| HS Code | 334592 |
| Chemical Name | Sorbic Acid |
| Systematic Name | (2E,4E)-Hexa-2,4-dienoic acid |
| Cas Number | 110-44-1 |
| Molecular Formula | C6H8O2 |
| Molar Mass | 112.13 g/mol |
| Appearance | White crystalline powder with a faint acidic odor |
| Melting Point | 134.5 °C |
| Boiling Point | 228 °C (decomposes) |
| Solubility In Water | 1.5 g/L at 20 °C |
| Pka | 4.76 |
| Density | 1.27 g/cm³ |
| Flash Point | 127 °C |
| E Number | E200 |
As an accredited Sorbic Acid factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sorbic Acid, 25 kg net, packaged in double-lined polyethylene bags inside sealed fiber drums with clear hazard labeling. |
| Container Loading (20′ FCL) | Sorbic Acid packed in 25 kg bags on pallets, loaded into a 20′ FCL container, approximately 20 metric tons per shipment. |
| Shipping | Sorbic acid ships as a stable, non-hazardous crystalline powder in sealed, moisture-resistant bags or drums. Keep dry, cool, and away from strong oxidizers. Standard freight is suitable; no special hazmat labeling required. Ensure containers are intact to prevent dust release and contamination during transit. |
| Storage | Store sorbic acid in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and moisture. Keep containers tightly sealed and clearly labeled, preferably in original packaging. Protect from strong oxidizing agents and incompatible materials. Maintain stable temperatures and avoid excessive humidity to preserve stability and prevent degradation or clumping. |
| Shelf Life | Sorbic acid has a typical shelf life of two years when stored in a cool, dry, tightly sealed container away from light. |
In yeast-leavened and chemically leavened bakery products with post-bake water activity (aw) between 0.86 and 0.96, sorbic acid is incorporated at 0.03–0.10% on flour weight, either as a dry pre-blend with sodium chloride and diacetyl tartaric acid esters of mono- and diglycerides or as a 20–30% dispersion in a high-melting fat to prevent localized acid hydrolysis of starch. Sorbic acid exerts antifungal activity through the undissociated molecule; with a pKa of 4.76, a mixed dough at pH 4.9 leaves approximately 42% of total sorbate in the membrane-active neutral form, while a post-bake crumb at pH 4.4 retains close to 70%. This pH dependency drives buffer selection: monocalcium phosphate or citric acid is dosed at 0.2–0.5% of flour weight to depress finished crumb pH below 5.0, and water activity is measured by dew-point hygrometry following ISO 18787. In straight-dough systems evaluated on spiral mixers with tool speeds of 60–75 rpm, addition of sorbic acid at the start of mixing at 0.10% extends yeast lag phase by 15–25 min and reduces proof volume at 60 min by 6–10% in published baking trials; moving the acid addition to the final 2 min of mixing or applying a post-bake surface spray reduces the fermentation interference. On tortilla hot-press lines with dough temperature 34–38 °C and conveyor cooling to 26 °C over 12–18 min, a 10% potassium sorbate solution applied as a mist before stacking produces mold-free shelf life beyond 21 days at aw 0.92, but condensation inside polypropylene packaging can cause sorbate migration to the film and reduce headspace efficacy. Sorbic acid is not a direct substitute for calcium propionate in high-pH lean doughs above pH 5.5, where the undissociated fraction falls below 15% and required doses exceed sensory thresholds for bitterness.
