Download LESSON 1.3 WORKBOOK Food Safety

LESSON 1.3 WORKBOOK
Food Safety
DEFINITIONS OF TERMS
Microbe — A microorganism,
such as a bacteria or virus, that
causes a disease or fermentation.
Heavy metal —
­ A metal with
relatively high density or a high
relative atomic weight. Lead,
mercury and cadmium are all
heavy metals.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 1.3
In Lesson 1.2 we identified food additives and investigated their pros and cons; today we will focus
on how food can be contaminated by microbes or
harmful chemicals. We have seen how vast and
complex the process of food production can be.
Food can be contaminated with microbes or harmful chemicals at each stage of production: growth,
harvest, processing, transport, sales and preparation. In this lesson, real cases of food-borne
illnesses will be discussed to illustrate how food
contamination can impact our health.
How does our food get contaminated?
What is the difference between a food additive and a contaminant? Food contaminants are chemicals or
microbes that accidentally enter our food system and are harmful to human health. Using this definition,
some chemicals can be unintentional food additives and food contaminants. Being a contaminant implies
that the chemical or microbe is harmful to your health. Identifying contaminants and their sources can be
challenging, and consumers may consider a certain chemical or food additive a contaminant even though
it is not officially recognized by the government as a harmful substance. For example, some people believe
that eating GMO crops is harmful to their health, even though there hasn’t been enough scientific research
to either support or deny this claim
You’ve probably had food in your house contaminated by fungus in the form of mold. Food left in the
refrigerator, or bread left uneaten is a perfect environment for mold spores. Fortunately, mold is a visibly
obvious food contaminant, so we can avoid eating it. Other food contaminants are not so obvious, like
bacteria or heavy metal poisoning, and can cause hundreds or thousands of people or pets to get sick
before the contaminant is identified. Additionally, even if a contaminant is identified, the complexity of the
food production process may make it very hard to find the source.
1. The difference between food
additives and contaminants is:
aa. Food additives are always added
intentionally.
bb. Contaminants are always added
intentionally.
cc. Contaminants are harmful to
your health, additives aren’t.
dd. They are the same.
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LESSON READINGS
Contamination of food when it is growing
Bacteria and fungi, like mold, require water and a
food source to survive. These microbes can come
into contact with our food supply in many ways,
starting when the food is being grown. Factory
farming has led to livestock being raised in close
living quarters, which encourages the spread of
infectious diseases. Like we learned in Lesson 1.2,
livestock may be administered antibiotics to prevent
Figure 1: Manure lagoons located
the transmission of disease, but some bacteria can
next to large feeding facilities have
still find their way into the manure of the animals,
ideal conditions for microbes to thrive.
where the bacteria thrive on the organic matter. In
These microbes can contaminate our
meat, or even crops growing nearby.
large animal feeding facilities the manure is collected
in ponds called manure lagoons, like the one on the
right (Figure 1), where the waste can be managed
before re-entering the water system. Bacteria from these lagoons can be transmitted to other livestock or
even onto produce growing nearby through water or wildlife.
Some contaminants enter the food supply from the environment. Mercury is abundant in the environment
and is converted to the neurotoxin methylmercury by bacteria in water. When consumed by humans,
methylmercury can cause nerve damage, fatigue and learning delays. Fish are our primary dietary
source or methylmercury. Although we can all tolerate a
low amount of methylmercury, children and breast-feeding
women are at risk for methylmercury poisoning. To limit
exposure, do not eat fish with high levels (swordfish,
mackerel and tilefish) and limit your consumption to fish
with lower levels (white tuna, shrimp, pollock, salmon and
catfish).
Wo r k b o o k
Lesson 1.3
Figure 2: Heavy metals and
minerals are absorbed from
soils into the leaves and fruits
of plants.
Other heavy metals, like lead and cadmium, can contaminate crops through soil. Some regions are prone to having
higher metal content in the soil, like former industrial areas.
Along with helpful minerals, plants can absorb harmful
metals from the soil through their roots, ultimately leading
to a crop containing the chemical. Some of these metals
are essential to our health, like iron and zinc, while lead,
cadmium and arsenic are contaminates.
2. When being grown, foods can be
contaminated by:
aa. Natural chemicals they absorb
from their environment.
bb. Microbes they contact in their
environment.
cc. Chemicals humans have left in
their environment.
dd. All of the above.
