Sodium benzoate (E211) and potassium sorbate (E202) are the two most widely used food preservatives, and they are often considered side by side for drinks, sauces, dressings and fillings. Both are water-soluble salts of weak acids, and both work mainly against yeasts and moulds. The deciding factor is almost always pH, followed by taste, interactions and the rules for your food category.
At a glance (indicative)
- Parent acid and pKa: sodium benzoate releases benzoic acid, pKa about 4.2; potassium sorbate releases sorbic acid, pKa about 4.8.
- Effective pH range: benzoate works best at pH 4.5 or below, and ideally at 4.0 or lower; sorbate works up to about pH 6, and best at 5.5 or lower.
- Main targets: both act mainly on yeasts and moulds. Benzoate is particularly effective against yeasts in acidic drinks, while sorbate has broad antifungal activity and some activity against bacteria.
- Acid content: 1 kg sodium benzoate provides about 0.847 kg benzoic acid; 1 kg potassium sorbate provides about 0.746 kg sorbic acid.
- Solubility: both dissolve readily in water, which is why the salts rather than the free acids are normally used.
- Taste: benzoate can give a sharp or burning note at higher levels; sorbate is relatively neutral at typical levels.
- Watch-outs: benzoate with ascorbic acid can form trace benzene; sorbate inhibits baker's yeast and can be degraded by some moulds.
Why pH decides
Only the undissociated acid is strongly antimicrobial, and the undissociated share falls quickly as pH rises above the pKa. For benzoic acid, about 94% is undissociated at pH 3.0, 50% at pH 4.2 and only about 9% at pH 5.2. For sorbic acid, about 85% is undissociated at pH 4.0, about 37% at pH 5.0 and about 5% at pH 6.0.
In a soft drink at pH 3, both are effective, and benzoate is often chosen on cost-in-use and history. In a dip or cheese sauce at pH 5.5, benzoate has lost most of its activity, while sorbate still contributes. Measure pH on the finished, equilibrated product, because that is the pH the preservative works at.
Choosing by application
- Carbonated soft drinks and juice drinks (about pH 2.5–3.5): benzoate is traditional and effective. Sorbate, or a benzoate and sorbate blend, is used where brand owners want to reduce benzoate or manage the benzene risk. See our beverages hub.
- Sauces, dressings and pickles (about pH 3.5–4.5): benzoate or a blend. At the upper end of this range, sorbate carries more of the load. See our sauces, dressings and condiments hub.
- Cheese, dairy desserts and dips (about pH 4.5–6): sorbate, often with chilled storage.
- Cakes, fillings and toppings (about pH 5–7): sorbate in fillings and on surfaces, where permitted. For yeast-raised bread, propionates are the usual choice, because both sorbate and benzoate inhibit baker's yeast.
- Dried fruit and wine: sorbate, usually with sulphur dioxide.
Where sodium reduction matters, potassium benzoate (E212) behaves like sodium benzoate at an equivalent benzoic-acid dose. See potassium benzoate and sodium benzoate for grade details.
Interactions and quality risks
Benzene formation. In drinks that contain both benzoate and ascorbic acid (vitamin C), trace benzene can form, and heat, light and metal ions such as copper and iron accelerate the reaction. Manufacturers manage this by reformulating, for example by using sorbate or removing added ascorbic acid, by adding chelating agents, by using light-protective packaging and controlling storage temperature, and by testing finished products.
Yeast inhibition. Sorbate in yeast-raised dough slows fermentation, so it is applied to finished surfaces or used in fillings instead.
Sorbate degradation. Some moulds can decarboxylate sorbate to 1,3-pentadiene, which gives a kerosene-like or plastic off-odour. This usually signals a heavy mould load or an under-preserved product, and it is a reason to combine sorbate with good hygiene rather than rely on it alone. Sorbic acid solutions can also discolour slowly through oxidation, so make stock solutions fresh.
Regulatory checklist for the EU and UK
- Both preservatives are authorised, with the food categories and maximum levels set in Annex II of Regulation (EC) No 1333/2008 and the UK retained equivalent. Check the current annex for your exact category.
- Maximum levels are expressed as the free acid, and many categories set a combined limit for sorbates and benzoates, so convert your salt dose and add the contributions together.
- The grade must meet the purity criteria for E211 or E202 in Regulation (EU) No 231/2012 or its GB equivalent.
- On the label, declare the additive by class and name or E-number, for example "preservative: potassium sorbate" or "preservative: E202".
- Export markets have their own lists and limits, so check each destination separately.
Specification points to agree
- Assay, typically 99% or higher on a dry basis
- Loss on drying
- Acidity or alkalinity, and heavy-metal limits such as lead
- Physical form, such as powder, granules or extruded pellets, with granular forms reducing dust in manual dosing
- Conformity with the E-number specification, plus allergen and GMO statements; request the certificate scope with your quotation if you need halal, kosher or food-safety certification
For how these preservatives fit with acidulants, water activity and heat treatment, see our food preservatives and acidulants guide.
Frequently asked questions
Can sodium benzoate and potassium sorbate be used together?
Yes, and blends are common in drinks and sauces because each covers gaps in the other. Check whether your category sets a combined maximum, and add both contributions as free acid.
Which is better above pH 5?
Potassium sorbate. Benzoate loses most of its activity above about pH 4.5, while sorbate remains useful up to about pH 6.
Why was benzene found in a drink containing benzoate?
Benzoate can react with ascorbic acid to form trace benzene, particularly under heat, light and in the presence of metal ions. Reformulation, packaging and storage controls reduce the risk.
Is potassium sorbate natural?
Sorbic acid occurs naturally in some berries, but food-grade sorbic acid and potassium sorbate are produced synthetically.
Can either be used in bread?
Neither is a good choice for yeast-raised dough, because both inhibit yeast. Propionates are the standard bread preservatives, and sorbate is used on surfaces or in fillings where permitted.