Potassium sorbate is a common food preservative that is used to prevent mold, yeast growth, and spoilage in various foods. It is made by neutralizing sorbic acid with potassium hydroxide.
What is sorbic acid?
Sorbic acid is a naturally occurring compound that was first isolated from the berries of the mountain ash tree. It is a polyunsaturated fatty acid that has antimicrobial properties. Sorbic acid can inhibit the growth of mold, yeast, and fungi. This makes it useful as a preservative.
Commercially, sorbic acid is made synthetically through chemical reactions rather than extracted from mountain ash berries. The most common way to produce sorbic acid industrially is by dehydrogenating ketene and pentanol-1 in the liquid phase over a catalyst like zinc oxide. This produces sorbic acid with a high yield and purity.
How is potassium sorbate made?
Potassium sorbate is produced by neutralizing sorbic acid with potassium hydroxide. Sorbic acid is not very soluble in water on its own. By reacting it with potassium hydroxide, it forms the more water-soluble potassium salt known as potassium sorbate.
The chemical reaction results in the sorbic acid giving up a proton (H+) to the potassium hydroxide. This forms potassium sorbate and water as products.
C6H8O2 (sorbic acid) + KOH (potassium hydroxide) → C6H7O2K (potassium sorbate) + H2O (water)
This reaction is exothermic, meaning it gives off heat. It is typically carried out in an aqueous solution for ease of mixing and reaction. Once the reaction is complete, the potassium sorbate can be crystallized from the solution after water evaporation.
Potassium sorbate properties
Potassium sorbate is a white crystalline powder when pure. However, it is often appears as a translucent white granular material. Here are some key properties of potassium sorbate:
- Molecular formula: C6H7O2K
- Molar mass: 150.22 g/mol
- Density: 1.36 g/cm3
- Melting point: 270°C (518°F)
- Solubility: soluble in water (50 g/100 mL at 20°C)
Potassium sorbate exhibits both antifungal and antimicrobial activities. It is considered GRAS (generally recognized as safe) by the FDA when used as a preservative in foods.
Uses of potassium sorbate
Potassium sorbate is used primarily as a food preservative. Taking advantage of its antimicrobial effects, potassium sorbate prevents the growth of mold, yeast, and fungi in foods. Some common uses include:
- Preserving cheese
- Inhibiting yeast in wine
- Prolonging shelf life of baked goods
- Preventing mold in yogurt and other dairy products
- Preserving dried fruit
- Extending shelf life of dried meats like jerky
The antimicrobial activity of potassium sorbate increases as pH decreases below 6. This makes it especially useful in acidic foods. Potassium sorbate may be combined with other preservatives like sodium benzoate for greater preservation effects.
In addition to foods, potassium sorbate sees some uses in personal care products. It can be found in some lotions and creams. It also has applications in agriculture and pharmaceuticals.
Is potassium sorbate safe?
When used in appropriate amounts, potassium sorbate is considered very safe for humans. It is metabolized and excreted from the body very quickly. The FDA has approved potassium sorbate as a GRAS preservative, meaning there is no safety concern when added to foods in small quantities.
The acceptable daily intake (ADI) of potassium sorbate is 25 mg/kg of body weight per day. This allows for adequate margins of safety. Intake above the ADI over long periods of time may cause some side effects like nausea, diarrhea, or abdominal pain.
Allergic reactions to potassium sorbate are very rare but possible. People with allergies or sensitivities should check ingredient labels if concerned. But overall, potassium sorbate has a long history of safe use when used properly as an effective preservative in foods.
Comparison to sorbic acid
While chemically related, potassium sorbate and sorbic acid do have some key differences when used as preservatives:
| Property | Potassium Sorbate | Sorbic Acid |
|---|---|---|
| Solubility in water | Highly soluble | Slightly soluble |
| pH for optimal activity | Below 6.0 | Below 6.0 |
| Antimicrobial activity | High | High |
| Taste impact | Low | Can have more impact |
The potassium salt form has much greater solubility, allowing it to be mixed into aqueous foods and solutions more easily. The taste impact of potassium sorbate is also less than free sorbic acid.
In terms of antimicrobial efficacy, potassium sorbate and sorbic acid are similar. Overall, the properties of potassium sorbate make it the preferred choice for most food applications.
How much potassium sorbate is used in food?
The amount of potassium sorbate used in foods varies based on the specific product and desired shelf life. Some typical levels used are:
- Wine – 100-200 ppm
- Yogurt – 500-1000 ppm
- Cheese spreads – 2000-3000 ppm
- Dried fruit – 1000-2000 ppm
- Baked goods – 100-500 ppm
The maximum usage level allowed by the FDA is 0.3% by weight in food products. This keeps the preservative at safe levels while still providing microbial inhibition.
In some products like cheese and wine, potassium sorbate may be used at levels above 0.1% to control mold and yeast growth. The specific concentration depends on factors like pH, water activity, processing method, and other preservative additives being used.
