Artificial Butter Flavour (Diacetyl)

About

What it is and where it shows up.

Artificial butter flavour is a synthetic or nature-identical flavouring compound, with diacetyl (2,3-butanedione) as its primary active constituent, used to impart a characteristic buttery aroma and taste to foods such as microwave popcorn, margarine, baked goods, and dairy products. It is a volatile yellow liquid alpha-diketone also produced naturally during fermentation in butter, wine, beer, and dairy products.

Safety summary

The regulatory and scientific consensus.

Oral ingestion of diacetyl at typical food-use levels is classified GRAS by the FDA and presents no established risk to the general adult population. However, inhalation of diacetyl vapours—primarily an occupational concern—has been strongly linked to bronchiolitis obliterans ('popcorn lung'), a rare and irreversible obstructive lung disease documented in microwave popcorn factory workers. Emerging in-vitro research has raised preliminary concerns about diacetyl's ability to cross the blood-brain barrier and interact with amyloid peptides, but this has not been confirmed as a dietary risk for general consumers.

Regulatory landscape

What food-safety regulators have decided.

Jurisdiction	Status	Note
FSSAI (Food Safety and Standards Authority of India) (India)	Restricted	Diacetyl is permitted by FSSAI as a flavouring substance in table margarine and fat spread at a maximum level of 4 mg/kg. Artificial flavouring substances must be declared on labels under FSSAI Labelling & Display Regulations.source
EFSA (European Food Safety Authority) (European Union)	Approved	Diacetyl is regulated as a flavouring substance under Regulation (EC) No 1334/2008 on flavourings used in or on foods. It does not carry a dedicated E-number as a standalone food additive. EFSA's FAF Panel evaluates flavouring substances for safety prior to EU authorisation. No specific maximum use level has been established for diacetyl under the flavourings regulation; use is subject to good manufacturing practice (GMP).source
FDA (Food and Drug Administration) (United States)	Approved	Diacetyl is GRAS as a direct food additive under 21 CFR 184.1278. GRAS status applies to ingestion only; NIOSH has separately established occupational inhalation exposure limits for workers. The substitute flavouring 2,3-pentanedione (acetyl propionyl) is also GRAS per 21 CFR 172.515 but has similarly demonstrated respiratory toxicity via inhalation.source

Who should approach with care

Whose guidance would steer them away.

Other — Workers in food manufacturing, microwave popcorn production, or flavouring industries face serious inhalation risks from diacetyl vapours; NIOSH has established recommended occupational exposure limits and recommends respiratory protection and regular spirometry for exposed workers.

Asthma / Respiratory Disease (Other) — Individuals with pre-existing respiratory or airway disease may be more susceptible to any incidental inhalation of diacetyl vapours when handling or heating diacetyl-containing products (e.g., opening hot microwave popcorn bags), based on evidence of airway epithelial toxicity at elevated concentrations.

Infants — No specific paediatric oral safety data for diacetyl as a food additive has been established by FSSAI, FDA, or EFSA; infant exposure should be minimised given the lack of dedicated safety assessment for this age group.

Research citations

The sources behind this verdict.

1PubMed. Not Just an Aroma Compound: Expanding Perspectives on Diacetyl in Food Systems and Human Health, 2026. pmc.ncbi.nlm.nih.gov
2PubMed. Current perspective on amyloid aggregation accelerating properties of the artificial butter flavoring, diacetyl, 2024. pmc.ncbi.nlm.nih.gov
3PubMed. Models of Toxicity of Diacetyl and Alternative Diones, 2017. pmc.ncbi.nlm.nih.gov
4PubMed. Occupational Lung Disease Risk and Exposure to Butter-Flavoring Chemicals After Implementation of Controls at a Microwave Popcorn Plant, 2011. pmc.ncbi.nlm.nih.gov
5PubMed. Evaluation of the butter flavoring chemical diacetyl and a fluorochemical paper additive for mutagenicity and toxicity using the mammalian cell gene mutation assay in L5178Y mouse lymphoma cells, 2008. pubmed.ncbi.nlm.nih.gov
6NTP / NIOSH. Artificial Butter Flavoring and Constituents Diacetyl [CAS No. 431-03-8] and Acetoin [CAS No. 513-86-0]: Supporting Nomination for Toxicological Evaluation, 2007.

Independently researched6 citations