Red 40 lake or FD&C RED #40 or E129 or Allura Red AC is a chemical compound, a dye azo-derivative, water-soluble. (FDA clearance in 1971).

The name describes the structure of the molecule.

• FD&C stands for "Food, Drug, and Cosmetic" and refers to dyes and pigments that have been approved by the United States Food and Drug Administration (FDA) for use in foods, drugs, and cosmetics.
• Red No. 40, also known as Allura Red AC, is a synthetic red dye produced from petroleum. It is one of the most commonly used food dyes.

Description of raw materials used in production. 

• The raw materials utilized in the synthesis of Allura Red AC typically involve naphthalenesulfonate, phthalic anhydride, and benzenesulfonic acid among others.

Step-by-step summary of industrial production process.

• Preparation of Raw Materials. Raw materials are prepared and purified for use in the synthesis reaction.
• Synthesis Reaction. Raw materials undergo reactions in a controlled environment to form Allura Red AC dye.
• Purification. The crude dye is purified through various steps to remove impurities and other undesired components.
• Drying and Granulation. The dye is then dried and formed into a granular form for ease of use and transportation.

Form and color. FD&C Red No. 40 is a crystalline powder, water-soluble, and ranges in color from red to orange.

Commercial applications.

Food Industry. Widely used to color foods and beverages, providing a distinctive red hue.

Cosmetics and Personal Care Products. Applied in various products like lipsticks and shampoos to provide bright and appealing colors.

Pharmaceuticals. Used to color syrups, tablets, and capsules for easy differentiation and aesthetic reasons.

It has many synonyms, among which the most common is Red 40 or Allura Red AC and, in the list of dyes, CI 16035.

Safety

The US FDA (Food and Drug Administration) has approved the use of Red No. 40 and considers it generally safe when used according to guidelines. However, there are some concerns and studies suggesting it may cause allergic reactions in some people

The problem with azo dyes (monoazo or diazo) is photocatalytic degradation (1) leading to oxidation and the subsequent formation of impurities such as aromatic amines (2), some of which have carcinogenic activity. (1)

Allura Red AC Studies

• Molecular Formula: C₁₈H₁₄N₂Na₂O₈S₂
• Molecular Weight: 496.416 g/mol
• UNII: WZB9127XOA
• CAS: 25956-17-6  64553-31-7  66813-73-8
• EC Number: 247-368-0
• PubChem Substance ID 329755751
• MDL number MFCD00059526
• Colour Index Number 16035

Synonyms:

• Allura Red
• Allura red AC dye
• C.I. Food Red 17
• Food red 17
• Japan Food Red No. 40
• FD and C Red No. 40
• FD & C Red no. 40
• CCRIS 3493
• CI 16035
• HSDB 7260
• E129
• CI 16035
• Food Red No. 40
• FD&C Red No. 40
• Curry red
• Fancy Red
• Allura Red 40
• FDC Red 40
• Red No. 40
• FDC Red 40 dye
• Food Red No. 17
• AC1O1BOF
• DSSTox_CID_4436
• FD and C Red No.40
• EC 247-368-0
• DSSTox_RID_77395
• DSSTox_GSID_24436
• Sodium 6-hydroxy-5-((2-methoxy-5-methyl-4-sulfonatophenyl)diazenyl)naphthalene-2-sulfonate
• 6-Hydroxy-5-[2-(2-methoxy-5-methyl-4-sulfophenyl)diazenyl]-2-naphthalenesulfonic Acid Sodium Salt
• disodium (5E)-5-[(2-methoxy-5-methyl-4-sulfonatophenyl)hydrazinylidene]-6-oxonaphthalene-2-sulfonate
• 6-Hydroxy-5-[(6-methoxy-4-sulfo-m-tolyl)azo]-2-naphthalenesulfonic Acid Disodium Salt
• disodium (5Z)-5-[(2-methoxy-5-methyl-4-sulfonatophenyl)hydrazinylidene]-6-oxonaphthalene-2-sulfonate
• disodium;(5Z)-5-[(2-methoxy-5-methyl-4-sulfonatophenyl)hydrazinylidene]-6-oxonaphthalene-2-sulfonate
• disodium;6-hydroxy-5-[(E)-(2-methoxy-5-methyl-4-sulfonatophenyl)diazenyl]naphthalene-2-sulfonate
• 2-Naphthalenesulfonic acid, 6-hydroxy-5-((2-methoxy-5-methyl-4-sulfophenyl)azo)-, disodium salt
• Disodium 6-hydroxy-5-((6-methoxy-4-sulfo-m-tolyl)azo)-2-naphthalenesulfonate
• 2-Naphthalenesulfonic acid, 6-hydroxy-5-((6-methoxy-4-sulfo-m-tolyl)azo)-, disodium salt
• Disodium 6-hydroxy-5-((2-methoxy-5-methyl-4-sulfophenyl)azo)-2-naphthalenesulfonate
• Disodium 6-hydroxy-5-((2-methoxy-4-sulphonato-m-tolyl)azo)naphthalene-2-sulphonate
• 2-Naphthalenesulfonic acid, 6-hydroxy-5-(2-(2-methoxy-5-methyl-4-sulfophenyl)diazenyl)-, sodium salt (1:2)
• 2-Naphthalenesulfonic acid, 6-hydroxy-5-[2-(2-methoxy-5-methyl-4-sulfophenyl)diazenyl]-, sodium salt (1:2)
• disodium 6-hydroxy-5-[(E)-(2-methoxy-5-methyl-4-sulfonatophenyl)diazenyl]naphthalene-2-sulfonate
• SCHEMBL324089
• SCHEMBL340786
• C18H14N2Na2O8S2
• CHEMBL3188816
• DTXSID4024436
• Disodium 6-hydroxy-5-((2-methoxy-5-methyl-4-sulfophenyl)azo)-2-naphthalene- sulfonate
• Disodium 6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfophenyl)azo]-2-naphthalenesulfonate
• 2-Naphthalenesulfonic acid, 6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfophenyl)azo]-, disodium salt
• 6-Hydroxy-5-((2-methoxy-5-methyl-4-sulfophenyl)azo)-2-naphthalene- sulfonic acid, disodium salt