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24
LESSON READINGS
Contamination of food as it is preserved, processed or transported
During the canning or preservation process microbes can get
into the food. While most microbes need oxygen to survive,
Clostridium botulinum is a type of bacteria that lives in low
oxygen conditions, such as canned food. When consumed,
these bacteria can cause vomiting, diarrhea, double vision,
muscle weakness and even death. (Interestingly, the same
bacteria create the Botulinum toxin that paralyzes muscles,
Figure 3: Damaged cans
commonly known as Botox®.) If food is processed or transmay contain botulism.
ported in an unsterile environment bacteria contamination can
occur, and the microbes can live in our food unnoticed until they
cause severe illnesses. One example of a common microbial
food contaminant introduced during food processing is Listeria. When food processing equipment, like
those used to mechanically separate meats, is not cleaned properly the bacteria can get into the food. In
fact, Listeria can be found in many deli meats and some soft cheeses. Listeria infection can lead to diarrhea, fever and abdominal cramps. In fact, this is why pregnant women are recommended to avoid eating
lunch-meats and soft cheeses.
Chemical contamination can also be introduced during food processing. For example, some heavy metals
like cadmium, copper, iron, tin and zinc can be consumed by eating foods or beverages that are improperly processed, stored or cooked in containers containing these metals. Typically, food processors will put
foods through a metal detector before shipping them off to the consumer, but despite this precaution there
is still a risk of heavy metal poisoning from processed foods. Chemical contamination of foods can also
occur during food processing. For example, the common preservatives sodium benzoate and ascorbic
acid in soft drinks can react to make benzene, a chemical that is a known carcinogen, although the levels
of benzene in soda are low.
Step in Food Production
Growth of crops or livestock
Wo r k b o o k
Lesson 1.3
Growth of crops or livestock
Processing of food
Packaging of food
Possible Contaminant(s) Introduced
Pesticides, herbicides, heavy metals (mercury, lead,
cadmium), microbes
Microbes
Microbes, chemicals (benzene)
Heavy metals (copper, tin, zinc), plastics
3. All of the following are common
contaminants introduced during
food processing and transport,
except:
aa. Listeria.
bb. Salmonella.
cc. Mercury.
dd. Benzene.
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Figure 4: Common steps in food production where contamination may occur.
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LESSON READINGS
Transportation of food opens up another possibility of contamination. If food is transported in a temperature that promotes microbe growth, bacteria may grow to harmful levels before the food product reaches
the consumer. Additionally, large tanks that carry unpasteurized liquids need to be carefully cleaned
between shipments. Any error in proper cleaning could lead to growth of pathogenic bacteria. Another
common food contaminant introduced when food is growing and being transported is Salmonella. Eating
food contaminated with salmonella may lead to diarrhea, fever, abdominal cramps and vomiting. Salmonella may come in contact with the food when contaminated manure is used to fertilize crops or when
contaminated shipping containers or ice contact the food.
Organism
Salmonella
Onset after Signs & Symptoms Duration
ingesting
6-48 hours Diarrhea, fever,
4-7 days
abdominal cramps,
vomiting
Listeria
3-70 days
monocytogenes
Methylmercury Varies
Diarrhea, fever,
abdominal cramps
Impaired vision;
tingling in hands, feet
and around mouth;
lack of coordination;
muscle weakness
5-10 days
Food Sources
Eggs, poultry, meat, unpasteurized milk or juice, cheese,
contaminated raw fruits and
vegetables
Milk, soft cheeses, deli meats
SympLarge fish, shark
toms are
irreversible
Figure 5: Three common sources of foodborne illness with short description of symptoms.
Protecting yourself from contaminated foods
The FDA is responsible for maintaining food safety
Wo r k b o o k
Lesson 1.3
We previously learned that the Food and Drug Administration in the United States regulates what additives can be in our food. The FDA also tests food for contaminants. Unfortunately, the FDA cannot test
everything because there is so much food, so instead they take small, random samples in an effort to
prevent tainted food products from reaching the consumer. This doesn’t always work, and sometimes food
that has a contaminant is eaten, leading to illness. You will see some real cases of microbial and chemical
food contamination in Lesson 1.3 and you will try to identify the source and cause of the illness.
