A film forming composition and a polymeric film or coating comprising hemicellulose and at least one component selected from the group consisting of plasticizers, cellulose, and an oligomer or polymer, is disclosed, said polymeric film or coating further comprising at least one additive/reactant increasing the liquid/moisture resistance and mixed with and/or reacting with the hemicellulose and said at least one component before or in conjunction with the forming of the film or coating. The use of said film or coating is also disclosed. Further, a method for the manufacture of said polymeric film or coating is disclosed, as well as a method for improving the liquid/moisture resistance of hemicellulose. Said at least one additive/reactant increasing the liquid/moisture resistance is either a cross-linking agent or a hydrophobizing agent. In another preferred embodiment the additive is a 2: 1 layered phyllosilicate. The additive forms a nanocomposite with the hemicellulose as a matrix. The hemicellulose/phyllosilicate nanocomposite reinforced material provides excellent liquid/moisture resistance. Heat treatment of all of the films increases their liquid/moisture resistance and reduces their oxygen permeability.