Abstract: The objective of this study was to explore the formation process, molecular interactions, and microstructure of whey protein concentrate (WPC) gels by a dynamic rheometer, a microrheometer, a circular dichroism spectrometer, a fluorescence spectrophotometer and a scanning electron microscope (SEM). Furthermore, the mechanisms for the effects of heating temperature (60 and 85 ℃) and pH (2.0, 4.5, 7.0 and 9.0) on the properties and microstructures of WPC gels were discussed. The results indicated that pH affected the gel structure by changing the charge density of WPC. After heat treatment at 85 ℃, the protein molecules were unfolded more sufficiently and exhibited a lower content of α-helix structure. In addition, the wavelength of maximum endogenous fluorescence intensity was red-shifted. The WPC gel formed at 85 ℃ showed higher elastic and viscous moduli as well as elasticity index and macroscopic viscosity index, and lower solid-liquid balance value. In addition, higher temperature could promote the formation of hydrogen bonds, disulfide bonds and hydrophobic interactions, thus improving the properties and microstructure of WPC gels.

Key words: whey protein concentrate; gel; heating temperature; charge density; gel properties; gel structure; interaction force