Agriculture Reference
In-Depth Information
gelatin were affected by the CNT addition, resulting in more elastic and harder
films than the control film, but without affecting the tensile strength. The inclusion
of CNT to the gelatin matrix modified appreciably the internal film morpho-
structure, with no effect on its surface.
7.2.5 Biodegradable Packaging Materials
Due to their unique properties and wide range of applications, plastic has its own
place in the market and our lives. Since the beginning of its mass production in the
1940s, the amount of produced plastic has been increasing steadily: more than
300 million tons were produced worldwide in 2010. The amount of plastic
manufactured in only the first decade of the current century is similar to the total
produced in the entire last century (Thompson et al.
2009
). One of the consequences
is that plastic packaging waste is an important part of municipal solid waste. There
are increasing environmental concerns of the amount of plastic waste, which has
resulted in the strengthening of various regulations to reduce it. Many of the
oil-based polymers are virtually nonbiodegradable and, due to the complexity of
the composites, are also difficult to recycle or reuse (Song et al.
2009
). There are
concerns about the use of nonbiodegradable packaging materials over exhausting
natural resources, other environmental burdens, and also about food safety; this has
led to an increasing demand for biodegradable packaging materials (biopolymers)
created from renewable sources as an alternative to conventional plastics,
especially for disposable applications and use in short-term packaging (Weber
et al.
2002
; Sorrentino et al.
2007
; Siracusa et al.
2008
).
Biodegradable polymers are polymers that are capable of being decomposed by
bacteria or other living organisms. Biopolymers are obtained from renewable
resources and are biodegradable at the end of their life. They are an environmen-
tally friendly substitute for the use of conventional plastic materials that are
nonbiodegradable and nonrenewable. They provide barrier to gas and solutes and,
as the conventional polymers, can improve the quality of foods and extend their
shelf life. However, there are concerns about the use of these materials related to
their degradation rates under certain conditions, microbial growth potential, release
of harmful compounds, or variation in their mechanical properties during storage.
In fact, they have higher hydrophilicity and poor mechanical properties compared
to the conventional polymers, and also poor processability, which is a major
limitation for their industrial use (Cabedo et al.
2006
). Carbohydrate and protein
packaging films present good barrier properties against oxygen up to intermediate
relative humidity and good mechanical properties; however, they have a hydro-
philic nature, and so, their barrier properties to water vapor are low. Although
currently many researchers are dealing with improving the biopolymer properties
and there has been some success, their mechanical, physical, and thermal properties
are not sufficient for the use of biopolymers in industrial applications.
