Biopolymers as emulsifying wall material for encapsulation

Another characteristic property of many biopolymers (proteins, modified starch, chitosan, etc.) which is useful for the encapsulation of bioactive molecules is their ability to adsorb at the oil-water interface and to form adsorbed layers that are capable of stabilizing oil-in-water (OAV) emulsions against coalescence (see Table 2.2). It is worthwhile to note here that the formation of an emulsion is one of the key steps in the encapsulation of hydrophobic nutraceuticals by the most common technique used nowadays in the food industry (spray-drying). The adsorption of amphiphilic biopolymers at the oil-water interface involves the attachment of their hydrophobic groups to the surface of the oil phase (or even their slight penetration into it), whilst their hydrophilic parts protrude into the aqueous phase providing a bulky interfacial layer. 

All these microcapsules were found to be roughly spherical in shape and of similar size (14-18 pm) (Drusch, 2007). A mixture of chitosan, maltodextrin and whey protein isolate was also found to be also a good wall material for encapsulation of fish oil using an ultrasonic atomizer followed by freeze-drying of the microcapsules (Klaypradit and Huang, 

The use of freeze-drying avoids an inherent disadvantage of spray drying, i.e., the elevated processing temperature, which accelerates the oxidation of polyunsaturated lipids. 

Mixtures and Complexes of Proteins with Polysaccharides as Deliveiy Vehicles 

Mixed protein/polysaccharide micro-beads have also been found to be promising delivery vehicles for immobilized bifidobacteria (Guerin et al, 2003). Such micro-beads were made by a transacylation reaction involving the formation of amide bonds between protein and alginate (Levy and Edwards-Levy, 1996). This produces a membrane on the bead surface, protecting the immobilized bifidobacteria against both the very acidic conditions (pH 1-2) and the pepsin activity in the stomach. 

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