135
Microwave-Assisted Extraction (MAE)
Microwaves are the electromagnetic waves in the range between 300 MHz and
300 GHz on the electromagnetic spectrum. These consist of two oscillating perpendicular fields: electric and magnetic fields. The frequency bands at 0.915 and
2.450 GHz have been mostly utilized at homes in ovens and operate at 2.450 GHz
(wavelength, 12.2 cm; energy 0.94 J/mol). At such frequencies, rotation of the polar
molecules of a microwave-irradiated matrix and/or solvent takes place which in turn
creates heat. Here the transfer of energy can be explained on the basis of dipole rotation involving the reversal of dipoles in polar molecules; and ionic conduction,
involving displacement of charged ions present in the solvent (Routray and Orsat
2012). But the generation of heat can take place only if the material absorbs some
energy i.e. it possesses dielectric losses. The positive side of using microwave
assisted extraction is that as compared to the conventional heating, there is no temperature gradient. With respect to the pectin modifying effects of microwave assisted
extraction, various works have been carried as in case of pectin extracted from
grapefruit by (Bagherian et al. 2011). The workers reported that using microwave
power (0.45, 0.63, and 0.9 kW) not only increased yield of pectin but also the values
for DE increased generally with increasing microwave power and time
(70.96–80.89%). However the technology bears the cost constraint and cannot be
employed on commercial scale. A lot of investigation needs to be carried to bring
it to use.
Enzyme-Assisted Extraction (EAE)
There is a growing pressure on food and pharmaceutical industries to replace extraction methods based on solvents with some novel methods in order to prevent the
presence of trace chemical solvents in products from solvent-based extraction processes. For this purpose, the use of enzymes is finding its way to extract and modify
various polysaccharides owing to their selective reactivity and ability to catalyse
reactions. Enzymes have a widespread use in food processing sector such as clarification of juices. Similarly the use of enzymes for extraction of seaweed hydrocolloids, carrageenan, alginate and agar modified the physicochemical properties of the
marine polysaccharide (Rhein-Knudsen et al. 2015). The network of the polysaccharides in the plant cell is comprised of cellulose, hemicellulose (like xyloglucan),
and pectin and protein. With respect to pectin, the cellulose/xyloglucan network is
implanted in its matrix along with a protein network. So the cell wall along with the
various cell components can be degraded using enzymes such as cellulases, hemicellulases and proteases with minimal pectinolytic activity. So we can have two
approaches as regards to enzyme assisted extraction i.e.: (1) Degrading pectin using
enzymes followed by isolation of pectin fragments e.g. galacturonic acid, and (2)
using enzymes capable of deconstructing plant cell wall and isolating pectin
(Panouille et al. 2006). However the method requires a good deal of knowledge both
of the catalytic action of the selected enzymes and the optimum conditions for their
Pectin
Microwave-Assisted Extraction (MAE)
Microwaves are the electromagnetic waves in the range between 300 MHz and
300 GHz on the electromagnetic spectrum. These consist of two oscillating perpendicular fields: electric and magnetic fields. The frequency bands at 0.915 and
2.450 GHz have been mostly utilized at homes in ovens and operate at 2.450 GHz
(wavelength, 12.2 cm; energy 0.94 J/mol). At such frequencies, rotation of the polar
molecules of a microwave-irradiated matrix and/or solvent takes place which in turn
creates heat. Here the transfer of energy can be explained on the basis of dipole rotation involving the reversal of dipoles in polar molecules; and ionic conduction,
involving displacement of charged ions present in the solvent (Routray and Orsat
2012). But the generation of heat can take place only if the material absorbs some
energy i.e. it possesses dielectric losses. The positive side of using microwave
assisted extraction is that as compared to the conventional heating, there is no temperature gradient. With respect to the pectin modifying effects of microwave assisted
extraction, various works have been carried as in case of pectin extracted from
grapefruit by (Bagherian et al. 2011). The workers reported that using microwave
power (0.45, 0.63, and 0.9 kW) not only increased yield of pectin but also the values
for DE increased generally with increasing microwave power and time
(70.96–80.89%). However the technology bears the cost constraint and cannot be
employed on commercial scale. A lot of investigation needs to be carried to bring
it to use.
Enzyme-Assisted Extraction (EAE)
There is a growing pressure on food and pharmaceutical industries to replace extraction methods based on solvents with some novel methods in order to prevent the
presence of trace chemical solvents in products from solvent-based extraction processes. For this purpose, the use of enzymes is finding its way to extract and modify
various polysaccharides owing to their selective reactivity and ability to catalyse
reactions. Enzymes have a widespread use in food processing sector such as clarification of juices. Similarly the use of enzymes for extraction of seaweed hydrocolloids, carrageenan, alginate and agar modified the physicochemical properties of the
marine polysaccharide (Rhein-Knudsen et al. 2015). The network of the polysaccharides in the plant cell is comprised of cellulose, hemicellulose (like xyloglucan),
and pectin and protein. With respect to pectin, the cellulose/xyloglucan network is
implanted in its matrix along with a protein network. So the cell wall along with the
various cell components can be degraded using enzymes such as cellulases, hemicellulases and proteases with minimal pectinolytic activity. So we can have two
approaches as regards to enzyme assisted extraction i.e.: (1) Degrading pectin using
enzymes followed by isolation of pectin fragments e.g. galacturonic acid, and (2)
using enzymes capable of deconstructing plant cell wall and isolating pectin
(Panouille et al. 2006). However the method requires a good deal of knowledge both
of the catalytic action of the selected enzymes and the optimum conditions for their
Pectin