| pH of aqueous system | Undissociated sorbic acid (%) | Ionized sorbate (%) |
|---|---|---|
| 3.0 | 98.3 | 1.7 |
| 4.0 | 85.2 | 14.8 |
| 4.5 | 64.5 | 35.5 |
| 5.0 | 36.5 | 63.5 |
| 5.5 | 15.4 | 84.6 |
| 6.0 | 5.4 | 94.6 |
Under the US standard of identity for pasteurized process cheese spread, 21 CFR 133.179, sorbic acid or potassium sorbate is permitted up to 0.3% by weight of the finished product. In a 60% moisture, 20% fat spread prepared at pH 5.4, a 0.2% sorbic acid dose leaves only 18.6% undissociated acid, because product pH is well above the 4.76 pKa; the remaining ionized sorbate has negligible antifungal membrane activity. Formulators therefore run preservation challenge studies with a mixed inoculum of Aspergillus niger, Penicillium commune, and Zygosaccharomyces bailii rather than single-species mold plates, and the relevant enumeration method is ISO 21527-1 for high-moisture dairy matrices. In a batch Stephan cooker with indirect steam jackets and a 85–92 °C hold of 5–8 min, heat-stable potassium sorbate shows no measurable loss of the conjugated diene structure by UV absorption at 252 nm, but adding free acid before emulsifying salts can precipitate calcium sorbate in hard water with calcium hardness above 120 mg/L CaCO3. On continuous chilled-roll lines, potassium sorbate is added as a 25% aqueous solution after trisodium citrate or disodium phosphate has dispersed and the molten cheese mass reaches 70 °C; this prevents curd particle sludge on scraped surface heat exchanger blades. Sorbate does not control post-process aerobic sporeformers at pH 5.8 in extended chilled storage beyond 90 days, which is an explicit limitation when packages are opened and reclosed under refrigerated distribution.
Residual sugar above 1.5 g/L in still wine is a refermentation risk if viable Saccharomyces cerevisiae remains after coarse filtration. Potassium sorbate is dosed at 100–200 mg/L of sorbic acid equivalent in the final blend tank, after complete malolactic conversion and after 0.45 µm crossflow filtration, because sorbic acid inhibits yeast but does not destroy bacteria. Under Commission Regulation (EC) No 606/2009, the maximum sorbic acid content in wine is 200 mg/L. At a white wine pH of 3.2, the undissociated fraction is 97.3%; at a red wine pH of 3.6, it is 93.5%; this accounts for the comparatively low dose. If viable lactic acid bacteria remain, particularly Oenococcus oeni, sorbate can be converted to 2-ethoxyhexa-3,5-diene, producing geranium-leaf taint at sensory thresholds below 100 ng/L. The compound is therefore contraindicated after incomplete malolactic fermentation, and lees resuspension after addition is avoided. On a 10,000 L stainless steel tank, 1.0–2.0 kg of potassium sorbate is pre-dissolved in 50 L of cold water and metered through a bottom-valve dosing line while a centrifugal pump recirculates at 5,000–8,000 L/h for 20 min. Free SO2 is maintained at 0.5–0.8 mg/L molecular form to prevent oxidation and bacterial conversion of sorbate; sorbic acid is not a replacement for sulfur dioxide in wine.
| Application | Regulatory or standard reference | Numerical constraint |
|---|---|---|
| Bakery products | EU Regulation (EC) No 1333/2008, E200; US FDA 21 CFR 182.3089 | 0.03–0.10% flour weight, process-dependent |
| Processed cheese spread | US FDA 21 CFR 133.179 | 0.3% by weight maximum |
| Still wine | Commission Regulation (EC) No 606/2009 | 200 mg/L maximum |
| Cosmetic preparations | EU Regulation (EC) No 1223/2009, Annex V | 0.6% as acid in ready-for-use preparation |
| Compound feed | EU Regulation (EC) No 1831/2003, technological additive group 1a | 0.02–0.3% dry matter, storage-dependent |
In leave-on and rinse-off emulsions formulated at pH 4.8–5.2, potassium sorbate is used at 0.2–0.5% of sorbic acid equivalent, commonly with phenoxyethanol at 0.4–0.6% to broaden antibacterial coverage, because sorbate alone is predominantly fungistatic and weak against Pseudomonas aeruginosa in challenge testing. Annex V of Regulation (EC) No 1223/2009 permits sorbic acid and its salts up to 0.6% as acid in ready-for-use preparations. Preservation efficacy is evaluated under ISO 11930 by inoculating a 20 g sample with 10^5–10^6 CFU/g of Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, Aspergillus brasiliensis, and Escherichia coli; the sorbate system must achieve a 3-log reduction for bacteria at day 7 and no recovery at day 28 in leave-on formulations. Because sorbic acid has a pKa of 4.76, a high-pH liquid soap at pH 6.0 retains only 5.4% undissociated acid, making sorbate ineffective above pH 5.5; water phases are therefore buffered with citric acid or sodium citrate before preservative addition. In heated water phases above 70 °C, sorbic acid can undergo oxidative degradation in the presence of unsaturated oils and trace iron above 1 mg/kg, causing progressive yellowing of transparent gels; nitrogen blanketing and post-cooling addition below 40 °C limit the degradation pathway. A practical production limit is the free acid’s cold-water solubility of 1.6 g/L at 20 °C, which excludes direct dissolution of solid sorbic acid in cold-process emulsion concentrates.
