Nov. 22, 2021
Benzoic acid, a colourless aromatic carboxylic acid, occurs naturally in plants (fruits, nuts, spices and vegetables), fungi and animal tissues, but can also be produced by microorganisms during food processing and/or added as a food additive.
Abundant natural sources of benzoic acid are strawberries (up to 29 mg/kg), pepper and mustard seeds (up to 10 mg/kg), cloves, tansy, thyme and nutmeg (up to 50). Levels of benzoic acid in milk were also found to increase dramatically during fermentation, possibly due to the activity of lactic acid bacteria, Pseudomonas aeruginosa, E. coli. Levels of up to 24 mg/l were reported in fermented milk. Raw cow's milk cheese matured for 6 months can contain up to 250 mg/kg of benzoic acid.
Benzoic acid (CAS: 65-85-0) is an organic acid that was first used in food almost 100 years ago. It is naturally found in plums, cinnamon and cloves. The free acid form is insoluble in water and the sodium salt (sodium benzoate) is often used due to its greater solubility (into microorganisms. The most common uses of benzoic acid are in carbonated drinks, pickles, sauces and jellies. Non-food applications for the antibacterial properties of benzoic acid have been found in cosmetics. Parabens have antibacterial activity against moulds and yeasts and are used in beer, soft drinks and olives. Cosmetics and pharmaceuticals are the largest uses of parabens.
In addition to being naturally present in food, benzoic acid and its derivatives are often supplemented as antibacterial and fungal preservatives or flavouring agents. Benzoic acid has a low flavour threshold, low volatility and a broad spectrum of antibacterial activity. Although the undissociated form of benzoic acid has been shown to be more effective as an antimicrobial agent, salt is more commonly used in food applications due to its better water solubility.
The maximum antimicrobial activity of benzoic acid has been described for pH values between 2.5 and 4.5. It is clear that benzoic acid and its derivatives are therefore most commonly used as preservatives in acidic foods. However, when using benzoic acid as a food additive, care needs to be taken that the taste of the food is not altered to an unacceptable degree. Benzoic acid is known to cause tingling in the mouth, increase sweetness, reduce sourness and saltiness and strongly inhibit bitterness.
Benzoic acid is used as a preservative in a variety of foods. Benzoic acid impedes the growth of yeasts and moulds and the effective agent is the undissociated acid. The main food groups contributing to dietary intake of benzoic acid are the following permitted food groups: various foods 200-1000 mg/kg (prepared salads, sweets etc. 1500 mg/kg; food supplements, pickled vegetables 2000 mg/kg; liquid eggs 5000 mg/kg; cooked seafood 2000-6000 mg/kg) and soft drinks 150 mg/kg (non-alcoholic beer 200 mg/kg (sacramental grape juice 2000 mg/kg, liquid tea concentrate 600 mg/kg). The Acceptable Daily Intake (ADI) for benzoic acid is 5 mg/kg body weight.