pregnant

women to bisphenol A could affect fetal

brain development, and exposure of infants

and children to the chemical could affect the

nervous system and accelerate puberty. 37

Food Packaging Packaging plays an important role in food preservation; it keeps molds and bacteria out, keeps moisture in, and protects food from physical damage. An open package of refrigerated cheddar cheese will be moldy in a few days, but an unopened package will stay fresh for weeks.

Food packaging is continually being improved. In the past two decades, for instance, consumer demand for fresh and easy-to-prepare foods has led manufacturers to offer partially cooked pasta, vegetables, seafood, fresh and cured meats, and dry products such as whole-bean and ground coffee in packaging that, if unopened, will keep perishable food fresh much longer than will conventional packag- ing. Modified atmo sphere packaging (MAP) uses plastics or other packaging materials that are impermeable to oxygen. The air inside the package is vacuumed out in

order to remove the oxygen. The product can then remain pack- aged in a vacuum, or the package can be infused with another gas, such as carbon dioxide or nitro- gen. The lack of oxygen prevents the growth of aerobic bacteria, slows the ripening of fruits and vegetables, and slows down oxida-

tion reactions, which cause discoloration in fruits and veg- etables and rancidity in fats.

Technology for Keeping Food Safe 491

Food Additives What keeps bread from molding, gives marga- rine its yellow color, and keeps Parmesan cheese from clumping in the shaker? The answer to all these questions is food additives. Substances that are intentionally added to foods are called direct food additives. Other substances that get into food unintentionally—such as the oil used to lubricate food processing machinery— are referred to as indirect food additives. The FDA regulates the amounts and types of direct and indirect food additives in food.

Regulating food additives Food additives improve food quality and help protect us from disease, but if the wrong additive is used or the wrong amount is added, it could do more harm than good. A manufacturer that wants to use a new food additive must submit to the FDA a petition that describes the chemical composition of the additive, how it is manufactured, and how it is detected in food. The manufacturer must prove that the additive will be effective for its intended purpose at the

proposed levels, that it is safe for its intended use, and that its use is necessary. Additives may not be used to disguise inferior products or deceive consumers. They cannot be used if they significantly destroy nutrients or if the same effect can be achieved through sound manufacturing processes.

More than 600 chemicals defined as food additives were already in common use when legislation regulating food additives was passed. To accommodate substances that the FDA or the USDA had already de- termined to be safe, they were designat- ed as prior-sanctioned substances and are exempt from regulation. The nitrates

and nitrites used to retard the growth of Clostridium botulinum in cured meats are prior-sanctioned substances, for instance. However, their use has been controversial be- cause they form carcinogenic nitrosamines in the diges- tive tract. They are still allowed in foods, however, because they prevent botulism, and there is little evidence that they pose a serious risk in the amounts consumed in the human diet ( ).38

To minimize any risk posed by nitrosamines without increasing the risk of bacterial food-

borne illness, the FDA limits the amount of nitrate and nitrite that can be added to food

and requires the addition of antioxidants such as vitamin C, which reduce nitrosamine

formation, to foods that contain these additives. Consumers can reduce nitrosamine

exposure by limiting their consumption of cured meat to 3 to 4 ounces per week and

maintaining adequate intakes of the antioxidant vitamins C and E.

INGREDIENTS: MECHANICALLY

SEPARATED CHICKEN, WATER, PORK,

MODIFIED CORN STARCH, DEXTROSE,

SALT, BEEF, CONTAINS 2% OR LESS

OF THE FOLLOWING: CORN SYRUP,

FLAVORINGS, SODIUM PHOSPHATES,

POTASSIUM LACTATE, SODIUM

DIACETATE, SODIUM ASCORBATE

(VITAMIN C), OLEO RESIN OF PAPRIKA,

SODIUM NITRITE

direct food addi-

tive A substance that

is intentionally added

to food. Direct food

additives are regu-

lated by the FDA.

indirect food addi-

tive A substance that is expected to unin-

tentionally enter food

during manufacturing

or from packaging.

