Abstract
Starch and chitosan are biodegradable biopolymers with film-forming ability. In previous studies, the addition of chitosan to wheat starch-based film-forming solutions led to a slight improvement in the mechanical properties of the films, although the water barrier properties of the films were worsened due to the highly hydrophilic nature of chitosan. Tannic acid (TA), which is a polyohenol with antioxidant activity, can interact with macromolecules such as chitosan by means of crosslinking reactions. This in turn can affect the water vapour permeability and mechanical properties of chitosan-based films. However, the effect of tannic acid (TA) incopororation on the properties of pea starch (PS):chitosan (CH) films has not been evaluated yet, to the best of our knowledge. The aim of this work was to evaluate the impact of the addition of TA on the physical properties of CH and PS:CH films. High molecular weight CH films and PS:CH films (4:1 ratio) with and without TA (polymer: TA ratio 1:0.04) were prepared by castingand keeping the total amount of polymer constant. Films were conditioned at 25ºC and 75% relative humidity for at least 15 days prior evaluating the optical and mechanical properties together with water vapour permeability of the films. The addition of TA led to a reduction in the internal transmittance values of the films, and a decrease in lightness and hue as compared to pure polymer films.PS:CH films had a significantly lower equilibrium moisture content (EMC) than CH films. The addition of TA led to slightly decrease in the equilibrium moisture content of both CH and PS:CH films. Water vapour permeability values of PS:CH were significantly lower as compared to CH films. In both polymer matrices, WVP was not significantly affected by TA addition (p<0.05).
