Overview of Chemicals in Food
“We the chefs have a responsibility to learn about the chemical makeup of food.”- Joel
Robuchon.
Today more Americans are focusing on nutritious and safe food. Recommendations from the
"Dietary Guidelines for Americans, 2010" emphasize eating fruit, vegetables, whole grains and
low-fat or fat-free milk and milk products. We should include lean meats, poultry, fish, beans,
eggs and nuts. We are urged to limit consumption of foods that are high in saturated fat, trans fat,
cholesterol, sodium and sugar. We are required to consume adequate micronutrients, vitamins,
minerals, fibers and foods low in calories, which can be obtained by eating fresh fruits and
vegetables. We try to stay away from food that can cause weight gain or health issues. We check
nutrition labels to make sure we are consuming the correct amounts of sodium, sugar, fats,
vitamins, minerals, and calories. However, American consumers don’t realize there are other
things they need to be aware of in their foods: hazardous chemicals or food contamination.
Food contamination is the presence in food of harmful chemicals and microorganisms, which
can cause consumers to get sick. This book addresses the chemical contamination of foods, and
not microbiological contamination. Chemical food safety issues have been the center of media
attention over the past decade. Because of advances in analytical detection, chemists can now
analyze for and detect more chemicals at much lower concentrations in more foods. They can
detect a chemical in nanograms per milliliter (ng/mL or one-billionth of a gram in a milliliter)
levels and this raises the question if these levels cause more health problems and concerns about
the food supply for consumers than those chemicals detected at the micrograms per milliliter
(µg/mL or one-millionth of a gram in a milliliter) level. Although Americans enjoy one of the
safest food supplies in the world, the impact of chemical contaminants on consumer health and
well-being is often apparent only after many years of prolonged exposure at low levels (e.g.
cancer).
Chemical contaminants can occur in our food from many sources. They can be introduced at
any point in the food chain during production of the raw material, processing, retail distribution,
food preparation and consumption. Chemicals that may enter the food supply include the
presence of agrochemicals (e.g. pesticides), natural toxins (e.g. mycotoxins), processingproduced toxins (e.g., acrylamide, trans fats, furan), food allergens, heavy metals (e.g. lead,
arsenic, mercury, cadmium), industrial chemicals (e.g. benzene, perchlorate), contaminants from
packaging materials (e.g. bisphenol A), and deliberate contaminants (e.g. melamine) in our food
and animal feed. They typically cause a health concern. The U.S. Food and Drug
Administration’s program for chemical contaminants in food
(http://www.fda.gov/Food/FoodborneIllnessContaminants/ChemicalContaminants/) provides an
overview of the chemicals of concern. Some of these that will be discussed in this book include
the following:
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Pesticides. Pesticides are used to control insects, weeds, and disease throughout the world.
People can be exposed to pesticides by different routes including occupation, in the home, at
school and in their food. Pesticides are commonly used on fruits and vegetables to control pests
that may damage the crops during production, storage or transport. Although their use enhances
crop yield and improves the quality of the food produced, pesticide residue levels in food can
have a negative effect on the health of humans. Infants, young children, the fetus, and the
elderly are more susceptible to pesticide poisoning. Pesticides can affect the nervous, endocrine,
immune, and reproductive systems.
Eating pesticide-contaminated foods is the most common route of exposure. Chemicals that
are no longer used but do not breakdown can remain in the environment for a long period of
time. For example, most people in the United States still have detectable levels of DDT in their
bodies even though it was banned in the U.S. in 1972. Therefore, it is beneficial to find ways to
reduce the levels of pesticide residue in food such as produce to lower the exposure and risk to
human health.
Acrylamide and furan. Most aisles of our grocery stores contain processed foods: canned,
frozen, pasteurized, or microwavable. These have extra sugars, salt and additives to prolong
their shelf-life. Many people work and when they get home look for a quick, convenient way to
make dinner and they turn to these processed foods. No one has time to prepare meals from
scratch as our mothers did. Not only may these processed foods have decreased nutrient levels,
but produce chemical and physical changes that can cause a food to be hazardous or
contaminated. Heating of foods can generate many different kinds of potentially hazardous
chemicals, some of which are carcinogenic and genotoxic.
Acrylamide and furan are examples of chemicals that form as a result of heat treatment of
food. Cooking or heat processing causes free amino acids and sugars to react via the Maillard
reaction, which is a chemical reaction between amino acids and reducing sugars that gives
browned foods their desirable flavor. However, some Maillard reactions form toxic products,
such as acrylamide.
Acrylamide forms in carbohydrate-rich foods that are subject to high temperatures (>120°C)
processes such as frying, baking, and extrusion. It is not formed in food that has been boiled or
in foods that is not heated. It has been found in potatoes, cereal products, and coffee.
