Study of Hydroxymethylfurfural Formation from Acid Degradation of the Amadori Product in Milk-Resembling Systems

5-(Hydroxymethyl)-2-furfuraldehyde (HMF) is formed upon heat treatment of milk and milk-resembling systems by the Maillard reaction, via its Amadori product lactulosyllysine, as well as by isomerization and subsequent degradation of sugars. An improved method for the evaluation of the lysine modification caused by the Maillard reaction is presented. It is based on the indirect determination of the Amadori product as “bound” HMF by reverse-phase HPLC. The best digestion conditions have been settled at 2 mg of freeze-dried protein/mL of 0.3 N oxalic acid. In this work the “bound” HMF formation from acidic degradation of the Amadori product at temperatures between 110 and 150 °C and for times up to 30 min in a milk-resembling system has been studied.