Analysis of trace volatiles in low-density polyethylene materials using TD-GC×GC-FID/TOFMS and its correlation with human sensory panel testing

For an in-depth understanding and optimal control of sensory properties of food packaging materials, the combination of both detailed sensory and instrumental analysis is important, as was demonstrated in this study for a set of high-pressure low-density polyethylene (LDPE) resins that are used in extrusion coating applications. Sensory discrimination tests allowed the differentiation of the LDPE grades studied, based on the inherent odor of LDPE pellets, as well as taste and odor ratings of water exposed to pellet samples and extruded films. Additionally, sensory descriptive analysis showed differences in specific odor characteristics among the LDPE grades, highlighting the relative importance of “waxy”, “green”, and “solvent-like” odor notes. By means of thermal desorption followed by comprehensive two-dimensional gas chromatography (TD-GC×GC-FID/TOFMS) a series of trace level carbonyl compounds were separated from the complicated matrix of mainly aliphatic volatiles. The differentiation of LDPE resins, as determined through Principal Components Analysis, yielded comparable results whether based on volatile compounds or sensory data. In addition, the fruity/green/floral-fatty odor characteristics of the identified carbonyl compounds align with the descriptive sensory analysis results. The final odor impact of these carbonyl compounds in a food packaging application based on LDPE will be determined by a combination of concentration, odor thresholds, volatility as well as water solubility of the aroma compounds.