61
polymer chains mobility and must be compatible with the film-forming polymers;
(Fan et al. 2018), oligosaccharides, polyols and lipids are chemically compatible
(Lopez et al. 2008; Sothornvit et al. 2005). Excessive addition of plasticizing agents
will result in rubbery, sticky films. Thus, it is necessary to optimize the amount of
plasticizing agent used in a formulation to attain desired film properties. Starch in
presence of a plasticizer (water, glycerol, sorbitol, etc.), high temperature and shearing melts and fluidizes that enables its use in injection, extrusion and blowing equipment, such as those for synthetic plastics. Thermoplastic starch can be prepared by
altering the moisture/plasticizer content, amylose/amylopectin ratio of raw material
and the temperature and pressure in the extruder, such starch can have different
viscosity, mechanical strength, water solubility and water absorption (Mohanty
et al. 2000). Large amount of researches have been performed on the plasticization
of thermoplastic starch using glycerol (Forssell et al. 1997), sorbitol (Gaudin et al.
1999), urea, formamide (Ma et al. 2004), dimethyl sulfoxide (Nakamura and
Tobolsky 1967) and low molecular weight sugars (Kalichevsky et al. 1993).
Thermoplastic starch cannot be used in many applications due to its inferior
mechanical and water barrier properties, its generally suggested to blend starch with
other biodegradable polymers compatible with starch such as Poly lactic acid
(PLA), polyvinyl alcohol (PVOH) and others. The starch-co-polymers films have
shown better mechanical and water barrier properties. They find use mainly in soluble compostable foams, expanded trays, shape molded parts, and expanded layers
as a replacement of polystyrene.
Starch as an Active Packaging Films and Coatings
The development of coatings based on starch has brought a significant increase in
their applications and in the amount of products that can be treated, extending the
shelf life of fruits and vegetables due to the selective permeability of these polymers
to O 2 and CO 2 or development of films loaded with antioxidants and antimicrobial
agents. Edible coatings create a passive modified atmosphere, which can influence
various changes in fresh and minimally processed foodstuff in some areas such as,
color, firmness, sensory quality, microbial growth inhibition, ethylene production
and volatile compounds as a result of anaerobic processes (Oms-Oliu et al. 2008).
Starch films incorporated with tea polyphenol (TP) were developed to produce
active food packaging. TP addition led to an important improvement in antioxidant
capability, as well as inhibition efficiency against the microorganisms of S. aureus
and E. coli. However, a decrease in mechanical properties of films was observed
(Fenga et al. 2018). The biodegradable films with antioxidant properties were developed, using cassava starch combined with biomass or biomass extract of microalgae
Heterochlorella luteoviridis and Dunaliella tertiolecta. The addition of biomass
increases film elongation, rupture and reduced the tensile strength and Young’s
modulus. The film containing 2.0% of H. luteoviridis extract presented the lowest
water vapor permeability and good mechanical characteristics (Carissimi et al.
Recent Advances in the Application of Starch and Resistant Starch
polymer chains mobility and must be compatible with the film-forming polymers;
(Fan et al. 2018), oligosaccharides, polyols and lipids are chemically compatible
(Lopez et al. 2008; Sothornvit et al. 2005). Excessive addition of plasticizing agents
will result in rubbery, sticky films. Thus, it is necessary to optimize the amount of
plasticizing agent used in a formulation to attain desired film properties. Starch in
presence of a plasticizer (water, glycerol, sorbitol, etc.), high temperature and shearing melts and fluidizes that enables its use in injection, extrusion and blowing equipment, such as those for synthetic plastics. Thermoplastic starch can be prepared by
altering the moisture/plasticizer content, amylose/amylopectin ratio of raw material
and the temperature and pressure in the extruder, such starch can have different
viscosity, mechanical strength, water solubility and water absorption (Mohanty
et al. 2000). Large amount of researches have been performed on the plasticization
of thermoplastic starch using glycerol (Forssell et al. 1997), sorbitol (Gaudin et al.
1999), urea, formamide (Ma et al. 2004), dimethyl sulfoxide (Nakamura and
Tobolsky 1967) and low molecular weight sugars (Kalichevsky et al. 1993).
Thermoplastic starch cannot be used in many applications due to its inferior
mechanical and water barrier properties, its generally suggested to blend starch with
other biodegradable polymers compatible with starch such as Poly lactic acid
(PLA), polyvinyl alcohol (PVOH) and others. The starch-co-polymers films have
shown better mechanical and water barrier properties. They find use mainly in soluble compostable foams, expanded trays, shape molded parts, and expanded layers
as a replacement of polystyrene.
Starch as an Active Packaging Films and Coatings
The development of coatings based on starch has brought a significant increase in
their applications and in the amount of products that can be treated, extending the
shelf life of fruits and vegetables due to the selective permeability of these polymers
to O 2 and CO 2 or development of films loaded with antioxidants and antimicrobial
agents. Edible coatings create a passive modified atmosphere, which can influence
various changes in fresh and minimally processed foodstuff in some areas such as,
color, firmness, sensory quality, microbial growth inhibition, ethylene production
and volatile compounds as a result of anaerobic processes (Oms-Oliu et al. 2008).
Starch films incorporated with tea polyphenol (TP) were developed to produce
active food packaging. TP addition led to an important improvement in antioxidant
capability, as well as inhibition efficiency against the microorganisms of S. aureus
and E. coli. However, a decrease in mechanical properties of films was observed
(Fenga et al. 2018). The biodegradable films with antioxidant properties were developed, using cassava starch combined with biomass or biomass extract of microalgae
Heterochlorella luteoviridis and Dunaliella tertiolecta. The addition of biomass
increases film elongation, rupture and reduced the tensile strength and Young’s
modulus. The film containing 2.0% of H. luteoviridis extract presented the lowest
water vapor permeability and good mechanical characteristics (Carissimi et al.
Recent Advances in the Application of Starch and Resistant Starch