Physico-chemical features of complex coacervation

In a critical and definitive review of this area (de Kruif et al.. 2004), the following general features of complex coacervation were asserted  

There is evidence that random mixing of partially charge-neutralized hydrated polyelectrolyte complexes inside the coacervate phase imparts higher configurational entropy to these less stiff polyelectrolyte molecules as compared to those in the pre-coacervation phase (Kaibara et al., 

The trend in microencapsulation research nowadays is to replace the traditional gelatin + gum arabic system by other biopolymers. The motivation is to design capsules with improved properties, and also to avoid the use of gelatin for health, ethical or religious reasons (de Kruif et al., 2004). For example, gelatin has been replaced by plant proteins in mixtures with gum arabic (Ducel et al., 2004). The physicochemical condi- 

Peniche et al. (2004) successfully encapsulated up to 65 % of shark liver oil (rich in polyunsaturated fatty acids) in chitosan/alginate capsules in order to mask the oil s unpleasant taste. Here again it was found that the chitosan coating allowed a greater degree of control of capsule permeability. The capsules could be degraded by enzymes such as lipase or pancreatin. They were initially resistant to the acid environment of the stomach, although after 4 hours under intestinal conditions (pH = 7.4) the capsule walls were finally disrupted. 

Finally, we note here that the dehydration of biopolymers associated with their attractive non-ionic interactions (dipole-dipole, hydrophobic) can increase the contribution of the mixing entropy. This in turn can lead to a tendency towards enhancement of the thermodynamically favourable interactions between them (Appelqvist and Debet, 1997 Cai and Arnt-field, 1997 Semenova a/., 1991b). 

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