Improved method for the determination of furosine in food by capillary electrophoresys

A previously described method for determination of furosine by capillary zone electrophoresis in food has been improved for greater accuracy and sensitivity. Acid-hydrolysed samples are subjected to solid phase extraction, then dried and redissolved before injection. Electrophoretic separation is performed in a fused silica capillary tube (50 mum inside diam.) with an extended-path-length detection cell using a 3-(N-morpholino)-2-hydroxypropanesulphonic acid solution at pH 7.0 as run buffer. The in-laboratory repeatability was within +or-7.1% at the 95% confidence level when the amount of furosine ranged between 8 and 250 mg/100 g protein. The value of both repeatability and sensitivity fulfill the requirements stated in the EU and Italian regulations for furosine determination in pasteurized milk and Mozzarella cheese. The data obtained on 48 different food samples including heat-treated milk, cheeses and durum wheat products were comparable with those obtained by an HPLC method and proved to be accurate for furosine values up to at least 400 mg/100 g protein. The furosine values found in cultured fresh cheese samples suggest that the use of this furosine index holds promise for the characterization of this type of cheese.