Structure of Particulate Whey Protein Gels:  Effect of NaCl Concentration, pH, Heating Temperature, and Protein Composition

In this study whey protein gels were investigated with the aim of further testing a model and ideas developed previously. Measurements on the kinetics of the denaturation/aggregation process, dynamic rheology, gel permeability, and confocal scanning laser microscopy were combined. A broad set of experimental parameters was investigated: NaCl concentration, pH, heating temperature, and protein composition. This resulted in large variations in kinetics and the gel structures formed. The kinetics of the aggregation process determine the amount of aggregated material at the gel point, whereas the primary spatial structure is directly related to this amount of aggregated protein. The primary spatial structure essentially does not change after the gel point. The protein incorporated after the gel point induces a “thickening” of the strands in the gel network and a “decoration” of the pores in the gel. The consequence is that gel permeability decreases only slightly after the gel point but that gel rigidity increases greatly. Keywords: Whey; protein; gelation; permeability; rheology