Determination of Benzoic and Sorbic Acids in Labaneh by High-Performance Liquid Chromatography

Benzoic and sorbic acid contents of 14 packaged commercial labanch (concentrated set yogurt) samples were determined by HPLC method using a reverse phase C-18 column and a mobile phase of 90: 10, phosphate buffer: methanol. There was a linear relationship between peak area versus benzoic and sorbic acids concentrations between 32 and 300 mg/l. Recoveries of benzoic acid added at 31.8 and 63.6 mg/100 g to commercial packaged labanch, averaged 90.3 and 90.6% with coefficient of variability (cv.) of 0.5 and 0.2, respectively. Recoveries of sorbic acid added at 28.0 and 56.0 mg/100 g labanch, averaged 101.1 and 974% with cv. of 0.5 and 0.8, respectively. Benzoic acid was detected in eight labaneh samples in the range of 33-2000 mg/kg while sorbic acid was detected in seven samples, and it ranged between 87 and 900 mg/kg. Three samples were found to contain both benzoic and sorbic acids. Six labanch samples contained low levels of benzoic acid (< 32 mg/kg). These are probably the indigenous benzoic acid normally encountered with in some fermented dairy products. (C) 1999 Academic Press