Manipulation of Adsorption Behaviour at Liquid Interfaces by Changing Protein–Polysaccharide Electrostatic Interactions - Food Colloids: Self-Assembly and Material Science - page 197

AIR/OIL
WATER

E

E

WATER

C C

D D

B B

A A

Figure 1 Schematic model for polysaccharide-controlled protein adsorption at the air-
water or oil-water interface: A, partitioning of free protein and protein bound
to polysaccharide; B, diffusion of protein-polysaccharide complex in the bulk;
C, availability of complexed protein for the interface; D, diffusion of free
protein in the bulk; E, kinetic barrier to protein adsorption

of foam and emulsion formation. Parameters that can be used to manipulate
protein-polysaccharide interactions in the bulk are the protein-polysaccharide-
binding affinity (through the pH, ionic strength and charge density/distribution
on individual ingredients) and the mixing ratio via paths A and C, and the
molecular weight of the polysaccharide via path B.
Anionic polysaccharides can be used in combination with proteins to prevent
aggregation and creaming of emulsion droplets. 18-23 However, depending on
the relative concentrations, the added polysaccharides can also decrease emul-
sion stability due to bridging flocculation. 13 Through layer-by-layer deposition
on emulsion droplets of oppositely charged proteins, polysaccharides and
surfactants, 24,25 one may control the net charge on the droplets and enhance
the emulsion stability by electrostatic repulsion. Through their electrostatic
interaction with proteins, anionic polysaccharides that are not surface-active
are able to affect surface rheological properties by coadsorption. 14,26 Ducel and
co-authors 27 have reported that oil-water interfacial rheological properties of
plant protein-arabic gum coacervates are related to the interfacial rheological
properties of the protein used. Schmitt et al. 15 have described an effect of ageing
time of b-Lg-acacia gum complexes on air-water surface rheology in terms of
reorganization of the complexes at the interface. The elastic behaviour of
adsorbed protein layers at air-water or oil-water interfaces may affect foam
and emulsion stabilizing ability. 28 A mechanistic understanding is still lacking,
however, of how the surface rheological behaviour depends on parameters like
charge density of the polysaccharides, protein/polysaccharide mixing ratio, ionic
strength and the order of adsorption to the interface - simultaneous or sequential.