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Last Update: 01/31/00

Determination of Off-Odors and Other Volatile Organics in Food Packaging Films by Direct Thermal Analysis-GC-MS

by Thomas Hartman, CAFT, Rutgers University, New Brunswick, NJ

INTRODUCTION

This investigation was conducted to determine the compounds responsible for an off-odor in a polypropylene food packaging film manufactured from a recycled resin feedstock. The off-odor was not present in films made under identical conditions using new resin. Therefore, it was our intention to obtain a profile of the volatile organic compounds from both film samples and look for differences which may be the cause of the off-odor complaint.

Aliquots of both packaging films were subjected to direct thermal analysis-gas chromatography-mass spectrometry (TA-GC-MS) using a Scientific Instrument Services (SIS) model TD-1 Short Path Thermal Desorber accessory. Both films were found to contain over 175 volatile organic compounds. However, the film made from recycled resin was found to contain a cluster of approximately 25 peaks in the low boiling region of its gas chromatogram which were absent in the film made from virgin resin. These peaks were identified as a mixture of C-7 to C-9 aliphatic and olefinic hydrocarbons with branched, linear and cyclic species present. Perhaps even more significant from an organoleptic viewpoint was the presence of N,N-dimethylformamide. The aromatic compound toluene was also detected. Based on this data, it was judged that these compounds were the cause of the off-odor in the recycled films.

Additional compounds which were found in both films included a range of phthalate ester plasticizers, phenolic antioxidants, as butylatedhydroxytoluene (BHT), paraffinic hydrocarbons used as mold release agents and a series of sesquiterpenoid compounds, as alpha-copaenes and alpha & beta-ylangenes.

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