Interactions between whey proteins and polysaccharides, in particular the formation of food-grade soluble complexes, are of interest because of potential functional and health benefits. A specific application that has not received much attention is the use of complexes for enhanced colloidal stability of protein sols, such as protein-containing beverages. In beverages, the primary goal is the formation of complexes that remain dispersed after thermal processing and extended storage. This review highlights recent progress in the area of forming whey protein–polysaccharide soluble complexes that would be appropriate for beverage applications. Research in this area indicates that soluble complexes can be formed and stabilized that are reasonably small in size and possess a large surface charge that would predict colloidal stability. Selection of specific proteins and polysaccharides can be tailored to desired conditions. The principal challenges involve overcoming restrictions on protein concentration and ensuring that protein remains bioavailable.

Charge density of polysaccharides and biopolymer ratio are the major factors affecting their intragastric gelation and their digestion properties.

The aim of this work is to investigate the effect of pectin on in vitro digestion of whey protein. Digestion of heated whey protein isolate (WPI) and pectin solutions (WPI–pectin) as influenced by pectin concentration and pH was studied under simulated gastric conditions. Electrophoresis, dynamic light scattering, colorimetric measurements, and gel microstructures were used to study the digestion pattern. At low pectin concentration (0.25% w/w), pectin did not significantly influence the degradation of whey protein. Increasing the pectin concentration to 1% led to extensive intragastric gelation immediately after mixing with simulated gastric fluid. The microstructure of intragastric gel from WPI–pectin at pH 6.0 showed a more interconnected and denser gel network than that at pH 7.0. More protein and pectin were involved in the gelation at pH 6.0 than pH 7.0. The digesta of samples at pH 6.0 was mainly composed of peptides, while that at pH 7.0 mostly consisted of aggregates and crosslinked peptides. This study suggests that WPI–pectin at high biopolymer ratio formed intragastric gel in simulated gastric models, which could delay protein digestion and potentially slow gastric emptying and promote satiety.

The influence of the molecular weight (Mw; 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 ζ-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-Mw CMC was more effective in enhancing surface properties and providing better stability against creaming compared with lower-Mw CMC. Maximum stability was achieved with mixed WPI-CMC stabilized emulsion containing 0.08% CMC 2,500 kDa.

In this study, heated whey protein isolate and pectin complexes (HCPX) formed at pH > isoelectric point (pI) were used to stabilize oil-in-water emulsions containing 5% oil and 1.5% (wt%) protein at pH 5.5. The effects of pectin concentration and heating temperature on emulsification and emulsion stabilization properties were determined. The HCPX were produced by heating mixed 3% (wt) whey protein isolate and pectin (0.1 or 0.3 wt%) at pH 6.2 and 75 or 85°C for 15 min. Aggregate sizes significantly increased with increasing heating temperature but decreased with the addition of pectin. The HCPX became more negatively charged with increasing pectin concentration; however, the effect of heating temperature was significant only at 0.1% pectin. Unheated complexes and HCPX successfully adsorbed at the oil-in-water interface and improved the emulsification properties as shown by higher negative charge and smaller droplet sizes. Despite the presence of pectin, rheological properties of the emulsions were not significantly different. All complexes showed increased emulsion stability; however, HCPX made at 85°C formed emulsions that were the most stable against creaming and heating.