Red 40 (Allura Red AC) & Red 40 Lake
Synonyms: FD&C Red No. 40, CI 16035, E129 (food); Red 40 Aluminum Lake (oil-dispersible pigment)
Functions (food/cosmetic/pharma): Red 40 is a water-soluble bright red dye (slightly bluish shade) for aqueous systems; Red 40 Lake is an insoluble pigment for anhydrous/lipid phases (lipsticks, pressed powders, fat coatings).

Definition
Red 40 is a synthetic azo dye supplied as the sodium salt and used widely to deliver a vivid, clean red hue in beverages, confectionery, icings, syrups, oral liquids, and water-based cosmetics. Red 40 Lake is produced by laking the dye onto aluminum hydroxide/oxide (and related aluminum salts), giving an oil-dispersible pigment with minimal bleeding in low-water matrices.

Calories (energy value)
0 kcal per 100 g (non-nutritive colorant/pigment).

Composition and structure

• Soluble dye: Allura Red AC, sodium salt (CI 16035).

• Lake: dye (typically ~10–40% loading) anchored to hydrated alumina; balance is mineral substrate and trace moisture.

• Physical form: soluble dye as red powder/granules; lake as fine red powder with controlled particle-size distribution (PSD).

Key physicochemical properties

• Solubility: dye freely soluble in water, insoluble in oils; lake insoluble in both water and oils (must be dispersed).

• Color metrics: λmax ~504–510 nm in water (near neutral pH). Shade shifts slightly with pH/ionic strength (more bluish in mildly alkaline media).

• pH tolerance (dye): stable across ~pH 2–10; sensitive to strong oxidizing/reducing environments (e.g., ascorbate + transition metals).

• Light/heat: generally good stability in typical processing; protect from severe redox stress and metal catalysis.

• Metal sensitivity: Fe³⁺/Cu²⁺ can dull or shift tone—EDTA/citrate chelation helps in beverages and gels.

Manufacturing overview

• Red 40 (soluble dye)

  1. Azo coupling of sulfonated aromatic intermediates under controlled conditions.

  2. Neutralization to the sodium salt.

  3. Purification (filtration, washing, ion-exchange/deionization) to reduce inorganic salts, subsidiary colors, and heavy metals.

  4. Drying & standardization (moisture, tinctorial strength), optional granulation for dust control.

• Red 40 Lake (aluminum lake pigment)

  1. Prepare aqueous dye solution at controlled pH/ionic strength.

  2. Generate aluminum hydroxide in situ (aluminum salt + base) or use a slurry of hydrated alumina.

  3. Laking/co-precipitation: add dye to substrate under controlled pH/temperature/agitation to anchor dye anions to alumina.

  4. Aging (surface charge stabilization) → filtration & thorough washing (remove unbound dye/salts).

  5. Drying → milling/classification (e.g., jet-milling) to target PSD; optional surface treatment for better wetting.

  6. QC: shade/strength, PSD (D10/D50/D90), moisture/volatile matter, heavy metals to ultra-low levels, residual water-soluble dye, aluminum content.

Advantages and limitations

• Red 40 (dye): high color strength, clean bright hue, easy dosing in water, broad pH window; may bleed/migrate in moist matrices and is unsuitable for oils.

• Red 40 Lake: no bleeding in anhydrous/fat phases, excellent for lip products and coatings; requires proper dispersion (wetting + shear) and careful PSD selection to avoid speckling.

Application areas

• Food (E129): soft drinks, syrups, confectionery, gel desserts, ices, bakery icings/fillings (aqueous phase). Lakes may be permitted for fat-based confectionery coatings where regulations allow.

• Cosmetics: shampoos, body washes, water-based makeup (dye); lipsticks, balms, pressed/loose powders, nail enamel (lake).

• Pharma: oral liquids/suspensions (dye), tablet/capsule coatings (dye or lake), brand/dose identification.

Formulation guidance

• Dye (aqueous): pre-dissolve in water or glycerin; add under agitation. Use chelators (EDTA/citrate) when hard water or metals are present; maintain pH ~2–9 for best stability; minimize redox stress (ascorbate + Fe/Cu).

• Lake (anhydrous/lipid): pre-disperse in low-viscosity esters (e.g., MCT, isododecane, light alkyl benzoates) with suitable wetting agents; apply high shear (three-roll mill/ball mill or high-shear mixer). Calibrate wax/oil balance in lipsticks for uniform payoff.

• PSD selection: finer PSD improves hiding and uniformity but may increase viscosity; coarser grades can speckle—optimize for the vehicle.

• Co-coloring: blend with Yellow 5/6, Blue 1, or iron oxides to tune from strawberry to ruby to deep crimson.

Quality & specifications (typical themes)

• Identity/strength by UV–Vis (λmax, absorbance).

• Subsidiary colors within narrow limits.

