A method of manufacturing a multilayer or a monolayer plastic container is disclosed. The container has a barrier layer manufactured from (i) a polyester resin, preferably an aromatic polyester resin such as a polyethylene terephthalate, (ii) a polyamide material, preferably an aromatic polyamide material, and (iii) an oxygen scavenging material, preferably a transition method. The present invention also provides containers having a multilayer or a monolayer body. In the preparation of the barrier layer. a preform first is prepared by an injection-molding process wherein a preblend containing a diluent polyester, polyamide material, and an oxygen scavenging material is added to a base polyester during the injection molding process. The preform then is expanded to form a container.