In this work, the saccharides with
different structures and molecular
weights were evaluated as a plasticizer for starch-based materials,
in which the saccharides from monosaccharides, such as glucose, mannose,
fructose, xylose, and disaccharides including sucrose and maltose,
to dextrin with different molecular weights, were used. As expected,
starch and these saccharides are fully compactable and miscible since
they have similar chemical components. These saccharides must work
together with water or polyols to act as co-plasticizers since they
are all in solid-state under dry conditions. Many monosaccharides
or disaccharides with ring structures can stably stay in the starch
matrix without affecting the microstructures of the polymer chains
significantly, but the monosaccharides with linear structures, such
as fructose and xylose, showed much more efficiency to destroy the
ordered structures and enhance the movement of polymer chains, which
results in higher efficiency of plasticization. All these saccharides
can generally increase the stability of moisture containing in the
starches because of the strong bonding by hydroxyl groups. Thermal
properties of the starch-based films were investigated by differential
scanning calorimetry, thermal-gravimetric analysis, and dynamic mechanical
analysis, and morphologies and microstructures of the films were studied
by scanning electron microscopy and X-ray diffraction. These saccharides
did not affect the gelatinization temperature of the starch. Both T
g and crystallinity of starch were decreased
with additional saccharides, indicating that the rigid crystalline
range in starch was destroyed. This research not only increased the
knowledge of the plasticizing mechanism but also can be used for developing
various starch-based products, including food and packaging.