Furan is generated in heat-treated commercial foods and it is produced through heating of
natural food constituents and reactions of carbohydrates, ascorbic acid, and polyunsaturated fatty
acids in food. It can be found in roasted coffee, instant coffee, and processed baby foods.
Acrylamide and furan are both potential human carcinogens that occur in food as a result of
cooking or heat processing. Both compounds became internationally important food
contaminants within the last several years.
Trans fatty acids and benzene. Several chemicals are formed through nonthermal processes or
during storage. Two of these chemical hazards that have been in the public and scientific media
include trans fatty acids in hydrogenated fats and oils and benzene in soft drinks.
Recently, health implications have been associated with trans fatty acids in foods. Trans fatty
acids are commercially produced by partial hydrogenation of edible oils. Partially hydrogenated
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oils have been used in food for many reasons. Hydrogenation increases product shelf life and
decreases refrigeration requirements. Hydrogenation is a chemical reaction between molecular
hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as
nickel, palladium or platinum. Trans fatty acids are found in foods such as margarines, spreads,
shortenings, frying fats, and specialty fats and occur naturally in foods such as milk, butter, and
tallow. Trans fat has been shown to consistently be associated with risk of coronary heart
disease in part by raising levels of the low-density lipoprotein LDL (so-called "bad cholesterol"),
lowering levels of the high-density lipoprotein HDL ("good cholesterol"), and increasing
triglycerides in the bloodstream. Health professionals recommend reducing consumption of
foods containing trans fatty acids. On 16 June 2015, the FDA finalized its determination that
trans fats are not generally recognized as safe, and set a three year time limit for their removal
from all processed foods.
Benzene, a carcinogenic chemical, has been found in soft drinks and is a public health
concern. This contamination has caused an uproar among environmentalists and health officials.
The benzene forms from decarboxylation, a chemical reaction that removes a carboxyl group and
releases carbon dioxide (CO2), of the preservative benzoic acid in the presence of ascorbic
acid (vitamin C) and metal ions (iron and copper) that act as catalysts, especially under heat and
light. Benzoic acid is often added to drinks as a preservative in the form of its salts sodium
benzoate (E211), potassium benzoate (E 212), or calcium benzoate (E 213). Citric acid may
accelerate production of benzene when combined with these acids. Other factors that affect the
formation of benzene are heat and light. Storing soft drinks in warm conditions speeds up the
formation of benzene. The regulatory limit for benzene in drinking water and bottled water is 5
nanograms per milliliter, but there is no limit on soft drinks. Benzene levels detected in some
soft drink products were higher than the regulatory limit of bottled water. Soft drink
manufacturers have reformulated their beverages to reduce or eliminate benzene formation.
Benzene levels in some soft drink products and especially in new beverage formulations need to
be monitored to ensure that benzene levels are minimized.
Bisphenol A. Food packaging is essential to the food manufacturing process. It is important
that there is no migration of the chemicals from the packaging into the food. Care must be taken
when manufacturing proper packaging. Bisphenol A (BPA) has attracted much public attention.
This compound is used to make certain plastics and epoxy resins. In the food industry, it is used
to make polycarbonate bottles and epoxy resins. Polycarbonate is used in water and baby
bottles, and epoxy resins are used as coatings on the inside of many food and beverage cans.
Studies have shown that BPA can migrate from packaging material into a variety of canned
vegetables and fruits, meats, beverages, and liquid infant formulas. Because of its estrogenic
effects, there is concern about BPA’s suitability in food containers. In July 2012, the FDA
announced that it would no longer allow BPA in baby bottles and children’s drinking cups.
However, there are no restrictions for its use in other consumer products.
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Food allergens. Food allergies can range from mildly irritating to life-threatening. An estimated
30,000 Americans go to the emergency room each year to get treated for severe food allergies,
according to the Food Allergy and Anaphylaxis Network (FAAN). It is estimated that 150 to 200
Americans die each year because of allergic reactions to food. According to the Centers for
Disease Control and Prevention, food allergies are a growing food safety and public health
concern that affect an estimated 4%–6% of children in the United States. Researchers estimate
that up to 15 million Americans have food allergies. Eight foods account for 90 percent of all
reactions: milk, eggs, peanuts, tree nuts, soy, wheat, fish and shellfish. Even trace amounts of a
food allergen can cause a reaction.
As of today, there has been no known treatment for life-threatening food allergens, only
prevention of the allergic reaction by avoidance of exposure to the allergen. The Food Allergen
Labeling and Consumer Protection Act (FALCPA) was introduced in 2004 by the FDA to
improve food labeling information for the millions of consumers who suffer from food allergies.
