proteins or to transcription factors (Mishra et al. 2016). In that way, it is strongly
suggested that AE can influence the synthesis of secondary metabolites. The most
common acoustic emission utilized for the stimulation of bioactive compounds is
ultrasound (US). Several mechanisms of how the US interacts within the cell have
been proposed. When the US is applied, cavitation bubbles creates a pressure zone
change that occurs and increases up to 400 km h
−1 , causing higher porosity, rupture
or removal of cell membranes, facilitating the mass transfer from the cells’ interior
when imploding (Toma et al. 2001; Vinatoru 2001). In that way, the increase of
natural bioactive compounds may be caused by better extractability due to rupture
of membranes of cell organelles, however, when a decrease is presented, it could be
explained by the creation of reactive forms of oxygen (ROS) during cavitation, and
that the collapsing bubbles release high doses of energy, raising the temperature
(>5000 K) enough to decompose polyphenols (Witrowa-Rajchert et al. 2014;
Kentish and Ashokkumar 2011). The second possible explanation is an enhancement of enzymes activity when the US is applied by contact, leading to phenolic
compounds’ reduction, more significantly after longer treatment time (Wiktor et al.
2016). Ampofo and Ngadi (2020) established that elicitation of common beans with
the US, increased the accumulation of stress markers from the onset until the
process was arrested, signifying a demand for sprout protection, resulting in an
elevated stimulation of defense phenolic triggering enzymes (PAL and TAL), and
final biosynthesis of phenolic compounds. In that way, application in food or plants
of US treatment should be studied to find the optimal time, frequency, and intensity
in order to optimize the production of secondary metabolites. Table 5.3 summarizes
some examples of the application of acoustic emissions on plants or foods with a
commercial interest and presents the effect on the production of natural bioactive
compounds.
5.2.3 Nanoparticles
Nanoparticles (NPs) vary in size from 1 to 100 nm and have physicochemical
properties, due to their dimensions, which generate a high added value for the
nanotechnology industry (Yokel and MacPhail 2011). Nanoscale materials can be
found on medical imaging, drug delivery, personal care products, cosmetics,
clothing, electronics, agrochemicals, motor vehicles, among other products and
applications (Vance et al. 2015; Yokel and MacPhail 2011). The metal-based NPs
most commonly studied and found in industrial products are Cd (cadmium) in
various complexes, GaAs (gallium arsenide), Au (gold), Ni (nickel), Pt (platinum),
Ag (silver), Al 2 O 3 (aluminum oxide or alumina), CeO 2 (cerium dioxide or ceria),
SiO 2 (Silicon dioxide or silica), TiO 2 (titanium dioxide or titania), ZnO (zinc
oxide), CuO (copper oxide), and Fe 3 O 4 /Fe 2 O 3 (iron oxides) (Khot et al. 2012;
Yokel and MacPhail 2011). Among the carbon-based nanomaterials often studied
are fullerene, single-walled carbon nanotubes (SWCNTs), and multiwalled carbon
nanotubes (MWCNTs) (Balbus et al. 2007).
166
H. Aguirre-Becerra et al.
suggested that AE can influence the synthesis of secondary metabolites. The most
common acoustic emission utilized for the stimulation of bioactive compounds is
ultrasound (US). Several mechanisms of how the US interacts within the cell have
been proposed. When the US is applied, cavitation bubbles creates a pressure zone
change that occurs and increases up to 400 km h
−1 , causing higher porosity, rupture
or removal of cell membranes, facilitating the mass transfer from the cells’ interior
when imploding (Toma et al. 2001; Vinatoru 2001). In that way, the increase of
natural bioactive compounds may be caused by better extractability due to rupture
of membranes of cell organelles, however, when a decrease is presented, it could be
explained by the creation of reactive forms of oxygen (ROS) during cavitation, and
that the collapsing bubbles release high doses of energy, raising the temperature
(>5000 K) enough to decompose polyphenols (Witrowa-Rajchert et al. 2014;
Kentish and Ashokkumar 2011). The second possible explanation is an enhancement of enzymes activity when the US is applied by contact, leading to phenolic
compounds’ reduction, more significantly after longer treatment time (Wiktor et al.
2016). Ampofo and Ngadi (2020) established that elicitation of common beans with
the US, increased the accumulation of stress markers from the onset until the
process was arrested, signifying a demand for sprout protection, resulting in an
elevated stimulation of defense phenolic triggering enzymes (PAL and TAL), and
final biosynthesis of phenolic compounds. In that way, application in food or plants
of US treatment should be studied to find the optimal time, frequency, and intensity
in order to optimize the production of secondary metabolites. Table 5.3 summarizes
some examples of the application of acoustic emissions on plants or foods with a
commercial interest and presents the effect on the production of natural bioactive
compounds.
5.2.3 Nanoparticles
Nanoparticles (NPs) vary in size from 1 to 100 nm and have physicochemical
properties, due to their dimensions, which generate a high added value for the
nanotechnology industry (Yokel and MacPhail 2011). Nanoscale materials can be
found on medical imaging, drug delivery, personal care products, cosmetics,
clothing, electronics, agrochemicals, motor vehicles, among other products and
applications (Vance et al. 2015; Yokel and MacPhail 2011). The metal-based NPs
most commonly studied and found in industrial products are Cd (cadmium) in
various complexes, GaAs (gallium arsenide), Au (gold), Ni (nickel), Pt (platinum),
Ag (silver), Al 2 O 3 (aluminum oxide or alumina), CeO 2 (cerium dioxide or ceria),
SiO 2 (Silicon dioxide or silica), TiO 2 (titanium dioxide or titania), ZnO (zinc
oxide), CuO (copper oxide), and Fe 3 O 4 /Fe 2 O 3 (iron oxides) (Khot et al. 2012;
Yokel and MacPhail 2011). Among the carbon-based nanomaterials often studied
are fullerene, single-walled carbon nanotubes (SWCNTs), and multiwalled carbon
nanotubes (MWCNTs) (Balbus et al. 2007).
166
H. Aguirre-Becerra et al.