Plasticization Efficiency and Characteristics of Monosaccharides, Disaccharides, and Low-Molecular-Weight Polysaccharides for Starch-Based Materials

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 Tg 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.