Food labeling of the presence of major food allergens provides awareness to sensitive consumers
regarding products they should avoid consuming. However, allergens can still inadvertently
appear in a product because of incorrect labelling or cross-contamination during manufacturing.
Mycotoxins. Mycotoxins are toxic secondary metabolites, chemicals that are not directly
involved in the normal growth, development, or reproduction of an organism, produced by
certain fungi that occur naturally and can contaminate food during growth in the field,
processing, transportation or storage. These toxic metabolites can cause important economic
loss. Mycotoxins are considered both poisonous and chronic hazards and are best avoided by
implementing good agricultural and manufacturing practices. Many mycotoxins are stable to
heat and food processing procedures and are found in many agricultural products including
grains, fruits, and vegetables. The most toxin-producing fungi found in food, the Penicillium,
Fusarium, and Aspergillus genera, are the greatest significance in food safety. From the more
than 1000 mycotoxins that are known to form, those having the most public health and economic
relevance include the aflatoxins, ochratoxins, trichothecenes, zearalenone, and fumonisins.
Consumers may exhibit various toxicological outcomes from ingestion. Some mycotoxins of
greatest concern are aflatoxins in corn, peanuts, tree nuts, rice and cottonseed; fumonisins in
corn, wheat, barley, and rice; and ochratoxin in wheat, barley, oats, rye, sorghum peanuts, wine,
beer and raisins. Government agencies have tried to control mycotoxins in the food supply by
establishing guidelines and action levels and monitoring the food supply. Many international
agencies are attempting to universally standardize regulatory limits for mycotoxins. The U.S.
Food and Drug Administration has regulated and enforced limits on concentrations of
mycotoxins in foods and feed industries since 1985. However, there is still not enough data on
some mycotoxins in the U.S. due to the lack of reliable testing methods.
As the U.S. population has grown in both size and ethnic diversity, the quantity and variety of
food consumed and imported in the United States has increased correspondingly. According to
the U.S. Department of Agriculture Economic Research Service, in 2009, U.S. food consumption
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totaled 654 billion pounds, or more than 2,100 pounds per capita. Of this amount, imports
accounted for 17 percent (110 billion pounds), or 358 pounds per capita.
Imports have increased in the United States because much of the fresh food cannot be
produced domestically due to climate conditions or can grow only in certain seasons. Also,
some imported foods cost less to produce than the domestically grown ones. Consumers prefer
an increasingly wider selection of food products, such as tropical fruit, vegetables, nuts, premium
coffee, wines and beers, cheeses, confections, grain products, and processed meats that they
cannot obtain domestically.
FDA has more than 1,300 inspectors conducting field activities, primarily food and feed
inspections and investigational activities. The FDA inspectors sample just 1.3 percent of all
imported food shipments entering the country and perform few on-site inspections of foreign
farms and food processing plants. According to the FDA, about $2 trillion worth of products
enter the U.S. each year from more than 230 countries, which makes it impossible to physically
examine every product entering the country. Since there are not enough inspectors at the borders,
there have been incidents of illegal food imports entering the U.S. The FDA is responsible for
inspecting all imported foods except for meat and egg products, which are regulated by the Food
Safety and Inspection Service, part of the U.S. Department of Agriculture.
Importers of food products into the U.S. are responsible for ensuring that the products are
safe, clean, nutritious, and labeled according to U.S. requirements. Foreign inspectors are
required to identify potential food safety problems before products arrive in the United States, to
determine whether a firm is in compliance with FDA’s requirements and food safety standards,
to assist FDA in determining admission status for food products imported into the United States,
and to help ensure that food products that FDA is in charge of meet U.S. requirements under the
Federal Food, Drug and Cosmetic (FD&C) Act. Different countries have different regulations
than the U.S. Both imported and domestically-produced foods must meet the same food safety
requirements to prevent intentional and inadvertent contamination of food.
Melamine. There were several food recalls of melamine after pets were poisoned and children
had severe kidney damage due to melamine-contaminated food. In 2007, pet food manufacturers
issued recalls after they found their products had been contaminated with melamine. This caused
serious illnesses or deaths in some of the animals that had eaten them. The U.S. FDA first
detected and identified the melamine adulterant in pet food. The pet foods contained wheat
gluten and rice protein as sources of protein for the animals’ diets. The wheat gluten and rice
protein contained melamine, amelide, amiline, and/or cyanuric acid and were imported from a
manufacturer in China. Cats and dogs consuming the food developed symptoms of kidney
failure, including loss of appetite, vomiting, lethargy, frequent urination, increased thirst and in
some cases, ultimately death. Melamine, in combination with amelide, aniline, and/or cyanuric
acid appears to form highly insoluble crystals in the animal’s kidney, resulting in kidney damage.