Indirect food additives

are regulated by the

FDA.

492 CHAPTER 13 How Safe Is Our Food Supply?

Common food additives40 Table 13.6

Type of additive What’s on the label What they do Where they are used

Technology for Keeping Food Safe 493

Sensitivities to additives Some individuals are allergic or sensitive to certain food additives. For example, the flavor enhancer monosodium glutamate (MSG), commonly used in Chinese food, can cause adverse reactions known as MSG symptom complex or Chinese restaurant syndrome in sensitive individuals (see Chapter 6). Sulfites can cause symptoms ranging from stomachache and hives to severe asthma. Sulfites are used as preservatives in baked goods, canned foods, condiments, and dried fruits. Sensitive individuals can identify foods that contain sulfites by checking food labels. The forms of sulfites allowed in packaged foods include sulfur dioxide, sodium sulfite, sodium and potassium bisulfite, and sodium and potassium metabisulfite. Foods served in restaurants may also contain sulfites. For example, a potato dish served in a restaurant may be prepared using potatoes that were peeled and soaked in a sulfite solution before cooking.

Color additives can also cause adverse reactions. FD&C yellow no. 5, for instance, listed as tartrazine on medicine labels, may cause itching and hives in sensitive people. It is found in beverages, desserts, and processed vegetables. Color additives are listed in the ingredient list along with other food additives. Colors in foods are clas- sified as certified or exempt. Certified colors are human- made, meet strict specifications for purity, and must be listed by name in the ingredient list. Colors that are ex- empt from certification include pigments from natural sources such as dehydrated beets and carotenoids; these may be listed collectively in the ingredient list as “artifi- cial color.”

A second category that is not subject to food additive regulation consists of substances generally recognized as

safe (GRAS), based either on their history of use in food before 1958 or on published scientific evidence. However, just because a substance is on the GRAS or prior-sanctioned list doesn’t mean that it is safe or that it will stay on these lists. If new evidence suggests that a sub- stance in either category is unsafe, the FDA may take action to require

that the substance be removed from food products. Substances that are toxic at some level of consump-

tion may be harmless at a lower level. To ensure that addi- tives are safe, most of those that are allowed in foods can be added only at levels 100 times below the highest level that has been shown to have no harmful effects. This is a greater margin of safety than exists for many vitamins and other naturally occurring substances.

The regulations for substances that cause cancer are far more rigid because of the Delaney Clause, part of the 1958 Food Additives Amendment. It states that a sub- stance that induces cancer in either an animal species or humans, at any dosage, may not be added to food. Debate continues regarding whether the Delaney Clause should be liberalized to allow the use of substances that are added at a level so low that they would not represent a significant health risk.

Identifying food additives Food additives are used to make food safer; maintain palatability and wholesomeness; improve color, flavor, or texture; aid in processing; and enhance nutritional value (Table 13.6 ). Their use ensures the availability of wholesome, appetizing, and affordable foods that meet consumer demands throughout the year. The FDA’s database Everything Added to Food in the United States lists more than 3000 additives.39 Many of these, such as sugar and spices, are used in homes every day. Other additives may sound like a chemical soup: calcium propionate in bread, disodium EDTA in kidney beans, and BHA in potato chips. Understanding what these chemicals are used for can help make the ingredient list a source of information rather than a cause for concern.

generally rec-

ognized as safe

(GRAS) A group

of chemical addi-

tives that are consid-

ered safe, based on

their long-standing

presence in the

food supply without

harmful effects.

1. What is pasteurization? 2. How does irradiation help extend the shelf life

of food? 3. How does modified atmosphere packaging pre-

vent food spoilage? 4. Why are food additives regulated?

