Page 97 - Analytical method for food addtives

E210–13: Benzoic acid 55

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The NMKL–AOAC method was collaboratively tested on apple juice, almond
paste and fish homogenate [at 0.5–2 g/kg levels], representing carbohydrate-rich,
pasty, fat-rich, carbohydrate-rich and protein-rich foods. In this method benzoic
acid is isolated from food by extraction with ether and successive partitioning into
aqueous NaOH and CH Cl . Acids are converted to trimethylsilyl (TMS) esters
2 2
and determined by GC. Phenylacetic acid is used as internal standard for benzoic
acid. A summary of the procedure for this method is given in the Appendix and the
performance characteristics are given in Table 7.3.
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The AOAC liquid chromatographic method was collaboratively tested on
orange juice and is applicable to the determination of 0.5–10 ppm benzoic acid in
orange juice. In this method benzoic acid in solid-phase extracted orange juice is
separated by liquid chromatography on C18 column, detected by ultraviolet
absorbance at 230 nm, and quantitated by external standard. A summary of the
procedure for this method is given in the Appendix and a summary of the statistical
parameters in Table 7.4.
A suitable HPLC method for benzoic acids in foodstuffs was collaboratively
tested on orange squash, cola drinks, beetroot and pie filling and is applicable to the
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determination of 50–2000 mg/kg benzoic acid in foodstuffs. In this method
liquid foods not containing insoluble matter are diluted with methanol. Other foods
are extracted by shaking with methanol, centrifuging and filtering. The concentra-
tion of benzoic acid in the clear extract is measured using reverse-phase liquid
chromatography with UV detection. A summary of the procedure for this method
is given in the Appendix and a summary of the statistical parameters in Table 7.5.

7.3 Recommendations
There are many methods available for the analysis of benzoic acids in foods and the
decision as to which should be used depends on the matrix to be analysed. The
majority of methods are for liquids i.e. beverages, sauces, yogurt etc. and further
method development may be required to adapt them to be applicable for all
matrices.

7.4 References
1 ‘AOAC Official Method 983.16. Benzoic acid and sorbic acid in food, gas-chromato-
graphic method. NMLK-AOAC method’, AOAC Official Method of Analysis (2000)
47.3.05 p 9.
2 ‘Simultaneous determination of sorbic acid, benzoic acid and parabens in foods: a new
gas chromatography–mass spectrometry technique adopted in a survey on Italian foods
and beverages’, De Luca C, Passi S, Quattrucci E. Food Additives and Contaminants
(1995) 12(1), 1–7.
3 ‘Simple and rapid method for the determination of sorbic acid and benzoic acid in foods’,
Choong Y-M, Ku K-L, Wang M-L, Lee M-H. J Chinese Agricultural Chemical Society.
(1995) 33(2), 247–261. [Chinese]