Determination of iodine value in frying oils with NIR spectroscopy

Significance of the topic

Monitoring the iodine value (IV) in frying oils is essential for ensuring oxidative stability, nutritional quality and safety in food production. Soybean and palm oil blends offer a balance of mild taste and thermal stability but require precise control of saturation levels to maintain performance under high-temperature cooking.

Goals and Overview of the Study

This application note demonstrates a rapid, non-destructive near-infrared spectroscopy (NIRS) method for quantifying iodine value in soybean-palm oil blends. The study aims to replace time-consuming titration and chromatographic methods with a one-minute NIRS analysis for routine quality control.

Methodology and Used Instrumentation

A series of 21 oil blends with IV ranging from 60 to 130 g/100 g were prepared and measured in transmission mode. Samples were preheated at 60 °C to ensure consistent liquid state.

• DS2500 Liquid Analyzer (Metrohm)
• NIRS XDS Vial Heater
• DS2500 Holder for 8 mm vials
• Vision Air Complete software

Spectral data were collected across 400–2500 nm and analyzed using multivariate calibration to develop a prediction model.

Main Results and Discussion

The Vis-NIR spectra exhibited distinct absorption features correlating with unsaturation levels. The calibration model achieved an R2 of 0.999, with a standard error of calibration of 0.20 g/100 g and cross-validation error of 0.22 g/100 g. Such accuracy matches or exceeds conventional titration results while eliminating chemical reagents.

Benefits and Practical Applications

NIRS analysis reduces time to result from 1–2 hours to under one minute per sample. It requires no sample preparation or hazardous chemicals, lowering laboratory workload and operational costs. This method is suitable for on-line process control as well as routine lab QC.

Future Trends and Opportunities

Integration of NIRS sensors into production lines will enable real-time monitoring of oil blending and frying processes. Advances in miniaturized spectrometers and chemometric algorithms will further enhance portability, robustness and multi-analyte capabilities across diverse food matrices.

Conclusion

Near-infrared spectroscopy using the Metrohm DS2500 Liquid Analyzer offers a rapid, accurate and environmentally friendly alternative for determining iodine value in soybean-palm oil blends. This approach streamlines quality control workflows and supports high-throughput analysis in food laboratories and production environments.

References

• AOCS Cd 1b-87, Iodine Value by Wijs Method
• AOCS Cd 1e-01, Near-Infrared Spectroscopy Guidelines