Determination of free fatty acids (FFA) in edible oils with 859 Titrotherm

Importance of the topic

Free fatty acid (FFA) content is a key quality parameter in edible oils. Elevated FFA levels indicate hydrolytic rancidity, reduced shelf life and off­-flavors, which impact consumer safety and product value. Rapid, accurate FFA determination supports quality control, regulatory compliance and product standardization in the food industry.

Objectives and study overview

This bulletin presents a thermometric titration method using the Metrohm 859 Titrotherm system to quantify FFA in olive, rapeseed and sunflower oils. The approach leverages the exothermic hydrolysis of paraformaldehyde catalyzed by excess hydroxide to identify the titration endpoint. Key goals include establishing a robust procedure for titer determination, blank correction and sample analysis under non­-insulated conditions.

Methodology and instrumention

Samples are dissolved in a 1:1 (v/v) toluene/2-­propanol mixture. Paraformaldehyde (95 %) serves as catalyst. Titrant is standardized tetrabutylammonium hydroxide (TBAOH, 0.01 mol/L in 2-propanol). The 859 Titrotherm with integrated Dosino dosing units (5 mL and 50 mL) and Thermoprobe monitors temperature changes at constant titrant addition rate (5 mL/min). Method blank and titer are calculated via linear regression of multiple aliquots using tiamo™ software.

Key results and discussion

The titer determination yielded slopes near unity and correlation coefficients R² ≥ 0.993. Method blanks ranged from 0.228 to 0.339 mL titrant. Measured FFA expressed as total acid number (TAN, mg KOH/g) were: olive oil 0.70, rapeseed oil 0.05 and sunflower oil 0.065, with relative standard deviations below 5 % (n=3). The thermometric endpoint is sharp and reproducible, allowing precise quantification without temperature insulation.

Benefits and practical applications

• Rapid analysis with single exothermic endpoint detection
• Minimal sample preparation and solvent use
• High precision and repeatability under ambient conditions
• Fully automated titrations via tiamo™ for titer, blank and sample evaluation
• Applicability to quality control in food industry and research laboratories

Future trends and possibilities

Advancements may include integration of inline sample feeders, expanded catalyst systems for other non­-aqueous titrations and miniaturized thermometric sensors for at­line or field applications. Coupling with spectroscopic or chromatographic detectors could broaden analyte scope beyond FFA.

Conclusion

The Metrohm 859 Titrotherm offers an efficient, accurate thermometric titration route for FFA determination in edible oils. The method’s automation, robustness and low detection limits make it a valuable tool for routine quality control and advanced research in lipid analysis.