Effects of chitosan molecular weight (1815 and 366 kDa), type of acid (1% acetic, formic, and propionic acid, or 0.5% lactic acid) and plasticizer (0, 25% glycerol or sorbital w/w chitosan) on the mechanical, water barrier, and antibacterial properties of β-chitosan films were investigated. Tensile strength (TS) of high molecular weight (Hw) films was 53% higher than that of low molecular weight (Lw) ones, acetate, and propionate films had the highest TS (43 and 40 MPa) among tested acids, and plasticizer-reduced film TS 34%. Film elongation at break (EL) was higher in Hw films than in Lw ones, in which formate and acetate films were the highest (9% and 8%, respectively), and plasticizer increased the film EL 128%. Molecular weight of chitosan did not influence water vapor permeability (WVP) of the films. Acetate and propionate films had lower WVP than other acid types of films, and plasticizer increased film WVP about 35%. No difference was found between glycerol and sorbitol films in terms of film mechanical and water barrier properties. Lw β-chitosan films showed significant antibacterial activity against E. coli and L. innocua. This study demonstrated that β-chitosan films are compatible to α-chitosan films in physicochemical properties and antibacterial activity, yet with simple sample preparation.

Jeremy L. Chen and Yanyun Zhao
Short Description: 
The release of active chitosan fragment from the film matrix acts as an antibacterial agent, making β-chitosan films suitable as intelligent food wraps or coatings for a wide range of food products to control moisture loss and prevent surface bacterial gr
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Entry Date: 
Wednesday, June 26, 2013
10 pp.
Source (Journal Article): 
Journal of Food Science 77(5):E127-E136
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