Comparison of Physicochemical and Antioxidant Properties of Egg-White Proteins and Fructose and Inulin Maillard Reaction Products

The Maillard reaction (MR), involving the condensation of a carbonyl group of reducing sugar and an amino group of protein, can change functional properties of proteins. In this study, chemical characteristics and functional properties of glycosylated albumin, ovomucoid, and lysozyme (egg proteins) and casein with fructose or inulin through the MR were evaluated. The protein and sugar mixtures were heated at 60 °C and 79% relative humidity for 3 days. Chemical characteristics of the egg protein–sugar Maillard reaction product (MRP) mixtures were evaluated by fluorescence development, absorbance intensity (at 420 nm), and color change. Functional properties of the protein–sugar MRP mixtures were also evaluated, including emulsifying activity, emulsion stability, and antioxidant activity. The protein–sugar conjugates were found to have significant (p < 0.05) changes compared to the controls (unheated protein–sugar samples) in color, fluorescence, and absorbance intensity. All protein–sugar MR models exhibited a change in emulsifying activity, with Csn–Fru MRP displaying the greatest significant (p < 0.05) improvement. In addition, all protein–sugar MR models exhibited changes in emulsion stability, with Ovo/Inu MRP displaying the greatest significant (p < 0.05) change. All protein–sugar MR models exhibited great scavenging activity towards 1,1-diphenyl-2-picryl-hydrazyl radical at MRP concentrations of 0.2, 0.5, and 1.0 mg/mL. With the exception of the 0.2 mg/mL MRP concentration, there was a significant difference (p < 0.05) between the heated protein–fructose and the heated protein–inulin MRPs.