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Diacetyl

Diacetyl

Overview
Diacetyl is a natural byproduct of fermentation
Fermentation (biochemistry)
Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen,...

. It is a vicinal
Vicinal (chemistry)
In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not....

 diketone
Diketone
A diketone is a molecule containing two ketone groups. The simpliest diketone is diacetyl, also known as 2,3-butanedione. Diacetyl, acetylacetone, and hexane-2,5-dione are examples of 1,2-, 1,3-, and 1,4-diketones, respectively...

 (two C=O groups, side-by-side) with the molecular formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 C4H6O2. Diacetyl occurs naturally in alcoholic beverages and is added to some foods to impart a buttery flavor.

Diacetyl and acetoin are two compounds that give butter
Butter
Butter is a dairy product made by churning fresh or fermented cream or milk. It is generally used as a spread and a condiment, as well as in cooking applications, such as baking, sauce making, and pan frying...

 its characteristic taste. Because of this, manufacturers of margarine
Margarine
Margarine , as a generic term, can indicate any of a wide range of butter substitutes, typically composed of vegetable oils. In many parts of the world, the market share of margarine and spreads has overtaken that of butter...

s or similar oil
Vegetable fats and oils
Vegetable fats and oils are lipid materials derived from plants. Physically, oils are liquid at room temperature, and fats are solid. Chemically, both fats and oils are composed of triglycerides, as contrasted with waxes which lack glycerin in their structure...

-based products typically add diacetyl and acetoin (along with beta carotene for the yellow color) to make the final product butter-flavored, because it would otherwise be relatively tasteless.

At low levels, diacetyl contributes a slipperiness to the feel of the alcoholic beverage
Alcoholic beverage
An alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...

 in the mouth.
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Unanswered Questions
Encyclopedia
Diacetyl is a natural byproduct of fermentation
Fermentation (biochemistry)
Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen,...

. It is a vicinal
Vicinal (chemistry)
In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not....

 diketone
Diketone
A diketone is a molecule containing two ketone groups. The simpliest diketone is diacetyl, also known as 2,3-butanedione. Diacetyl, acetylacetone, and hexane-2,5-dione are examples of 1,2-, 1,3-, and 1,4-diketones, respectively...

 (two C=O groups, side-by-side) with the molecular formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 C4H6O2. Diacetyl occurs naturally in alcoholic beverages and is added to some foods to impart a buttery flavor.

In food products


Diacetyl and acetoin are two compounds that give butter
Butter
Butter is a dairy product made by churning fresh or fermented cream or milk. It is generally used as a spread and a condiment, as well as in cooking applications, such as baking, sauce making, and pan frying...

 its characteristic taste. Because of this, manufacturers of margarine
Margarine
Margarine , as a generic term, can indicate any of a wide range of butter substitutes, typically composed of vegetable oils. In many parts of the world, the market share of margarine and spreads has overtaken that of butter...

s or similar oil
Vegetable fats and oils
Vegetable fats and oils are lipid materials derived from plants. Physically, oils are liquid at room temperature, and fats are solid. Chemically, both fats and oils are composed of triglycerides, as contrasted with waxes which lack glycerin in their structure...

-based products typically add diacetyl and acetoin (along with beta carotene for the yellow color) to make the final product butter-flavored, because it would otherwise be relatively tasteless.

In alcoholic beverages


At low levels, diacetyl contributes a slipperiness to the feel of the alcoholic beverage
Alcoholic beverage
An alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...

 in the mouth. As levels increase, it imparts a butter
Butter
Butter is a dairy product made by churning fresh or fermented cream or milk. It is generally used as a spread and a condiment, as well as in cooking applications, such as baking, sauce making, and pan frying...

y or butterscotch
Butterscotch
Butterscotch is a type of confectionery whose primary ingredients are brown sugar and butter, although other ingredients such as corn syrup, cream, vanilla, and salt are part of some recipes...

 flavor (butterscotch itself may have no diacetyl in it at all).

In some styles of beer (e.g. in most beers produced in the British Isles, such as English Pale ales) the presence of diacetyl can be acceptable or desirable at low or, in some cases, moderate levels. In other styles the presence of diacetyl is considered a flaw or undesirable.