The Chinese suppliers had added these compounds to the pet food to increase the measured
level of protein. These adulterants are high in nitrogen and artificially provided high protein
levels when the wheat gluten/rice protein samples were tested. FDA issued import alerts after it
detected melamine in wheat gluten and rice protein products.
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In September 2008, several companies in China were connected to a scandal involving milk
and infant formula which had been adulterated with melamine, leading to kidney stones and
other renal failure, especially among young children. By December 2008, nearly 300,000 people
had become ill, with more than 50,000 infant hospitalizations and six infant deaths. Melamine
was added to increase the protein content after water was added to fraudulently dilute the milk.
Melamine can cause the protein content of food to appear higher than the true value.
Because of the highly publicized incidents of food contamination and adulteration in the
Chinese food supply and in U.S. food imports, a U.S. Government Interagency Working Group
on Import Safety issued an Action Plan for Import Safety and the U.S. FDA issued a Food
Protection Plan in 2007. FDA opened its first overseas office in China in 2008.
Toxic Metals: Lead-based and other heavy-metal based inks used for labeling candy wrappers
have been a regulatory issue in the past. Although the U.S. and European Union have banned the
use of heavy metal-based inks in food wrappers, lead has been found in the wrappers of candy
imported from Mexico. Lead-based inks have been found on both the exterior and interior
surfaces. It becomes a problem when lead from a lead-based printing ink is found on the portion
of the package that directly contacts the food or, if the lead migrates into the packaged food. The
product would be in violation of the Federal Food, Drug, and Cosmetic Act. Certain ingredients
such as chili powder and certain types of salt used in Mexican candy products also may contain
lead. In 2006, FDA issued guidance regarding lead to lower children’s exposure to small traces
of lead present in certain candies and set a limit of 0.1 mg/kg. Ceramic pottery made by several
manufacturers in Mexico that can be used as serving bowls also contain lead that may leach into
food. In 2010, FDA published guidance for industry to address safety and labeling concerns for
traditional pottery that may contain lead. Lead exposure in small amounts does not cause a
significant health risk. However, exposure to larger amounts can cause lead poisoning, which
can affect almost every part of our body.
Arsenic is present in the environment as a naturally occurring substance or as a result of
contamination from human activity. It exists in at least two forms, inorganic and organic. It is
more toxic in its inorganic form, which is carcinogenic. Arsenic in the food supply has created
much discussion in recent years among the public, scientific and regulatory fields. The U.S.
Environmental Protection Agency (U.S. EPA) established exposure limits of arsenic and lead in
drinking water of 10 ng/mL and 15 ng/mL, respectively. Apple juice was also found to contain
arsenic because lead arsenate pesticides were a popular pesticide for apple and other fruit
orchards used in Canada, the U.S., New Zealand, and Australia. These trees absorb arsenic from
the soil and water. In 2013, the FDA proposed an action level of 10 ng/mL, for apple juice,
similar to that for water. Arsenic may be present in many foods including grains, fruits, and
vegetables due to absorption through the soil and water. While most crops don’t readily take up
much arsenic from the ground, rice is different because it takes up arsenic from soil and water
more readily than other grains. In addition, some seafood has high levels of less toxic organic
arsenic. There are no standards for arsenic in food products although food sources are the main
source of exposure. Long-term exposure to high levels of arsenic is associated with higher rates
of skin, bladder, and lung cancers, as well as heart disease.
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To increase consumers’ safety with regard to contaminants, FDA developed the FDA Food
Protection Plan in 2007, which focuses on both domestic and imported food and attempts to
address both unintentional and deliberate contamination of the nation’s food supply. This plan
relies on an approach of prevention, intervention and response to build safety into every step of
the food supply chain. It complements the Presidential Initiative: Import Safety Action Plan that
recommends how the U.S. can improve the safety of all imported products. The Import Safety
Action Plan lays out short-term and long-term recommendations to increase product safety at
every step of the import life cycle. Together, these efforts will provide a food protection
structure that ensures that the U.S. food supply remains safe.
Although safe levels of human exposure have been set for many chemicals, there is concern
that many more new chemicals may be on the rise and which may cause detrimental effects as
some of the aforementioned chemicals. However, the effects of low level exposures to
chemicals are uncertain.
Consumers are encouraged to avoid imported foods as well as specific fruits and vegetables.
They are advised to purchase organic products instead of conventional ones and to avoid those
fruits and vegetables that contain the highest levels of pesticide contamination. Organic products
are produced without the use of toxic and persistent pesticides and synthetic nitrogen fertilizers,
antibiotics, synthetic hormones, genetic engineering or irradiation. According to the Centers for
Disease Control and Prevention (CDC), those who consume large amounts of fruits and
vegetables on a daily basis are less likely to suffer from health problems such as high blood
pressure, type 2 diabetes and stroke.
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