When sorbic acid replaces benzoate in ambient acidified oil-in-water dressings at pH 3.6–4.1, the target total sorbate is 0.05–0.10% by mass, delivered as potassium sorbate to avoid the 1.6 g/L cold-water solubility limit of the free acid. In a 1,000 kg batch prepared in a 1,500 L vacuum emulsifier with a high-shear rotor-stator running at 3,000 rpm for 12 min, potassium sorbate is pre-dissolved in the aqueous phase with salt, sugar, and vinegar before oil addition; adding solid sorbic acid after emulsification produces visible crystals on fill-line filter mesh above 20 µm. The preservative must inhibit Zygosaccharomyces bailii, an osmotolerant spoilage yeast that ferments high-sugar vinegar systems even at pH 3.2; challenge testing under ISO 21527-1 with 10^3 CFU/g inoculum requires no visible colonies at 25 °C for 28 days. Sorbic acid at 0.08% is effective against vegetative yeast but not against acetic acid bacteria in aeration gaps of partially filled containers; therefore fill temperature above 70 °C and nitrogen-assisted oxygen displacement are maintained. In emulsions with 30–50% oil and starch-based thickeners, sorbate at the upper range can reduce viscosity by 8–15% in accelerated 35 °C storage over 90 days due to acid hydrolysis of modified starch, requiring a rheology recheck against ISO 3219 using a cone-and-plate viscometer at 25 °C.
Technical-grade sorbic acid is metered into compound feed via micro-dosing lines at 0.02–0.3% of dry matter to suppress mould during storage when grain moisture exceeds 14.5% and water activity exceeds 0.70. The product is registered in the EU under Regulation (EC) No 1831/2003 as a technological feed additive in the preservatives functional group, with the same active chemical identity as food additive E200. In a 10 t/h pellet mill with a 4.5 mm die and 75–85 °C conditioner outlet temperature, sorbic acid is prediluted on a limestone carrier at 1:9 before the conditioner; undiluted acid at the same injection point creates dark acid-etched spots on the die face and increases pelletizer current by 5–8 A due to localized attack on the conditioning chamber. Because the free acid dissolves only at 1.6 g/L in water at 20 °C, the sodium or potassium salt is used for liquid post-pelleting sprays in high-moisture pet foods and feed blocks. During high-temperature extrusion at 115–130 °C with 25–30% process moisture, steam distillation can reduce total sorbate recovery by 10–20% depending on vent configuration; published recovery data for specific twin-screw profiles remains limited, and production trials typically over-dose or move to post-extrusion vacuum coating. Moisture-transfer rate in the cooling counterflow air stream, not dry-mix inclusion rate alone, determines final sorbate retention in porous pellets, because condensation at the pellet core transports water-soluble sorbate outward and produces surface concentration gradients.
