Determination of Low Levels of Free Fatty Acids in Edible Fats and Oils

Significance of the Topic

Free fatty acids (FFA) in edible fats and oils are key indicators of product quality, freshness and shelf life. Even trace levels of FFA can signal hydrolytic rancidity, affect taste and odor, and may impact regulatory compliance. Reliable detection of FFA below 0.1 mg KOH/g (0.05% w/w oleic acid equivalent) supports quality control in food production and ensures consumer safety.

Aims and Study Overview

This application note presents a thermometric titration method using paraformaldehyde as an end-point indicator for precise quantification of low FFA levels in edible fats and oils. The goal is to achieve reproducible results with minimal sample preparation and rapid analysis, extending sensitivity to below 0.05% w/w oleic acid equivalent.

Methodology

Samples (≈5 g) of melted or liquid fat are weighed into a titration beaker and dissolved in a 75:25 (v/v) toluene/2-propanol mixture. Approximately 0.5 g paraformaldehyde is added as a thermometric indicator. Titration is performed with 0.01 mol/L KOH in 2-propanol at a delivery rate of 10 mL/min. Key parameters include a 30 s delay before titration start, stirring speed setting of 15, and a data smoothing factor of 75. The endpoint is detected as an endothermic inflection caused by base-catalyzed depolymerization of paraformaldehyde. A blank determination across 2–7 g of low-acid sample yields a regression intercept (≈0.38 mL) used for correction. FFA and total acid number (TAN) are calculated from corrected titre volumes, sample mass and titrant concentration.

Used Instrumentation

• Thermometric titrator with precise temperature sensor
• Dosino dosing unit equipped with soda-lime guard tube for CO2 protection
• 150 mL titration beakers and adjustable mechanical stirrer
• Laboratory microwave oven for melting solid fats

Main Results and Discussion

Analysis of solid fats (n≥6 for each sample) demonstrated FFA values expressed as oleic, palmitic and lauric acids at 0.038–0.062% w/w with standard deviations below 0.0014%. Corresponding TAN values ranged from 0.076 to 0.124 mg KOH/g. Blank regression exhibited excellent linearity (R2 = 0.9993), confirming reliable endpoint detection despite the weak titrant strength. Data precision and low detection limits underscore the method’s suitability for routine quality assessment.

Benefits and Practical Applications

• High sensitivity for trace FFA determination
• Rapid, automated endpoint detection without visual indicators
• Minimal sample preparation and solvent consumption
• Robust blank correction for accurate low-level measurement
• Applicability in food quality control, R&D and regulatory testing

Future Trends and Applications

Advancements may include integration with inline process analyzers for real-time monitoring, miniaturized portable titration systems for on-site testing, and the use of greener solvents or alternative eco-friendly reagents. Coupling with digital laboratory networks and IoT platforms could further streamline quality assurance workflows.

Conclusion

The described thermometric titration method delivers precise, reproducible and low-level determination of free fatty acids in edible fats and oils. Its automation, sensitivity and straightforward blank correction make it an effective tool for analytical laboratories committed to maintaining high quality and safety standards.

References

• Carneiro M. J. D., Feres Júnior M. A., Godinho O. E. S. Determination of the acidity of oils using paraformaldehyde as a thermometric end-point indicator. J. Braz. Chem. Soc. 13(5):692-694 (2002).