There is provided a method (200) for decreasing acetaldehyde level in a molded article. The method (200) of decreasing acetaldehyde content in a molded article to be produced comprises introducing (202) into a feed throat (120) of an injection unit (100) a PET material to be plasticized, the PET material having been dried in a pre-treatment chamber (130); and introducing (204) into the feed throat (120) an un-treated agent (136) configured to increase moisture level of the PET material to be plasticized. In some embodiments of the present invention, the un-treated agent (136) is also configured to provide additional lubrication to the plasticizing screw (106).