Determination of antioxidant content with PEG as carrier material

Significance of the Topic

Understanding and monitoring antioxidant levels is critical for assessing the shelf life and quality of food, cosmetic and industrial products. The Rancimat method with a polyethylene glycol (PEG) carrier offers a rapid approach to estimate antioxidant capacity, expressed as α-tocopherol equivalents.

Study Objectives and Overview

This study aimed to establish a calibration protocol using α-tocopherol standards with PEG as carrier material to derive equivalent antioxidant content via oxidation induction times measured on an 892 Professional Rancimat. The method was applied to diverse matrices to demonstrate reliability and comparability.

Methodology and Instrumentation

The procedure involves weighing sample or standard together with PEG in a Rancimat reaction vessel and running the analysis at 120 °C under constant airflow. Secondary oxidation products are transferred into a measuring solution and detected by conductivity increase; the induction time marks onset of rapid oxidation. Calibration used α-tocopherol standards from 25 to 250 mg/kg, generating a linear regression (R² = 0.998).

Main Results and Discussion

• Calibration exhibited excellent linearity (R² = 0.998), confirming method accuracy.
• Antioxidant equivalents (mg α-tocopherol/kg) obtained for various products: cervelat (86.8 ± 5.5%), bratwurst (84.0 ± 1.1%), moisturizer (65.1 ± 8.9%), body lotion (58.1 ± 6.1%), dark chocolate (68.2 ± 4.7%), coffee powder (1590.1 ± 7.5%), green tea (7423.7 ± 7.8%).
• No sample preparation required, preserving matrix integrity but limiting differentiation between antioxidant species.

Benefits and Practical Applications

• Rapid throughput with eight simultaneous measurements.
• Minimal sample handling and preparation.
• Direct assessment of complex matrices without extraction.
• Standardized α-tocopherol equivalent values facilitate quality control across diverse products.

Future Trends and Potential Applications

The method could be combined with chromatographic techniques to distinguish individual antioxidants. Automation and integration with software platforms will further increase throughput. Exploration of other carrier materials and temperature protocols may extend applicability to novel matrices and emerging industries.

Conclusion

The PEG-based Rancimat approach provides a fast, reproducible way to quantify antioxidant capacity in complex samples, expressed as α-tocopherol equivalents. While it does not identify specific antioxidants, its simplicity and high precision make it suitable for routine quality control and shelf life assessment.

Reference

Pokhrel K.; Kourimská L.; Rudolf O.; et al. Oxidative Stability of Crude Oils Relative to Tocol Content from Eight Oat Cultivars: Comparing the Schaal Oven and Rancimat Tests. Journal of Food Composition and Analysis. 2024;126:105918.