Diacetyl is produced during fermentation as a by-product of valine
Valine
Valine is an α-amino acid with the chemical formula HO2CCHCH2. L-Valine is one of 20 proteinogenic amino acids. Its codons are GUU, GUC, GUA, and GUG. This essential amino acid is classified as nonpolar...

 synthesis, when yeast produces α-acetolactate
Acetolactate
α-Acetolactic acid is a precursor in the biosynthesis of the branched chain amino acids valine and leucine. α-Acetolactic acid is produced from two molecules of pyruvic acid by acetolactate synthase. α-Acetolactic acid can also be decarboxylated by alpha-acetolactate decarboxylase to produce...

, which escapes the cell and is spontaneously decarboxylated
Decarboxylation
Decarboxylation is a chemical reaction that releases carbon dioxide . Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carbonation, the addition of CO2 to...

 into diacetyl. The yeast then absorbs the diacetyl, and reduces the ketone
Ketone
In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...

 groups to form acetoin and 2,3-butanediol, relatively flavorless compounds.

Beer sometimes undergoes a diacetyl rest, in which its temperature is raised slightly for two or three days after fermentation is complete, to allow the yeast to absorb the diacetyl it produced earlier in the fermentation cycle. The makers of some wines, such as Chardonnay
Chardonnay
Chardonnay is a green-skinned grape variety used to make white wine. It is originated from the Burgundy wine region of eastern France but is now grown wherever wine is produced, from England to New Zealand...

, deliberately promote the production of diacetyl because of the feel and flavor it imparts. It is present in many California chardonnays known as "Butter Bombs," although there is a growing trend back toward the more traditional French styles.

Concentrations from 0.005 mg/L to 1.7 mg/L were measured in chardonnay wines, and the amount needed for the flavor to be noticed is at least 0.2 mg/L.

In milk products


In milk, sour cream, cultured buttermilk or fermented butter are produced by inoculating pasteurized cream or milk with a lactic starter culture, churning (agitating) and holding the milk until a desired pH drop (or increase in acidity) is attained. This cultured sour cream, butter and buttermilk which are made by fermenting pasteurized and homogenised light cream or milk owes its tart flavour to lactic acid bacteria and its buttery aroma and taste to diacetyl.

Mosquito repellant


Hexanol
Hexanol
Hexanol may refer to any of the following 17 isomeric organic compounds with the formula C6H13OH:...

and 2,3-butanedione are strong inhibitors of the CO2-sensitive neurons in the fruit fly. CO2 emitted in human breath is the main attractant for the Culex
Culex
Culex is a genus of mosquito, and is important in that several species serve as vectors of important diseases, such as West Nile virus, filariasis, Japanese encephalitis, St. Louis encephalitis and avian malaria....

mosquito to find people.

Worker safety


The United States National Institute for Occupational Safety and Health
National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health is the United States’ federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the Centers for Disease Control and Prevention within the U.S...

 has suggested that diacetyl, when used in artificial butter flavoring (as used in many consumer foods), may be hazardous when heated and inhaled over a long period.

Workers in several factories that manufacture artificial butter flavoring have been diagnosed with bronchiolitis obliterans
Bronchiolitis obliterans
Bronchiolitis obliterans , also called obliterative bronchiolitis and constrictive bronchiolitis , is a rare and life-threatening form of non-reversible obstructive lung disease in which the bronchioles are compressed and narrowed by fibrosis and/or inflammation...

, a rare and serious disease of the lungs. The cases found have been mainly in young, healthy, non-smoking males. There are no known cures for bronchiolitis obliterans except for lung transplantation.

While several authorities have called the disease "Popcorn Worker's Lung," a more accurate term suggested by other doctors may be more appropriate, since the disease can occur in any industry working with diacetyl: diacetyl-induced bronchiolitis obliterans.

After the workers filed a lawsuit against the manufacturers, the United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

 began an investigation into the chemical properties of microwave popcorn butter flavoring. In March 2004, former microwave popcorn plant employee Eric Peoples, of Joplin, Missouri
Joplin, Missouri
Joplin is a city in southern Jasper County and northern Newton County in the southwestern corner of the US state of Missouri. Joplin is the largest city in Jasper County, though it is not the county seat. As of the 2010 census, the city population was 50,150...

