Formation of whey protein isolate (WPI)-dextran conjugates in aqueous solutions

The conjugation reaction between whey protein isolate (WPI) and dextran in aqueous solutions via the initial stage of the Maillard reaction was studied. The covalent attachment of dextran to WPI was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with both protein and carbohydrate staining. The formation of WPI-dextran conjugates was monitored by a maximum absorbance peak at approximately 304 nm using difference UV spectroscopy. The impact of various processing conditions on the formation of WPI-dextran conjugates was investigated. The conjugation reaction was promoted by raising the temperature from 40 to 60 degrees C, the WPI concentration from 2.5 to 10%, and the dextran concentration from 10 to 30% and lowering the pH from 8.5 to 6.5. The optimal conjugation conditions chosen from the experiments were 10% WPI-30% dextran and pH 6.5 at 60 degrees C for 24 h. WPI-dextran conjugates were stable under the conditions studied.