Fatty acids infrared spectroscopy

Infrared spectra of fats and oils are similar regardless of their composition. The principal absorption seen is the carbonyl stretching peak which is virtually identical for all triglyceride oils. The most common appHcation of infrared spectroscopy is the determination of trans fatty acids occurring in a partially hydrogenated fat (58,59). Absorption at 965 - 975 cm is unique to the trans functionaHty. Near infrared spectroscopy has been utilized for simultaneous quantitation of fat, protein, and moisture in grain samples (60). The technique has also been reported to be useful for instmmental determination of iodine value (61). 

Measurement of Unsaturation. The presence of double bonds in a fatty acid side chain can be detected chemically or through use of instmmentation. Iodine value (IV) (74) is a measure of extent of the reaction of iodine with double bonds the higher the IV, the more unsaturated the oil. IV may also be calculated from fatty acid composition. The cis—trans configuration of double bonds may be deterrnined by infrared (59) or nmr spectroscopy. Naturally occurring oils have methylene-intermpted double bonds that do not absorb in the uv however, conjugated dienes maybe deterrnined in an appropriate solvent at 233 nm. 

Amides can be titrated direcdy by perchloric acid ia a nonaqueous solvent (60,61) and by potentiometric titration (62), which gives the sum of amide and amine salts. Infrared spectroscopy has been used to characterize fatty acid amides (63). Mass spectroscopy has been able to iadicate the position of the unsaturation ia unsaturated fatty amides (64). Typical specifications of some primary fatty acid amides and properties of bisamides are shown ia Tables 5 and 6. 

Immersion of fatty acid films into solutions of metal ions, as already indicated, results in an intercalation of the metal ions into the planes formed by the carboxylate head groups of the fatty acids. This can be accomplished in M-FA films where the FA has been regenerated by exposure to H2S [Eq. (4)] or in FA films deposited without any metal ions. Subsequent exposure of the films to H2S has been shown to result in the formation of the metal sulfide. This intercalation/sulfidation (i/s) cycle can be repeated several times to increase the concentration of the metal sulfide in the film. This process has been investigated forCdS (34,39,42,43), PbS (39,43,44), ZnS (39,43), and HgS (45) produced in M-FA films, using Fourier-transform infrared (FTIR) and UV/visible spectroscopies, QCM gravimetry, and atomic force microscopy (AFM). 

Mossoba, M.M., Kramer, J.K.G., Fritsche, J., Yurawecz, M.P., Eulitz, K., Ku, Y., and Rader, J.I. 2001 a. Application of standard addition to eliminate conjugated linoleic acid and other interferences in the determination of total trans fatty acids in selected food products by infrared spectroscopy.. /. Am. Oil Chem. Soc. 78 631-634. 

Aspartic peptidases, 365 Atmospheric pressure chemical ionization (APCI), used with LC/MS ATR-FTIR. see Attenuated total reflection Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), trans fatty acids, 505-511 Autoxidation. see also Oxidation discussed, 535 of lipids, 558, 627 prevention of, 558... 

Fourier transform infrared spectroscopy with attenuated total reflection (ATRFTIR), trans fatty acids, 505-511... 

Infant formula, tocopherol/tocotrienol analysis, 479, 487, 489 (table) Infrared spectroscopy, see also Fourier transform infrared spectroscopy fat measurement, 572 trans fatty acids, 505 Infrared/ultrasonic scanner for emulsion creaming, 597-598 Injection techniques for GC, 449 Insoluble recombinant proteins, purification of, 276... 

Koca, N., Rodriguez-Saona, L. E., Harper, W. J., and Alvarez, V. B. (2007). Application of Fourier transform infrared (FTIR) spectroscopy for monitoring short-chain free fatty acids in Swiss cheese. J. Dairy Sci. 90, 3596-3603. 

Y. Takeuchi, H. Yasukawa, Y. Yamaoka, Y. Kato, Y. Morimoto, Y. Fukomori, and T. Fukada, Effect of fatty acids, fatty amines and propylene glycol on rat stratum corneum hpids and proteins in vitro measured by Fourier Transformed Infrared/Attenuated Total Reflectance spectroscopy. Chem. Pharm. Bull. 40 1887-1892 (1992). 

Buermeyer, J., Lamprecht, S., Rudzik, L. 2001. Application of infrared spectroscopy to the detection of free fatty acids in raw milk. Deutsch. Milchwirtsch. 52, 1020-1023. 