494 CHAPTER 13 How Safe Is Our Food Supply?

Biotechnology LEARNING OBJECTIVES

1. Explain how genetic engineering introduces new traits into plants.

2. List ways in which genetic engineering is being used to enhance the food supply.

3. Discuss some potential risks associated with genetic engineering.

4. Describe how genetically modified foods and crops are regulated to ensure safety.

iotechnology alters the characteristics of organisms by making selective changes in their DNA. The concept is not new. For cen- turies, farmers have selected seeds from

plants with the most desirable characteristics to plant for the next year’s crop, bred the animals that grew fastest or

produced the most milk to improve the productivity of the next gen- eration of animals, and crossbred plant varieties to combine the de- sired traits of each. However, these traditional methods may require many generations to produce the desired results. Biotechnology uses

genetic engineering to select genes for specific traits. Ge- netic engineering has significantly sped up the process of modifying the traits of organisms. Like all other new tech- nologies, however, it may introduce new risks.

How Biotechnology Works Genetically modified (GM) crops are created through genetic en- gineering: A piece of DNA con- taining the gene for a desired characteristic is taken from plant, animal, or bacterial cells and transferred to plant cells (Figure 13.20). The DNA is then referred to as recombinant DNA because the new DNA is a combination of

the DNA from two organisms. The modified cells are then allowed to divide into more and more cells and eventually

biotechnol-

ogy The process

of manipulating life

forms via genetic

engineering in order

to provide desirable

products for

human use.

Engineering a genetically modified plant Figure 13.20

P R

O C

E S

S D

IA G

R A

THE PLANNER

6 7

Nucleus

Plant cell wall

Special culture

medium allows

the cells to dif-

ferentiate into the

various types of

cells that make up

a whole plant.

Compare the number of genes trans- ferred by genetic engineering to the number transferred by traditional plant breeding.

T h i n k C r i t i c a l l y

genetic engineer-

ing A set of tech-

niques used to ma-

nipulate DNA for the

purpose of changing

the characteristics of

an organism or creat-

ing a new product.

recombinant DNA

DNA that has been

formed by joining

DNA from different

sources.

transgenic An

organism with a gene

or group of genes in-

tentionally transferred

from another species

or breed.

differentiate into the various types of cells that make up a whole plant. The new plant is a transgenic organism. Each cell in the new plant contains the transferred gene for the desired trait. This technique is used to introduce characteris- tics such as disease and drought resistance into plants. Genetic engineering is more difficult in animals because animal cells do

The desired gene is identified.

The gene is clipped out using

DNA-cutting enzymes.

Various techniques are used

to transfer the gene into the

plant cell.

The gene migrates to

the cell’s nucleus and

is integrated into the

plant’s DNA.

Modified plant cells

are identified and

placed into cell culture

medium to multiply.

Each mature

plant carries

the new

gene and

the trait

for which it

codes.

Nutrition InSight The potential of biotechnology

a. Insect-resistant corn is created by

inserting a gene from the bacterium Bacillus thuringiensis (or Bt). The gene produces a protein called Bt toxin that is toxic to certain

insects, such as this European corn borer,

but safe for humans and other animals. The

presence of the new gene improves the

crop yield and also reduces the amounts of

chemical pesticides that need to be applied.

c. Half the world’s population depends on rice

as a dietary staple, but rice is a poor source

of vitamin A. Genetically modified rice, called

golden rice (seen here compared with white

rice) for the color imparted by the -carotene

pigment, has the potential to significantly

increase vitamin A intake (discussed further

in Chapter 14 Debate). One variety contains enough provitamin A in 1/2 cup of dry rice to

provide more than 50% of the RDA for a child.44

1992 1994 1996 1998 2000 Year

Virus introduced

GM seeds released

P a

p a

ya p

ro d

u ct

io n

( m

ill io

n p

o u

n d

70b. In the 1990s the papaya crop

in Hawaii was severely diminished

by the papaya ring-spot virus (PRSV).

In response, researchers developed

papaya that is genetically enhanced

to resist PRSV. The seeds were

released for commercialization in

1998, allowing Hawaiian papaya

production to rebound.42 This was

the first genetically enhanced fruit

crop on the market. Genes for

resistance to various viruses have

also been used to create virus-

resistant strains of potatoes, squash,

cucumbers, and watermelons.43

enzymes. Rennet, an enzyme used in cheese production; enzymes used in the production of high-fructose corn syrup; and the enzyme lactase, used to reduce the lactose content of milk, are now all produced by GM microbes.

