By Hong-Sik Hwang
This short offers a finished evaluation of NMR spectroscopy, overlaying recommendations resembling 1H, 13C, and 31P NMR, that are trustworthy instruments to figure out lipid oxidation point, to spot oxidation items, and to clarify oxidation mechanism. The short exhibits that 1H NMR spectroscopy always demonstrates reliability, accuracy, comfort, and benefits over traditional analytical equipment in choice of the extent of oxidation of fit for human consumption oil in the course of frying and garage via tracking adjustments in numerous proton indications of oil, together with olefinic, bisallylic and allylic protons. this contemporary analytical strategy is proven inside this article for use to spot oxidation items, together with basic oxidation items reminiscent of hydroperoxides and conjugated dienes and secondary items similar to aldehydes, ketones, epoxides and their derivatives. by way of making a choice on intermediates and ultimate oxidation items, many oxidation mechanisms will be elucidated. a comparatively more moderen process, the textual content demonstrates that 13C NMR and 31P NMR spectroscopy may also supply additional info at the molecular constitution of an oxidation product. Backgrounds, ideas, and merits over traditional equipment, newest advances, and destiny customers of those equipment are discussed.
Advances in NMR Spectroscopy for Lipid Oxidation evaluate begins through protecting some of the mechanisms of lipid oxidation, together with a variety of tips on how to ascertain oxidation items. NMR spectroscopy is then lined, together with its purposes in meals. the following part specializes in 1H NMR Spectroscopy, together with its use for evaluate of lipid oxidation in the course of oil garage and frying. the next part makes a speciality of 13C NMR spectroscopy, together with its use in settling on and choosing oxidation items and mechanisms. a last part makes a speciality of 31<
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Additional info for Advances in NMR Spectroscopy for Lipid Oxidation Assessment
Furthermore, the current criterion for the safety level of oxidized oil is the amount of polar compounds in oil, while it was reported that the amount of polar compounds could not be representative of the safety level. It was reported that oils with the same amount of polar compounds had different compositions of oxidation products, such as genotoxic and cytotoxic 4-hydroxy-alkenals (Guillén and Uriarte 2012c). The old criterion for the safety level of edible oil should be re-considered. Since the NMR method can be used not only to monitor the oxidation of lipids, but also to identify and quantify a specific oxidation product, it can be a better method to determine the safety level of oil.
31P NMR spectroscopy can be used as a reliable method to determine fatty acid distribution and also to assess oxidation of vegetable oils. The NMR instrument is in general very expensive and many small laboratories cannot afford this instrument. This seems to be one of the major reasons that the NMR method is not widely used for the assessment of lipid oxidation. Another hurdle for the utilization of the NMR method is that many scientists are not very familiar with the NMR instrument and think that it is complicated and difficult to use.
In contrast, concentrations of (E)-2-alkenals, n-alkanals, and 4-oxoalkanals increased during the whole period of heating time (40 h). The NMR signals of hydroperoxide protons were not observed in this study and the peroxide value of the oil remained almost constant throughout the oil degradation process. Very similar trends in the formation of these aldehydes were also observed with linseed oil heated at 190 °C for 20 h (Guillén and Uriarte 2012a), extra virgin olive, sunflower, and virgin linseed oils (Guillén and Uriarte 2012c) during heating at a frying temperature (190 °C).