References________________________________________________________________________

(1) Li M, He W, Liu Y, Wu H, Wamer WG, Lo YM, Yin JJ. FD&C Yellow No. 5 (tartrazine) degradation via reactive oxygen species triggered by TiO2 and Au/TiO2 nanoparticles exposed to simulated sunlight. J Agric Food Chem. 2014 Dec 10;62(49):12052-60. doi: 10.1021/jf5045052. Epub 2014 Nov 24. PMID: 25393426.

Abstract. When exposed to light, TiO2 nanoparticles (NPs) become photoactivated and create electron/hole pairs as well as reactive oxygen species (ROS). We examined the ROS production and degradation of a widely used azo dye, FD&C Yellow No. 5 (tartrazine), triggered by photoactivated TiO2 NPs. Degradation was found to follow pseudo-first order reaction kinetics where the rate constant increased with TiO2 NP concentration. Depositing Au on the surface of TiO2 largely enhanced electron transfer and ROS generation, which consequently accelerated dye degradation. Alkaline conditions promoted ROS generation and dye degradation. Results from electron spin resonance spin-trap spectroscopy suggested that at pH 7.4, both hydroxyl radical (•OH) and singlet oxygen ((1)O2) were responsible for dye discoloration, whereas at pH 5, the consumption of (1)O2 became dominant. Implications for dye degradation in foods and other consumer products that contain both TiO2 and FD&C Yellow No. 5 as ingredients are discussed.

(2) Belai N, White SR. Determination of Unsulfonated Aromatic Amines in FD&C Yellow No. 5 and FD&C Yellow No. 6 by Liquid Chromatography-Triple Quadrupole Mass Spectrometry. J AOAC Int. 2019 Mar 1;102(2):580-589. doi: 10.5740/jaoacint.18-0165. 

Abstract. Background: This paper describes a simple and sensitive ultra-HPLC-triple quadrupole MS (LC-MS/MS) method for the determination of six unsulfonated aromatic amines in the color additives FD&C Yellow No. 5 (Y5) and FD&C Yellow No. 6 (Y6). The six amines determined by this method are aniline (ANL), benzidine (BNZ), 4-aminobiphenyl (4ABP), 4-aminoazobenzene (4AAB), 2-aminobiphenyl (2ABP), and 4-aminobenzonitrile (4ABN). Objective: This method is intended for use in batch certification of the color additives by the U.S. Food and Drug Administration (FDA) to ensure that each lot meets published specifications for coloring foods, drugs, and cosmetics. Methods: A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure is used for extraction of the amines. Quantitative determination was performed in electrospray positive ionization and multiple-reaction monitoring modes. Results: Validation of the method demonstrated overall recovery of 101-115% and precision of 1.74-9.78% for all analytes. Excellent regression coefficients were obtained, with values >0.999. Conclusions: The validated method was successfully used for the analyses of 30 Y5 and Y6 samples and provided results that are consistent with results from the current method used by FDA, with greater sensitivity and low matrix effects. Highlights: The validation results demonstrate that the new LC-MS/MS method is applicable for use in routine batch certification.

 Kobun Rovina, Shafiquzzaman Siddiquee and Sharifudin M. Shaarani  Extraction, Analytical and Advanced Methods for Detection of Allura Red AC (E129) in Food and Beverages Products  Front Microbiol. 2016 May 27;7:798. doi: 10.3389/fmicb.2016.00798.