Pullulan films, oxygen permeability

Purified pullulan is a white, non-hygroscopic powder which dissolves in hot or cold water. Pullulan does not provide high viscosity solutions at low concentration. The most important property of pullulan is the ability to form films. The films are prepared by dissolving pullulan in water at 5-10% concentration and continually drying the solution applied to a smooth surface. The major advantage of pullulan films is the very low oxygen permeability. The oxygen permeability of pullulan films and three films of commerce are shown in Table IV. (3)... 

Table IV. Oxygen Permeability of Pullulan Films Sample...

Pullulan in aqueous or moistened powder form can be converted into odorless, transparent and tenacious films by any usual method. In comparison with other films, these films have remarkably low oxygen permeability and surpass others as oxidation-preventive barriers. Moreover, the films can be prepared with water as the sole plasticizer. A slight addition of polyhydric alcohol will lead to the production of more flexible films, if desirable. Pullulan with a molecular weight exceeding 150,000 is preferable for film formation. 

Pullulan is a polysaccharide obtained from the fermentation of starch by the yeast Aurobasidiutn pullulans. It is edible and tasteless. It is used as edible films for food packaging with high oxygen permeability, oral care products, adhesives, thickeners, stabilizers, etc.. 

Pullulan is composed primarily of maltotriose units linked in a-1,6 fashion and is produced as an extracellular secondary metabolite of some fungi. Because of its natural origin, pullulan was commercialized as a food source and has been accepted as a coating material for foods. It is a water-soluble polymer that provides transparent films of low oxygen permeability for foods. The film can be obtained by casting a 1-20% aqueous solution of pullulan on a metal plate roller, or, similarly to starch, pullulan can be molded with heat and pressure if a suitable amount of water is added as plasticizer [484, 485]. 

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