Biotechnology also has great potential for addressing the problem of world hunger and malnutrition. Although world hunger is rooted in political, economic, and cultural issues that cannot be resolved by agricultural technology alone, GM crops that target some of the major nutritional deficiencies worldwide are being developed. To address protein deficiency, varieties of corn, soybeans, and sweet potatoes with enhanced levels of essential amino acids are being developed. To address vitamin A deficiency, genes that code for the production of enzymes needed for the synthesis of the vitamin A precursor -carotene have been inserted into rice (Figure 13.21c).44 To address multiple nutrient deficiencies, the BioCassava Plus program has used biotechnology to develop cassava with increased zinc, iron, protein, and vitamin A levels.45

not take up genes as easily as plant cells do, and making copies of these cells (clones) is also more difficult. Howev- er, these techniques have been used to produce cows that yield more milk, cattle and pigs with more meat on them, and sheep that grow more wool.41

Applications of Biotechnology The techniques of biotechnology can be used in a variety of ways in food production to alter quantity, quality, cost, safety, and shelf life. By making plants resistant to herbi- cides, insects, and various plant diseases, this technology has increased crop yields and reduced damage from insects and plant diseases (Figure 13.21a and b). By altering enzyme activity and other traits, biotechnology is being used to increase the shelf life of fresh fruits and vegetables and create products that have greater consumer appeal, such as seedless grapes and watermelons.

Biotechnology is also used in food processing. For example, many foods are produced with the help of

THE PLANNER

496 CHAPTER 13 How Safe Is Our Food Supply?

genes. If farmers plant only GM insect-resistant, high- yielding crops, other species and varieties may eventually become extinct, and the genes for the traits they possess may be lost forever.

Another environmental issue is the possibility that GM crops will create “superweeds.” This might occur, for example, if a trait such as increased rate of growth introduced into a domesticated plant species were passed on to a related wild species. This could produce a fast- growing weed, or superweed, that would compete with the domesticated species. As a safeguard, plant developers are avoiding introducing genes for traits that could increase a plant’s competitiveness or other undesirable properties in weedy relatives.

There is also concern that crops that have been engi- neered to produce pesticides will promote the evolution of pesticide-resistant insects. An illustration is the case of in- sects that feed on plants modified to produce the Bt toxin (see Figure 13.21a). As more and more of the insects’ food supply consists of plants that produce this pesticide, only insects that carry genes that make them resistant to Bt toxin survive and reproduce. This increases the number of Bt-resistant insects and therefore reduces the effectiveness of Bt toxin as a method of pest control. Although an impor- tant concern when growing GM crops, pesticide-resistant insects may also evolve when pesticides are sprayed on crops.

Regulation of GM food products The most common GM crops are soybeans, corn, cotton, and rapeseed (or canola) (Figure 13.22). Therefore, foods produced in the United States that contain corn or high-fructose corn syrup, such as many breakfast cereals, snack foods, and soft drinks; foods made with soybeans and foods made

Risks and Regulation of Biotechnology The rapid advancement of biotechnology during the past decade has created the potential for health problems and environmental damage. Regulations are in place to con- trol the use of genetic engineering and GM products. De- spite these precautions, many consumers and scientists believe that the impact of this booming technology has not yet become apparent. They urge that this technology be used with caution to avoid health or environmental im- pacts that outweigh the benefits.

