Preparation of laminated film from cassava starch and chitosan

Abstract

Chitosan/cassava starch laminated film designed for food packaging was prepared by coating viscous chitosan solution onto the free starch film using an automatic coating applicator. 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. After allowing open air drying, the laminated films were investigated the physical structure, mechanical, and physical properties. The X-ray patterns of chitosan/cassava starch laminated films showed the reflection of B-type starch crystalline shifting to slightly higher degrees at about 17.2 ํ (2 theta) (free starch film found at 17.0 ํ (2 theta) while that of chitosan appeared as a smaller peak at about 22.2 ํ (2 theta) (free chitosan film prepared by casting technique found at 21.1 ํ (2 theta). 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, indicating their good adhesion. Coating of chitosan solutions led to an improvement in several film properties including mechanical and physical properties. An increase in chitosan coating concentration resulted in a significant increase in tensile strength. The results on mechanical properties showed a significant increase in tensile stress at maximum load and tensile modulus, and a decrease in % elongation at break of laminated film containing low glycerol content. Film strength along machine direction is higher than that of transverse direction because of the higher molecular orientation 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 causes a reduction of wettability as well as water vapor permeability which are preferable for packaging film application.