Foaming properties of potato proteins recovered by complexation with carboxymethylcellulose

A protein isolate, with a 74.4% (w/w) protein content, was recovered from a simulated potato processing plant waste effluent by complexation with carboxymethylcellulose. The protein solubility of the isolate was satisfactory, it decreased in the presence of NaCl, but was not markedly affected by heat treatment. The isolate exhibited remarkable foaming and foam stabilizing properties, compared with lyophilized egg white, which are attributed to the very high surface activity of the potato protein molecules, which following adsorption at a/w interfaces, result in a much higher surface pressure development compared with egg albumen. A significant part of the foaming ability and the high surface activity of the isolate should be connected with the presence in the isolate of a small fraction of proteins with a relatively low molecular weight. The sulfhydryl groups of these proteins, following adsorption at the a/w interface, during the process of foam formation and denaturation are oxidized leading to the possible formation of intermolecular disulfide linkages.     

The rheology of tomato seed protein isolate films at the corn oil-water interface

Tomato seed proteins adsorbed at the corn oil-water interface formed, after long ageing times, interfacial films with viscoelastic properties. The viscoelastic parameters of the films, derived by analysis of creep compliance-time curves, were markedly influenced by the aqueous phase protein concentration and showed maxima at a certain concentration which probably corresponded to monolayer saturation coverage. Tomato seed protein film viscoelasticity is greater than that of soybean protein, the parameters of which also show maxima at certain protein concentration. The lowering of pH brings about a decrease in tomato seed protein film viscoelasticity, a fact that could be the result of less molecular unfolding and consequently, less extensive intermolecular hydrophobic interaction.     

MINOR SURFACE-ACTIVE LIPIDS OF OLIVE OIL AND VISCOELASTICITY OF PROTEIN FILMS AT THE OLIVE OIL-WATER INTERFACE

The influence of the minor surface-active lipids of olive oil on the viscoelastic parameters of bovine serum albumin, sodium caseinate and egg yolk films, formed following adsorption at the olive oil-protein solution interface, was studied. All the parameters substantialy decreased in the case of bovine serum albumin when surface-active lipids were removed from the olive oil while the absence of these components resulted in purely viscous films in the cases of sodium caseinate and egg yolk. Protein film viscoelasticity is probably influenced by olive oil surface-active lipids as a result of their interactions with adsorbed and unfolded protein molecules at the oil-protein solution interface.     

The influence of egg yolk lipoproteins on the rheology and stability of O/W emulsions and mayonnaise

Several variables influence the time dependent reduction of interfacial tension by egg yolk lipoproteins at a groundnut oil-water interface. These are pH, NaCl, methanol and temperature, and they affect the degree of micelle breakdown and subsequent molecular unfolding and rearrangement following adsorption. Diffusion to the interface is a rate controlling factor when the aqueous phase contains a very low concentration of egg yolk, but only in the early stages of adsorption. Otherwise, penetration of the interface by low density lipoproteins, breakdown of micelles and configurational changes predominate.