processing equipment, good functional properties, and they can be manufactured in
bulk at competitive costs [6].
2.1 Starch
Starch is a polysaccharide containing vast numbers of glucose units linked together
by glycosidic bonds which are made up usually of amylopectin (75–80%) and
amylose (20–25%). Starch is produced as reserve material in plants such as corn,
rice, cassava, oat, wheat, barley, soybean, and potatoes in granule form, varying in
size (0.5–175 μm) and in composition. They are hydrophilic, and the water content
of starch varies with relative humidity. In starch, the amylopectin contributes for
crystalline areas and the amylose for amorphous areas. Due to the hydrophilic nature
and processability, there are limitations regarding application of starch as a packaging material. This problem can be solved by adding plasticizers like carboxylic
acid, sorbitol, or glycerol or by blending with polymers like polyols, epoxides, or
poly(ε-caprolactone) (PCL).
The polymers have distinct chemical structures and it causes immiscibility issues
when blended with starch; this can be solved by an alternative approach of grafting
vinyl and acrylic monomers on the starch polymer chain, thereby enhancing its
hydrophilicity or hydrophobicity; this may depend on the processing condition. A
number of essential characteristics such as flexibility or elongation and hardness can
be adjusted by modifying the concentrations of plasticizers added.
Flexibility of a blended polymer can be easily enhanced by increasing the
plasticizer content. When compared to pure starch or chemically modified starch,
thermoplastic starch provides finer phase dispersion in the blend system [7, 8]. Thermoplastic starch can be produced by blending glycerol with starch subsequent to the
gelatinization process. Though TPS has excellent oxygen barrier properties, due to
their hydroscopic nature, they can’t be used for packaging liquid food and high
moisture-containing products. Thermal and mechanical properties of thermoplastic
starch can be increased by adding aliphatic polyesters like PHBV, PLA, PCL, etc.,
and the strength of the plastics may vary depending on the polymer blend [9]. Thermoplastic materials from starch can be utilized for manufacturing plates, food
wrappings, and food containers and cups [10].
Thermoplastic starch was blended with talc nanoparticles, and by thermocompressing, the films’ packaging bags were made. The maximum strength was
obtained for films added with 3 wt% of talc; however, the films displayed poor water
vapor barrier and mechanical properties when compared to plain starch films. Corn
starch can be used to produce 100% biodegradable polymers when blended with
plasticizers, and the resin manufactured can be transformed into injection-molded
pieces, loose-fill packaging material, and films [11].
The films made up of starch are odorless, colorless, and tasteless, and they have
showed low humidity and less permeability to oxygen [12]. When compared with
plain starch film, films made by blending PCL (up to 10% wt) with citric acid and
Recent Developments in Food-Based Bioplastics Production
111
bulk at competitive costs [6].
2.1 Starch
Starch is a polysaccharide containing vast numbers of glucose units linked together
by glycosidic bonds which are made up usually of amylopectin (75–80%) and
amylose (20–25%). Starch is produced as reserve material in plants such as corn,
rice, cassava, oat, wheat, barley, soybean, and potatoes in granule form, varying in
size (0.5–175 μm) and in composition. They are hydrophilic, and the water content
of starch varies with relative humidity. In starch, the amylopectin contributes for
crystalline areas and the amylose for amorphous areas. Due to the hydrophilic nature
and processability, there are limitations regarding application of starch as a packaging material. This problem can be solved by adding plasticizers like carboxylic
acid, sorbitol, or glycerol or by blending with polymers like polyols, epoxides, or
poly(ε-caprolactone) (PCL).
The polymers have distinct chemical structures and it causes immiscibility issues
when blended with starch; this can be solved by an alternative approach of grafting
vinyl and acrylic monomers on the starch polymer chain, thereby enhancing its
hydrophilicity or hydrophobicity; this may depend on the processing condition. A
number of essential characteristics such as flexibility or elongation and hardness can
be adjusted by modifying the concentrations of plasticizers added.
Flexibility of a blended polymer can be easily enhanced by increasing the
plasticizer content. When compared to pure starch or chemically modified starch,
thermoplastic starch provides finer phase dispersion in the blend system [7, 8]. Thermoplastic starch can be produced by blending glycerol with starch subsequent to the
gelatinization process. Though TPS has excellent oxygen barrier properties, due to
their hydroscopic nature, they can’t be used for packaging liquid food and high
moisture-containing products. Thermal and mechanical properties of thermoplastic
starch can be increased by adding aliphatic polyesters like PHBV, PLA, PCL, etc.,
and the strength of the plastics may vary depending on the polymer blend [9]. Thermoplastic materials from starch can be utilized for manufacturing plates, food
wrappings, and food containers and cups [10].
Thermoplastic starch was blended with talc nanoparticles, and by thermocompressing, the films’ packaging bags were made. The maximum strength was
obtained for films added with 3 wt% of talc; however, the films displayed poor water
vapor barrier and mechanical properties when compared to plain starch films. Corn
starch can be used to produce 100% biodegradable polymers when blended with
plasticizers, and the resin manufactured can be transformed into injection-molded
pieces, loose-fill packaging material, and films [11].
The films made up of starch are odorless, colorless, and tasteless, and they have
showed low humidity and less permeability to oxygen [12]. When compared with
plain starch film, films made by blending PCL (up to 10% wt) with citric acid and
Recent Developments in Food-Based Bioplastics Production
111