Acetylated Starch (CAS#9045-28-7) – E1420 Food Additive, Modified Thickener & Oilfield Chemical

1. Properties:

• Appearance and Physical Form: Acetylated starch (starch acetate, CAS#9045-28-7) is supplied as a white to off-white free-flowing powder or granules, produced from various botanical sources (potato, corn/maize, tapioca/cassava, or wheat). Pregelatinised grades are available as flakes, amorphous powder, or coarse particles for instant thickening applications.
• Solubility: The product is insoluble in cold water and ethanol (96%). Upon heating in water, acetylated starch forms a typical colloidal solution with viscous and thickening properties. The improved solubility of acetylated starch relative to native starch arises from acetylation, which reduces inter‑ and intra‑molecular hydrogen bonding within the starch matrix.
• Chemical Properties: Acetylated starch is a non‑ionic, chemically modified starch produced by esterifying food-grade native starches with acetic anhydride or vinyl acetate under alkaline conditions, in accordance with Good Manufacturing Practice (GMP). The acetylation introduces acetyl groups (–CO–CH₃) onto the hydroxyl groups (–OH) at the C-2, C-3, and C-6 positions of the α-d-glucose units in the starch polymer. This chemical modification disrupts the crystalline structure of native starch, weakening the interactions between starch molecules and reducing the tendency of the polymer to re‑associate (retrogradation).
  • Low Gelatinization Temperature: Acetylation lowers the pasting temperature of starch to approximately 60–70°C, compared to 80–85°C for native starch. This allows the starch to hydrate and thicken at lower processing temperatures, conserving energy and preserving the flavour and colour of heat‑sensitive ingredients.
  • Excellent Freeze‑Thaw Stability: By reducing retrogradation and syneresis (water separation), acetylated starch significantly improves freeze‑thaw stability. It can withstand multiple freeze‑thaw cycles without weeping or textural breakdown, making it indispensable for frozen food applications.
  • High Paste Clarity: The introduction of acetyl groups reduces the turbidity of starch pastes, producing clear, translucent, or transparent gels. This is particularly important for visually appealing sauces, fruit fillings, and glazes where clarity is a quality parameter.
  • Acid, Heat, and Shear Resistance: Acetylation enhances the resistance of starch to acidic conditions (stable as low as pH 3–4), high‑temperature processing (e.g., retorting, UHT), and mechanical shear encountered in industrial mixers, pumps, and homogenisers. The paste viscosity is well‑maintained under these harsh processing conditions.
  • Digestibility and Caloric Value: Starch acetate containing up to 2.5% acetyl groups is approximately 93.7% as digestible as native starch (Turner, 1961). Digestibility by fungal amyloglucosidase ranges from 68–81% of that of native starch, while digestibility by pancreatic and porcine mucosal enzymes is approximately 90% of unmodified starch. No significant difference in caloric value has been observed between native and acetylated starch.
  • Film‑Forming and Emulsifying Properties: Acetylated starch exhibits enhanced water/oil absorption capacity, emulsifiability, and film‑forming properties. It forms oxygen‑impermeable edible films, making it suitable for coatings and biodegradable packaging applications.
  • Regulatory Status: Acetylated starch (E1420) is approved as a food additive with no specified maximum usage level (quantum satis) and is considered safe for general food use, including infant formula and weaning foods. The acceptable daily intake (ADI) is “not specified,” the highest safety classification.

