Natural polymer, xylan, extract from agricultural by-products as cereal hulls and husks, both food production wastes. The material in powder form is dissolved in water and is coated with paper or cardboard made from recycled or virgin fibres. It is a very good barrier against oxygen, fat, mineral oils and other volatile organic contaminants, for solid and liquid food packaging, as environmentally-sustainable and responsible alternative to traditional solutions, such as aluminium and metallised foils.