In the ethanol colorimetric determination of sorbic acid in foods

Sorbic acid in foods was extracted by dialysis, then 0.1M nitric acid and 1% iron (III) nitrate soln. were added to the extract and the mixture was heated in a boiling water bath. Next, thiobarbituric acid (TBA) was added to the reaction mixture in the boiling water bath and heated for 10 minutes. The reaction mixture was cooled to room temperature and the absorbance at 532nm was measured. It was found that this method could be applied to foods containing ethanol without difficulty and was not disturbed so much by other food additives probably used with sorbic acid. Thus, sorbic acid in various commercial foods could be determined in a short time by this method.