13
before the presence of foodstuffs. There are several mechanisms to satisfy this function which are activated by humidity, radiation and temperature (Thomas et al. 2018).
Considering the incorporation of active agents in the packaging material, there
are two alternatives: into polymer film or on film surface. Depending on the type
and design of packaging, as well as the foodstuff, there is a more appropriate option
to incorporate active agents into the packaging material. With regard to the inclusion of the activity in bulk polymer film, material processing generally involves the
combination of active agents with polymer, thus obtaining a concentrate which can
later be used in the manufacture of packaging. Thus, this concentrate is fed to different processes to obtain flexible or rigid packaging via blown extrusion, casting,
compression, injection molding, among others (Somade and Adegboye 2018). The
proportion of concentrate used in these processes is established in terms of the
required concentration of active agent in the final packaging material to protect the
packaged food. The inclusion of activity in the bulk polymer film allows providing
high efficiency as the active compound slowly migrates from the packaging material to the food. In this sense, the fact that active agent could be released over a long
period allows to offer protection during transport, storage and shelf life of packaging.
Another alternative to include active agents in the packaging system is to anchor
them on the material surface (Romani et al. 2020). In this case, active component
can act via direct contact with the packaged food (Lee et al. 2015). The incorporation of the active agent at the product contact side presents some benefits compared
to its bulk incorporation into polymer film. This alternative allows to preserve the
bulk properties of the packaging material and reduce the agent concentration.
Various technologies related to the incorporation of activity on the surface of the
packaging film have been reported. One of these techniques is the solution casting
which involves the dispersion of an active agent in a polymer dissolution in a solvent medium which is poured on film surface (Bastarrachea et al. 2011). This
method, despite being widely used at the laboratory level, has some disadvantages
because the polymers used in the packaging material are dissolved at high temperatures using organic solvents, which affects the stability and efficiency of the active
compounds. Another method to incorporate active agents on the surface of packaging material is via immobilization. Due to the inert nature of the polymers, a surface
modification is necessary to functionalize the material and promote the immobilization of active compounds. In this sense, surface activation can be carried out through
physical (corona discharge, flame, plasma and ultraviolet (UV) radiation) and wet
(use of corrosive liquids) methods (Bastarrachea et al. 2015). In general, physical
methods are more widely used than wet methods on an industrial scale, since corrosive liquids are not required. The aim of these methods is to generate reactive
groups on the film surface by anchoring active compounds via covalent or noncovalent immobilization (Mishra 2019). Another alternative to include active agents
on the packaging surface is the photo-grafting. This technique allows to obtain
active films due to the grafting of polymer chains onto the surface by exposure to
UV light. The active agents can also be incorporated during this process or by subsequent immobilization after grafting.
2 Active Packaging Films Based on Polyolefins Modified by Organic and Inorganic…
before the presence of foodstuffs. There are several mechanisms to satisfy this function which are activated by humidity, radiation and temperature (Thomas et al. 2018).
Considering the incorporation of active agents in the packaging material, there
are two alternatives: into polymer film or on film surface. Depending on the type
and design of packaging, as well as the foodstuff, there is a more appropriate option
to incorporate active agents into the packaging material. With regard to the inclusion of the activity in bulk polymer film, material processing generally involves the
combination of active agents with polymer, thus obtaining a concentrate which can
later be used in the manufacture of packaging. Thus, this concentrate is fed to different processes to obtain flexible or rigid packaging via blown extrusion, casting,
compression, injection molding, among others (Somade and Adegboye 2018). The
proportion of concentrate used in these processes is established in terms of the
required concentration of active agent in the final packaging material to protect the
packaged food. The inclusion of activity in the bulk polymer film allows providing
high efficiency as the active compound slowly migrates from the packaging material to the food. In this sense, the fact that active agent could be released over a long
period allows to offer protection during transport, storage and shelf life of packaging.
Another alternative to include active agents in the packaging system is to anchor
them on the material surface (Romani et al. 2020). In this case, active component
can act via direct contact with the packaged food (Lee et al. 2015). The incorporation of the active agent at the product contact side presents some benefits compared
to its bulk incorporation into polymer film. This alternative allows to preserve the
bulk properties of the packaging material and reduce the agent concentration.
Various technologies related to the incorporation of activity on the surface of the
packaging film have been reported. One of these techniques is the solution casting
which involves the dispersion of an active agent in a polymer dissolution in a solvent medium which is poured on film surface (Bastarrachea et al. 2011). This
method, despite being widely used at the laboratory level, has some disadvantages
because the polymers used in the packaging material are dissolved at high temperatures using organic solvents, which affects the stability and efficiency of the active
compounds. Another method to incorporate active agents on the surface of packaging material is via immobilization. Due to the inert nature of the polymers, a surface
modification is necessary to functionalize the material and promote the immobilization of active compounds. In this sense, surface activation can be carried out through
physical (corona discharge, flame, plasma and ultraviolet (UV) radiation) and wet
(use of corrosive liquids) methods (Bastarrachea et al. 2015). In general, physical
methods are more widely used than wet methods on an industrial scale, since corrosive liquids are not required. The aim of these methods is to generate reactive
groups on the film surface by anchoring active compounds via covalent or noncovalent immobilization (Mishra 2019). Another alternative to include active agents
on the packaging surface is the photo-grafting. This technique allows to obtain
active films due to the grafting of polymer chains onto the surface by exposure to
UV light. The active agents can also be incorporated during this process or by subsequent immobilization after grafting.
2 Active Packaging Films Based on Polyolefins Modified by Organic and Inorganic…