Alternatives to potassium sorbate
There are some alternatives that can be used in place of potassium sorbate as food preservatives. Common natural alternatives include:
- Salt – Sodium chloride inhibits microbial growth through the osmotic effect
- Sugar – High sugar concentrations preserve foods by binding water
- Vinegar – The acetic acid in vinegar acts as an antimicrobial
- Rosemary extract – Rosemary contains antioxidant compounds that can prevent spoilage
- Natamycin – Produced by bacteria, natamycin is used to prevent mold in dairy products
Chemical preservative alternatives include:
- Benzoic acid
- Sulfur dioxide
- Sodium nitrite
- Calcium propionate
However, potassium sorbate is popular because it is effective at low concentrations, inexpensive, and generally recognized as safe (GRAS) without effecting flavor or texture.
Is potassium sorbate natural?
Most potassium sorbate used in the food industry is chemically synthesized rather than extracted from natural sources. For this reason, it is not considered a natural preservative by most definitions. However, potassium sorbate is naturally occurring in some unprocessed foods.
Berries like rowanberries, chokeberries, and sea buckthorn contain significant levels of natural potassium sorbate. Estimated concentrations of over 1% potassium sorbate can be present in these berries. Some other fruits and vegetables also contain trace amounts.
While synthetically produced, potassium sorbate is identical chemically to the potassium sorbate found naturally in certain plant foods. The human body metabolizes both forms the same way. So while not a “natural preservative”, potassium sorbate does not contain any artificial chemicals.
The “natural” label is debated when it comes to food additives and preservatives. But potassium sorbate has a simple chemical structure and mode of action, making it generally recognized as safe whether produced synthetically or extracted from plants.
Is potassium sorbate organic?
Potassium sorbate can be used in products certified organic under USDA regulations. Preservatives like potassium sorbate are allowed in organic processed foods as long as they are on the National List of Approved and Prohibited Substances.
However, the use of potassium sorbate is more restricted in organic food processing compared to conventional foods. Organic regulations require the use of cultural, biological, mechanical or physical methods first to try and control microbial growth. Chemical preservatives like potassium sorbate can only be used if those methods are insufficient.
Additionally, potassium sorbate would need to be organic certified itself for use in certified organic products. This means it must be produced without synthetic solvents, irradiation, or chemical treatment.
So while allowed in organic foods, potassium sorbate faces more limitations and scrutiny. Food manufacturers turning to organic production may need to reformulate products to reduce or eliminate the potassium sorbate levels relied on in conventional processing.
Is potassium sorbate vegan?
Yes, potassium sorbate is considered vegan. Veganism excludes the use of animal products. Potassium sorbate is not derived from any animal sources.
The main components used to produce potassium sorbate commercially are ketene and pentanol. Ketene is produced from acetone and pentanol is produced from petrochemical feedstocks, neither of which originate from animals.
Some alternative preservatives like natamycin, nisin, and lysozyme are derived from animal sources and thus not vegan. But potassium sorbate has no animal origin or ingredients, making it compatible with a vegan diet.
Vegans still need to check product labels, as potassium sorbate is commonly used as an additive in many non-vegan foods. But potassium sorbate itself contains no animal products or byproducts.
Is potassium sorbate kosher?
Potassium sorbate is generally recognized as kosher. It meets kosher dietary laws and is acceptable for use in kosher certified products when produced properly.
For a preservative to be kosher, it must not contain any non-kosher ingredients or come into contact with non-kosher substances during production. Potassium sorbate does not contain any meat or dairy products that would violate kosher laws.
In addition, all equipment used in the manufacturing process must only use kosher ingredients and be sanitized between batches. Reputable kosher certified potassium sorbate goes through oversight to ensure compliance with these kosher standards.
Orthodox Union and Star-K are examples of certifying agencies that provide kosher certification of potassium sorbate. Foods that contain kosher certified potassium sorbate can display these kosher symbols on the packaging.
Checking for kosher symbols provides assurance that food additives like potassium sorbate adhere to kosher dietary restrictions. This allows potassium sorbate to be used in kosher food production.
Conclusion
Potassium sorbate is a synthetically produced salt form of sorbic acid used widely as a preservative in food products. It inhibits mold, yeast, and other microbes from growing by interrupting their cellular enzymatic pathways.
While not derived from natural sources, potassium sorbate is considered very safe at approved usage levels. It has GRAS status from the FDA and can be used in organic certified products within the regulations. Potassium sorbate provides an effective method for controlling microbial growth and extending shelf life.
When looking for alternatives to traditional synthetic preservatives, options like cultured dairy, fermented foods, vinegar, salt, and herbs can provide naturally antimicrobial effects. But potassium sorbate is likely to remain a popular choice for processed foods due to its potent preservative effects, reasonable cost, and lack of flavor impact.