Consumer concerns Consumer safety concerns related to GM foods include the possibility that the nutrient content of a food may have been negatively affected or that an allergen or a toxin may have inadvertently been introduced into a food that was previously safe. For example, if DNA from fish or nuts—foods that commonly cause allergic reactions—were introduced into soybeans or corn, these foods would then be dangerous to individuals allergic to fish or nuts. To prevent this kind of situation from occurring unintentionally, biotechnology companies have established systems for monitoring the allergenic potential of proteins used for plant genetic engineering. In 1996, allergy testing successfully prevented soybeans containing a gene from a Brazil nut from entering the market.46

Environmental concerns An environmental concern about GM crops is that they will be used to the exclusion of other varieties, thereby reducing biodiversity. The ability of populations of organisms to adapt to new conditions, diseases, or other hazards depends on the presence of many different species and varieties that provide a diversity of

Year

A cr

e s

o f G

M c

ro p s

(m ill

io n s)

100

150

200

250

300

350

1996 1998 2000 2002 2004 2006 2008

Despite concerns about the impact of GM crops, the

number of acres planted with them worldwide has risen

steadily.

Summary 497

Keeping food safe from farm to table

Summary

1Keeping Food Safe 466 Most food-borne illness is caused by food contaminated with disease-causing microbes; occasionally, it can be caused by chemical contaminants in food. The harm caused by contaminants in the food supply depends on the type of toxin, dose, length of time over which the contaminant is consumed, how it is metabolized and excreted, and the size, age, and health of the consumer.

The food supply is monitored for safety by food manufactur- ers, as shown here, and regulatory agencies at the inter- national, federal, state, and local levels. Federal programs promote the use of Hazard Analysis Critical Control Point (HACCP) systems to prevent and eliminate food contami- nation rather than catch it after it occurs. Consumers can prevent most cases of food-borne illness by following safe food-handling and preparation guidelines.

THE PLANNER

supply before its safety has been established, the FDA has asked developers to provide them with information about the safety of the new plants at a relatively early stage of development.47

The USDA regulates agricultural products and re- search concerning the development of new plant varieties, including those developed through genetic engineering. The EPA regulates any pesticides that may be present in foods and sets tolerances for these pesticides. This includes GM plants containing proteins that protect them from insects or disease.

with cottonseed and canola oils, are likely to contain GM ingredients. You don’t recognize these foods as genetically modified because they appear no different from other foods, and food manufacturers are not required to provide special labeling unless the food is known to pose a potential risk.

To ensure that GM plants and foods cause no harm to consumers or to the environment, the FDA, the USDA, and the EPA are all involved in overseeing plant biotech- nology. Safety and environmental issues are monitored at all stages of the process. The FDA regulates the safety and labeling of foods containing GM ingredients. Labeling of foods containing GM ingredients is required only if the nutritional composition of the food has been altered; if it contains potentially harmful allergens, toxins, pesticides, or herbicides; if it contains ingredients that are new to the food supply; or if it has been changed significantly enough that its traditional name no longer applies. Premarket ap- proval is required when the new food contains a substance that is not commonly found in foods or when it contains a substance that does not have a history of safe use in foods. To prevent material from a new plant variety in- tended for food use from inadvertently entering the food

1. Where does the DNA introduced into GM plants come from?

2. How does biotechnology increase crop yields? 3. Why might a GM food cause an allergic reaction

when the unmodified food does not? 4. What types of GM foods carry special labels?

498 CHAPTER 13 How Safe Is Our Food Supply?

Pesticides help increase crop yields and the quality of pro- duce. To decrease the risk of pesticide toxicity, tolerances are established, and foods are monitored for pesticide resi- dues. Safer pesticides are being developed, and U.S. farmers are reducing the amounts applied by using integrated pest management (IPM) and organic food production methods.

2Pathogens in Food 470 The pathogens that affect the food supply include bacteria, viruses, molds, parasites, and prions. Some bacteria cause food-borne infection because they are able to grow in the gastrointestinal tract when ingested. Others produce toxins in food, and consumption of the toxin causes food-borne intoxication.

Viruses do not grow on food, but when consumed in food, they can reproduce in human cells and cause food-borne illness.

Molds that grow on foods produce toxins that can harm consumers.

Parasites include microscopic single-celled animals, as well as worms that can be seen with the naked eye. They are consumed in contaminated water or food.

