Influence of the molecular weight of carboxymethylcellulose on properties and stability of whey protein-stabilized oil-in-water emulsions

The influence of the molecular weight (M-w; 270, 750, and 2,500 kDa) and concentration of carboxymethylcellulose (CMC) on the stability and properties of whey protein isolate (WPI)-stabilized oil-in-water emulsions were assessed by measuring zeta-potential, droplet size, apparent viscosity, protein surface coverage, and creaming stability. Emulsions were prepared to contain 5% oil, 0.5% WPI, and 0 to 0.5% CMC at pH 7. After emulsification, pH was adjusted to 5.2. In the absence of CMC, the WPI-stabilized emulsion was unstable to droplet flocculation and coalescence due to the relatively low droplet charge. Emulsions stabilized by mixed WPI-CMC had improved surface properties as well as reduced droplet flocculation, as indicated by increased negative charges and protein surface coverage as well as smaller droplet size. Increased viscosity due to nonadsorbed CMC also contributed to increased stability at high CMC concentration. The high-M-w CMC was more effective in enhancing surface properties and providing better stability against creaming compared with lower-M-w CMC. Maximum stability was achieved with mixed WPI-CMC stabilized emulsion containing 0.08% CMC 2,500 kDa.