Author(s):
Casariego, A. 
; Souza, B. W. S. ; Vicente, A. A. ; Teixeira, J. A. ; Cruz, L. ; Díaz, R.
Date: 2007
Persistent ID: http://hdl.handle.net/1822/7456
Origin: RepositóriUM - Universidade do Minho
Subject(s): Chitosan; Edible coating; Surface properties; Gas permeability
Description
Edible coatings can act as moisture, lipid, and gas barriers and can improve the textural properties
of foods or serve as carriers of functional agents such as colors, flavors, antioxidants, nutrients and
antimicrobials. The objectives of this work were to study the potentialities of chitosan (obtained from lobster of
the cuban coasts) coating to extend the shelf life of fruits. To do so, the surface properties of tomato and carrot
were characterized and the wettability properties of chitosan edible coatings were studied. In such coatings,
parameters such as chitosan concentration and effects of type and concentration of hydrophilic plasticizer or
surfactant on wettability of chitosan coatings were evaluated, as well as the respective barriers properties to
gases.
It was possible to determine the values of the polar and dispersive components of the superficial tension, that
are 3.32 and 25.24 mN/m, respectively, for the tomato and 0.48 and 25.62 mN/m, respectively, for the carrot;
being the superficial tensions of the tomato and carrot the sum of the two components (28.55 and 26.40 mN/m)
respectively. Both are therefore, low energy surfaces.
The results of wettability determinations allowed to adjust one factorial model that suggests an increase of the
spreading coefficient as the chitosan concentration decreases and Tween concentration increases. The best
values of wettability correspond to the following coating composition: 1.5 % (w/v) of chitosan and 0.1 % (w/w)
of Tween 80.
A correlation has been found between the water vapor, oxygen and carbon dioxide permeability coefficients,
and glycerol concentration (while keeping Tween and chitosan concentrations constant). In the absence of
glycerol, a decreased permeability to the gases was observed.
An increase of the chitosan concentration decreases a lightness and increase yellow color of coatings. The
chitosan coatings with glycerol showed high values lightness and were more transparent and yellowier than
those without glycerol.
