Enrichment of Sunflower Oil with γ‐Tocopherol. Study by ¹H NMR of Its Effect Under Accelerated Storage Conditions

Abstract

The effect of the enrichment of sunflower oil with γ‐tocopherol on the evolution of its oxidation is the subject of this study. Sunflower oil and samples of this oil enriched with different γ‐tocopherol concentrations are submitted to accelerated storage conditions and their evolution, until total polymerization is monitored by 1H NMR spectroscopy. The concentrations of linoleic acyl groups, of primary and of a great number of secondary oxidation compounds are determined throughout the process. These concentrations, and the times at which the main changes in them occur are analyzed to elucidate if they are valid markers of the global effect of γ‐tocopherol enrichment. It is proved for the first time that certain comparisons between concentrations of some of the compounds formed in oxidation can lead to erroneous conclusions about the effect of this enrichment. It is shown that, during a first short period of time under accelerated storage conditions, the higher the concentration of γ‐tocopherol the faster the degradation of linoleic acyl groups and the higher the concentration of hydroperoxides; after this first period this relationship is more complex. Generally, the higher the γ‐tocopherol concentration the slower the degradation of the oil, except in the first period. Practical Applications: This study provides very valuable information about the effect caused by enrichment with γ‐tocopherol on sunflower oil oxidative stability and oxidation across a very broad range of concentrations. In addition, the amount of information obtained can be of great importance from several points of view because the oxidation process has been monitored globally. This may be of interest not only to researchers involved in the analysis of oxidation mechanisms but also to those in the field of technology and edible oil legislation, and even to those worried about edible oil safety and its effect on nutrition and health. Another important feature of this study, from the practical point of view, is the methodology used because it does not involve the chemical modification of the sample and the same 1H NMR spectrum is able to provide information about all the above‐mentioned aspects. Sunflower oil enriched with different levels of γ‐tocopherol. Concentrations of primary and secondary oxidation compounds after 4 and 9 days, respectively, under accelerated storage conditions.

Enrichment of flaxseed (Linum usitatissimum) oil with carotenoids of sea buckthorn pomace via ultrasound-assisted extraction technique

“…Such protection can be understood and explained by the capacity of the antioxidants to scavenge free radicals (via electro paramagnetic resonance spectroscopy) that are responsible for the oxidative destruction of lipids, nucleic acids, and proteins ( Chemat et al, 2000 , Espín et al, 2000 ). Electro paramagnetic resonance spectroscopy has found a wide variety of applications in detecting free radicals owing to its high sensitivity to unpaired electrons Martínez-Yusta and Guillén (2019) . The close interaction of DPPH with the free radical scavengers present in the enriched flaxseed oil presented a reduced signal intensity relative to pure flaxseed oil and DPPH stock solution EPR spectra ( Fig.…”

Effect of the Enrichment of Corn Oil With alpha- or gamma-Tocopherol on Its In Vitro Digestion Studied by 1H NMR and SPME-GC/MS; Formation of Hydroperoxy-, Hydroxy-, Keto-Dienes and Keto-E-epoxy-E-Monoenes in the More alpha-Tocopherol Enriched Samples

“…In these studies, alpha tocopherol exhibits a prooxidant effect, which increases in line with its concentration, whereas gamma-tocopherol only accelerates oxidation at very early oxidation stages. However, the global effect in the total oxidation process could be considered antioxidant [7][8][9].…”

“…In spite of this, the knowledge of the effect that this enrichment provokes in foods when they are submitted to different processes is scarce. Recently, it has been shown that some compounds, attributed to antioxidant ability, act as prooxidants in some foods, when submitted to certain oxidative conditions [7][8][9]. Taking into account all of the above mentioned, the study of the effect of the enrichment of lipid foods with compounds, with potential antioxidant ability on their behavior during digestion, is important for both industry and consumers.…”

Evaluation of the Oxidation Degradation Process of Biodiesel via 1H NMR Spectroscopy

“…1 H NMR (proton nuclear magnetic resonance) spectroscopy has been used along with standard analysis to analyze oils and its compositions regarded to acylglycerols, fatty acid alkyl esters (FAAEs), its byproducts. 29 Martínez-Yusta et al 3 studied the sunflower oil degradation process with accelerated storage. Howell et al 30 investigated the steps of the castor oil degradation.…”

“…There is also the possibility of the formation of decomposition products as: acids, aldehydes, esters, ketones, peroxides and alcohols. 3 In the degradation can occur the formation of gums that can clog the injection systems. Also, the hydroperoxides presence with high levels of acids from the oxidation can generate corrosion in the fuel system.…”