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

Abstract

Benzoic and sorbic acid contents of 14 packaged commercial labaneh (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 labaneh, 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 labaneh, averaged 101·1 and 97·4% 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 labaneh 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.