Study On Gelatin Edible Films By Tiwn Screw Extrusion Casting And Their Blending Modification

Biodegradability of biopolymer films has led to a growing interest in their use as edible food packaging. Gelatin edible film is a kind of natural biologic film with a matrix of food grade gelatin.It lias good tensile strength, heat sealing, air resistance, oil resistance. It can be applied as a coating on food, used as a wrap or made into pouch to hold the food to protect it against external factors like water, oxygen, carbon dioxide and lipids to enhance the storage life of the foods.In the recent past it have been studied that gelatin edible films were most produced from solution casting methods, which are time consuming and are not appropriate for commercial production. Thus, one of the objectives of this investigation was to produce gelatin edible films by twin-screw extrusion casting method, using mixing feed of dry and wet gelatin. The method was one step and the films were uniform, good plasticizing and had low moisture content. The optimum process conditions:screw speed was240rpm,barrel temperature was set at105℃or115℃, glycerol content in gelatin film was20%and25%. It was obvious that glycerol content and environmental humidity effected the drying rate of the films. And the drying rate of gelatin film increased with the decrease of environmental humidity, decreased with the increase of glycerol content.Comparison with steel belt casting method and one-screw extrusion and heat-pressing method, the process of twin-screw extrusion casting method was more practical and efficient. But the gelatin films prepared by twin-screw extrusion casting method had less tensile strength, tear strength, glass transition temperature, moisture,than the films by steel belt casting method; and the elongation at break, moisture permeability were contrast.In order to enhance the properties of gelatin edible films, this study work was to fabricate novel edible films on carboxymethyl cellulose (CMC)/gelatin blends. The CMC/gelatin blend films were added by glycerol as a plasticizer and prepared by solution casting method.The effect of CMC content on the film structure, thermal stability, water solubility, water sorption and mechanical properties were investigated. The Mai Hard reaction between CMC and gelatin was showed by FTIR analysis. DSC results showed that CMC/gelatin blend film had the only Tg, TGA results showed that the blends had the only heat decomposition temperature, indicating that CMC and gelatin were good compatibility. With the increase of CMC content, mechanical properties of CMC/gelatin blend films were enhanced, and their water sensitivity decreased.