It is not too difficult to make a highly stable proteinbased oil-in-water emulsion under favourable thermodynamic and solution conditions. But all too often this stability
is lost when the emulsion is subjected to environmental
stresses during storage or subsequent processing. McClements (pp. 305–313) reviews some recently devised
strategies for overcoming emulsion instability problems
arising from mechanical stresses and thermal stresses during
processing operations such as pasteurization, homogenization, chilling, freezing and drying. Attention has to be
directed towards each of the three main modes of oil-inwater emulsion instability: creaming, flocculation and
coalescence. Of particular note is the benefit of sequentially
forming multiple layers of food biopolymers around oil
droplets by exploiting the strong electrostatic attraction
between proteins and other species (emulsifiers, polysaccharides) that carry opposite net charges. Experiments in
McClements’s own laboratory have demonstrated that
droplets coated by multi-layer membranes can exhibit
greatly improved stability towards environmental stresses
compared with those stabilized by adsorbed monolayers.
This behaviour is attributed to increased interfacial layer
thickness and enhanced surface viscoelasticity.