Ismail, A.A., van de Voort, F.R., Emo, G., Sedman, J. 1993. Rapid quantitative determination of free fatty acids in fats and oils by Fourier transform infrared spectroscopy. J. Am. Oil Chem. Soc. 70, 335-341. 

It has been suggested that these ceramides form a gel-phase membrane domain within the skin. Straight fatty acid chains as well as the small polar head groups on the ceramides are thought to produce a tightly packed domain which is less fluid and thereby less permeable than other liquid crystalline domains which are also present. Recent evidence using differential scanning calorimetery (DSC) and infrared absorption spectroscopy analyses verifies the presence of gel phases within the stratum comeum. 

In addition to calorimetry, information to establish the mode of adsorption is often obtained spectroscopically. Changes in the optical properties of (groups on) the surface or the adsorptive may be monitored. As an Illustration of the former. Rochester studied adsorption from the gas euid liquid phase on rutile (TiOj) and used infrared spectroscopy to distinguish between attachment at different surface hydroxyls. As an example of an ESR study, McBride investigated the adsorption of fatty acids on amorphous alumina from methanol by labelling them with a spin probe. Relevant information could be... 

Menikh A, Nyholm P-G, Boggs JM. Characterization of the inter-achon of Ca with hydroxy and non-hydroxy fatty acid species of cerebroside sulfate by fourier transform infrared spectroscopy and molecular modeling. Biochemistry 1997 36 3438-3447. 

Langmuir-Blodgett Films of Azobenzene-Containing Long Chain Fatty Acids and Their Salts Studied by Ultraviolet-visible and Infrared Spectroscopy. Langmuir 10, 236i (1994). 

Sato, X, Ozaki, Y., and Iriyama, K. Molecular a r laon and photoisomerization of Laiigmuir-Blodgett-fihns of azobenzene-containing long-diain fatty-acids and tiieir salts studied by ultraviolet-visible and infrared spectroscopies. 1994, 10, 2363-2369. 

This section on chemical factors related to quality in soybeans is divided into subparts on protein and oil, fatty acids, amino acids, tests for protein, carbohydrates and sugars, and other factors that are often discussed, particularly as soybeans are enhanced for more specific end uses. The other factors include tests for fiber, phosphorus, to-copherols, and isoflavones. The intent is to discuss the importance of these factors, to provide background, and, because of increased use of near-infrared spectroscopy as a measurement method for whole and ground soybeans, to include that technology in the discussion of test measurements. While many primary and other methods for measuring these chemical factors are available, this chapter does not intend to cover those methods. 

Nimaiyar et al. (2004) also found stearic acid to be the most difficult fatty acid to predict using Fourier-Transform near-infrared spectroscopy over the 833 to 2500 nm range. Stearic acid had the lowest R value and lowest RPD value of all five fatty acids tested. 

Pazdernik, D.L. A.S. Killam J.FI. Orf Analysis of amino and fatty acid composition in soybean seed, using near infrared reflectance spectroscopy. Agron.f. 1997, 89, 679-685. 

As described in Section 3.1, Baier et al. (1974) have used a machined germanium prism to sample surface organic monolayers in the manner developed earlier by Blodgett (1934,1935) for fatty acid films. The basis of their analytical method, infrared spectroscopy by the technique of internal reflections inside the machined prisms, is only qualitative but serves very well to examine the chemical nature of the surface organics. It is well known that when an internal reflection prism made of a material with a sufficiently high index of refiraction such as germanium is used, the internal reflection IR spectrum obtained suffers no band distortion or band shift when compared to conventional transmission spectra of the same substance (Barr and Flournoy, 1969). 

Sierra et al. in 2007 conducted a study for the rapid prediction of the fatty acid (FA) profile of ground using near infrared transmittance spectroscopy (MT). The samples were scanned in transmittance mode from 850 to 1050 nm. MT spectra were able to accurately predict saturated R2=0,837, branched R2=0,701 and monounsaturated R2=0,852 FAs. Results were considered interesting because intramuscular fat content and composition influence consumer selection of meat products. 

Sierra, V. Aldai, N. Castro, P. Osoro, K. Coto-Montes, A. Oliva, M (2007). Prediction of the fatty acid composition of beef by near infrared transmittance spectroscopy. Meat Science Vol.78, pp. 248-255... 

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