Agriculture Reference
In-Depth Information
7.2.4 Edible Coatings
Edible films are defined as a thin layer of material that can be ingested and act as a
barrier to oxygen, solute movement, and moisture for the food. This material can be
disposed as a continuous layer between food components or can be coating the
whole food (Guilbert
1986
). Edible films and coatings have many advantages over
synthetic films, and for this reason, there has been many research in this area in the
last years. Their main advantage over traditional synthetics is that they can be
ingested along with the packaged products. If the films are eaten, packaging
disposal problem is avoided, and even if the films are not eaten, as they are
produced exclusively from renewable, edible ingredients can still contribute to
the reduction of environmental pollution because they are supposed to degrade
faster than polymeric materials (Bourtoom
2008
).
The purposes of using coatings and films, depending on the food, are to hinder
the migration of different components of the food or the ambient like moisture, oil,
carbon dioxide, oxygen, and aromas, make the food more attractive, enhance its
mechanical properties and integrity, and carry food additives or nutritional supple-
ments (Kester and Fennema
1986
; Krochta and Mulder-Johnston
1997
). An edible
film coating, acting as a barrier to oxygen, moisture, or aromas, can also help cut in
packaging requirements and, therefore, waste. For example, a multilayer plastic
package can be reduced to a single-component recyclable package if the barrier
characteristics of an edible film permit to do so (Miller and Krochta
1997
). The
sensory characteristics of an edible film, which are of importance on its function-
ality, such as transparency, gloss, color sticking, and roughness can be selected
depending on the purposes (Debeaufort et al.
1998
). Edible films and coatings can
also contain food additives to improve the general coating performance (i.e.,
strength, flexibility, or adherence); enhance the food texture, flavor, and color;
and control microbial growth (Cuppet
1994
).
In this area of food packaging, nanotechnology can be applied in two ways: On
the one hand, the edible film can be a nanolaminate, manufactured as various
nanolayers of diverse materials, added one at a time using the electrostatic attrac-
tions between the different layers. On the other hand, the edible film can be a
nanocomposite, incorporating nanoparticles or emulsified nanodroplets containing
active ingredients to enhance texture, appearance, or taste.
A nanolaminate is a really thin film with food grade composed of two or more
layers with nanometer dimensions (1-100 nm per layer), where the individual
laminates are physically or chemically bonded with each other. A very good control
of the properties of the laminate can be obtained by a layer-by-layer (LBL)
preparation of the coating (Weiss et al.
2006
). This is the main advantage over
conventional edible coatings used as barrier layers to increase shelf life (gums and
waxes). The process of coating foods with nanolaminates consists in spraying or
dipping layer by layer a series of solutions containing target compounds to the
surface of the food (McClements et al.
2005
). The electrodeposition technique can
