Chemical properties and antioxidative activity of glycated α-lactalbumin with a rare sugar, d-allose, by Maillard reaction

The Maillard reaction (MR) is an ubiquitous reaction of condensation of a reducing sugar with amino groups of protein, which may improve the functional and/or biological properties of foods. The present study was carried out to determine the degree of α-lactalbumin (α-LA) conjugation with a rare sugar (d-allose, All) and two alimentary sugars (d-fructose, Fru; d-glucose, Glc) through MR and the extent to which these reactions could convey antioxidant activity to α-LA. The MR was generated in dry state at 50 °C and 55% relative humidity for up to 48 h. The results showed that the conjugation rate and fluorescence development of α-LA modified with All were faster than that of those modified with Glc and Fru, respectively. Furthermore, α-LA modified with All exhibited the highest tetrazolium salt (XTT) reducibility and radical cation (ABTS+)-scavenging activity. There was a good correlation between the fluorescence temporal patterns and biochemical activity of the different sugar-protein conjugates. Thus, the protein glycated with All could be used in formulated food as a functional ingredient, with a strong antioxidant activity, for scavenging free radicals and delaying deterioration due to oxidation.