26 Encapsulation of Microalgal Pigments
645
others) directly influence the encapsulation characteristics, including the encapsulation efficiency, stability, solubility, and activity of the compound a be encapsulated.
Table 26.3 shows the main wall materials used in microencapsulation techniques.
In relation to the microencapsulation process, the techniques are classified into
three ways: (I) physical methods, (II) physical-chemical methods, and (III) chemical methods (Tyagi et al. 2011). Table 26.4 demonstrates the techniques and their
classifications.
In this sense, there is a great need for the development of microencapsulation
strategies based on the knowledge of the active agents and their desired beneficial
effects, formulating coating materials with the required functional properties, as
well as the selection of suitable encapsulation techniques and adjusting the specific
conditions of processing for the core materials (Ye et al. 2018).
Thus, the importance of microencapsulation for the protection and supply of
microalgae and its by-products is shown in Table 26.5, which shows a literature
review of coating techniques and materials being used in microalgae research. In
addition, the following will be covered a bit about each technique.
The solvent evaporation technique involves four major steps: (I) forming a
suspension, emulsion, or solution, by dispersing the coating polymer and the active
compound in an organic solvent; (II) by agitation, static mixing, extrusion, or dripping, emulsification of the organic phase (dispersed phase) is carried out in an aqueous
phase (continuous phase); (III) removal of the solvent by evaporation or liquid extraction, and (IV) recovery of the particles by filtration or centrifugation, as well as drying
thereof. It is considered an interesting technique, since it offers soft processing conditions, easy use, suitable for large scale, less amount of residual solvent, and does not
interfere in the characteristics of the active compounds (Hwisa et al. 2013).
Complex coacervation can be basically defined as a phenomenon of liquid-liquid
phase separation between biopolymers with opposing charges through electrostatic
interaction. Factors such as pH, polymer concentration, polymer mixing ratio, ionic
strength, and temperature may interfere with the formation of complex coacervates
(Eghbal and Choudhary 2018). According to Ozkan et al. (2019) is superior to other
microencapsulation techniques due to low processing temperature, high encapsulation efficiency, no need for specific equipment and simple conditions such as nontoxic solvents and low stirring. However, the complexity of the technique must be
taken into account. Thus, its use for microalgae is still scarce.
The techniques based on supercritical fluids use these fluids as solvents that
have properties (density, solvation power, and gases) between the liquids, as well
as temperature, and pressure below the critical point. They are compounds such as
carbon dioxide, water, propane, nitrogen, etc. Processes based on supercritical fluids
are generally classified into three categories: (I) solvent; (II) anti-solvent, and (III)
solute, depending on the function of the supercritical fluid. Furthermore, techniques
based on supercritical fluids may be an alternative to the disadvantages presented
by some conventional techniques, such as low size control and particle morphology,
degradation and loss of biological activity in temperature sensitive compounds, and
low encapsulation efficiency (Ozkan et al. 2019).
645
others) directly influence the encapsulation characteristics, including the encapsulation efficiency, stability, solubility, and activity of the compound a be encapsulated.
Table 26.3 shows the main wall materials used in microencapsulation techniques.
In relation to the microencapsulation process, the techniques are classified into
three ways: (I) physical methods, (II) physical-chemical methods, and (III) chemical methods (Tyagi et al. 2011). Table 26.4 demonstrates the techniques and their
classifications.
In this sense, there is a great need for the development of microencapsulation
strategies based on the knowledge of the active agents and their desired beneficial
effects, formulating coating materials with the required functional properties, as
well as the selection of suitable encapsulation techniques and adjusting the specific
conditions of processing for the core materials (Ye et al. 2018).
Thus, the importance of microencapsulation for the protection and supply of
microalgae and its by-products is shown in Table 26.5, which shows a literature
review of coating techniques and materials being used in microalgae research. In
addition, the following will be covered a bit about each technique.
The solvent evaporation technique involves four major steps: (I) forming a
suspension, emulsion, or solution, by dispersing the coating polymer and the active
compound in an organic solvent; (II) by agitation, static mixing, extrusion, or dripping, emulsification of the organic phase (dispersed phase) is carried out in an aqueous
phase (continuous phase); (III) removal of the solvent by evaporation or liquid extraction, and (IV) recovery of the particles by filtration or centrifugation, as well as drying
thereof. It is considered an interesting technique, since it offers soft processing conditions, easy use, suitable for large scale, less amount of residual solvent, and does not
interfere in the characteristics of the active compounds (Hwisa et al. 2013).
Complex coacervation can be basically defined as a phenomenon of liquid-liquid
phase separation between biopolymers with opposing charges through electrostatic
interaction. Factors such as pH, polymer concentration, polymer mixing ratio, ionic
strength, and temperature may interfere with the formation of complex coacervates
(Eghbal and Choudhary 2018). According to Ozkan et al. (2019) is superior to other
microencapsulation techniques due to low processing temperature, high encapsulation efficiency, no need for specific equipment and simple conditions such as nontoxic solvents and low stirring. However, the complexity of the technique must be
taken into account. Thus, its use for microalgae is still scarce.
The techniques based on supercritical fluids use these fluids as solvents that
have properties (density, solvation power, and gases) between the liquids, as well
as temperature, and pressure below the critical point. They are compounds such as
carbon dioxide, water, propane, nitrogen, etc. Processes based on supercritical fluids
are generally classified into three categories: (I) solvent; (II) anti-solvent, and (III)
solute, depending on the function of the supercritical fluid. Furthermore, techniques
based on supercritical fluids may be an alternative to the disadvantages presented
by some conventional techniques, such as low size control and particle morphology,
degradation and loss of biological activity in temperature sensitive compounds, and
low encapsulation efficiency (Ozkan et al. 2019).