648
B. de Souza Fonseca et al.
The lyophilization encapsulation technique is composed of different stages: (I)
freezing; (II) sublimation; (III) desorption; and (IV) storage (Ray et al. 2016). The
advantages that lyophilization presents in relation to other techniques are the low
temperature and the absence of air during the process, being a simple process, besides
avoiding deterioration by oxidation or chemical reactions, being able to be used for
natural oils, pigments, aromas, and water-soluble compounds, thus being the most
suitable technique for drying thermosensitive substances.
Ionic gelation is based on the crosslinking of polyelectrolytes by multivalent
ions such as Ca
2+ , Ba
2+ , and Al
3+ and can be applied by extrusion or emulsification/gelation. Extrusion is more common and occurs by dripping an aqueous polymer
solution through a syringe or an extruder nozzle into a solution containing CaCl 2 . The
emulsification/gelation basically occurs by the production of an emulsion containing
the hydrophobic active component in a polymer solution and is dripped in a calcium
solution, which can be carried out externally, where the Ca
2+ ions are added from
an external source to the polymer solution, or internally, where the calcium salts are
added by dripping to the polymer solution, resulting in the production of particles.
This technique does not require specific equipment and application of heat treatments, making it advantageous and presenting as an alternative for the encapsulation
of highly reactive and sensitive compounds, increasing their stability during storage.
In addition, it is a technique that has been widely used for many years (Niizawa et al.
2019).
The spray drying technique consists in the production of highly dispersed powders
from the atomization of a fluid within a drying chamber containing a heated air,
causing the solvent to evaporate uniformly and rapidly by means of direct contact,
obtaining the powdered product (Bora et al. 2018). It is an advantageous technique because it is considered fast, continuous, simple, economical, and easy reproducibility, besides high encapsulation efficiency and high physical, chemical, and
microbial stability. In addition, it is the most commonly used technique for the
encapsulation of compounds for the food industry (Wang et al. 2017).
Finally, from this review, it can be observed that the techniques of ionic gelation
and spray drying are widely used for this purpose. Thus, Table 26.6 reports the
diversity of researches conducted with microalgae and their by-products, using these
techniques.
Future perspectives
The microencapsulation of microalgal compounds, nowadays, appears as an alternative to the vulnerability of these compounds. However, because its use in this sense
is recent, it is necessary to develop further research involving pigments that have
not yet been encapsulated, as well as, the more detailed study related to the different
techniques and their materials, the applicability of microalgal compounds in different
products, besides the possibility of the reduction to the nanoscale, which can be very
promising for the protection and application of these compounds.
B. de Souza Fonseca et al.
The lyophilization encapsulation technique is composed of different stages: (I)
freezing; (II) sublimation; (III) desorption; and (IV) storage (Ray et al. 2016). The
advantages that lyophilization presents in relation to other techniques are the low
temperature and the absence of air during the process, being a simple process, besides
avoiding deterioration by oxidation or chemical reactions, being able to be used for
natural oils, pigments, aromas, and water-soluble compounds, thus being the most
suitable technique for drying thermosensitive substances.
Ionic gelation is based on the crosslinking of polyelectrolytes by multivalent
ions such as Ca
2+ , Ba
2+ , and Al
3+ and can be applied by extrusion or emulsification/gelation. Extrusion is more common and occurs by dripping an aqueous polymer
solution through a syringe or an extruder nozzle into a solution containing CaCl 2 . The
emulsification/gelation basically occurs by the production of an emulsion containing
the hydrophobic active component in a polymer solution and is dripped in a calcium
solution, which can be carried out externally, where the Ca
2+ ions are added from
an external source to the polymer solution, or internally, where the calcium salts are
added by dripping to the polymer solution, resulting in the production of particles.
This technique does not require specific equipment and application of heat treatments, making it advantageous and presenting as an alternative for the encapsulation
of highly reactive and sensitive compounds, increasing their stability during storage.
In addition, it is a technique that has been widely used for many years (Niizawa et al.
2019).
The spray drying technique consists in the production of highly dispersed powders
from the atomization of a fluid within a drying chamber containing a heated air,
causing the solvent to evaporate uniformly and rapidly by means of direct contact,
obtaining the powdered product (Bora et al. 2018). It is an advantageous technique because it is considered fast, continuous, simple, economical, and easy reproducibility, besides high encapsulation efficiency and high physical, chemical, and
microbial stability. In addition, it is the most commonly used technique for the
encapsulation of compounds for the food industry (Wang et al. 2017).
Finally, from this review, it can be observed that the techniques of ionic gelation
and spray drying are widely used for this purpose. Thus, Table 26.6 reports the
diversity of researches conducted with microalgae and their by-products, using these
techniques.
Future perspectives
The microencapsulation of microalgal compounds, nowadays, appears as an alternative to the vulnerability of these compounds. However, because its use in this sense
is recent, it is necessary to develop further research involving pigments that have
not yet been encapsulated, as well as, the more detailed study related to the different
techniques and their materials, the applicability of microalgal compounds in different
products, besides the possibility of the reduction to the nanoscale, which can be very
promising for the protection and application of these compounds.