Identification of odor-active compounds resulting from thermal oxidation of polyethylene

Thermal processing of synthetic polymers in the presence of oxygen into food-packaging materials can result in the formation of byproducts which impart off-odors or raise toxicological questions. Volatiles from the thermal oxidation of polyethylene were collected and analyzed by gas chromatography/olfactometry (GCO; CharmAnalysis). Fourteen odor-active compounds, most of which occurred in amounts that were too low to be detected instrumentally, were present. Overall odor was waxlike but individual components were fruity, herbaceous, rancid, metallic, waxy, pungent, or orange. Eight of the 14 compounds were identified and confirmed by matching mass spectra to those of standards. All were C6-C-9 saturated or unsaturated aldehydes and ketones. Approximately 46 % of the aroma from oxidized polyethylene resulted from hexanal, 1-hepten-3-one, 1-octen-3-one, octanal, 1-nonen-3-one, nonanal,trans-2-nonenal,and diacetyl. alpha-Unsaturated aldehydes and ketones are responsible for much of the off-odor associated with thermally oxidized PE.