Developing a Sustainable FTIR Spectroscopic Method for Quantifying Unsaturation in Commercially Available Edible Oils

ABSTRACT Quantifying the degree of unsaturation in edible oils is imperative for the estimation of nutritional value and health implications, as unsaturated fats play a key role in regulating cardiovascular parameters. In this study, Fourier‐transform infrared (FTIR) spectroscopy was used to develop a rapid, univariate, sustainable, and non‐destructive analytical method to quantify the unsaturation contents of commercially available edible oils, using mustard and soybean oils as model compounds. While multiple spectral features can serve as markers of oil unsaturation, specifically the alkene, CH stretching peak near 3006 cm −1 , the asymmetric bending modes near 1417 cm −1 , and the cis‐alkene out‐of‐the‐plane bending band near 722 cm −1 , the primary analytical strategy in this framework measures the density of double bonds based on the isolated aliphatic CC stretching vibration peak centered near 1651 cm −1 . This foundational approach substantially reduces reagent and solvent volume relative to classical titrimetric frameworks and eliminates the need for stoichiometric halogen addition reagents (ICl/IBr) and their corrosive by‐products, although chloroform, itself a hazardous halogenated solvent, is still used as an inert diluent at greatly reduced volume (≈10–20 μL per determination vs. ≈85 mL of combined reagents/solvent per Hanus titration). The constructed optical calibration frameworks indicated highly reproducible linear relationships between the IR peak intensities and the volumetric oil concentration fractions, yielding correlation coefficients ( R 2 ) of 0.9302 for mustard oil and 0.9357 for soybean oil. Parallel validations conducted using the traditional chemical Hanus method yielded R 2 values of 0.9981 and 0.9952, respectively, describing the internal linearity of each method against oil concentration individually. Direct agreement between FTIR‐predicted and Hanus‐measured IVs was assessed by back‐calculating a predicted IV for every standard and commercial brand and regressing it against the corresponding Hanus‐measured IV: for mustard oil ( n = 11:6 standards +5 brands), IV Hanus = 0.9311 × IV predicted +4.69 ( R 2 = 0.9351), with a Bland–Altman mean bias of +0.80 g I 2 /100g and 95% limits of agreement (LOAs) of −8.13 to +9.73 g I 2 /100g; for soybean oil ( n = 6 standards), IV Hanus = 0.9385 × IV predicted +5.72 ( R 2 = 0.9367), with a mean bias of 0.00 g I 2 /100g and 95% LOAs of −11.47 to +11.47 g I 2 /100g. Precision analysis across multiple commercial brands yielded excellent relative standard deviation (RSD) of 2.75% for mustard oil samples and 3.99% for soybean oil samples (inter‐brand RSD, reflecting genuine brand‐to‐brand compositional variation superimposed on instrumental repeatability of 0.81%–0.89% per brand), confirming the reliability and the reproducibility of the developed method. These findings demonstrate that the proposed transmission FTIR method serves as a robust, reagent‐sparing and environmentally friendly alternative for quality control testing of mustard and soybean oil industry.