Whey surface activity

Benichou, A., Aserin, A., Lutz, R., Garti, N. (2007). Formation and characterization of amphiphilic conjugates of whey protein isolate (WPI) / xanthan to improve surface activity. Food Hydrocolloids, 21, 379-391. 

El-Rafey, M. S. and Richardson, G. A. 1944. The role of surface-active constituents involved in the foaming of milk and certain milk products. II. Whey, skimmed milk and their counterparts. J. Dairy Sci. 27, 19-31. 

Although the volume of foam was increased by limited proteolysis, the stabilities of the foams, defined as the time required for one half of the weight of the foam to drain from the foam as free liquid, were greatly decreased by this same limited proteolysis. Presumably the increased initial polypeptide concentration in the hydrolysates favors more air incorporation. However, the polypeptides apparently do not have the surface activity required to give a stable foam. The decrease in foam stability becomes evident in the first 30 min of the enzyme reaction. Further hydrolysis results in peptides which lack the ability to stabilize the air cells of the foam. Thus a limited hydrolysis may be advantageous for utilizing whey proteins in foams since the specific volumes of the foams were increased 25% by such treatment. The decrease in foam stability which results from limited hydrolysis can be compensated for by adding stabilizers such as carboxymethyl cellulose (19,27). 

There are not many reports about the influence of size and molecular weight on the surface activity of proteins. It was shown [55] that sodium caseinate and proteins from whey concentrate diffuse to the... 

After homogenization, the milk proteins readily adsorb to the bare surface of the fat droplets. The proteins are mostly adsorbed on the aqueous side of fat-matrix interface, with hydrophobic parts at the interface. Free casein, casein micelles and whey have different surface activities, so they adsorb differently onto the fat droplets for example, casein adsorbs more than whey. Proteins are very good at stabilizing oil-in-water emulsions against coalescence because they provide a strong, thick membrane around the fat droplet. Interactions between the proteins on the outside of the droplets make it harder for the droplets to come into close contact. This is known as steric stabilization. 

However, when lowering the subphase concentration below 10 3 wt% the surface activity of the caseinates is more drastically lost than for the WPC, as revealed by Figure 5. Evidently, the caseinates do not seem to be able to spread sufficiently at the interface to form a monolayer at these low concentrations. This seems though to be the case for the whey proteins, which are more surface active than the caseinates in this concentration region. 

Detergent and surface-active agents, e.g., detergent enzymes, bleach powder, emulsifying agents, etc. Food industry, e.g., milk, whey, egg, soya protein, etc. 

With a few exceptions, most of the detailed research has been performed on relatively few proteins. Of these, the caseins (a , B and k) and whey proteins P-lactalbumin and B-lactoglobulin) predominate. This is principally because these proteins are readily available in pure and mixed forms in relatively large amounts they are all quite strongly surfactant and are already widely used in the food industry, in the form of caseinates and whey protein concentrates or isolates. Other emulsifying proteins are less amenable to detailed study by being less readily available in pure form (e.g., the proteins and lipoproteins of egg yolk). Many other available proteins are less surface active than the milk proteins, for example, soya isolates (49), possibly because they exist as disulfide-linked oligomeric units rather than as individual molecules (50). Even more complexity is encountered on the phos-phorylated lipoproteins of egg yolk, which exist in the form of granules (51), which themselves can be the surface-active units (e.g., in mayonnaise) (52). 

---