Oxidation stability of spices and seasonings with the PEG method

Significance of Oxidation Stability Analysis in Spices and Seasonings

Spices and seasonings are valued not only for their flavor but also for their antioxidant properties, which contribute to food preservation and health benefits. Monitoring oxidation stability helps maintain product quality, extend shelf life and ensure consumer safety.

Study Objectives and Overview

This application note presents a rapid, direct analysis of oxidation stability in various spices and seasonings using the polyethylene glycol (PEG) method with a Rancimat system. The goal is to evaluate antioxidant capacity without time-consuming sample preparation, in accordance with AOCS Cd 12b-92 and ISO 6886 standards.

Methodology and Instrumentation

The analysis employs an 892 Professional Rancimat equipped with eight measuring positions. Key points:

• No sample preparation is needed; the entire powdered or sliced spice matrix is analyzed.
• Samples are mixed with PEG and exposed to a controlled airflow at 120 °C.
• Volatile oxidation products are carried into a measuring solution where conductivity is monitored continuously.
• The induction time, marked by a sharp rise in conductivity, indicates oxidation stability.

Main Results and Discussion

Induction times (mean of four replicates) measured at 120 °C reveal significant differences among spices:

• Rosemary (sliced): 8.70 h, reflecting high natural antioxidant content.
• Black pepper (ground): 2.92 h, nearly double that of white pepper.
• Curry powder: 1.97 h; caraway: 1.87 h.
• White pepper (ground): 1.45 h; seasoning blend: 0.66 h; granulated garlic: 0.47 h.

Relative standard deviations remained below 9 %, demonstrating good reproducibility.

Benefits and Practical Applications

The PEG-Rancimat approach delivers a fast, reliable measure of antioxidant capacity across complex spice matrices without extraction steps. Simultaneous analysis of eight samples enhances laboratory throughput. Disposable reaction vessels and dishwasher-safe accessories minimize cleaning time and improve reproducibility.

Future Trends and Potential Applications

Integration of automated data handling and temperature profiling could further refine induction time measurements. Extending this method to spice blends, extracts and finished food products may support broader quality control and research into novel natural antioxidants.

Conclusion

The PEG method on the 892 Professional Rancimat offers an effective, high-throughput solution for assessing oxidation stability in spices and seasonings. It provides clear differentiation among products based on antioxidant content and supports robust quality monitoring in the food industry.