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Sorbic acid, the linear unsaturated monocarboxylic acid 2,4-hexadienoic acid, is supplied as a white crystalline powder or granular solid with the food-additive identifier E200 and CAS registry number 110-44-1. The molecular formula C6H8O2 and molar mass 112.13 g/mol define the anhydrous form used in food preservation, cosmetic preservation, and feed preservation. The product is not assigned a single ISO model number; commercial model designations remain supplier-specific and commonly distinguish granular 20/40 mesh from fine powder 80/120 mesh grades. The normative identity is the FCC monograph and the entry for E200 in EU Regulation EC 1333/2008. In the United States, sorbic acid is affirmed as GRAS under 21 CFR 182.3089. The compound has a pKa of 4.76 at 25 °C, a melting range of 132–135 °C, and a water solubility of 0.16 g/100 mL at 20 °C. This solubility profile separates sorbic acid from its potassium salt and from sodium benzoate, and the pH-dependent dissociation equilibrium controls antimicrobial function.
The preservative effect of sorbic acid depends on the undissociated acid fraction, which diffuses across the microbial cell membrane and then dissociates inside the cell to depress intracellular pH. Using the Henderson-Hasselbalch relationship at 25 °C, the undissociated acid fraction is 85.2% at pH 4.0, 64.5% at pH 4.5, 36.5% at pH 5.0, 15.4% at pH 5.5, 5.4% at pH 6.0, and 1.8% at pH 6.5. This decline defines the operational upper boundary near pH 6.5 for most single-preservative applications. In comparison, benzoic acid has a pKa of 4.20; at pH 5.0 its undissociated fraction is only 13.7%. Therefore sorbic acid retains a measurable active acid fraction in weakly acidic matrices where benzoate systems are largely dissociated. Preservative efficacy in cosmetic matrices can be verified by challenge testing according to ISO 11930:2019, but food matrices require product-specific challenge protocols because composition and water activity alter minimum inhibitory concentrations.
In processed cheese, sorbic acid is dry-blended at 1000–3000 mg/kg as sorbic acid equivalent using a loss-in-weight feeder discharging into a horizontal ribbon blender. Batch-to-batch assay variation at low addition rates is reduced by pre-blending one part sorbic acid with five parts sodium chloride or starch before the main blending step. A rotary sifter with 20 mesh screen removes agglomerates that otherwise survive low-shear mixing. In surface application on baked goods, a 0.03–0.1% w/w solution is sprayed after baking; addition to yeast-leavened dough above approximately 0.05% w/w can suppress Saccharomyces cerevisiae proofing because the undissociated acid interferes with fermentation before baking. In wine, EU Regulation EC 1333/2008 permits sorbic acid-sorbates at 200 mg/L as sorbic acid; addition occurs after malolactic fermentation and before bottling to reduce the risk of secondary fermentation. In leave-on and rinse-off cosmetics, EU Cosmetics Regulation Annex V/57 permits sorbic acid at 0.6% w/w as acid in the ready-to-use preparation. For cold-process liquid products, the free acid is pre-dissolved in propylene glycol or ethanol because its water solubility is too low for direct dissolution at 20 °C. Published data for specific feed matrix configurations is limited, but compound feed preservation commonly uses sorbic acid in premixes at 0.025–0.1% w/w for mold control.
The selection between sorbic acid, potassium sorbate, sodium benzoate, and calcium propionate is governed by solubility, pKa, regulatory status, and the pH window of the finished product. Table 1 compares the quantitative parameters that determine preservative function in aqueous food and cosmetic systems.
