Red 40
Synonyms: Allura Red AC, FD&C Red No. 40, CI 16035, E129 (food use); insoluble variant: Red 40 Lake (Aluminum Lake of CI 16035)
Functions (food/cosmetic/pharma): water-soluble red colorant (bright, slightly bluish red), tonalizer for aqueous systems; as a lake, an insoluble pigment for anhydrous/lipid phases
Definition
Red 40 is a synthetic azo dye supplied as the sodium salt, highly water-soluble, used to impart a vivid red shade to beverages, confections, bakery icings, pharmaceuticals, and aqueous cosmetics. Red 40 Lake is produced by laking the dye onto aluminum hydroxide, yielding an oil-dispersible pigment for lipsticks, pressed powders, coatings, and other low-water matrices.
Calories (energy value)
0 kcal per 100 g (synthetic colorant; no metabolizable energy).
Composition and structure
Colorant: Allura Red AC, sodium salt (CI 16035).
Purity controls: tight limits on subsidiary colors, inorganic impurities, and heavy metals (Pb, As, Cd, Hg); salt/volatiles within spec.
Physical form: red powder or granules (shade varies slightly with pH/ionic strength).
Physicochemical properties (indicative)
Solubility: freely soluble in water; insoluble in oils (use Lake form for oils).
λmax (UV–Vis): typically ~504–510 nm in water at near-neutral pH.
pH tolerance: color stable over ~2–10; hue shifts subtly with pH (more bluish in alkaline).
Light/heat stability: generally good; susceptible to strong oxidants and reducing systems (e.g., ascorbate + transition metals).
Metal sensitivity: Fe³⁺/Cu²⁺ can affect tone; chelators (EDTA/citrate) help maintain clarity and shade.
Manufacturing overview (soluble dye)
Azo coupling from sulfonated aromatic intermediates under controlled conditions.
Neutralization to the sodium salt.
Purification (filtration, washing, ion-exchange/deionization) to reduce salts/by-products/metals.
Drying and standardization (moisture, tinctorial strength); optional granulation for better handling.
(For Red 40 Lake: co-precipitate the dye onto aluminum hydroxide, then wash, dry, and micronize/classify to target particle-size distribution.)
Advantages and limitations
Advantages (soluble): strong color strength, clean shade, easy dosing in aqueous systems, broad pH window.
Limitations: bleeding/migration in moist matrices; not suitable for lipid phases (use Lake). Sensitive to strong redox environments; potential interactions with sulfites/ascorbate in metal-rich systems.
Application areas
Food (E129): soft drinks, syrups, confections, gel desserts, ice creams/ices, bakery icings/fillings (aqueous phase).
Cosmetics: shampoos, shower gels, liquid soaps, aqueous make-up; Red 40 Lake for lip products and pressed powders.
Pharmaceuticals: syrups, suspensions, tablets/capsule coatings; also used for dose/brand identification.
Formulation guidelines
Pre-dissolve in water or glycerin; add to batch under agitation to avoid clumping.
Chelation: include EDTA/citrate to minimize metal-induced haze/tone drift, especially in hard-water beverages.
pH control: keep within ~2–9 for optimal stability; avoid strong oxidants/reductants.
Electrolyte load: high ionic strength can reduce clarity—optimize salts/acids and consider fining/filtration.
Lake use: pre-disperse in low-viscosity esters/oils; employ high shear (three-roll/ball mill) for lipsticks/pressed powders to achieve uniform payoff.
Safety and regulatory
EU (Cosmetics, Reg. 1223/2009): CI 16035 listed in Annex IV (approved colorants) with purity specifications; generally allowed across categories within spec.
EU (Food): E129 authorized with category-specific limits and an ADI; foods containing certain azo dyes (including E129) require the label warning “may have an adverse effect on activity and attention in children.”
USA (FDA): FD&C Red No. 40 and its Aluminum Lakes are certifiable color additives; batch certification is mandatory. Certain drug/cosmetic uses require label declaration.
Hypersensitivity: rare reports of urticaria or intolerance in sensitive individuals; overall incidence is low.
Heavy metals: comply with strict limits for Pb, As, Cd, Hg (and Sb for lakes).
Il problema legato ai coloranti azoici (monoazo o diazo) è la degradazione fotocatalitica (1) che porta ad un'eventuale ossidazione ed alla successiva formazione di impurità come le ammine aromatiche alcune delle quali svolgono attività cancerogena.
Stability, storage, quality
Store cool, dry, and protected from light, in sealed, opaque containers.
Shelf life: typically 36–60 months under proper storage.
QC: UV–Vis identity/strength (λmax, absorbance), tinctorial strength, solution pH, insolubles, trace metals, and (for lakes) PSD (D10/D50/D90) and aluminum content.
Troubleshooting
Fading or browning: often due to oxidants/reductants (e.g., ascorbate + Fe/Cu). Add chelators, adjust redox environment, or protect with appropriate antioxidants; review packaging O₂ ingress.
Haze/precipitation: high electrolytes or metal ions—reduce ionic load, add chelators, or fine/filter.
Migration in icings/creams: replace part of soluble Red 40 with Red 40 Lake in fat phases or use barrier coatings.
Conclusion
Red 40 (CI 16035 / E129) is a workhorse bright red for aqueous foods, cosmetics, and pharmaceuticals, valued for high strength, clean hue, and wide pH stability. The Lake form extends use to oily/anhydrous applications. With proper purity control, pH/metal management, and appropriate selection of soluble vs lake, formulators can achieve consistent, compliant, and long-lasting red shades.
- Formula molecolare: C18H14N2Na2O8S2
- Peso molecolare: 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
Sinonimi:
- 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