2. Applications:

Food & Beverage Industry (Primary – E1420 Thickener, Stabilizer, Texturizer):

• Canned Foods and Retorted Products (Soups, Sauces, Vegetables): Acetylated starch provides excellent heat stability and acid resistance, preventing thinning and syneresis during high‑temperature retort processing (121°C). It maintains consistent viscosity and texture throughout shelf life, even in low‑pH formulations such as tomato‑based products. Typical use level: 1–4%.
• Frozen Foods (Ready Meals, Vegetables, Sauces in Ice Cream): The superior freeze‑thaw stability of acetylated starch makes it the preferred choice for frozen products. It prevents water separation (syneresis) after multiple freeze‑thaw cycles, preserving the creamy, homogenous texture of sauces and fillings. Frozen sauces and vegetables enhanced with acetylated cross‑linked waxy maize starch display enhanced freeze‑thaw resilience.
• Bakery Fillings and Glazes (Pie Fillings, Pastry Cream, Fruit Preparations): Acetylated starch provides a smooth, glossy texture and high clarity to fruit fillings and bakery glazes. It prevents boil‑out during baking and maintains viscosity upon cooling, resulting in clean, attractive product presentation.
• Sauces, Dressings, and Condiments (Mayonnaise, Ketchup, Salad Dressings, Gravy): The starch functions as a non‑ionic thickener and stabiliser, providing desirable body and mouthfeel without masking flavour. Its resistance to low pH (3–4) makes it suitable for vinegar‑based dressings and ketchup.
• Processed and Imitation Cheese (Cheese Spreads, Slices, Analogues): Acetylated starch contributes to melt, stretch, and sliceability in processed cheese products while providing excellent transparency and elasticity. It also functions as a gelling agent, delivering melt and stretch characteristics essential for cheese analogue formulations.
• Dairy Products and Frozen Desserts (Yoghurt, Puddings, Custards, Ice Cream): The starch improves texture, creaminess, and freeze‑thaw stability while preventing whey separation.
• Baby Food and Weaning Formulae: Acetylated starch is approved for use in infant formulas and baby food as a safe thickening agent, providing appropriate viscosity for safe swallowing and improved texture. Its high purity and safety profile make it a preferred choice for sensitive populations.
• Instant Noodles, Pasta, and Surimi (Imitation Crab): In noodles and pasta, acetylated starch reduces dehydration time, improves elasticity, and provides a firm, springy texture. In surimi seafood products, it functions as a binder and water‑holding agent, improving yield and texture.
• Gluten‑Free and Clean‑Label Products: As a plant‑derived, non‑GMO, non‑allergenic ingredient, acetylated starch is widely used in gluten‑free bakery (breads, cakes, cookies) and clean‑label formulations to replace the functional properties of gluten.
• Confectionery and Snacks (Gummies, Marshmallows, Extruded Snacks): The starch functions as a gelling agent, binder, and texturizer, providing the desired chewiness, hardness, and mouthfeel.

Oil & Gas Industry – Drilling Fluids & Enhanced Oil Recovery (Fluid Loss Control & Viscosifier):

• Water‑Based Drilling Mud (WBM) Fluid Loss Reducer: Acetylated starch is employed as a high‑performance filtration control agent and viscosifier in water‑based drilling fluids. Studies have demonstrated that mud samples containing acetylated cassava or maize starch exhibit the smallest filtrate volumes and filtrate losses within American Petroleum Institute (API) specifications. Importantly, acetylated starch outperforms conventional carboxymethyl cellulose (CMC) under high‑pressure, high‑temperature (HPHT) wellbore conditions, maintaining its fluid‑loss control properties where native starch would thermally degrade.
• Drill‑In, Completion, and Workover Fluids: The non‑ionic nature and reversible filter cake formed by acetylated starch make it an ideal additive for drill‑in and completion fluids where reservoir protection is critical. The thin, deformable filter cake is easily removed during well clean‑up, minimising formation damage.
• Enhanced Oil Recovery (EOR): Acetylated cassava starch has been investigated for use in hybrid nanofluids with silica nanoparticles for chemical EOR applications. The acetylation enhances viscosity and thermal stability, while silica nanoparticles contribute interfacial activity and wettability alteration.
• Cementing Slurries: Acetylated starch acts as a fluid loss control additive and rheology modifier in oil well cement slurries, reducing filtrate invasion into permeable formations and preventing gas migration during cement setting.

