SODIUM PROPIONATE

CAS Number: 137-40-6
 Synonyms: Propionic acid sodium salt; E281; Sodium propanoate; Mycoban; Napropion; Impedex; Propionan sodný (Czech)
Physical Properties:
Appearance: White or colorless crystalline powder or granules (hygroscopic, deliquescent in humid air).
Solubility: Very soluble in water (approx. 100 g/100 mL at 15°C); slightly soluble in ethanol; practically insoluble in acetone and diethyl ether.
Molecular weight: 96.06 g/mol (anhydrous); 114.08 g/mol (as monohydrate; the monohydrate is common in commerce).
Melting point: 285-286°C (decomposes; does not truly melt).
pH (10% solution): 8.0–9.5 (alkaline due to hydrolysis to propionic acid + NaOH).
Density: 1.44 g/cm³ (crystalline).
Stability: Stable under normal storage; deliquescent so must be stored in airtight containers. Decomposes at high temperatures (>300°C) to sodium carbonate and organic vapors.
Odor: Very faint, characteristic propionic acid smell (much less pungent than the free acid).
Applications:
Bakery (primary use): Bread (white, whole wheat, rye), tortillas (corn and flour), English muffins, bagels, pita, flatbreads, cakes (especially those with high moisture), buns, rolls, and specialty breads (gluten-free, keto).
Cheese and dairy: Processed cheese slices, cheese spreads, cottage cheese, sour cream, yogurt (less common due to flavor).
Meat products: Some sausages and luncheon meats (surface treatment).
Animal feed: Pelleted feeds for cattle, pigs, poultry, and pets (to prevent mold and bacterial spoilage, especially in high-moisture conditions).
Cosmetics and personal care: Preservative in creams, lotions, shampoos, and conditioners (often in combination with sodium benzoate or potassium sorbate).
Pharmaceuticals: Preservative in oral liquid medicines and topical ointments.
Industrial: Corrosion inhibitor in coolants and cutting fluids; intermediate for organic synthesis.
Description:
 Sodium propionate (E281) is the sodium salt of propionic acid and is the most widely used propionate preservative in the food industry, especially in bakery products. Unlike liquid propionic acid (E280), which is corrosive, volatile, and has a strong odor, sodium propionate is a solid powder that is easy to weigh, handle, and incorporate into dry dough mixes. It is non-volatile and has only a faint, barely noticeable odor at typical usage concentrations (1000-4000 ppm in the finished product). Upon addition to dough, sodium propionate dissociates into sodium and propionate ions. The propionate ion then acts as the active antimicrobial agent, but only after it is protonated (converted to propionic acid) by the slightly acidic dough environment (pH 5.0-6.0). At bread pH (~5.5), approximately 30-40% of the propionate is in the undissociated acid form (the active species). This is sufficient to inhibit mold spore germination and mycelial growth. The mechanism (as described for E280) involves diffusion of undissociated propionic acid into the microbial cell, acidification of the cytoplasm, and metabolic disruption. Sodium propionate is particularly effective against Aspergillus, Penicillium, Cladosporium, Fusarium, and the rope-forming Bacillus subtilis and B. mesentericus. It is less effective against yeasts (including baker's yeast, Saccharomyces cerevisiae), which is essential for bread production because yeast fermentation must proceed normally. At the recommended usage levels (2000-3500 ppm based on flour weight), sodium propionate typically reduces bread shelf life from 3-5 days to 14-21 days before visible mold appears. The ADI for sodium propionate (as propionic acid equivalents) is "not specified" (safest category) according to JECFA, because propionic acid is a normal human metabolite absorbed from the diet (e.g., from Swiss cheese, which contains up to 10,000 ppm propionic acid) and rapidly oxidized via the propionyl-CoA carboxylase pathway. In fact, propionate is one of the main volatile fatty acids produced by human gut microbiota from dietary fiber fermentation. There is no evidence of carcinogenicity, genotoxicity, or reproductive toxicity. The main limitation of sodium propionate is its "metallic" or "slightly salty" off-taste when used at high levels (>5000 ppm). For this reason, bakers often combine lower levels of sodium propionate with other preservatives (e.g., potassium sorbate, calcium propionate, cultured whey) to achieve mold inhibition without flavor defects. Another limitation: sodium propionate is not effective in high-pH products (e.g., cakes using baking soda as leavening, which raises pH to 7.5-8.5). In such products, less than 1% of propionate is in the active undissociated form, making it ineffective; calcium propionate or sorbic acid are preferred. In gluten-free breads, which have higher moisture content and often lack natural mold inhibitors (e.g., wheat gluten doesn't contribute, but gluten-free flours tend to be more susceptible), sodium propionate is essential, often used at up to 4000 ppm. For low-sodium applications, calcium propionate (E282) or potassium propionate (E283) are alternatives. In the European Union, sodium propionate is authorized for bakery, fine bakery wares, cheese products, and confectionery. In the US, it is GRAS (21 CFR 184.1784). Notably, some "clean label" breads replace E281 with cultured wheat flour or cultured corn flour (fermented with Propionibacterium freudenreichii) which produces propionic acid, but the effect is chemically identical. In animal feed, sodium propionate is widely used as a mold inhibitor in poultry feed stored in humid tropical climates, and it also has a slight antibacterial effect against Salmonella and Escherichia coli. However, in high concentrations, it can reduce feed palatability for some animals (pigs may refuse feed above 5000 ppm). In cosmetics, sodium propionate is used at 1-3% as a preservative in rinse-off products and at lower levels in leave-on products. Overall, sodium propionate is a safe, effective, and economical mold inhibitor for bakery, but its sodium content (approximately 24% sodium by weight) should be considered in low-sodium diet formulations.

SAFETY INFORMATION ABOUT SODIUM PROPIONATE

First aid measures:
Description of first aid measures:
General advice:
Consult a physician. 
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
 
If inhaled:
If breathed in, move person into fresh air. 
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately. 
Wash off with soap and plenty of water.
Consult a physician.
 
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
 
If swallowed:
Do NOT induce vomiting. 
Never give anything by mouth to an unconscious person. 
Rinse mouth with water. 
Consult a physician.
 
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
 
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment. 
 
Avoid breathing vapours, mist or gas. 
Evacuate personnel to safe areas.
 
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
 
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste. 
Keep in suitable, closed containers for disposal.
 
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
 
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place. 
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
 
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
 
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles. 
Faceshield (8-inch minimum). 
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
 
Skin protection:
Handle with gloves. 
Gloves must be inspected prior to use. 
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product. 
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices. 
Wash and dry hands.
 
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
 
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls. 
 
If the respirator is the sole means of protection, use a full-face supplied air respirator. 
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so. 
Do not let product enter drains.
Discharge into the environment must be avoided.
 
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions. 
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
 
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company. 
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product