[Fluorescence spectra analysis of whey protein isolate-dextran conjugate]

The mixed whey protein isolate (WPI)-dextran was treated by dry-heating to prepare Maillard reaction products (MRPs), which was characterized by the browning. The free amino groups content significantly decreased by 35.77% and 30.53% in glycated protein samples, as the molecular weight of dextran increased from 67 to 150 kD, respectively. This suggested that it was more difficult to be linked with WPI molecule when the chain length of dextran was increased. The characteristic of WPI-dextran conjugate was studied by fluorescence spectra in the paper. The maximum fluorescence intensity at 405 nm was obviously enhanced and G67 showed high fluorescence intensity than G150 over the wavelength range form 350 to 500 nm. This result revealed that the flourescent substance, a feature in Maillard reaction model system, was generated. As showed in the fluorescence spectra, the maximum fluorescence intensity at 470 nm was significantly decreased and the fluorescence intensity in each solution was in the order as follows: WPI>G150>G67. Moreover, the measurement of surface hydrophobicity index further showed that the hydrophobicity of WPI could be suppressed due to these two kinds of different molecular weight dextran.