THE INFLUENCE OF PH ON THE NONVOLATILE REACTION-PRODUCTS OF AQUEOUS MAILLARD MODEL SYSTEMS BY HPLC WITH DIODE-ARRAY DETECTION

Aqueous solutions of sugar (xylose or glucose) and amino acid (glycine or lysine monohydrochloride), one molal with respect to each reactant , were heated without control of the pH for up to 120 min. Total react ion products were analysed by HPLC with diode array detection and the data obtained were distinctive and different from those of the corresp onding model systems maintained at pH 5 throughout heating. Less unres olved material and variations in its chromatographic behaviour suggest ed differences in the melanoidins formed. Resolved peaks from the xylo se-lysine and glucose-lysine systems were grouped into spectral famili es, based on their diode-array spectra. For xylose-lysine, seven of th ese peaks were common to the systems heated both with and without pH c ontrol for 15 min (based on retention time and spectral matching). No peaks were common to both glucose-lysine systems heated for 120 min. ( C) 1998 Elsevier Science Ltd. All rights reserved.