, was awarded $20 million for permanent lung-injuries sustained while on the job. On July 19, 2005, jurors awarded $2.7 million to another popcorn plant worker in Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...

 for his claim of diacetyl-induced respiratory problems.

On July 26, 2006, the International Brotherhood of Teamsters
Teamsters
The International Brotherhood of Teamsters is a labor union in the United States and Canada. Formed in 1903 by the merger of several local and regional locals of teamsters, the union now represents a diverse membership of blue-collar and professional workers in both the public and private sectors....

 and the United Food and Commercial Workers
United Food and Commercial Workers
The United Food and Commercial Workers International Union is a labor union representing approximately 1.3 million workers in the United States and Canada in many industries, including agriculture, health care, meatpacking, poultry and food processing, manufacturing, textile, G4S Security, chemical...

 petitioned the U.S. Occupational Safety and Health Administration
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...

 to promulgate an emergency temporary standard to protect workers from the deleterious health effects of inhaling diacetyl vapors. The petition was followed by a letter of support signed by more than thirty prominent scientists. The matter is under consideration. On 21 January 2009, OSHA issued an advance notice of proposed rulemaking for regulating exposure to diacetyl. The notice requests respondents to provide input regarding adverse health effects, methods to evaluate and monitor exposure, the training of workers. That notice also solicited input regarding exposure and health effects of acetoin, acetaldehyde
Acetaldehyde
Acetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...

, acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

 and furfural
Furfural
Furfural is an organic compound derived from a variety of agricultural byproducts, including corncobs, oat, wheat bran, and sawdust. The name furfural comes from the Latin word , meaning bran, referring to its usual source....

.

There are currently two bills in the California Legislature to ban the use of diacetyl.

A 2010 OSHA Safety and Health Information Bulletin and companion Worker Alert recommend that employers use safety measures to avoid exposing employees to the potentially deadly effects of butter flavorings and other flavoring substances containing diacetyl or its substitutes.

Consumer safety


Dr. Cecile Rose, pulmonary specialist at Denver's National Jewish Medical and Research Center
National Jewish Medical and Research Center
National Jewish Health is a research institute located in Denver, Colorado specializing in respiratory, immune and allergic research and treatment. It was founded in 1899 to treat tuberculosis, and is today considered one of the world's best medical research and treatment centers...

, in a letter, warned federal
Federal government of the United States
The federal government of the United States is the national government of the constitutional republic of fifty states that is the United States of America. The federal government comprises three distinct branches of government: a legislative, an executive and a judiciary. These branches and...

 agencies or regulators that consumers
Consumer
Consumer is a broad label for any individuals or households that use goods generated within the economy. The concept of a consumer occurs in different contexts, so that the usage and significance of the term may vary.-Economics and marketing:...

, not just factory
Factory
A factory or manufacturing plant is an industrial building where laborers manufacture goods or supervise machines processing one product into another. Most modern factories have large warehouses or warehouse-like facilities that contain heavy equipment used for assembly line production...

 workers, are in danger
Risk
Risk is the potential that a chosen action or activity will lead to a loss . The notion implies that a choice having an influence on the outcome exists . Potential losses themselves may also be called "risks"...

 of contracting bronchiolitis obliterans
Bronchiolitis obliterans
Bronchiolitis obliterans , also called obliterative bronchiolitis and constrictive bronchiolitis , is a rare and life-threatening form of non-reversible obstructive lung disease in which the bronchioles are compressed and narrowed by fibrosis and/or inflammation...

 from fumes produced by microwaving popcorn containing diacetyl. David Michaels of the George Washington University
George Washington University
The George Washington University is a private, coeducational comprehensive university located in Washington, D.C. in the United States...

 School of Public Health first published Rose's letter on his blog
Blog
A blog is a type of website or part of a website supposed to be updated with new content from time to time. Blogs are usually maintained by an individual with regular entries of commentary, descriptions of events, or other material such as graphics or video. Entries are commonly displayed in...

. However, the only sample data known-to-date is the case where a consumer, who ate at least two bags of buttery microwave popcorn daily for 10 years, became diagnosed with the same disease affecting workers exposed to the substance, bronchiolitis obliterans. His lung problems were linked to breathing the vapors; although rare, the reported man's kitchen also had diacetyl levels comparable to those in popcorn plants.

