The objective of this study was to investigate the effect of the addition of methylcellulose and carboxymethylcellulose
on the thermal, mechanical and water adsorption properties of starch-based films plasticized
with glycerol or polyethylene glycol (PEG). Mechanical tests showed that as the methylcellulose
and carboxymethylcellulose proportion increased, starch films became more resistant to break, resulting
in higher TS values. Besides there has been a positive effect on the elasticity of starch films realized by a
considerable increase in E% values. Depending on the plasticizer type, either single or dual glass transitions
were seen in DSC thermograms. One glass transition temperature was observed for films plasticized
with glycerol, on the contrary, dual glass transitions were detected for PEG plasticized films. This behavior
was attributed to the phase separation of the PEG. In addition, the presence of an endothermic peak in
the thermograms of PEG plasticized films was taken as another indicator of the phase separation. As a
result, it was suggested that PEG was not as compatible as glycerol with the composite polysaccharide
matrix and plasticizer type was the main factor that shaped the thermal profiles of the film samples.
Water adsorption isotherm data showed that samples displayed nonlinear sorption profile which is typical
for hydrophilic films. In all films tested, equilibrium moisture contents, increased almost linearly up
to a aw of 0.65–0.85, beyond where a sharp increase was noted. Adsorption data was adequately fitted by
BET and GAB models. Eventually, it can be concluded that film forming properties of starch can be
improved by incorporation of methylcellulose and carboxymethylcellulose to the polymer matrix.