Survay of construction method and properties of emulsion & bi-layer edible films

Today's applying biodegrade able packaging such as edible coatings and films have attracted greater attention due to having natural products and lack of environmental pollution. Carbohydrate and proteins create a network responsible for good mechanical properties, but their inherent hydrophilic nature makes them a poor barrier for water vapor transfer. On the contrary, lipids have excellent water vapor barriers because of their hydrophobic character, but films made from lipids alone have poor mechanical properties. Therefore, with combination of these two materials, the produced composite film, has desirable properties. A composite film can be produced as either a bi-layer or a stable emulsion. Therefore, composite edible films have better moisture-barrier properties and also, due to the improved mechanical properties, they create better protect from food. So, the shelf life of food will be increased. In this review, has been focused on the preparation techniques, properties and advantages of composite edible films relative to one-layer edible films.