Abstract: A mixture of a polyester or a polyamide, such as poly(ethylene terephthalate) PET, and a suitable stabilizer selected from the group consisting of certain Mannich base compounds, when extrusion compounded exhibits a lower residual acetaldehyde content than does PET or polyamide alone when similarly treated. The invention pertains to any polyester or polyamide used in the manufacture of molded articles, fibers, or films, for instance bottles or containers which are used to store consumer materials, for example food, beverages and water.