Benzoic acid and sorbic acid are widely used in the food industries as preservatives with the standards for use. However, especially, benzoic acid is found in the food sometimes which has not been added to it. Therefore, the contents of natural benzoic acid and sorbic acid must be clarified to distinguish it from the added ones as food additives in foods not permitted the use of these preservatives. In this study, we investigated the contents of benzoic acid and sorbic acid in 39 samples including 24 fruits by HPLC and LC/MS/MS methods with two different preparations, steam distillation and solvent extraction. In steam distillation, the mean contents of benzoic acid were ranging from 1 to 424mg/kg in 29 samples, while in solvent extraction, the mean contents of that were ranging from 1 to 126mg/kg in 15 samples. On the other hand, sorbic acid was not detected in these samples using both preparations. In terms of errors in detection, solvent extraction was found more suitable for the extraction of free benzoic acid from foods, compared to the steam distillation. LC/MS/MS method gave accurate results for detection of benzoic acid and sorbic acid in foods containing much impurity.