| Parameter | Sorbic acid | Potassium sorbate | Sodium benzoate | Calcium propionate |
|---|---|---|---|---|
| CAS registry number | 110-44-1 | 24634-61-5 | 532-32-1 | 4075-81-4 |
| pKa at 25 °C | 4.76 | 4.76 | 4.20 | 4.87 |
| Water solubility at 20 °C | 0.16 g/100 mL | 58.2 g/100 mL | 62–66 g/100 mL | 49 g/100 mL |
| Useful pH window | ≤ 6.5 | ≤ 6.5 | ≤ 4.5 | ≤ 6.0 |
The free acid and potassium sorbate differ mainly in solubility and handling. Potassium sorbate dissolves rapidly in cold water and is preferred in beverage concentrates, sauces, and high-water systems. The conversion factor is 1.34 g potassium sorbate per gram of sorbic acid to deliver equivalent sorbic acid activity. Unlike sodium benzoate, sorbic acid retains measurable activity above pH 4.5 because its pKa is higher by 0.56 units. Unlike calcium propionate, sorbic acid is generally used at lower addition levels against yeast and mold, but it is less compatible with yeast-leavened dough before proofing.
FCC food-grade sorbic acid is controlled against the monograph limits shown in Table 2. The powder is typically assayed by nonaqueous titration after dissolution in ethanol; residual moisture is determined by vacuum oven at 60 °C for 4 h or by Karl Fischer titration per ISO 760:1978; melting range is measured by the capillary method of USP <741>; elemental impurities are measured by ICP-MS according to USP <233>. Particle-size distribution is supplier-specific and is not fixed by the FCC monograph.
| Parameter | Limit | Method |
|---|---|---|
| Assay on anhydrous basis | 99.0–101.0% | FCC titration |
| Melting range | 132–135 °C | USP <741> |
| Loss on drying | ≤ 0.5% | Vacuum oven, 60 °C, 4 h |
| Lead | ≤ 2 mg/kg | ICP-MS, USP <233> |
| Arsenic | ≤ 3 mg/kg | Hydride AAS |
| Sulfated ash | ≤ 0.1% | FCC residue on ignition |
| Particle size | Supplier-specific; granular grade typically ≥ 95% through 20 mesh | ASTM E11 sieve analysis |
For finished-product verification, sorbic acid in milk and milk products can be determined by ISO 9231:2008; in other food matrices, liquid chromatographic procedures such as AOAC 983.16 are commonly applied. The choice of method depends on fat content, protein load, and interfering preservatives. Matrix effects must be confirmed by recovery studies because sorbic acid can bind to proteins and partition into lipid phases.
At pH 6.2, the undissociated fraction of sorbic acid is approximately 3.5%, and at pH 6.5 it falls to 1.8%. In high-water products above this range, the free acid is not the preferred form because it may crystallize in cold liquid and contributes insufficient active acid. Potassium sorbate, with a water solubility of 58.2 g/100 mL at 20 °C, is used instead. A production-scale dosing system for potassium sorbate typically uses a stainless-steel mixing tank with a propeller mixer at 300–500 rpm and a positive-displacement pump; an in-line strainer of 100 µm removes undissolved scale before homogenization. Dry storage of sorbic acid should be maintained below 30 °C and below 60% RH to limit caking. The conjugated diene structure is susceptible to oxidation, so strong oxidizing agents should be avoided. Aqueous formulations containing transition metal ions such as copper or iron may exhibit accelerated auto-oxidation of sorbic acid, particularly at elevated temperature. In alkaline slurries above pH 7.0, salt formation increases solubility but reduces the concentration of the active undissociated acid.
In oil-in-water emulsions, the measured octanol-water partition coefficient log P of 1.33 indicates that sorbic acid partitions into the internal oil phase, reducing the aqueous concentration available for microbial inhibition. Published data for exact partition corrections across emulsion types is limited. For this reason, emulsion formulations frequently add the preservative to the water phase before emulsification and confirm preservative capacity by challenge testing per ISO 11930:2019. Unlike sodium benzoate, the pH activity of sorbic acid extends into food systems at pH 5.0–6.0; unlike calcium propionate, its antimicrobial spectrum is biased toward yeast and mold control at lower addition levels, but it is less suitable for yeast-leavened dough before proofing.