Chemical-physical changes in sugar-amino acid model systems due to Maillard reaction. Note 1 - The evolution of the pH and the colour of the glucose-lysine model system heat treated

In thermally processed foods, the Maillard reaction occurs when carbonyl gr oups, usually from reducing sugars, condense with free amino acids, peptide s and proteins. This reaction which is responsible for the development of c olour and flavour, can strongly influence the quality and the acceptability of processed foods. In the present work, the Maillard reaction was studied in aqueous model systems that consisted of glucose and lysine, heat treate d at 100 degreesC for different times. The glucose-water and lysine-water m odel systems were analyzed too. The values of pH in the model systems gluco se-lysine, brightness variable (L*)(1) and chromaticity coordinates (a*, b* ) were measured. Brightness value (L*) resulted as the earliest indicator f or the nbn-enzymic browning reaction.(1) The values of pH in the glucose-wa ter and lysine-water were measured too.