4 Fabrication Methodologies
Microencapsulation is defined as a technology for packaging solids, liquids or
gaseous materials into miniature, sealed capsules that can release their contents at
controlled rates under the influences of specific conditions. A microcapsule consists
of a semi-permeable, spherical, thin and strong membrane surrounding a solid or
liquid core, with a diameter varying from a few microns to 1 mm. In a broad sense,
encapsulation can be used for many applications in the food industry, including
stabilizing the core material, controlling the oxidative reaction, providing sustained
or controlled release (both temporal and time-controlled release), masking flavours,
colours or odours, extending the shelf life and protecting components against
nutritional loss. Various biopolymers such as alginate, chitosan, CMC, carrageenan, gelatin and pectin are mainly applied, using various microencapsulation
technologies. Microcapsules and microspheres can be engineered to gradually
release active ingredients. A microcapsule can be opened by many different
means, including fracture by heat, solvation, diffusion and pressure. A coating
may also be designed to open in specific areas of the body. A microcapsule
containing acid-labile core materials that is consumed by gastrointestinal fluids
must not be fractured until after it passes through the stomach. A coating can
therefore be used that is able to withstand acidic conditions in the stomach and
allows those active ingredients to pass through the stomach. Encapsulation technology is widely used in foods and pharmaceutical manufacturing to control the
release of active ingredients, protect ingredients from the environment, lower
flavour loss during the product shelf-life, extend the flavour perception and
mouth-feel over a longer period of time, and enhance the ingredient bioavailability
and efficacy.
4.1 Spray Drying
Spray drying is the most commonly used microencapsulation technique in the food
industry [37–39]. The process is relatively simple and easily converts liquids to
powders and protects volatile compounds against degradation and oxidation [40].
Consequently, spray drying has been used to encapsulate a variety of substances,
for example, flavours, vitamins, fish oils and flavours [41].
The principle steps of the process involve preparation and homogenization of the
dispersion, atomization of the dispersion and subsequent dehydration of the
atomized particles (as depicted in Fig. 3). The dispersion is prepared by mixing
the core material into a liquid coating material. This mixture is homogenized and
sprayed into a hot chamber, whereby water is evaporated off the surface of the
atomized particles to produce capsules [42, 43]. A cyclone separates capsules,
which are subsequently collected .
The stability of capsules prepared using spray drying is a consequence of the
chemical and physical properties of the coating and core materials, atomization and
Biopolymeric Micro- and Nanoparticles: Preparation, Characterization and. . .
279
Microencapsulation is defined as a technology for packaging solids, liquids or
gaseous materials into miniature, sealed capsules that can release their contents at
controlled rates under the influences of specific conditions. A microcapsule consists
of a semi-permeable, spherical, thin and strong membrane surrounding a solid or
liquid core, with a diameter varying from a few microns to 1 mm. In a broad sense,
encapsulation can be used for many applications in the food industry, including
stabilizing the core material, controlling the oxidative reaction, providing sustained
or controlled release (both temporal and time-controlled release), masking flavours,
colours or odours, extending the shelf life and protecting components against
nutritional loss. Various biopolymers such as alginate, chitosan, CMC, carrageenan, gelatin and pectin are mainly applied, using various microencapsulation
technologies. Microcapsules and microspheres can be engineered to gradually
release active ingredients. A microcapsule can be opened by many different
means, including fracture by heat, solvation, diffusion and pressure. A coating
may also be designed to open in specific areas of the body. A microcapsule
containing acid-labile core materials that is consumed by gastrointestinal fluids
must not be fractured until after it passes through the stomach. A coating can
therefore be used that is able to withstand acidic conditions in the stomach and
allows those active ingredients to pass through the stomach. Encapsulation technology is widely used in foods and pharmaceutical manufacturing to control the
release of active ingredients, protect ingredients from the environment, lower
flavour loss during the product shelf-life, extend the flavour perception and
mouth-feel over a longer period of time, and enhance the ingredient bioavailability
and efficacy.
4.1 Spray Drying
Spray drying is the most commonly used microencapsulation technique in the food
industry [37–39]. The process is relatively simple and easily converts liquids to
powders and protects volatile compounds against degradation and oxidation [40].
Consequently, spray drying has been used to encapsulate a variety of substances,
for example, flavours, vitamins, fish oils and flavours [41].
The principle steps of the process involve preparation and homogenization of the
dispersion, atomization of the dispersion and subsequent dehydration of the
atomized particles (as depicted in Fig. 3). The dispersion is prepared by mixing
the core material into a liquid coating material. This mixture is homogenized and
sprayed into a hot chamber, whereby water is evaporated off the surface of the
atomized particles to produce capsules [42, 43]. A cyclone separates capsules,
which are subsequently collected .
The stability of capsules prepared using spray drying is a consequence of the
chemical and physical properties of the coating and core materials, atomization and
Biopolymeric Micro- and Nanoparticles: Preparation, Characterization and. . .
279