• Heavy metals (Pb, As, Cd, Hg) at very low levels; antimony control for lakes.

• Moisture/volatile matter, insolubles (for the dye), aluminum content & PSD (for lakes).

• Micro not usually a primary concern for dry pigments but good practice applies.

Safety and regulatory

• EU (Cosmetics, Reg. 1223/2009): CI 16035 listed in Annex IV (approved colorants) with purity specs; lakes also permitted within specs.

• EU (Food): E129 authorized with category-specific limits and an ADI (Acceptable Daily Intake) established by risk assessors; foods containing certain azo dyes require the label warning “may have an adverse effect on activity and attention in children.”

• USA (FDA): FD&C Red No. 40 and Aluminum Lakes are certifiable color additives; batch certification is mandatory. Specific drug/cosmetic uses may require label declaration.

• Hypersensitivity: overall low incidence; rare cases of urticaria/intolerance reported—ensure compliant labeling where required.

• Nutrition: non-caloric; not a source of protein/fat/carbohydrates.

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

Stability, storage, and shelf life

• Store cool, dry, and protected from light, in sealed, opaque packaging.

• Avoid prolonged exposure to oxidants/reductants and transition-metal contamination.

• Typical shelf life: 36–60 months when properly stored.

• For lakes, keep dry to prevent caking; maintain closed containers to avoid moisture uptake.

Troubleshooting

• Fading/browning in beverages: redox reactions (ascorbate + Fe/Cu). Remedy: chelators, adjust redox, oxygen control, appropriate packaging.

• Haze/precipitation: high electrolytes or metals—lower ionic strength, add chelators, or polish filter.

• Bleeding in icings/creams: replace some soluble dye with Red 40 Lake in fat phases or use barrier coatings.

• Speckling in lipsticks/powders: improve dispersion (wetting agent + higher shear) or select a finer PSD grade.

Conclusion
Red 40 (CI 16035 / E129) is a workhorse bright red for aqueous foods, cosmetics, and pharmaceuticals, prized for high strength, clean hue, and broad pH tolerance. The Aluminum Lake extends performance to oily/anhydrous systems with superior bleed resistance. With sound purification, metal/pH management, appropriate grade/PSD selection, and robust dispersion, formulators can achieve stable, compliant, and reproducible red shades across product categories.

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) Barros, W. R., Steter, J. R., Lanza, M. R., & Motheo, A. J. (2014). Degradation of amaranth dye in alkaline medium by ultrasonic cavitation coupled with electrochemical oxidation using a boron-doped diamond anode. Electrochimica Acta, 143, 180-187.

Abstract. Amaranth dye is used widely in the processing of paper, textiles, foods, cosmetics, beverages and medicines, and effluents contaminated with this compound are discharged daily into the environment. Recent studies have shown that azo dyes, especially those such as amaranth dye that have been classified as endocrine disruptors, may cause adverse effects to animal and human health. This paper describes the application of electrochemical oxidation (with a boron-doped diamond BDD thin-film anode) coupled with ultrasound sonolysis (20 kHz and 523 W cm−2) to the removal of amaranth dye from dilute alkaline solution. The electrochemical and sonoelectrochemical processes (ECh and SECh, respectively) were carried out at constant current density (10 to 50 mA cm−2) in a single compartment cylindrical cell. Sonolysis was virtually less useful for the decolorization and degradation of amaranth dye, whilst ECh and SECh were more effective in degrading the dye with almost complete removal (90 - 95%) attained after 90 min of experiment at an applied current density of 50 mA cm−2. Degradation of the dye followed pseudo first-order kinetics in both processes, but the rate of reaction was faster with the SECh treatment confirming a synergistic effect between the cavitation process and the electrochemical system. Additionally, at low applied current densities (10 and 25 mA cm−2), SECh was considerably more effective than ECh for the amaranth dye mineralization. Although at 35 and 50 mA cm−2, the two processes showed the respective removal of total organic carbon values: (i) 85% for the ECh and 90% for the SECh at 35 mA cm−2; (ii) 96% for the ECh and 98% for the SECh at 50 mA cm−2. It is concluded that SECh presented the most favorable results for the decontamination of wastewaters containing azo dye compounds.

Rovina K, Siddiquee S, Shaarani SM. 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. 

Abstract. Allura Red AC (E129) is an azo dye that widely used in drinks, juices, bakery, meat, and sweets products. High consumption of Allura Red has claimed an adverse effects of human health including allergies, food intolerance, cancer, multiple sclerosis, attention deficit hyperactivity disorder, brain damage, nausea, cardiac disease and asthma due to the reaction of aromatic azo compounds (R = R' = aromatic). Several countries have banned and strictly controlled the uses of Allura Red in food and beverage products. This review paper is critically summarized on the available analytical and advanced methods for determination of Allura Red and also concisely discussed on the acceptable daily intake, toxicology and extraction methods.