Gelation encapsulation

Ui The enzymatic charge offered for immobilization in U/g of support, U t the enzymatic charge theoretically immobilized in U/g of support, R1 the immobilization yield, defined as (C/rr/Ui)x 100, U i the measured immobilized enzyme activity, in U/g of biocatalyst, RA the activity recovered in the immobilized enzyme, defined as (Uei/[/it)=< 100, Note I gelation/encapsulation=45 °C, ethanolic/acid medium, 155 min, aging=18 h at 4 °C, drying=suck dried by vacuum, followed by a 24-h resting period in a desiccator All the results of this immobilization are the averages of duplicates. 

The enzymatic charge per gram of support, U, was calculated from the biocatalyst mass obtained after the process of gelation/encapsulation (90.01 g) and the offered enzymatic charge (960 U). 

PMBV and PVA can spontaneously form a hydrogel without using any crosslinkers. Even in cell culture conditions, the gelation can be confirmed. Therefore, it was possible to encapsulate cells in the PMBV/PVA hydrogel. The encapsulation method is illustrated in Fig. 6. 

Lasic DD, Frederik PM, Stuart MCA, Barenholz Y, McIntosh TJ. Gelation of liposome interior. A novel method for drug encapsulation. FEBS Lett 1992 312 255-258. 

One of the more spectacular examples of the development of novel interactions for nanostructuring of food systems is the self-assembly of partially hydrolysed molecules of a-lactalbumin at neutral pH in the presence of appropriate cations (Ca2+, Mn2+, Zn2+, Cu2+ or Al3+). These ordered nanostructures possess enhanced functionality for thickening, gelation and encapsulation, as compared to the individual protein molecules or their disordered aggregates. The molecules assemble into rather stiff nanotubes with a cavity diameter of 16 nm and a length of a few micrometres (Figure 1.1). The specific ion size and its preferred ligand coordination number seem to play a key mechanistic role. But hydrolysis is needed to make the a-lactalbumin prone to self-assembly. 

For reasons that are probably unrelated to their technical performance, these covalent protein-polysaccharide conjugates have not yet been used commercially in food systems. But it seems that it is only a matter of time before the impressive potential of these highly functional ingredients becomes exploited on a commercial scale in various food applications — not just for emulsification, but also for foaming, gelation, waterholding, and encapsulation. 

Fig. 7. An optical transmitted light micrograph of a single H micron carbon fiber in an epoxy matrix. The fiber had not been degassed before encapsulation. The volatile material on the surface vaporized around the time of gelation creating large voids around the fiber...

The enzyme, normally in solution, is added and after aging either a thin film or a gel can be formed with the encapsulated molecules. Depending upon the acid used, the solution pH and other conditions, gelation can take from 1 min up to several days. The sol-gel matrix shows many advantages (i) the ability to entrap a large amount of enzyme, (ii) retention of the enzymatic activity due to the sufficiently mild conditions of the sol-gel process,... 

Other protein systems have been successfully used for encapsulation. For example, conjugated linoleic acid has been microencapsulated using whey proteins (Jimenez et al. 2004). A whey protein bead delivery system was prepared by emulsification of soybean oil containing retinol with pre-denatured whey protein followed by the addition of calcium ions to induce gelation. The encapsulant system protected... 

Cho, Y.H., Shim, H.K., and Park, J. (2003). Encapsulation of fish oil by an enzymatic gelation process using transglutaminase cross-linked proteins. J. FoodSci. 68, TlYl-212 i. 

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