Pharmaceutical Industry – Excipient and Formulation Aid:

• Tablet Binder: Acetylated starch functions as an effective binder in tablet formulations, providing good flow and compression properties. Its enhanced swelling power and water absorption capacity facilitate uniform granule formation and tablet hardness. Studies have shown acetylated starch to be a useful binder when a tablet with fast disintegration is desired.
• Tablet Disintegrant: The improved swelling power and water absorption capacity of acetylated starch promote rapid tablet disintegration upon contact with gastrointestinal fluids, accelerating drug release.
• Controlled‑Release and Sustained‑Release Formulations: Due to its reduced digestibility and enhanced stability, acetylated starch serves as a polymeric excipient in controlled‑release and sustained‑release oral dosage forms, modulating drug release profiles over extended periods.
• Bulking Agent, Film Former, and Granulation Aid: Acetylated starch is used as a bulking agent in low‑dose formulations, as a film former for coated tablets, and as a wet granulation aid in the manufacture of solid dosage forms.

Paper Industry – Coating & Surface Treatment:

• Paper Coating Binder: Acetylated starch functions as a binder and adhesive in paper coating formulations, enhancing surface strength, printability, gloss, and resistance to ink feathering.
• Surface Sizing Agent: In surface sizing, acetylated starch improves paper surface properties, including smoothness, stiffness, and water resistance. It can also be used as a filler and stability increasing agent for paper.
• Pigment Dispersant: The starch aids in the uniform dispersion of pigments (clay, calcium carbonate, titanium dioxide) in coating colour formulations.

Textile Industry – Warp Sizing and Finishing:

• Warp Sizing Agent: Acetylated starch is used in textile warp sizing to improve yarn strength, reduce hairiness and breakage during weaving, and enhance fabric quality. The esterified starch provides extremely high viscosity stability.
• Textile Printing Thickener: It functions as a thickener in textile printing pastes, providing sharp pattern definition, uniform dye transfer, and easy wash‑off after printing.
• Fabric Finishing: Acetylated starch imparts stiffness and body to finished fabrics.

Adhesives & Industrial Binders:

• Biodegradable Adhesives: As a renewable, biodegradable polymer, acetylated starch is used as a base for environmentally friendly adhesives, including laminating adhesives, paper bag adhesives, wallpaper pastes, and envelope glues. Esterified starch can provide extremely high viscosity stability, a key requirement for adhesive applications.
• Packaging Adhesives: The starch functions as a binder in corrugated board adhesives and carton sealing glues.
• Foundry Binders: Acetylated starch is used as a binder in foundry sand for metal casting applications.

Other Industrial Applications:

• Construction Materials: Acetylated starch is used as a binder in gypsum board, wall putties, and dry‑mix mortar formulations, improving workability and adhesion.
• Water Treatment: The starch functions as a flocculant and coagulant aid in industrial wastewater treatment and sludge dewatering operations.
• Agrochemicals: Acetylated starch is used as a binder, thickener, and suspending agent in pesticide and fertiliser formulations.
• Biodegradable Films & Packaging: The film‑forming properties of acetylated starch are exploited in the production of biodegradable food packaging films, edible coatings for fruits and vegetables, and disposable cutlery.
• Personal Care & Cosmetics: Acetylated starch is used as a thickening agent, binder, and film former in cosmetic formulations.

