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Research Project: Adding Value to Plant-Based Waste Materials through Development of Novel, Healthy Ingredients and Functional Foods

Location: Healthy Processed Foods Research

Title: Properties of edible films based on pullulan-chitosan blended film-forming solutions at different pH

item LI, YUE - Jiangnan University
item Yokoyama, Wallace - Wally
item WU, JIA - Jiangnan University
item MA, JIANGUO - Jiangnan University
item ZHONG, FANG - Jiangnan University

Submitted to: RSC Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2015
Publication Date: 12/9/2015
Citation: Li, Y., Yokoyama, W.H., Wu, J., Ma, J., Zhong, F. 2015. Properties of edible films based on pullulan-chitosan blended film-forming solutions at different pH. RSC Advances. 5:105844-105850. doi: 10.1039/C5RA21876D.

Interpretive Summary: Pullulan films have poor mechanical properties. In combination with chitosan pullulan films have increased tensile strength and extensibility. The molecular conformation of chitosan is dependent on pH. At low pH the chitosan molecule is more linear due to repulsion of like positive charges on the polymer chain. Extension of the chitosan molecule is necessary for good mechanical properties.

Technical Abstract: Influences of solution pH on the properties of pullulan-chitosan blended (Pul-Chi) films and the rheological properties of film-forming solutions were investigated. The extended conformation of chitosan in pH 4.0 solution increased intermolecular interactions with pullulan compared to the more compact coiled form, resulting in higher tensile strength and barrier properties of the Pul-Chi film and higher viscosity of the film-forming solution. The water solubility (Ws) of the Pul-Chi film decreased to 35% above pH 4.0. Water content, thickness and Percentage elongation (E%) all decreased with the decreasing pH. Fourier Transform infrared spectroscopy (FTIR) analysis suggested that the formation of –NH3+ and intermolecular hydrogen bonds increased the amide II bending mode. At pH below 4.0, shielding of the protonated amine groups caused decreasing in bending frequency. X-ray diffraction (XRD) peak for crystallite chitosan was not observed in Pul-Chi films. The properties of Pul-Chi films depended on the conformation changes of chitosan molecules and can be controlled by pH.