Improperly folded prion proteins cause bovine spongiform encephalopathy (BSE) in cattle. The risk of acquiring the human form of this deadly degenerative neurological disease is extremely low.

The risk of food-borne illness can be decreased through proper food selection, preparation, and storage to kill pathogens or minimize their growth. These steps are emphasized by the Fight Bac! campaign illustrated here.

Safe food handling, storage, and

Small marine animals

Water plants and microscopic animals

Small fish (sardines and herring)

Large fish (tuna)

Concentrations are greater in large fish such as tuna than in algae (tiny marine organisms) or in small fish such as sardines and herring.

3 Agricultural and Industrial Chemicals in Food 481 Contaminants in the environment can find their way into the food supply. Those that deposit in the fatty tissue of animals are not eliminated, leading to bioaccumulation as they pass through the food chain, as illustrated here.

Contamination throughout the food

Clean Wash hands and surfaces often.

Chill Refrigerate promptly

Separate Don’t cross- contaminate.

Cook Cook to proper temperatures.

K e

e p

o o

d S a f e F r o

m B

a c

te r

IG H T B A C !

BA C!

Summary 499

Direct food additives are used to preserve or enhance the appeal of food. Indirect food additives are substances known to find their way into food during cooking, process- ing, and packaging. Both are FDA regulated. Accidental contaminants, which enter food when it is handled or pre- pared incorrectly, are not regulated by the FDA.

5 Biotechnology 494 Biotechnology produces genetically modified (GM) crops by transferring a gene for a desired characteristic from one organism to another, as shown here. The result is a transgenic organism.

Engineering a genetically modified

Industrial pollutants such as PCBs have contaminated some waterways and the fish and shellfish that live in them. Larger, longer-lived fish and those that live in contaminated waters have the highest concentrations.

Antibiotics and hormones are used in animal food produc- tion. The amounts entering the food supply pose little risk, but the use of antibiotics contributes to the development of antibiotic-resistant strains of bacteria.

Consumers can reduce the amounts of pesticides and other environmental contaminants in food by carefully selecting and handling produce, selecting saltwater varieties of fish caught far offshore in unpolluted waters, and trimming fat from meat, poultry, and fish before cooking.

4Technology for Keeping Food Safe 487 Heating foods to high temperatures, cooling them to low temperatures, and altering levels of acidity, moisture, and oxygen prevent food spoilage and lengthen shelf life by killing microbes or slowing their growth.

Irradiation preserves food by exposing it to radiation. This process kills microbes, destroys insects, and slows the ger- mination and ripening of fruits and vegetables. Irradiated foods can be identified by the symbol shown here.

TREATED BY IRRADIATION

Packaging keeps molds and bacteria out of foods, keeps moisture in, and protects food from physical damage. Modified atmosphere packaging (MAP) reduces the oxygen available for microbial growth. The safety of packaging materials must be considered because components of packaging can leach into food.

Biotechnology has the potential to improve the volume, safety, and quality of the food supply, but it also has the potential to introduce allergens or toxins into foods or to negatively affect nutrient content. Environmental concerns about the use of GM crops include reduction of biologic diversity, creation of “superweeds,” and evolution of pesticide-resistant insects. Regulations are in place to control the use of genetic engineering and GM products.

Plant cell wall

Nucleus

500 CHAPTER 13 How Safe Is Our Food Supply?

Key Terms

Online Resources

www.

WileyPLUS

Critical and Creative Thinking Questions 1.

Campylobacter

Salmonella

What is happening in this picture? 501

7. Brassica is a genus of plants that includes cabbage and broc- coli, as well as a number of weeds. What risks might be as-

sociated with the use of a new genetically engineered variety

of Brassica that grows faster and produces more seeds than traditional varieties?

5. Fermentation, a process that uses microbes to convert carbo-

hydrates into alcohols or acids, is used to produce alcoholic

beverages and yogurt. Explain how fermentation converts

milk into yogurt and why yogurt will keep longer than milk.

