Potassium Sorbate
Properties
| State | Solid at room temperature |
| Color | White crystalline powder or granules |
| Solubility | Very soluble in water (58.2 g/100 mL at 20 °C) |
| Melting Point | 270 °C (decomposes) |
About Potassium Sorbate
Potassium sorbate, the potassium salt of 2,4-hexadienoic acid, sits at C6H7KO2 and 150.217 g/mol. The free acid (sorbic acid) was first isolated in 1859 from rowan berries (Sorbus aucuparia), giving the molecule its name, but potassium sorbate is what shows up on ingredient lists because it dissolves at 58 g per 100 mL water versus sorbic acid's 0.16 g — three orders of magnitude difference that decides whether a winemaker can dose a tank or has to dump powder into wort. As a preservative it works by penetrating microbial cell membranes in its undissociated acid form (pKa 4.76), then dropping the cytoplasmic pH and uncoupling proton-motive-force transport. The mode kills yeasts and molds reliably below pH 6 and is the standard wine stabilizer that lets winemakers bottle off-dry whites without re-fermentation. EFSA classifies it E202 with an ADI of 25 mg/kg body weight, the highest tier of food-additive safety; it metabolizes via beta-oxidation in the human body just like any other dietary fatty acid. You'll find it in wine (especially residual-sugar styles), cheese rinds, dried fruit, baked goods, soft drinks, fountain syrups, and the preservative slot of most water-based cosmetics where parabens have been phased out.
Where you'll encounter it
If you've ever drunk a bottle of off-dry Riesling, eaten a slice of supermarket cheesecake, or pumped a hand soap labeled paraben-free, you've consumed potassium sorbate. In a small commercial winery, the standard residual-sugar stabilization protocol is to add 200 mg/L potassium sorbate plus 25-30 mg/L free SO2 immediately before bottling — the sorbate handles surviving yeast cells and the SO2 handles the lactic acid bacteria that sorbate doesn't touch. Skip either one and the bottles will start showing geranium taint or referment in storage. In a cosmetic formulation lab, swapping methylparaben for potassium sorbate at 0.3% means dropping the pH below 5.5 with citric acid because sorbate loses efficacy above pH 6 — that's the trade-off that makes 'paraben-free' formulations slightly more pH-sensitive.
Common Uses
- Wine stabilization at 200 mg/L to prevent re-fermentation in residual-sugar bottlings
- Preservative E202 in cheese rinds, yogurts, dried fruit, and bakery fillings
- Paraben replacement in pH-adjusted shampoos, lotions, and cosmetic emulsions
- Mold inhibitor in soft drink syrup, juice concentrate, and fountain beverage lines
- Pet food preservative in semi-moist dog and cat formulations
- Eye drop and contact lens solution preservative at sub-percent concentrations
- Tobacco preservative in pipe and cigar humidor blends
Safety Information
GHS: not classified as hazardous. Oral LD50 in rats around 4920 mg/kg, comparable to table salt. EFSA's ADI is 25 mg/kg body weight per day, near the top of the food-additive safety scale. Rare cases of contact dermatitis from cosmetic concentrations have been reported but the responsible patch-test sensitivity is below 1% in screened populations. The two practical issues in formulation are: it loses antimicrobial efficacy rapidly above pH 6 because the undissociated acid form (the active species) drops below 50% of total above its pKa of 4.76; and dry potassium sorbate dust is mildly irritating to mucous membranes, so handle bulk powder with a respirator. Compatible with most food contact materials; no special disposal restrictions.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.