Periodate oxidation of xanthan gum and its crosslinking effects on gelatin-based edible films

Abstract

Oxidized xanthan gum with different aldehyde content is successfully prepared by periodate oxidization and used as a crosslinking agent for gelatin edible films. X-ray diffraction measurements and atomic force microscopy images demonstrate that degradation is concomitant with the oxidization process, leading to the decrease in crystallinity and the structure changes. Glycerol-plasticized gelatin–xanthan gum and gelatin–oxidized xanthan gum edible films are prepared using casting techniques. The optical properties studies show that all films are very transparent and have excellent barrier properties against UV light. Introducing aldehyde groups can improve the UV barrier properties, resulting from the increased CN groups by Schiff's base formation. Properties studies show that xanthan gum can drastically reduce the total soluble matter, moisture content and water vapor permeability and greatly improve the mechanical properties and thermal stability of gelatin films. With the increase of oxidization level of oxidized xanthan gum, the enhancement of water barrier properties, mechanical properties and thermal stability of gelatin–oxidized xanthan gum films is observed, which is mainly due to the covalently linking between the two polymers. Subsequently, the excessive degradation of xanthan gum will reduce the mechanical properties and thermal stability of gelatin films.