The Flavor and Extract Manufacturers Association
Flavor and Extract Manufacturers Association
The Flavor and Extract Manufacturers Association of the United States was founded in 1909 by several flavor firms in response to the passage of the Pure Food and Drug Act of 1906. Founding members were McCormick & Company, Ulman Driefus & Company, Jones Brothers, Blanke Baer Chemical Company,...

 recommended reducing diacetyl in butter
Butter
Butter is a dairy product made by churning fresh or fermented cream or milk. It is generally used as a spread and a condiment, as well as in cooking applications, such as baking, sauce making, and pan frying...

 flavorings (24 September 2007). The Pop Weaver brand popcorn from the Weaver Popcorn Company of Indianapolis
Indianapolis
Indianapolis is the capital of the U.S. state of Indiana, and the county seat of Marion County, Indiana. As of the 2010 United States Census, the city's population is 839,489. It is by far Indiana's largest city and, as of the 2010 U.S...

 was the first to replace its butter flavoring with a new ingredient
Ingredient
An ingredient is a substance that forms part of a mixture . For example, in cooking, recipes specify which ingredients are used to prepare a specific dish. Many commercial products contain a secret ingredient that is purported to make them better than competing products...

. Weaver makes also the Trail's End brand of popcorn, currently sold by the Boy Scouts of America
Boy Scouts of America
The Boy Scouts of America is one of the largest youth organizations in the United States, with over 4.5 million youth members in its age-related divisions...

 and Scouts Canada
Scouts Canada
Scouts Canada is a Canadian Scouting association that, in affiliation with the French-language Association des Scouts du Canada, is a member of the World Organization of the Scout Movement...

. In a press release dated December 17, 2007, ConAgra Foods
ConAgra Foods
ConAgra Foods, Inc. is an American packaged foods company. ConAgra's products are available in supermarkets, as well as restaurants and food service establishments. Its headquarters are located in Omaha, Nebraska...

, maker of Orville Redenbacher's
Orville Redenbacher
Orville Clarence Redenbacher was an American businessman most often associated with the brand of popcorn that bears his name.-Early life:...

 and Act II microwave popcorn brands, announced it had removed added diacetyl from all of its butter-flavored microwave popcorn varieties. The new products began hitting store shelves as early as October 2007.

European Union regulation


The European Commission
European Commission
The European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....

 has declared that diacetyl is legal for use as a flavouring substance in all EU states. As a diketone, diacetyl is included in the EU's flavouring classification Flavouring Group Evaluation 11 (FGE.11). A Scientific Panel of the EU Commission evaluated six flavouring substances (not including diacetyl) from FGE.11 in 2004. As part of this study, the Panel reviewed available studies on several other flavourings in FEG.11, including diacetyl. Based on the available data, the Panel reiterated the finding that there were no safety concerns for diacetyl's use as a flavouring. As a result of the Panel's 2004 study, acetylacetone
Acetylacetone
Acetylacetone is an organic compound that famously exists in two tautomeric forms that rapidly interconvert. The less stable tautomer is a diketone formally named pentane-2,4-dione. The more common tautomer is the enol form. The pair of tautomers rapidly interconvert and are treated as a single...

 (FL 07.191) was found to be genotoxic in vitro and in vivo, and was therefore deleted from the register of permitted flavouring substances. Recently, the European Food Safety Authority
European Food Safety Authority
The European Food Safety Authority is an agency of the European Union that provides independent scientific advice and communication on existing and emerging risks associated with the food chain, created by European Regulation 178/2002....

 (EFSA), the EU's food safety regulatory body, stated that its scientific panel on food additives and flavourings (AFC) was evaluating diacetyl along with other flavourings as part of a larger study. "The experts of the EFSA AFC panel and its working group on food additives will look at this issue to see if new scientific evidence is available that may require further actions. If the experts conclude that consumer exposure to diacetyl can reach levels well above those considered as safe and, that a possible health risk for consumers cannot be excluded when inhaling diacetyl, EFSA will give priority to the re-evaluation of this substance and provide detailed scientific advice."

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