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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. ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ 23 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. ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ 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. ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ Figure 4: Common steps in food production where contamination may occur. 25 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. ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ 26 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. ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ 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! ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ 28 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? _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ ____________________________________________________________________________________________________ Remember to identify your sources _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ _____________________________________________________________________________________________________ Wo r k b o o k Lesson 1.3 _____________________________________________________________________________________________________ ___________________________________________________________________________________________ 29 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 30