Sensitive determination of furosine in acid hydrolysates of foods was achieved by isocratic ion-pair reversed-phase HPLC and direct UV-detection within a run time of 5 minutes and levels lower than 1.5 mg per kg of protein. The formation of furosine during hydrolysis of food samples with hydrochloric acid of varying concentration was studied. Furosine formation increased linearly with acid concentration (4 to 8 mol/L).