Influence of Maillard conjugation on structural characteristics and rheological properties of whey protein/dextran systems

It is well known that protein/polysaccharide conjugates obtained by Maillard reaction (MR) have good emulsifying properties. However, there is little information about the use of these conjugates in gel systems. Structural characteristics and rheological properties of conjugates obtained by MR of whey protein isolate (WPI) and dextrans (DX) of various molecular weight (MW: 6, 40 and 70 kDa) were studied. Conjugation was confirmed by electrophoresis; browning intensity was measured by absorbance at 420 nm; and conformational changes were studied by fluorescence emission of tryptophan (Trp) (λex = 280 nm). Rheological properties were determined by oscillatory rheometry with temperature ramp (25–90 °C). After each measure, a mechanical spectrum (at 25 °C) was obtained. The electrophoresis indicated the presence of WPI/DX conjugates in all systems. Browning intensity increased with decreasing MW of DX. Fluorescence emission of WPI incubated increased, but decreased in WPI/DX incubated systems. The gelation time (obtained by G′–G″ crossover) and G′ value at 25 °C increased in conjugate systems compared with WPI alone. Stability of gel structures were shown by frequency sweeps.