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microcapsules decreased again (Pérez-Limiñana et al. 2014). The process, however, is not

without its challenges; aggregation and release problems (burst) have been reported, which

are not desirable for most of its applications (Yang X. et al. 2015).

12.2.2

Ionic-Gelation

Ionic-gelation is a method that has received a lot of attention specifically in the prepa-

ration of chitosan and sodium tripolyphosphate (TPP) microcapsules, which are used for

the in vivo administration of drugs (Fàbregas et al. 2013). The process is non-toxic, con-

venient, controllable without the need of organic solvents. The method involves the com-

plexation of physical crosslinking by electrostatic interaction between the negative and

positive charges of tripolyphosphate and chitosan instead of chemical crosslinking (Dong

et al. 2013; Fàbregas et al. 2013; Fan et al. 2012). This method has the advantage to avoid

the use of chemical cross-linkers and emulsifiers which are usually harmful or toxic (Fan

et al. 2012). The ionic gelation method is less expensive when comparing to the efficient

coacervation method. Abang et al (2012) proposed the use of inverse gelation to produce

spherical capsules with diameters around 3mm, but Martins et al. (2015) optimized the

process by adjusting the experimental conditions (wall material ratio and concentration,

curing time, stirring rate) and achieved core-shell microcapsules with a smaller 500µm

mean diameter.

12.2.3

Freeze-Drying

Freeze-drying, known as lyophilization, is a method used to dehydrate heat-sensitive

substances such as oils. It has been used to encapsulate fish oil and olive oil (Calvo et al.

2012; Heinzelmann et al. 2000). Freeze-drying operates by lowering pressure and freezing

the microencapsule material, followed by sublimation of ice into water vapour under re-

duced pressure (Krokida and Philippopoulos 2006). Advantages of freeze-drying include

ease of operation, simplicity and protection of heat sensitive materials (Bakry et al. 2016).

Velasco et al. (2003) found that freeze-drying reduced sensitivity of oils to oxidation but

decreased the encapsulation efficiency. Freeze drying involves a long process using high

amounts of energy, resulting in high cost. Additionally, the material (e.g. the oil) could be

more exposed to the environment because of high porous structures of microcapsules pro-

duced from freeze-drying, though this feature is advantageous when a high drug release is

required (Bakry et al. 2016; Sinha et al. 2007).

12.2.4

Spray-Drying

Spray drying is one of the oldest and most established process of encapsulation and

has been used to prepare pharmaceutical products such as granules, suspensions and dry

powders. Spray drying involves forming an emulsion by dispersing the core material in a

polymer solution; the emulsion is then homogenized and atomized into a drying chamber.

The method is commonly used to encapsulate core materials that are sensitive to heat, and

functional lipophilic ingredients (Berendsen et al. 2015; Dima et al. 2016; Munoz-Ibanez

et al. 2016). A disadvantage of spray drying is that the release properties can be affected

due to the formation of amorphous systems, which are thermodynamically unstable and