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5.5.5 Applications in Packaging Materials
Food quality is affected by lipid oxidation due to microbial growth, enzymatic
browning and vitamin loss. The mass transfer between packaging materials and
packed food exists in food storage (Gutiérrez and Álvarez 2017). Because of this
transfer, an antioxidant in the packing material can have a positive effect on food
quality. In fact, the addition of antioxidants in packing materials has become a standard process (Gutiérrez 2018; Toro-Márquez et al. 2018). Due to the properties of
lignin, it can be used as an alternative to toxic synthetic antioxidants and expensive
natural antioxidants in packing materials. There are two mechanisms in the antioxidative role that lignin plays in packaging materials. One is the migration of the free
radical scavenger from the packing materials to the food, the other is the presence
of free radical scavenging activity on the surface of packing materials (CrouvisierUrion et al. 2016). The mechanism of surface activity generally dominates.
In this sense, Dumitriu et al. (2018) prepared alginate/LS film by crosslinking
using two formulations with glutaraldehyde. The high LS content in the mixed film
improved protection against UV light and radical scavenging properties. L NPs
have a stronger effect than original lignin on antioxidant properties and thermal
stability (Dumitriu et al. 2018). Yang et al. (2016) achieved good interfacial adhesion and dispersion between L NPs into a PVA/Cs mixture. In addition, a synergistic
antioxidant effect between L NP and Cs in the composite appeared to have occurred.
The presence of L NP improved UV barrier property and thermal stability of ternary
PVA/Cs/L NP composite. The composite exhibited an ability to inhibit the growth
of Xanthomonas arboricola pv. pruni and Erwinia carotovora subsp. carotovora,
indicating that it can be applied as a packaging material for fruits and vegelates to
discourage bacterial contamination (Yang et al. 2016). Domenek et al. (2013) prepared PLA-lignin films by thermo-compression and twin-screw extrusion. The low
Mw fractions of lignin were released during the thermo-compressing process, and
the antioxidant activity of the PLA-lignin films increased with the increasing severity of heating due to the generation of more phenolic monomers during the process.
Aguié-Béghin et al. (2015) evaluated the antioxidant properties of lignin in two
complex matrices: an oil/water dispersion with potential use as a food matrix and
cellulose-based films as a model of the polymer matrix. Because the different lignins work differently in multiphasic systems, when a particular level of antioxidant
activity is required, such systems must be tested in simulations of the targeted application before being used.
Espinoza Acosta et al. (2015) found that alcohol soluble lignin (ASL)/starch
films showed good dispersibility without lignin agglomerations, or undissolved particles. The thermal degradation resistance and antioxidant activity of the films
increased due to the addition of ASL. ASL also had a plasticizing effect on lignin/
starch films, increasing the strain at break and decreasing the Young’s modulus and
maximum stress values of the films. In addition to the composite film prepared by
mixing lignin and starch, LS graft copolymers and starch synthesized by laccase
catalysis have also been reported by Shogren and Biswas (2013).
5 Lignin as a Natural Antioxidant: Property-Structure Relationship and Potential…
5.5.5 Applications in Packaging Materials
Food quality is affected by lipid oxidation due to microbial growth, enzymatic
browning and vitamin loss. The mass transfer between packaging materials and
packed food exists in food storage (Gutiérrez and Álvarez 2017). Because of this
transfer, an antioxidant in the packing material can have a positive effect on food
quality. In fact, the addition of antioxidants in packing materials has become a standard process (Gutiérrez 2018; Toro-Márquez et al. 2018). Due to the properties of
lignin, it can be used as an alternative to toxic synthetic antioxidants and expensive
natural antioxidants in packing materials. There are two mechanisms in the antioxidative role that lignin plays in packaging materials. One is the migration of the free
radical scavenger from the packing materials to the food, the other is the presence
of free radical scavenging activity on the surface of packing materials (CrouvisierUrion et al. 2016). The mechanism of surface activity generally dominates.
In this sense, Dumitriu et al. (2018) prepared alginate/LS film by crosslinking
using two formulations with glutaraldehyde. The high LS content in the mixed film
improved protection against UV light and radical scavenging properties. L NPs
have a stronger effect than original lignin on antioxidant properties and thermal
stability (Dumitriu et al. 2018). Yang et al. (2016) achieved good interfacial adhesion and dispersion between L NPs into a PVA/Cs mixture. In addition, a synergistic
antioxidant effect between L NP and Cs in the composite appeared to have occurred.
The presence of L NP improved UV barrier property and thermal stability of ternary
PVA/Cs/L NP composite. The composite exhibited an ability to inhibit the growth
of Xanthomonas arboricola pv. pruni and Erwinia carotovora subsp. carotovora,
indicating that it can be applied as a packaging material for fruits and vegelates to
discourage bacterial contamination (Yang et al. 2016). Domenek et al. (2013) prepared PLA-lignin films by thermo-compression and twin-screw extrusion. The low
Mw fractions of lignin were released during the thermo-compressing process, and
the antioxidant activity of the PLA-lignin films increased with the increasing severity of heating due to the generation of more phenolic monomers during the process.
Aguié-Béghin et al. (2015) evaluated the antioxidant properties of lignin in two
complex matrices: an oil/water dispersion with potential use as a food matrix and
cellulose-based films as a model of the polymer matrix. Because the different lignins work differently in multiphasic systems, when a particular level of antioxidant
activity is required, such systems must be tested in simulations of the targeted application before being used.
Espinoza Acosta et al. (2015) found that alcohol soluble lignin (ASL)/starch
films showed good dispersibility without lignin agglomerations, or undissolved particles. The thermal degradation resistance and antioxidant activity of the films
increased due to the addition of ASL. ASL also had a plasticizing effect on lignin/
starch films, increasing the strain at break and decreasing the Young’s modulus and
maximum stress values of the films. In addition to the composite film prepared by
mixing lignin and starch, LS graft copolymers and starch synthesized by laccase
catalysis have also been reported by Shogren and Biswas (2013).
5 Lignin as a Natural Antioxidant: Property-Structure Relationship and Potential…