Analysis of nonvolatile reaction products of aqueous Maillard model systems - The effect of time on the profile of reaction products

Aqueous one molal solutions of xylose and lysine monohydrochloride were refluxed for up to 120 min with the pH maintained at 5. Analysis of reaction mixtures by diode array HPLC revealed changes in the chromatograms with time of heating. Reaction products could be divided into four groups: unretained material, resolved compounds and two types of unresolved substances. Storage of the model system, heated for 15 min, at 40 degrees C for up to three weeks resulted in changes to the HPLC chromatograms which were different from those observed on prolonged heating. Two peaks became prominent on the chromatograms of the heated samples and one peak became prominent on the chromatograms of the stored samples. The progressive development of a complex of partially resolved peaks on storage at 40 degrees C provided another means of distinguishing between the heated and stored samples. The different chromatographic behaviours observed in samples subjected to prolonged heating or storage suggest that the presence of certain marker compounds in the system may provide information regarding sample history