3. Preparation Method:

• Laboratory Method: Acetylated starch can be synthesised in the laboratory by reacting native starch with acetic anhydride in an aqueous medium in the presence of sodium hydroxide (NaOH) as a catalyst. The reaction is carried out at 40°C and pH 9 for approximately 90 minutes. The degree of substitution (DS) is controlled by adjusting the reaction time, temperature, and the concentration of the acetylating agent. Higher DS products (up to 2.5) are soluble in organic solvents. Alternative green chemistry techniques, such as microwave heating, pulsed electric fields, ultrasonication, and extrusion, have also been demonstrated for the environmentally friendly synthesis of acetylated starch. The crude product is neutralised with dilute acid, washed with water, dried at 50–60°C, and milled to the desired particle size.
• Industrial Process: Industrial production of high‑quality acetylated starch (E1420) follows a large‑scale batch or continuous esterification process:
  1. Slurry Preparation: Native starch (from potato, maize, tapioca, or wheat) is slurried in water with stirring.
  2. Alkaline Activation: Sodium hydroxide is added to raise the pH to approximately 7.5–9.0, activating the hydroxyl groups on the starch molecules.
  3. Esterification (Acetylation): Acetic anhydride or vinyl acetate is slowly added to the activated starch slurry at a controlled temperature (40–70°C) under constant agitation. The reaction is maintained under alkaline conditions (pH 9–11) for 1–4 hours. Acetyl groups are covalently attached to the hydroxyl groups of the starch polymer via ester linkages.
  4. Termination & Neutralisation: After the desired degree of substitution (typically ≤0.1 DS, corresponding to ≤2.5% acetyl groups) is reached, the reaction mixture is neutralised with dilute hydrochloric or phosphoric acid to adjust the pH to 5.0–7.0.
  5. Purification (Washing): The crude acetylated starch is washed repeatedly with water to remove unreacted acetic anhydride, sodium acetate, and residual salts, followed by filtration or centrifugation.
  6. Optional Bleaching: The product may be bleached with hydrogen peroxide or sodium hypochlorite to improve whiteness.
  7. Drying: The purified wet starch cake is dried in flash dryers, rotary dryers, or fluidised bed dryers to a moisture content of ≤15% (cereal) or ≤18% (other starches).
  8. Milling & Sieving: The dried product is milled to break up agglomerates and sieved to the desired particle size distribution (typically 80–120 mesh).
  9. Blending & Quality Control: Batches are blended for consistency. Key quality parameters include acetyl group content (≤2.5% on dried basis, by titration), loss on drying (moisture), pH (4.5–7.0), viscosity (by Brabender or Brookfield), ash content (≤0.5%), heavy metals (lead, arsenic), sulfur dioxide content, vinyl acetate residue (≤0.1 mg/kg for food grade), microbiological limits (TAMC, TYMC, pathogens), and particle size distribution.
  10. Packaging: The finished product is packaged in 25 kg multi‑wall moisture‑proof bags with polyethylene liners, 500–1000 kg FIBC (jumbo bags), or bulk containers for shipment.

