Antioxidant activity developed at the different stages of Maillard reaction with milk proteins

This study analyzed the influence of different variables (temperature, mono and disaccharide, solid and liquid systems) on the antioxidant activity developed by Maillard reaction between milk proteins and reducing sugars. A comparison of the antioxidant properties developed during each stage of the reaction was also conducted. In the whey protein-lactose system stored at 37 degrees C and a(w) 0.52 only the initial stage of the Maillard reaction occurred and products with antioxidant activity were formed in low proportion. At 60 degrees C the reaction progressed to the second stage, and in the liquid system colored products were formed. Although in this latter system the reaction rate was lower than at intermediate a(w), the antioxidant activity was higher at the same degree of reaction progress. Similar results were observed when the effect of lactose and glucose was compared. In the system with lactose, more products with antioxidant activity were formed, but at a lower reaction rate. The antioxidant activity would be mainly related to the intermediate and especially the final stage. Milk powder, sweetened condensed milk and "dulce de leche" were also analyzed. The results obtained were in concordance with those of the model systems.