4. True or false: The FDA tests all food
for contamination:
aa. True.
bb. False.
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LESSON READINGS
Tracing food contamination is challenging
Food production is an international business, food from one farm can be shipped all over the world, leading to a worldwide outbreak of the foodborne illness. Who is to blame for this contamination? It is often
very difficult to determine where in the food production process the contaminant was introduced. Can
we ask farmers to prove that their food isn’t contaminated? How about the food manufacturers? These
are complex questions that are the central part of current debate about reforming the food production
business in an effort to hold all food production stakeholders responsible for food contamination. This is
a very hard process; for example, recently a frozen berry mix was found to contain a contaminant. In the
mix were berries from multiple countries and dozens of farms. How can investigators locate the primary
source of the contamination? They can’t!
Food safety at home
As consumers, it is nearly impossible to know
where your food comes from and how it was
grown or processed. To prevent a foodborne
illness from happening to you there are simple
preventative measures to take in your kitchen.
Always washing your produce will remove pesticides and herbicides, as well as any heavy metals
that are on the produce as dust. Always cooking
meat thoroughly will kill microbes living in the
raw meat, and keeping separate cutting boards
and knives for meat and produce will lower the
possibility that the bacteria from raw meat end up
in your uncooked food.
6. Organic food is safer to eat:
aa. True.
bb. False.
Figure 6: Keeping separate cutting boards will lower the possibility
that the bacteria from raw meat will
contaminate uncooked foods.
Is organic food better?
Wo r k b o o k
Lesson 1.3
5. All of the following are challenges
the FDA faces in determining the
source of a contaminant, except:
aa. It is impossible to determine
what the contaminant is.
bb. Produce from a single farm is
shipped all over the world.
cc. Produce from multiple farms is
used in a single product.
dd. The food can be contaminated
anywhere in the production
process.
Choosing to eat organic produce and meats may lower your consumption of specific contaminants, but
elevate your risks of others. Organic produce is not grown with synthetic herbicides and pesticides, and
are GMO free. Meats that have been raised organic are only fed organic feed, and are raised on land that
is free of synthetic fertilizers, pesticides and herbicides. However, they are also more likely to use natural
fertilizers like manure that may harbor microbial contaminants. In addition, some people argue that more
pesticides and herbicides are used on organic crops, because the types of herbicides and pesticides
allowed are not as effective as the synthetic versions. So, in order for those pesticides to be affective,
farmers may have to use more of them, leading to more of the chemicals on your food.
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27
LESSON READINGS
DEFINITIONS OF TERMS
Residue — A small amount of
something that remains after the
main part has gone.
For a complete list of defined
terms, see the Glossary.
Figure 5: Each year the non-profit organization
the Environmental Working Group compiles a list
of produce with the highest levels of pesticide
residues, called The Dirty Dozen.
Wo r k b o o k
Lesson 1.3
For consumers that are concerned about consuming chemical herbicides and pesticides, The Dirty
Dozen and the Clean Fifteen lists can be used as a guide. These lists are compiled each year from data
collected on all major types of produce grown or imported to the United States. The Dirty Dozen are the
fruits or vegetables with the highest levels of pesticide residue, and The Clean 15 are the fruits and vegetables with the lowest levels of pesticide residue. The types of produce that end up on The Dirty Dozen list
usually are those types that you eat the peel (like apples, grapes and nectarines), or root vegetables that
can soak up chemicals underground (like potatoes). Choosing the organic version of the produce on The
Dirty Dozen list may reduce your exposure to synthetic pesticides and herbicides, however the only way
to ensure that no pesticides and herbicides are on your produce is to grow it yourself on land that has not
been contaminated – which is not an easy option!
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STUDENT RESPONSES
Imagine that you were put in charge of preventing food contamination in processed foods. What steps would you take? What
challenges would you face?
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Remember to identify your
sources
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Wo r k b o o k
Lesson 1.3
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TERMS
TERM
DEFINITION
Heavy metals
A metal with relatively high density or a high relative atomic weight. Lead, mercury and cadmium are all
heavy metals.
Microbes
A microorganism, such as a bacteria or virus, that causes a disease or fermentation.
Residue
A small amount of something that remains after the main part has gone.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 1.3
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