Potassium sorbate

Potassium sorbate is the potassium salt of sorbic acid. Sorbic acid is a naturally occurring compound that is found in the berries of the mountain ash (rowan) tree (source).

When potassium sorbate is dissolved in water, a portion of it converts to sorbic acid—the active, anti-microbial form of the ingredient. Just how much active sorbic acid (and therefore anti-microbial action) is present in your formulation depends on the pH of the formulation. It is most active at pH 4.4 (70%). Its activity decreases sharply as the pH raises, dropping to 37% at pH 5 and 6% and pH 6 (source).

Potassium sorbate has GRAS (“generally recognized as safe”) status with the FDA as a food substance. It is a common food industry preservative, and is also used as as preservative ingredient in cosmetics, primarily to combat yeast and moulds.

As per Merck’s datasheet for RonaCare® Potassium Sorbate:

• Strong antifungal effect, anti-mold effect
• Moderate antibacterial effect (gram positive, gram negative)
• Synergistic effect with citric acid

Potassium sorbate

White solid; mine is in small sticks similar to the stick/noodle form of Sodium Coco Sulfate (SCS).

• Lotion Crafter: 0.1%–0.5%
• Making Cosmetics: 0.15–0.3% (if used alone), 0.1–0.2% (if used in combination with other preservatives)

Nothing noticeable

8 – 11

Potassium sorbate is more effective at lower pHs; I’d aim for below 5.

Water soluble, though the small sticks I have are quite slow to dissolve at room temperature.

Potassium sorbate is included in formulations for its anti-microbial benefits. As per Merck’s datasheet for RonaCare® Potassium Sorbate, it has “Strong antifungal effect, anti-mold effect” and “moderate antibacterial effect (gram positive, gram negative)”.

It should not be used as a stand alone preservative.

No, but if you’re a more experienced formulator who is interested in experimenting with natural preservatives it can be a good addition to your DIY pantry.

Potassium sorbate only exists as a refined ingredient.

Natural, inexpensive preservative ingredient.

As it requires a lower pH to work, potassium sorbate is not suitable for preservative use in higher pH products. Personally, I would not rely on it as an element of my preservation system in formulations with a pH above 5.

“Under certain conditions, sorbic acid may oxidize and cause slight color changes in the cosmetic product. This can normally be prevented by adding 0.1–0.3% citric acid to the product.” (Making Cosmetics)

“Sorbic acid is an unsaturated fatty acid and as such is subject to oxidation (use of an antioxidant like Mixed Tocopherols T50 is recommended). It is also sensitive to UV light and may turn yellow in solution.  Gluconolactone is reported to stabilize potassium sorbate against discoloration and darkening in aqueous solutions and may be useful in stabilizing sorbic acid in the water phase of a product.” (Lotion Crafter)

“Sorbic acid can cause contact dermatitis at concentrations above or below 0.5%. Studies show that if it is used at a concentration of no more than 0.2% it is unlikely to constitute a safety hazard.” (Lotion Crafter)

Please read this FAQ.

Combine potassium sorbate with other preservatives (sodium benzoate is a very common choice) and preservation strategies (e.g. ingredients that lower water activity, choosing packaging that reduces contamination potential) for improved performance.

Add potassium sorbate in the post-heat phase (as demonstrated by Lotion Crafter here) or cool down phase. Lotion Crafter and Voyageur Soap and Candle Co. recommend keeping potassium sorbate below 60°C (140°F).

Test and adjust the pH of the formulation to a pH of 4.5–5. I find potassium sorbate pulls the pH of formulations up a bit, requiring the addition of an acid to lower it to the effective range.

Inclusion of a chelator is recommended.

Packaging that protects products from UV is also recommended.

Stored somewhere cool, dark, and dry, potassium sorbate should last at least 3 years from the date of manufacture.

Several manufacturers sell preservatives that are a blend of potassium sorbate, sodium benzoate, and water. Examples include Euxyl® K 712 (Ashland), Sharomix 713 (Coast Southwest), and Dekaben BS (JAN DEKKER). The typical composition is ~30% sodium benzoate, ~15% potassium sorbate, and water to 100%. The recommended usage rate for these preservatives is generally 0.5–1.5% (resulting in 0.15–0.45% sodium benzoate + 0.075–0.225% potassium sorbate) at a maximum pH of 5.5.

30g (1.06oz)

 Buy it from an online DIY ingredient supplier or Amazon.