Mineral Oil Residues in Food Part 1- Dry Food (Flour, Noodles and Rice)

Significance of the Topic

Mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) are increasingly detected in dry foods such as flour, noodles and rice, raising safety concerns due to potential health risks and lack of regulatory limits in Europe.

Objectives and Overview of the Study

This work presents a streamlined analytical protocol enabling routine quantification of MOSH and MOAH in dry food matrices by combining liquid chromatography with gas chromatography–flame ionization detection (LC-GC-FID).

Methodology

Sample Preparation:

• Homogenization and grinding of dry food samples (1–10 g).
• Extraction with hexane/ethanol (1:1) containing internal standards for 2 h.
• Purification by water washing, centrifugation and drying over sodium sulfate.
• Concentration to 1 mL final volume and injection of 50 µL for LC separation.

Fraction Separation and Quantification:

• Online LC-GC interface separates MOSH and MOAH on a silica column with n-hexane/dichloromethane gradient.
• Transfer of each fraction to dedicated GC columns and simultaneous GC-FID detection.
• Quantification via internal standards and integration of hydrocarbon “humps” across defined carbon number ranges (C10–C16, C16–C25 for MOSH; C10–C25 for MOAH in dry foods).

Instrumentation

• LC: Shimadzu LC-20AD pump, Allure Silica column (250×2.1 mm, 5 µm), D2 UV detector (230 nm).
• LC-GC Interface: Axel Semrau LC-GC Chronect.
• GC: Shimadzu GC-2010 Plus with dual FID; Restek MXT Siltek guard and MTX-1 analytical columns; hydrogen carrier gas.

Main Results and Discussion

The method achieves clear separation of MOSH and MOAH fractions, demonstrated on spaghetti (MOSH 12.7 mg/kg in C16–C35 range) and rice samples (natural odd-chain alkanes C21–C35). Chromatograms show well-resolved humps and distinct internal standard peaks, ensuring accurate quantification.

Benefits and Practical Applications of the Method

• Fully automated workflow with high throughput suitable for routine quality control.
• Reliable separation and quantification of MOSH and MOAH in low mg/kg levels.
• Applicable to a range of dry, non-fatty food matrices.

Future Trends and Potential Applications

Adaptation to fatty food matrices and more complex sample types; integration with mass spectrometric detection for structural information; development of regulatory guidelines and limit values; expansion to emerging solvents and packaging-related contaminants.

Conclusion

The presented LC-GC-FID approach offers a fast, robust and fully automated solution for monitoring mineral oil hydrocarbons in dry food products, facilitating enhanced food safety assessments and laboratory efficiency.

References

1. EFSA Panel on Contaminants in the Food Chain (CONTAM). Scientific Opinion on Mineral Oil Hydrocarbons in Food. DOI:10.2903/j.efsa.2012.2704
2. Statista. Global per capita rice consumption since 2000.
3. International Pasta Organization. Pasta consumption data.
4. Bundesinstitut für Risikobewertung. Method for determination of hydrocarbons from mineral oils or plastics.