ACCURATE QUANTIFICATION OF FUROSINE IN MILK AND DAIRY PRODUCTS BY A DIRECT HPLC METHOD

An ion-pair reversed phase HPLC method using a C8 column and detection at 280 nm is proposed for determining furosine (.epsilon.-N-2-furoylmethyl-L-lysine) (FUR) in acid hydrolysed dairy products. The FUR response factor was evaluated by radiochemical counting of the radiocarbon in the peak of FUR derived from the hydrolysed heat-induced complex of casein-[U14C] lactose. 2-acetylfuran, which exhibits the same response factor, was used as external standard. The method allows FUR formation to be detected even in pasteurized milk and due to its sensitivity, repeatability, rapidity and low cost, it is suitable for routinely controlling the extent of the Maillard reaction in a wide range of heating conditions. A comparison of HPLC, GLC and IEC methods on several samples of milk and dairy products proves that, assuming the traditional amino acids as standard, the FUR value is underestimated at least by a factor of 2. The data reported in the literature for FUR content in dairy products are probably affected by the same type of error.