Preparation and properties evaluation of chitosan-coated cassava starch films

Chitosan-coated cassava starch films were prepared. In this study, chitosan coating solutions varying from 1 to 4 wt% were coated onto the free starch films containing 2, 3, 4, 5, and 6 wt% glycerol as a plasticizer. The X-ray patterns of the coated dry film showed that the reflection of B-type starch crystalline shifted to slightly higher degrees at about 17.2° (2θ) compared with the free starch film found at 17.0° (2θ). The shifting in starch diffraction peak was probably due to the change in its chain orientation caused by hydrogen-bonding interaction between chitosan and starch molecules, resulting in their good adhesion. Coating of chitosan solutions led to an improvement in several film properties including mechanical and physical properties. The results of mechanical properties evaluation showed that an increase in chitosan coating concentration resulted in a significant increase in tensile stress at maximum load and tensile modulus, and a decrease in percent elongation at break. Film strength along coating direction was higher than that of transverse direction as a result of force applied during coating process. Concerning physical properties, a remarkable decrease in water uptake was observed due to the contribution of hydrophobicity of chitosan coating layer. The hydrophobic acetyl groups of chitosan caused a notable reduction of wettability as well as water vapour permeability which are preferable for packaging film application.