Potassium sorbate
[CAS 24634-61-5]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic potassium
• Name: Potassium sorbate
• Synonyms: 2,4-Hexadienoic acid potassium salt; Sorbic acid potassium salt
• Molecular Formula: C₆H₇KO₂
• Molecular Weight: 150.21
• CAS Registry Number: 24634-61-5 (590-00-1)
• EC Number: 680-685-6
• SMILES: C/C=C/C=C/C(=O)[O-].[K+]

Properties

• Density: 1.361 g/mL (Expl.)
• Melting point: 270 °C (Expl.)
• Solubility: water 58.2 g/100 mL (20 °C) (Expl.)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H319
• Safety Statements: P264+P265-P280-P305+P351+P338-P337+P317

chemBlink Chemical Story

Potassium sorbate is one of the clearest examples of food preservation by weak-acid chemistry. It is the potassium salt of sorbic acid, an unsaturated six-carbon carboxylic acid first associated historically with rowan berries. The potassium salt became especially useful because it is much easier to dissolve in water than sorbic acid itself, allowing the preservative to be distributed uniformly through beverages, dairy products, sauces, bakery fillings, and other moist foods.

The important antimicrobial species is linked to sorbic acid's acid-base equilibrium. At lower pH, a larger fraction of sorbate exists as uncharged sorbic acid. The neutral form can cross microbial cell membranes more readily than the anion. Once inside a cell with a higher internal pH, it can dissociate, disturbing proton balance and interfering with metabolic processes. This is why sorbate preservatives are generally more effective in acidic foods than in neutral ones, and why they are particularly useful against yeasts and molds that often tolerate acidity better than many bacteria.

This pH dependence makes potassium sorbate a lesson in formulation chemistry. Simply knowing preservative concentration is not enough; one must also know food pH, water activity, microbial population, storage temperature, and other preservation hurdles. In yogurt, for example, potassium sorbate has been shown to suppress yeast and mold growth and extend acceptable storage characteristics. In a different matrix, the same nominal amount can perform differently if pH and composition change.

The molecule also illustrates why the salt and the acid should not be confused. Potassium sorbate, CAS 24634-61-5, is a crystalline, water-soluble material used for handling and dosing. Once dissolved, however, potassium sorbate and sorbic acid are connected by acid-base equilibrium. The potassium ion is mainly a counterion; antimicrobial action depends on the sorbate/sorbic-acid system and the environment in which it is used. Regulatory assessments therefore consider both chemical identity and the behavior of sorbic acid and its salts in foods.

Sorbate chemistry also has a stability dimension. Because the molecule contains conjugated double bonds, light, oxygen, processing conditions, and food composition can influence degradation and reaction products during storage. Modern regulatory reviews therefore examine not only acute antimicrobial function but also the chemical fate of sorbic acid and sorbates in real foods. This is another reason preservative technology is more than adding an ingredient at a legal concentration: the manufacturer must understand how the molecule behaves throughout the product's shelf life.

Potassium sorbate matters because it turns a simple equilibrium into practical control of spoilage. Its effectiveness does not come from being an indiscriminate biocide. Instead, food chemistry creates conditions in which enough membrane-permeable weak acid is present to inhibit organisms that would otherwise grow. That combination of solubility, pH-dependent activity, and relatively mild sensory impact explains why this simple unsaturated carboxylate became one of the best-known preservatives in modern food technology.

References:

1. EFSA Panel on Food Additives and Flavourings. EFSA Journal. 2019;17:5625. DOI: 10.2903/j.efsa.2019.5625.

2. Al-Ashmawy MAM, Ibrahim JI. International Journal of Dairy Technology. 2009;62:224-227. DOI: 10.1111/j.1471-0307.2009.00463.x.

3. U.S. FDA food additive information for sorbic acid and sorbate preservatives.

4. General food microbiology literature on weak-acid preservation.

Read more stories