Fast Ingredient Analysis of Edible Oils Using a Portable Raman Spectrometer

Importance of the Topic

Edible oils play a vital role in human nutrition and the food industry, with vegetable oils valued for their high mono- and polyunsaturated fatty acid content compared to animal fats. Rapid, accurate analysis of these oils is essential for quality control, ensuring product consistency and monitoring oxidation processes. Traditional laboratory methods like GC-MS are accurate but slow and require extensive sample preparation, highlighting the need for fast, field-deployable techniques.

Objectives and Study Overview

This application note explores the use of a portable Raman spectrometer paired with chemometric software to quantify key fatty acid components in five common edible oils (olive, camellia, peanut, sunflower, and rapeseed). The goal is to develop at-line predictive models that deliver rapid, nondestructive compositional analysis under real-world conditions.

Methodology

A total of 150 samples (30 per oil type) were measured. Raman spectra were acquired over 175–2600 cm⁻¹ using a 785 nm laser (9 s integration). Spectral preprocessing (background removal, Savitzky-Golay smoothing) enhanced signal quality. Partial least squares (PLS) regression in BWIQ software correlated Raman data with reference values for oleic acid, linoleic acid, mono- and polyunsaturated fatty acids, and saturated fatty acids obtained by GC-MS. Characteristic spectral regions linked to saturation and unsaturation were manually selected to optimize model performance.

Used Instrumentation

• i-Raman® portable spectrometer with CleanLaze® laser stabilization (785 nm)
• Spectral resolution down to 3 cm⁻¹, range up to 4000 cm⁻¹, TE-cooled 2048-pixel CCD
• Dedicated Raman cuvette holder (optical path 10 mm)
• BWIQ® chemometrics software for multivariate analysis and PLS regression

Key Results and Discussion

PLS models achieved high correlation coefficients (R) of 0.95–0.98 for oleic acid, linoleic acid, mono- and polyunsaturated fatty acids, with RMSEP values between 0.15 and 0.24. Saturated fatty acid prediction initially showed lower correlation (R=0.84) due to an outlier, which was identified and removed, improving model accuracy. Graphical prediction plots confirmed strong agreement between Raman-based predictions and GC-MS reference data.

Benefits and Practical Applications

The portable Raman approach offers rapid (<10 s), nondestructive analysis without solvents or elaborate sample prep. Measurements in disposable glass vials support at-line and field testing for quality assurance in food processing, verifying fatty acid profiles and monitoring oxidative changes in oils.

Future Trends and Potential Applications

• Development of dedicated calibration models for individual fatty acids to enhance accuracy
• Real-time monitoring of lipid oxidation during storage and processing
• Integration with IoT platforms for remote quality tracking
• Extension to other food matrices and industrial liquids

Conclusion

This study demonstrates that a portable Raman spectrometer combined with advanced chemometrics can reliably quantify key fatty acid components in edible oils, offering a fast, simple alternative to GC-MS. The method’s portability and minimal sample requirements enable effective at-line quality control in various production environments.

Reference

• Bernuy B., Meuren M., et al. Determination by Fourier Transform Raman Spectroscopy of Conjugated Linoleic Acid in I2-Photoisomerized Soybean Oil. J. Agric. Food Chem. 2009, 57(15), 6524–6527. DOI:10.1021/jf9003237
• Muik B., Lendl B., Molina-Diaz A. Direct monitoring of lipid oxidation in edible oils by Fourier transform Raman spectroscopy. Chem. Phys. Lipids 2005, (2). DOI:10.1016/j.chemphyslip.2005.01.003
• BWIQ Raman Quantitative Software. B&W Tek. www.bwtek.com/products/bwiq/
• AppNote 20120710C. B&W Tek Shanghai; Central South University; ChemSolve Ltd.