60
the use of biodegradable plastics with increasing availability of suitable materials
and because of societal and legislative pressure (Rasato 2009). The considerable
improvement of alternative protection methods, for example the use of biopolymers
which we can eat, from renewable sources or industrial by-products has been
achieved (Campos et al. 2011). The use of starch for edible films and coatings is a
subject of great interest due to their high biodegradability and characteristics to
increase the shelf life of foods (Baldwin et al. 1995). This section will cover film
forming ability of starch, physicochemical properties of these films and coating and
their applications in food industry. Other aspects related to the starch-based films or
packages, such as the effect of the addition of other components lipid, hydrocolloids, fillers, or active compounds will also be discussed.
Film Forming Ability of Starch and Manufacturing
Starch, is one of the most abundant natural polysaccharides having wide-ranging
functionality, available at relatively low cost and great ability to form transparent,
tasteless and odorless films, with very good oxygen barrier properties, which is very
useful for food preservation purposes. Nevertheless, structure of starch presents
some challenges to its potential applications in the packaging industry. Firstly, the
starch has high degree of hydrophilicity due to the presence of three hydroxyl
groups per D-glycosylic unit. Therefore, water is an effective plasticizer for this
polysaccharide and any gain or loss of moisture may result in significant changes in
physical and mechanical properties of starch-based materials. Secondly, native
starch is not thermoplastic, because it undergoes pyrolysis before the melting point
of crystalline regions in starch is reached. Hence, starch cannot be melt-processed
via conventional plastic equipment without plasticizers addition (Mohammadi et al.
2013). In order to overcome these limitation starch has been either blended with
other materials or chemically or physically modified to achieve balanced characteristics desired for film making properties (Shrestha et al. 2014). Consequently, starch
compatibility with other biodegradable polymers, such polycaprolactone or polylactic acid, cellulose, among others, as well as composites processing with microand nano-fillers have been broadly studied (Andersons et al. 2016). Starch films
may be obtained by two technological processes either by extrusion or casting
methods. Casting typically involves the gelatinization of an aqueous starch suspension and its subsequent dehydration under controlled conditions. It has been studied
extensively and mostly a related to coating on different surfaces like perishable
fruits and vegetables, meat sausage or on seeds and other food stuffs. This method
has several limitations like: restricted size and amount of the produced films, long
production times and large volumes of solvent disposal used in the process.
The starch material films are brittle with no flexibility and extensibility. To overcome this problem plasticizers are generally added to film formulations to aid processing operations and to modify final product properties. Plasticizers are low
molecular mass organic compounds, they reduce intermolecular forces and increase
M. Ahmad et al.
the use of biodegradable plastics with increasing availability of suitable materials
and because of societal and legislative pressure (Rasato 2009). The considerable
improvement of alternative protection methods, for example the use of biopolymers
which we can eat, from renewable sources or industrial by-products has been
achieved (Campos et al. 2011). The use of starch for edible films and coatings is a
subject of great interest due to their high biodegradability and characteristics to
increase the shelf life of foods (Baldwin et al. 1995). This section will cover film
forming ability of starch, physicochemical properties of these films and coating and
their applications in food industry. Other aspects related to the starch-based films or
packages, such as the effect of the addition of other components lipid, hydrocolloids, fillers, or active compounds will also be discussed.
Film Forming Ability of Starch and Manufacturing
Starch, is one of the most abundant natural polysaccharides having wide-ranging
functionality, available at relatively low cost and great ability to form transparent,
tasteless and odorless films, with very good oxygen barrier properties, which is very
useful for food preservation purposes. Nevertheless, structure of starch presents
some challenges to its potential applications in the packaging industry. Firstly, the
starch has high degree of hydrophilicity due to the presence of three hydroxyl
groups per D-glycosylic unit. Therefore, water is an effective plasticizer for this
polysaccharide and any gain or loss of moisture may result in significant changes in
physical and mechanical properties of starch-based materials. Secondly, native
starch is not thermoplastic, because it undergoes pyrolysis before the melting point
of crystalline regions in starch is reached. Hence, starch cannot be melt-processed
via conventional plastic equipment without plasticizers addition (Mohammadi et al.
2013). In order to overcome these limitation starch has been either blended with
other materials or chemically or physically modified to achieve balanced characteristics desired for film making properties (Shrestha et al. 2014). Consequently, starch
compatibility with other biodegradable polymers, such polycaprolactone or polylactic acid, cellulose, among others, as well as composites processing with microand nano-fillers have been broadly studied (Andersons et al. 2016). Starch films
may be obtained by two technological processes either by extrusion or casting
methods. Casting typically involves the gelatinization of an aqueous starch suspension and its subsequent dehydration under controlled conditions. It has been studied
extensively and mostly a related to coating on different surfaces like perishable
fruits and vegetables, meat sausage or on seeds and other food stuffs. This method
has several limitations like: restricted size and amount of the produced films, long
production times and large volumes of solvent disposal used in the process.
The starch material films are brittle with no flexibility and extensibility. To overcome this problem plasticizers are generally added to film formulations to aid processing operations and to modify final product properties. Plasticizers are low
molecular mass organic compounds, they reduce intermolecular forces and increase
M. Ahmad et al.