Rapid quantitative determination of free fatty acids in fats and oils by fourier transform infrared spectroscopy

Abstract

Rapid direct and indirect Fourier transform infrared (FTIR) spectroscopic methods were developed for the determination of free fatty acids (FFA) in fats and oils based on both transmission and attenuated total reflectance approaches, covering an analytical range of 0.2-8% FFA. Calibration curves were prepared by adding oleic acid to the oil chosen for analysis and measuring the C--O band @ 1711 cm -1 after ratioing the sample spectrum against that of the same oil free of fatty acids. For fats and oils that may have undergone significant thermal stress or extensive oxidation, an indirect method was developed in which 1% KOH/methanol is used to extract the FFAs and convert them to their potassium salts. The carboxylate anion absorbs @ 1570 cm -1, well away from interfering absorptions of carbonyNcontalning oxidation end products that are commonly present in oxidized oils. Both approaches gave results comparable in precision and accuracy to that of the American Oil Chemists' Society reference titration method. Through macroprogramming, the FFA analysis procedure was completely automated, making it suitable for routine quality control applications. As such, the method requires no knowledge of FTIR spectroscopy on the part of the operator, and an analysis takes less than 2 rain. KEY WORDS: Fats and oils, free fatty acids, Fourier transform infrared spectroscopy, quality control.

Analytical Methods to Evaluate the Quality of Edible Fats and Oils: The JOCS Standard Methods for Analysis of Fats, Oils and Related Materials (2013) and Advanced Methods

“…NIR spectroscopy is also capable of determining free fatty acids, trans fatty acids and oxidation products such as hydroperoxides, carbonyl compounds and polar compounds in edible fats and oils, although their sensitivity is low. Free fatty acids 44,45 are determined at 1882, 2010 and 2040 nm based on the C O overtone, while hydroperoxides PV 46 are determined at 1460-1480 nm and 2080 nm. Recently, the THz spectrometry that can scan the region between 10 and 400 cm 1 Fig.…”

Automated and Simultaneous Determination of Free Fatty Acids and Peroxide Values in Edible Oils by FTIR Spectroscopy Using Spectral Reconstitution

“…(2) and (4). 4 Figure 5 shows that the relationship between absorbance 542/555 cm -1 and PV was quite linear. This regression equation indicates that PV can theoretically be measured to within ±0.22 meq/kg over the range of 0 -25 meq/kg.…”

“…17 Figure 3 shows that a progressive increase in the FFA and TPPO at 1712 and 542 cm -1 as the proportion of the hexanoic acid and TPPO respectively, indicating that the COO -band had responded properly in IR spectrum 4 and the desired TPP AE TPPO conversion had taken place. 17 The FFA and TPPO absorbance bands at 1712 and 542 cm -1 can be used for FFA and PV analysis.…”

“…Figure 4 shows a non-ideal response to FFA concentration which can be attributed to concentration dependent hydrogen bonding between FFA carboxyl groups, 4 which differs in the two matrices due to their differences in polarity, the SR matrix being hydrophobic and having oil dependency from Eqs. (2) and (4).…”

Insights on novel particulate self-assembled drug delivery beads based on partial inclusion complexes between triglycerides and cyclodextrins

“…FT-IR spectroscopy was used to examine the oils degradation resulting from autoxidation (Ismail et al, 1993;Van de Voort et al, 1994). The characteristic degradation band (carbonyl stretching band (C¼O) at around 1710 cm À1 ) was absent in the spectra of freeze-and oven-dried beads stored for 6 months at 75% RH/40 C confirming the oil stability (Hamoudi et al, 2013).…”