Effect of glycerol and chitosan on physicochemical and microstructural properties of kithul (Caryota urens) starch films

Abstract

Edible film formation ability of kithul starch and chitosan with and without glycerol as a plasticizer and the corresponding physico-chemical, structural, and morphological characteristics of films produced were assessed in this study. Kithul starch extraction yield from kithul flour was 64 ± 0.54% and showed monoclinic structure crystallinity (type A pattern) by XRD. Granule morphology (shape, size, surface appearance) of kithul starch showed a wide range of spherical shapes with a small portion of oval and irregular globules by SEM. The average lengths of spherical, oval and irregular globular granules were 19 µm, 59 µm, and 28.67 µm and the average widths were 18 µm, 33µm, 20.89 µm respectively. Films were produced by solvent casting methodology where glycerol and or chitosan were added at varying concentrations viz., 0.4%, 0.9%, 1.4% and 1.9% (w/w). Film thickness, moisture content, film solubility, moisture content was measured and found a gradual incremental effect with the variation of higher glycerol concentration. Film opacity and swelling index decreased with increasing glycerol concentration. The intensity variation of XRD peaks revealed that the crystallinity of starch films was increased with glycerol concentration. In SEM analysis of kithul starch films, surface roughness and unevenness were increased with glycerol concentration. In kithul starch/chitosan films higher sticky nature and wrinkles have developed with the increase in chitosan content. Further studies are needed to prove the films containing kithul flour are a promising material for use as packaging material for maintaining food safety and extending the shelf life.