An adulterant is a chemical substance which should not be contained within other substances (e.g. food, beverages, fuels) for legal or other reasons. The addition of adulterants is called adulteration.
The word is appropriate only when the additions are unwanted by the recipient. Otherwise the expression would be food additive. Adulterants when used in illicit drugs are called cutting agents, while deliberate addition of toxic adulterants to food or other products for human consumption is known as poisoning.
In food and beverages
Examples of adulteration include:
- Mogdad coffee, whose seeds have been used as an adulterant for coffee
- Roasted chicory roots, whose seeds have been used similarly, starting during the Napoleonic era in France (and continuing until today as a moderately popular additive for cheaper coffee)
- Roasted ground peas, beans, or wheat, which have been used to adulterate roasted chicory
- Diethylene glycol, used by some winemakers to fake sweet wines
- Oleomargarine or lard, added to butter
- Alum is added to disguise usage of lower-quality flour in expensive flours
- Apple jellies, as substitutes for more expensive fruit jellies, with added colorant and sometimes even specks of wood that simulate strawberry seeds
- Artificial colorants, often toxic - e.g., copper, zinc, or indigo-based green dyes added to absinthe
- Sudan I yellow color, added to chili powder, as well as Sudan II, Sudan III, Sudan IV and Sudan Red G for red color
- Water, for diluting milk and beer and hard drinks
- Lactose is used to cut illegal cocaine.
- Low quality black tea, marketed as higher quality tea
- Starch, added to sausages
- Cutting agents, often used to adulterate (or "cut") illicit drugs - for example, shoe polish in hashish or amphetamines in ecstasy
- Urea, melamine and other non-protein nitrogen sources, added to protein products in order to inflate crude protein content measurements
- Powdered beechnut husk aromatized with cinnamic aldehyde, marketed as powdered cinnamon.
- High fructose corn syrup or cane sugar, used to adulterate honey; C4 sugars serve as markers, as detected by carbon isotopic signatures 
- Glutinous rice coloring made of hazardous industrial dyes, as well as tinopal to make rice noodles whiter (to serve as bleach)
- Noodles, meat, fish, tofu preserved with formaldehyde in tropical Asia, to prevent spoilage from the sun
- Water or brine injected into chicken, pork or other meats to increase their weight.
Historically, the usage of adulterants has been common in societies with few legal controls on food quality and/or poor/nonexistent monitoring by authorities; sometimes this usage has even extended to exceedingly dangerous chemicals and poisons. In the United Kingdom during the Victorian era, adulterants were quite common; for example, cheeses were sometimes colored with lead. Similar adulteration issues were seen in industry in the United States, until the passage of the Pure Food and Drug Act of 1906. More recently, adulterant use in the People's Republic of China has inspired much public attention. (See: Food safety in the People's Republic of China).
Adulterant usage was first investigated in 1820 by the German chemist Frederick Accum, who identified many toxic metal colorings in food and drink. His work antagonized food suppliers, and he was ultimately discredited by a scandal over his alleged mutilation of Royal Institution library books. The physician Arthur Hill Hassall later conducted extensive studies in the early 1850s, which were published in The Lancet and led to the 1860 Food Adulteration Act and subsequent further legislation.
At the turn of the 20th century, industrialization in the United States saw an uprise in adulteration and this inspired some protest. Accounts of adulteration led the New York Evening Post to parody:
Mary had a little lamb,
And when she saw it sicken,
She shipped it off to Packingtown,
And now it's labeled chicken.
However, even back in the 18th century, people recognized adulteration in food:
"The bread I eat in London is a deleterious paste, mixed up with chalk, alum and bone ashes, insipid to the taste and destructive to the constitution. The good people are not ignorant of this adulteration; but they prefer it to wholesome bread, because it is whiter than the meal of corn [wheat]. Thus they sacrifice their taste and their health. . . to a most absurd gratification of a misjudged eye; and the miller or the baker is obliged to poison them and their families, in order to live by his profession." - Tobias Smollet, The Expedition of Humphrey Clinker (1771)
A history of food poisoning and adulteration is found in the textbook, Death in the Pot: The Impact of Food Poisoning on History.
In drug tests
Adulterants can be also added to urine, in order to interfere with the accuracy of drug tests. These adulterants are often oxidative in nature - hydrogen peroxide and bleach have been used, sometimes with pH-adjusting substances like vinegar or sodium bicarbonate. These can be detected by drug testing labs, but some less expensive tests do not look for them.
Notable incidents of adulteration
- In 1987, Beech-Nut paid $2.2 million in fines for violating the Federal Food, Drug, and Cosmetic Act by selling artificially flavored sugar water as apple juice.
- In 1997, ConAgra Foods pled guilty to federal criminal charges that one of its units illegally sprayed water on stored grain to increase its weight and value.
- In 2007, samples of wheat gluten mixed with melamine, presumably to produce artificially inflated results from common tests for protein content, were discovered in many U.S. pet food brands, as well as in human food supply. The adulterated gluten was found to have come from China, and U.S. authorities concluded that its origin was the Xuzhou Anying Biologic Technology Development Company, a Xuzhou, China-based company. (See: Chinese protein adulteration.)
- In 2008, significant portions of China's milk supply were found to have been contaminated with melamine. Infant formula produced from melamine-tainted milk killed at least six children and were believed to have harmed thousands of others. (See: 2008 Chinese milk scandal.)
- In 2012, a study in India conducted by the Food Safety Standards Authority of India (FSSAI) across 33 states found that milk in India is adulterated with detergent, fat and even urea, as well diluted with water. Of the 1791 random samples from 33 states, just 31.5% of the samples tested (565) conformed to the FSSAI standards while the rest 1226 (68.4%) failed the test. See: 2012 India milk adulterant scandal.
- ^ Weise, Elizabeth (April 24, 2007). "Food tests promise tough task for FDA". USA Today. http://www.usatoday.com/money/industries/food/2007-04-25-melamine-usat_N.htm. Retrieved 2007-04-29.
- ^ 
- ^ a b VietnamNet:Hazardous chemicals need tougher controls
- ^ Burros, Marian (2006-08-09). "The Customer Wants a Juicy Steak? Just Add Water". The New York Times. http://www.nytimes.com/2006/08/09/dining/09well.html?ex=1159243200&en=17c3332c2ab7cd8d&ei=5070.
- ^ The fight against food adulteration, Noel G Coley, RSC, Education in chemistry, Issues, Mar 2005
- ^ Jeffrey M. Pilcher, Food in World History New York: Routledge, 2006, p. 59
- ^ Weston A.Price: Against the Grain, Section Bread to Feed the Masses
- ^ Satin, Morton, Death in the Pot: The Impact of Food Poisoning on History, 262 pages, Prometheus Books, (2007), ISBN 1-59102-514-1 
- ^ Juiceless baby juice leads to full-length justice|FDA Consumer
- ^ ConAgra Set to Settle Criminal Charges It Increased Weight and Value of Grain - New York Times