Agriculture Reference
In-Depth Information
coating is dependent upon spreading coefficient (or wetta-
bility) versus the surface properties of the fruits, in partic-
ular the dispersive component of the fruits' surface tension
(Cerqueira et al., 2009). Blending is also an approach to
improve coating properties through the possible synergis-
tic effects of the two components. For instance, blending
of 0.5% galactomannans (a new natural product) and 1.5%
collagen with an addition of 1.5% glycerol resulted in the
decrease of gas transfer rate in mango (Lima et al., 2010).
Composite films or coatings have also been developed to re-
place synthetic commercial waxes, for example, optimized
locust bean gum (LBG)-lipid composite coatings for man-
darins (Rojas-Argudo et al., 2009).
Edible coating appears to be a practical route to carry the
incorporated functional additives such as antimicrobials,
antioxidants, and texture-improving compounds. Uses of
various antimicrobial agents and incorporating them into
edible coatings were reviewed by Oms-oliu et al. (2010).
In the case of edible coating developments for tropi-
cal/subtropical fresh-cut fruits such as melon (Raybaudi-
Massilia et al., 2008), papaya (Tapia et al., 2008), and
pineapple (Montero-Calder on et al., 2008), edible coating
matrices were alginate-based coatings containing various
antimicrobial substances.
versatile biodegradable polymer whose properties, such
as degree of crystallinity, melting temperature, and glass
transition temperature can be tailored by controlling the
monomer composition of the two optical isomeric forms
L and D. Specific process technologies such as extrusion,
injection molding, injection stretch blow molding, cast-
ing, blown film, thermoforming, foaming, blending, fiber
spinning, and compounding have been discussed by Lim
et al. (2008).
Packaging technologies for processed tropical and
subtropical fruits
Aseptic packaging
Thermal processing is one of the oldest methods of pre-
serving fruit products, which remains common today due
to its long shelf life. However, high temperature is known
to reduce the freshness and organoleptic qualities of fruit
products. By reducing temperature and/or shortening pro-
cessing time, products are able to maintain quality as close
as possible to fresh fruits. Aseptic packaging has been de-
fined as packaging of commercially sterile products in ster-
ile containers under aseptic conditions (Robertson, 2006).
Aseptic processing and packaging have been developed pri-
marily to improve a product's quality, extend its shelf life,
and increase convenience. Application of aseptic process-
ing covers a wide range of presterilized and sterile prod-
ucts such as milk, milk products, desserts, puddings, juices,
soups, and sauces.
Sterilization methods commonly used for aseptic prod-
ucts are direct heating, indirect heating, and other methods
such as ohmic heating. Common methods for package ster-
ilization include heat or chemicals (e.g., H 2 O 2 by spraying
or dipping or in combination with UV or gamma rays).
Various aseptic packaging systems are classified by pack-
age forms, such as carton systems, can and cup systems,
and bottle systems. These offer key differences in perfor-
mance, such as quality and shelf life of products, as well as
convenience. Traditional carton systems contain multilayer
materials, of which the most common layers are an outer
polyethylene layer, a bleached paperboard layer, an ad-
hesive layer (e.g., polyethylene, ionomer), aluminum foil,
and two inner layers of polyethylene. These layers perform
different functions (Robertson, 2006).
Major aseptic fruit products are juices packed in lami-
nated cartons and fruit cubes packed in cups. Types of mate-
rials have an important effect on quality changes of packed
fruit juices. Mandarin juices in the paper carton with alu-
minum foil inner layer could maintain color changes and
ascorbic acid degradation as well as sensory quality better
Packaging from renewable resources
The current focus on packaging has shifted from conven-
tional petroleum-based packaging materials to renewable or
biodegradable packaging materials due to public conscious-
ness and environmental issue. The potentials and challenges
of using biodegradable polymers from renewable resources
have been well reviewed by several researchers (Siracusa
et al., 2008; Mahalik and Nambiar, 2010; Ahmed and
Varshney, 2011). Considerable research has been conducted
to develop and apply bio-based polymers made from a va-
riety of agricultural commodities over the last few years.
Such biopolymers include starches, cellulose derivatives,
chitosan/chitin, gums, proteins and lipids. Thin films can
be made from these materials and coatings to cover fresh
fruits or further processed foods to extend their shelf life.
Starch is the most important polysaccharide; it is the
most abundant in nature and relatively inexpensive. Natural
starch exists in granular form and, as such, it has been used
as a filler in polymers, but it can also be processed with
classical plastic processing technologies such as extrusion,
foaming, and film blowing after thermoplasticization, as
will be described in the following. The main hurdle for
starch is its hydrophilicity.
Polylactic acid or polylactides (PLA) is a biodegradable
thermoplastic derived from lactic acid which is a highly
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