Browning and Amino Acid Loss in Model Total Parenteral Nutrition Solutions

The kinetics of browning and amino acid loss due to the Maillard reaction was studied in model total parenteral nutrition (TPN) systems containing glucose and either lysine, tryptophan, and cysteine alone or in combination. Cysteine systems showed the highest molar rate of browning while lysine showed the slowest rate. The molar rate of browning with all amino acids combined was significantly less than that of the sum of the individual rates, indicating interactions or inhibition. TPN electrolytes had no significant effect on the browning rate. The amino acids showed an initial rapid pseudo‐first‐order decrease in concentration followed by an apparent recovery and stabilization at an equilibrium concentration of about 60‐80% of the original level.