Effects of glycosylated whey protein isolate on gelatinization, gel properties, and microstructure of wheat starch

Glycated whey protein isolate (gWPI) was produced by dry thermal reaction between whey protein isolate (WPI) and lactose, and its influence on the gelatinization, gel properties, and microstructure changes of wheat starch (WS) was systematically studied. Results showed that gWPI significantly inhibited starch gelatinization and improved starch gel properties. RVA and DSC analysis showed that gWPI decreased viscosity and gelatinization enthalpy (ΔH) in a concentration-dependent manner. When gWPI concentration was 12 %, the peak viscosity and ΔH decreased by 36 cP and 3.11 J/g, respectively. gWPI competed with WS for water and inhibited WS water absorption and expansion. Rheological results showed that the viscoelasticity of the gel decreased by adding gWPI and that of WS-gWPI was a pseudoplastic fluid with shear-thinning behavior. In addition, gWPI covered the WS surface in the form of hydrogen bonds, which inhibited the leaching of amylose, thereby reducing the particle size of the gelatinized starch and its iodine binding ability. AFM results showed that gWPI combined with WS weakened the aggregation of starch molecular chains and decreased the height of starch. In conclusion, gWPI can be used as a gelatinizing regulator to improve starch properties.