6. A train crash spills a load of industrial waste into a river that

feeds into a local reservoir. Bottled water is provided to the

residents of the community. How might this spill impact other

segments of the food supply?

What is happening in this picture?

1. How could ergotism cause individuals to appear “bewitched“?

2. Why might moldy rye have been more of a prob- lem in the 17th century than it is today?

3. Why doesn’t baking prevent this ailment?

T h i n k C r i t i c a l l y

These rye plants are infected with a fungus. When the grain is

consumed, the fungal toxins cause a syndrome called ergotism.

The symptoms include prickling skin sensations, facial distor-

tions, incomprehensible speech, paralysis, hallucinations, convul-

sions, and dementia. Ergotism may have caused some of the

symptoms exhibited by individuals who were supposedly cursed

by the “witches” of 17th-century Salem, Massachusetts.48

502 CHAPTER 13 How Safe Is Our Food Supply?

7. Below what temperature should food be refrigerated to re-

duce bacterial growth?

a. A b. B c. C d. D

Self-Test (Check Your Answers in Appendix K.)

1. What is the major cause of food-borne illness in the United

States today?

a. pesticides

b. microbes

c. environmental toxins

d. antibiotics

2. Which factor affects the likelihood that a contaminant will

cause food-borne illness in an individual?

a. body size

b. immune status

c. age

d. dose of toxin

e. all of the above

3. Foods on the GRAS list _________.

a. are definitely safe

b. have been used for years without ill effect

c. are green

d. do not need to be listed in an ingredient list

4. Which of the following is not true of a HACCP system?

a. It relies on visual food inspections.

b. It identifies steps in food production where contamination

can occur or be prevented.

c. Designing and implementing a HACCP system is the respon-

sibility of a food manufacturer.

d. It requires extensive record keeping.

e. It monitors critical points in food production and takes cor-

rective action if criteria are not met.

5. The foods that most frequently cause Salmonella infection are _________.

a. beef and pork

b. dairy products

c. eggs and poultry

d. shellfish

6. Pathogenic bacteria are killed by _________.

a. freezing

b. cooking

c. refrigeration

d. marinating

260°

220°

240°

200°

180°

160°

140°

120°

100°

80°

60°

40°

20°

0°

212°F

C100°F

B40°F

A0°F

8. Which organism can cause food-borne intoxication and can be

present in honey and home-canned foods?

a. Escherichia coli

b. Clostridium perfringens

c. Clostridium botulinum

d. Salmonella

9. Which of the following is most likely to be a concern in ham-

burger that is cooked to well done on a grill?

a. polycyclic aromatic hydrocarbons (PAHs)

b. Escherichia coli

c. Giardia

d. prions

Self-Test 503

14. At what step in the process shown here is recombinant DNA

formed?

a. 1

b. 3

c. 4

d. 6

e. 7

10. Raw hamburger patties are taken to the grill on a platter.

After being cooked, they are returned to the unwashed plat-

ter and served. This is an example of ___________.

a. efficient use of kitchen equipment

b. food intoxication

c. cross-contamination

d. a HACCP system

11. Glass that enters food from a broken jar is ___________.

a. regulated as an indirect food additive

b. not regulated

c. safe because the glass is sterilized

d. regulated as an accidental contaminant

12. Which organism in this diagram is most likely to contain the

highest concentration of industrial contaminants?

a. A b. B c. C d. D

Agricultural chemicals

Industrial wastes

A B

Groundwater, irrigation

water, waterways, lakes, oceans

6 7

Nucleus

Plant cell wall

13. The potential benefits of biotechnology include all of the fol-

lowing except _________.

a. increased biodiversity

b. enhanced disease resistance

c. improved crop yields

d. reduced pesticide use

15. The insignia shown here means the food _________.

a. is not safe to eat

b. has been irradiated

c. is radioactive

d. can safely be stored without refrigeration

Review your Chapter Planner on the chapter opener and

check off your completed work.

THE PLANNER

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