application of alternative food-preservation - Bentham Science

190 Application of Alternative Food-Preservation Technologies Gallo and Corbo
Chemical Methods
Emulsion Polymerization
In this method a water-insoluble monomer is added dropwise into the aqueous polymerization medium,
containing the ingredient to be encapsulated and a emulsifier. Initially, polymer molecules form primary nucleus,
thus they growing and entrapping the core material [2].
The size of the particles is ca. 50-500 μm [3].
Interfacial Polymerization
In this technology, the polycondensation of two complementary monomers takes place at the interface of two
immiscible phases, that are mixed under carefully-controlled conditions to form small droplets of one phase in
the other. For this process is it necessary to use a small amount of a suitable stabilizer to prevent droplet
coalescence or particle coagulation. Microcapsules can be either monocore or matrix type, depending on the
solubility of the polycondensate in the droplet phase [2].
This method was initially applied for the preparation of semipermeable artificial cells and then used for many
materials: solids, aqueous solution and organic liquids. The size of microcapsules varies from 2 to 6 µm to 2000
µm [3].
In-situ Polymerization
The process involves the direct polymerization of a single monomer shell carried out on a core materials surface.
Coating thickness is of 0.2-75 µm and the coating is uniform [4].
Coacervation
It is the most promising microencapsulation technology, because the recovery is up to 99%; this method is used
mainly to encapsulate flavour oil, fish oil, vitamins and enzymes [5].
This technique is carried out by preparing an aqueous polymer solution (1-10%) containing the core material at
40-50°C; a suitable stabilizer can be added to the mixture to maintain the individuality of the microcapsules. A
coacervating agent is gradually added to the solution, thus leading to the formation of partially desolvated
polymer molecules, and hence their precipitation on the surface of the core particles. The coacervation mixture is
cooled to about 5-20°C, followed by the addition of a crosslinking agent to solidify the microcapsule wall
formed around the core particles [2].
The most studied and well understood coacervation system is probably the gelatin/gum acacia system, which
presents a major drawback, due to the use of gelatin in foods. However, this issue could be solved by using an
enzymatic crosslinking [5].
Liposome
Developed in recent years, nowadays this technology is used routinely in food industry and in pharmaceutical
area, due to: the high encapsulation efficiency, the simple production method and the good stability of
capsules [5].
Liposomes or phospholipide vesicles are structures composed of a lipid vesicle bilayers and are generally large,
irregular and unilamellar. Chemically, liposome is an amphoteric compound containing both positive and
negative charges [6].
Today, the methods for liposome formation do not use the sonication or organic solvent, and allow the
continuous production of microcapsules on a large scale. Several authors have proposed different methods for
liposome production for microencapsulation technology [5].
The maximum particle size (16 μm) is obtained by using a liposome concentration of 4 g/l [6].