Diacetyl

CAS 431-03-8

Listed as a flavouring agent by the US.

Listed as flavouring agents and adjuvants (US)
Chemical structure of Diacetyl, from PubChem compound 650
Structure from PubChem CID 650 (National Library of Medicine, public domain). A depiction of one compound: where a listing covers a family, or a substance has no single structure, this page shows none.

Diacetyl is the compound that smells of butter. It forms naturally in butter, cultured cream and beer, and is added as a flavouring — most famously to butter-flavoured popcorn.

Where it is and isn’t permitted

Status of Diacetyl by jurisdiction. Every jurisdiction this site covers is listed, including those where the substance does not appear.
JurisdictionStatusScope and limitsCitation
Australia and New ZealandFood Standards Australia New ZealandNo listed food uses foundThis site has not matched this substance to any food use on this jurisdiction’s list of authorised food additives. A food additive may be used only in foods that list names. Flavourings, enzymes, processing aids and added nutrients are regulated separately and do not appear on it.
CanadaHealth CanadaNo listing matchedHealth Canada’s lists name additives without E or INS numbers, so this site matches them by exact name. A substance listed there under a name this site does not recognise has no row here.
European UnionEuropean Commission / EFSANo listed food uses foundThis site has not matched this substance to any food use on this jurisdiction’s list of authorised food additives. A food additive may be used only in foods that list names. Flavourings, enzymes, processing aids and added nutrients are regulated separately and do not appear on it.
Great BritainFood Standards Agency / Food Standards ScotlandNo listed food uses foundThis site has not matched this substance to any food use on this jurisdiction’s list of authorised food additives. A food additive may be used only in foods that list names. Flavourings, enzymes, processing aids and added nutrients are regulated separately and do not appear on it.
JapanConsumer Affairs AgencyNo listing matchedThis site imports only Japan’s list of designated additives (Appended Table 1 to the Regulations for Enforcement of the Food Sanitation Act), matched by English name. Existing additives, natural flavouring agents and ordinary foods used as additives are permitted outside that list and are not imported, so an empty row does not show that Japan does not permit the substance.
South KoreaMinistry of Food and Drug SafetyNo listing matchedThis site imports Part III of South Korea’s Standards and Specifications for Food Additives, matched by CAS number, then INS number, then exact name. Mixed preparations and sanitisers are not imported, and an entry whose identifiers disagreed with a page’s is held for review, so an empty row does not show that South Korea does not permit the substance.
United StatesFood and Drug AdministrationPermitted21 CFR 184.1278retrieved 2026-10-17
Codex AlimentariusCodex Alimentarius Commission / JECFANot listedDoes not appear on this jurisdiction’s permitted list. That is not the same as being prohibited.

How much is permitted

A listing usually limits the quantity as well as the food. Only one of the forms that takes is a figure: quantum satis and good manufacturing practice permit the amount the technological effect requires and no more, which is a limit rather than the absence of one. Figures below are the range across every food category this page is listed in, and categories differ between regulators — see how much is permitted.

United States—1 no quantity stated

No regulator sets a figure for Diacetyl. That is not an absence of control: where the listing says quantum satis or good manufacturing practice, the quantity is limited to what the effect requires.

What it is made from

Produced by fermentation or by chemical synthesis.

  • Vegan
  • Vegetarian

Compare other additives on the dietary indexes.

CAS registry number
431-03-8
InChIKey
QSJXEFYPDANLFS-UHFFFAOYSA-N
PubChem
CID 650

Every name it appears under

42 recorded names. A label may use any of them.

CAS registry number

  • 1173018-75-1
  • 431-03-8

As it appears in regulation

  • Diacetyl

Other names

  • 2,3 butandione
  • 2,3 Butanedione
  • 2,3-Butadione
  • 2,3-butandione
  • 2,3-Butanedione
  • 2,3-Butanedione (8CI,9CI)
  • 2,3-Butanedione, 97%
  • 2,3-Butanedione, analytical standard
  • 2,3-Butanedione-13C2
  • 2,3-diketobutane
  • 2,3-dioxobutane
  • 4-01-00-03644 (Beilstein Handbook Reference)
  • Biacetyl
  • Biacetyl; BDM
  • BRN 0605398
  • BUO
  • Buta-2,3-dione
  • butadione
  • Butan-2,3-dione
  • butane 2
  • butane-2
  • Butane-2,3-dione
  • Butanedione
  • CAS-431-03-8
  • CCRIS 827
  • Diacetyl
  • Diacetyl (natural)
  • Diacetyl 1000 microg/mL in Methanol
  • Diacetyl, natural, >=95%
  • Diketobutane
  • dimethyl diketone
  • Dimethyl glyoxal
  • dimethylglyoxal
  • FEMA No. 2370
  • Glyoxal, dimethyl-
  • HSDB 297
  • InChI=1/C4H6O2/c1-3(5)4(2)6/h1-2H
  • WLN: 1VV1

Systematic names

  • butane-2,3-dione

Hazard reference values

No reference value for this substance in the sources we hold.

Evidence and how bodies read it

Studies, and the differing conclusions regulators drew from them, are curated rather than machine-read, and none has been written for this substance yet.

Common questions

Assembled from what is above, in the words the questions are usually asked in. Each answer is the same statement the relevant section makes, with the same citations behind it.

What is Diacetyl?
Diacetyl is the compound that smells of butter. It forms naturally in butter, cultured cream and beer, and is added as a flavouring — most famously to butter-flavoured popcorn.
What is Diacetyl used for in food?
It is listed as a flavouring agent — the role the US assigns it. This page shows every function each regulator records, with the citation for each.
Is Diacetyl banned in Europe?
No. Diacetyl is not on the EU's list of authorised food additives, but it would not be expected to be: every role regulators give it — flavouring agent — the EU regulates under separate law. Its absence from the additives list says nothing about whether it is permitted in Europe.
Where is Diacetyl permitted?
Of the seven regulators this site reads, the US permits it. Each permission is for named foods at named levels, not a blanket one; the table on this page gives them with citations.
Is Diacetyl vegan?
Yes. Diacetyl is not derived from animals, and is suitable for vegetarians. This page says what it is made from and how.

Sources for this page

  • ecfr retrieved 2026-10-17

Full licence terms and publisher details on Sources. How this page is built and updated: Method.

Machine-readable: a JSON record of this additive is given on request —how to ask for access.

Follow changes to Diacetyl:Atom feed — regulatory events, and any change the weekly refresh detects in its provisions.