4. Safety Information:

• Hazard Classification: Under GHS/CLP Regulation (EC) No 1272/2008, starch acetate (acetylated starch) is generally classified as a non‑hazardous or very low hazard product. Hazard pictograms are generally not required for most commercial grades. The substance is not classified as a PBT (Persistent, Bioaccumulative, Toxic) or vPvB (very Persistent, very Bioaccumulative) substance under current EU criteria. However, high dust concentrations may carry hazard statement H335 (May cause respiratory irritation). The product is non‑flammable and non‑explosive under standard conditions.
• Health Hazards:
  • Inhalation: Inhalation of airborne starch dust may cause mild respiratory tract irritation, coughing, or sneezing in sensitive individuals. Prolonged exposure to high dust concentrations may cause respiratory discomfort.
  • Skin Contact: Generally non‑irritating to intact skin. Prolonged or repeated contact may cause mild mechanical irritation or drying due to the abrasive effect of the powder.
  • Eye Contact: May cause mild mechanical irritation due to dust particles.
  • Ingestion: Low acute oral toxicity (LD₅₀ > 5,000 mg/kg). The product is approved as a food additive (E1420) and is generally regarded as safe (GRAS) for human consumption. Acetylated starch is hydrolysed by intestinal enzymes and fermented by intestinal microbiota; it is not absorbed intact by the gut. Ingestion of large amounts may cause mild gastrointestinal discomfort (bloating, diarrhoea) due to its bulking effect.
• First Aid Measures:
  • Eye Contact: Rinse cautiously with plenty of water for several minutes. Remove contact lenses if present and easy to do. If eye irritation persists, seek medical attention.
  • Skin Contact: Wash skin with plenty of soap and water. Remove contaminated clothing. If skin irritation develops, seek medical advice.
  • Inhalation: Move person to fresh air. Keep at rest in a position comfortable for breathing. If symptoms (coughing, throat irritation) persist, seek medical advice.
  • Ingestion: Rinse mouth immediately. Do NOT induce vomiting. Drink water to dilute if conscious and able to swallow. Seek medical attention if a large amount is ingested or if symptoms develop.
• Fire & Explosion Hazards: Acetylated starch is not combustible, but it may burn if involved in a fire. Accumulated settled dust may form explosive concentrations in air when disturbed and dispersed, as with any organic dust. In case of fire, use water spray, foam, dry chemical powder, or CO₂ as extinguishing media. Thermal decomposition may produce irritating and toxic fumes including carbon monoxide (CO), carbon dioxide (CO₂), and low molecular weight organic compounds.
• Personal Protective Equipment (PPE):
  • Respiratory protection: Use a dust mask (N95 or P2 respirator) if airborne dust concentrations are present or when handling powder grades in poorly ventilated areas.
  • Eye protection: Safety glasses or dust‑resistant safety goggles to prevent mechanical eye irritation from dust particles.
  • Skin protection: Chemical‑resistant gloves (nitrile or neoprene) and protective clothing to minimise skin contact and dust exposure.
  • General hygiene: Wash hands thoroughly after handling. Do not eat, drink, or smoke in work areas. Minimise dust generation and avoid breathing dust.
• Environmental Precautions: Acetylated starch is a biodegradable modified natural polymer. The substance is not classified as hazardous to the aquatic environment under current EU criteria. However, frequent or large spills may have adverse effects on the environment. Avoid large‑scale release into natural water bodies, drains, or soil. Comply with local environmental regulations for disposal.
• Storage & Stability: Store in tightly closed, moisture‑proof containers in a cool, dry, well‑ventilated area away from direct sunlight, heat sources, and strong oxidising agents. Acetylated starch is hygroscopic; exposure to atmospheric moisture leads to caking, lump formation, and reduced functional performance. Under recommended storage conditions (room temperature, low humidity, <30°C), the product has a shelf life of 24 months to 5 years (grade dependent) in sealed original containers. Upon opening, use the product as quickly as possible to prevent moisture regain.
• Regulatory Compliance: Acetylated starch (starch acetate, CAS#9045-28-7, EC#618-556-3) is listed on EINECS, TSCA, DSL, AICS, NZIoC, ENCS, KECI, and other regional chemical inventories.
  • US FDA: Acetylated starch is affirmed as GRAS (Generally Recognized as Safe) under 21 CFR §172.892 for use as a direct food additive. It is also permitted for use as a food contact substance under multiple sections of 21 CFR.
  • EU Food Additive Status: Acetylated starch is authorised as a food additive under the designation E1420 pursuant to Regulation (EC) No 1333/2008 and meets the purity criteria set out in Commission Regulation (EU) No 231/2012. It is approved for use in food products across the European Union with no maximum usage level (quantum satis).
  • JECFA (Joint FAO/WHO Expert Committee on Food Additives): Starch acetate has an ADI (Acceptable Daily Intake) of “not specified”, the highest safety category, indicating no safety concern at any level of intake.
  • Kosher / Halal / Allergen‑Free: Kosher, Halal, and allergen‑free (gluten‑free, non‑GMO) certifications are available for food and pharmaceutical grades upon request.
  • Oilfield Compliance: Acetylated starch used as a drilling fluid additive may be subject to local environmental regulations for offshore and onshore discharge.