Mixed gels from whey protein isolate and cellulose microfibrils.

Whey proteins can form different gel structures ranging from fine-stranded to particulate when appropriate conditions are applied. By incorporating polysaccharides, the gelation of WPI can be influenced. We investigated the heat-induced gelation of whey protein isolate (WPI) in the presence of bacterial cellulose (BC) microfibrils at pH 7 at different concentrations of NaCl. Our results showed that WPI and BC microfibrils form a homogeneous dispersion at pH 7. Upon heating, the WPI gel was formed independently in the presence of the BC microfibril gel, resulting in the formation of a composite gel. The gel structure and gelation dynamics of WPI was not influenced by the presence of BC microfibrils. However, the presence of BC microfibrils increased the storage modulus of the WPI gel, with an increase being negligible when the strength of the WPI gel is above a certain value. With an increase of NaCl concentration, the WPI gel structure changes from fine-stranded to a particulate gel, while the BC microfibril gel structure remains unchanged. No macroscopic phase separation could be observed in the WPI-BC microfibril gels. Our results showed that the rheological properties and water holding capacity of the WPI-BC microfibril mixed gels are mainly dominated by the WPI.