Direct Thermal Extraction Analysis of Food Packaging Material

Importance of the Topic

Food packaging can interact with its contents through scalping and migration of volatile and semi-volatile compounds. These processes may lead to off-flavors, compromised quality, or safety concerns over a product’s shelf life. Rapid and reliable screening of packaging materials is therefore critical for food manufacturers to ensure product integrity and regulatory compliance.

Objectives and Study Overview

This study applied direct thermal extraction (DTE) coupled with gas chromatography–mass spectrometry (GC–MS) to assess the chemical profile of packaging materials from three brands each of crème-filled chocolate sandwich cookies, cheese-filled sandwich crackers, and soft and chewy candy. The goal was to identify both packaging-derived residues and compounds that had migrated from the food into the packaging, and to demonstrate quantification of key analytes.

Methodology and Instrumentation

Sample Preparation and Extraction

• Each packaging sample (25 mg) was placed directly into an empty thermal desorption (TDU) tube and sealed.
• Direct thermal extraction was performed under inert gas flow to release volatile and semi-volatile compounds.

Used Instrumentation

• GERSTEL MultiPurpose Sampler (MPS) with Thermal Desorption Unit (TDU 2) and Cooled Injection System (CIS 4)
• Agilent 7890A GC with 5977B MSD
• Column: 30 m Rxi-5Sil MS, 0.25 mm × 0.25 µm

GC/MS Conditions

• TDU program: 40 °C (0.5 min), 720 °C/min to 60 °C (7.5 min)
• PTV inlet: solvent vent (50 mL/min) at −150 °C to 280 °C (12 °C/s)
• Oven: 40 °C (1 min), 10 °C/min to 280 °C (3 min)
• Carrier gas: helium, 1 mL/min

Main Results and Discussion

Crème-Filled Sandwich Cookies
Brand A exhibited the highest extractable levels, including ink solvents (1-butoxy-2-propanol), adhesive plasticizers (dioctyl adipate), sulfonamides, and migrated flavor additives (ethyl vanillin, BHT). Brand B contained triacetin and vanillin from the food with lower sulfonamide levels. Brand C showed minimal residues, mainly styrene and limonene.

Soft and Chewy Candy
Brands D and F both released food flavor carriers (triacetin), flavoring esters (allyl hexanoate, benzyl acetate), and packaging antioxidants (2,4-di-tert-butylphenol) and plasticizers (dioctyl adipate). Brand D also contained trace sulfonamides. Brand E’s profile was dominated by migrated fruit esters (e.g., ethyl butyrate, isoamyl acetate), terpenes, and quantified benzaldehyde at 79 ± 6 ng per 25 mg sample.

Cheese-Filled Sandwich Crackers
Brands G and H shared food volatiles (hexanal, hexanoic acid, isopropyl esters) and packaging plasticizers (N-butyl benzenesulfonamide, tributyl acetylcitrate). Brand I contained ink solvents and diethyl phthalate. All three brands released nonanal and BHT.

Benefits and Practical Applications

DTE coupled with the GERSTEL MPS/TDU/CIS platform requires minimal sample preparation and allows rapid switching among liquid, headspace, SPME, and thermal extraction modes. This versatility supports both qualitative screening and quantitative determinations for quality control, product development, and competitive analysis in food packaging assessment.

Future Trends and Opportunities

Advancements may include integration with high-resolution MS for enhanced compound identification, development of standardized quantitative workflows for regulatory compliance, expansion to multilayer and biodegradable packaging, and full automation for high-throughput screening of food-contact materials.

Conclusion

Direct thermal extraction using the GERSTEL MPS/TDU/CIS system provides a robust, flexible, and rapid approach for profiling and quantifying volatile and semi-volatile compounds in food packaging. The method effectively identifies both packaging residues and migrated food components, supporting critical quality and safety evaluations.

Reference

Vernarelli L., Whitecavage J., Stuff J. Direct Thermal Extraction Analysis of Food Packaging Material. GERSTEL Application Note No. 203, 2019.