Pro- and Antioxidative Effect of α-Tocopherol on Edible Oils, Triglycerides and Fatty Acids

Effects of Endogenous Antioxidants in Camellia Oil on the Formation of 2-Monochloropropane-1, 3-diol Esters and 3-Monochloropropane-1,2-diol Esters during Thermal Processing

2-Monochloropropane-1, 3-diol (2-MCPD) esters and 3-monochloropropane-1,2-diol (3-MCPD) esters, a class of substances potentially harmful to human health, are usually formed during the refining of vegetable oils under high temperature. The effects of endogenous antioxidants in vegetable oils on the formation of 2- and 3-MCPD esters is still unknown. In this study, the effects of endogenous antioxidants (α-tocopherol, stigmasterol and squalene) on the formation of 2- and 3-MCPD esters in model thermal processing of camellia oil were investigated. The possible formation mechanism of 2- and 3-MCPD esters was also studied through the monitoring of acyloxonium ions, the intermediate ions of 2- and 3-MCPD esters formation, and free radicals by employing infrared spectra and electron paramagnetic resonance (EPR), respectively. The results indicated that the addition of α-tocopherol had either promoting or inhibiting effects on the formation of 2- and 3-MCPD esters, depending on the amount added. Stigmasterol inhibited the formation of 3-MCPD ester and 2-MCPD ester at low concentrations, while promoting their formation at high concentrations. Squalene exhibited a promotional effect on the formation of 3-MCPD ester and 2-MCPD ester, with an increased promotion effect as the amount of squalene added increased. The EPR results suggested that CCl3•, Lipid alkoxyl, N3• and SO3• formed during the processing of camellia oil, which may further mediate the formation of chlorpropanol esters. This study also inferred that squalene promotes the participation of the free radical in chlorpropanol ester formation.

ESR spin trapping for in situ detection of radicals involved in the early stages of lipid oxidation of dried microencapsulated oils

Different studies have shown that detection of free radicals by ESR spin trapping provides useful information on the susceptibility to oxidation of bulk oils and accordingly on the oxidative stability of different samples for comparative purposes. With the same goal, ESR spin trapping was evaluated in this work for in situ detection of radicals in dried microencapsulated oils (DMOs). By testing different oils, encapsulation matrices and oxidation conditions, results showed that ESR spin trapping can be useful to evaluate the oxidative susceptibility of DMOs, but ESR data should be interpreted cautiously, as the great complexity of the reactions involved may lead to data misinterpretations. Conditions for oxygen availability can have important impacts on the rates of both spin trapping and spin-adduct quenching affecting the levels of radicals observed. The kinetics of oxidation, spin trapping and spin-adduct decay should be known first in bulk oils for correct data interpretation in DMOs.

Study of pure and combined antioxidants for replacing TBHQ in soybean oil packed in pet bottles

Oils are subject to several reactions that lead to physical-chemical, sensory and nutritional deterioration. This deterioration process is called rancidity or lipid oxidation, a spontaneous and irreversible phenomenon that can be delayed by the addition of antioxidants. Usually, vegetable oil producers choose to add antioxidants to the upper limit permitted by applicable law as it is not entirely clear the ideal dosages of pure or combined antioxidants designated for this purpose. In order to determine the optimum dosage of antioxidants that minimizes the impact of lipid oxidation of soybean oil bottled in PET (ethylene terephthalate) and replace the traditional antioxidant tert-Butylhydroquinone (TBHQ), an accelerated oven shelf-life test was performed. The antioxidants ascorbyl palmitate (AP), mix of tocopherols and rosemary extract (RE) were evaluated, pure and in combination, at different dosages. Most of the evaluated antioxidants delayed lipid oxidation of soybean oil, but a mixture containing AP and RE presented results of TOTOX statistically lower (higher oxidative stability) than that with TBHQ. One the other hand, regarding OSI at 120 °C, the result obtained by that mixture was statistically lower (less oxidative stability) than that obtained with TBHQ, in both evaluated dosages.

Preliminary Study: Comparison of Antioxidant Activity of Cannabidiol (CBD) and α-Tocopherol Added to Refined Olive and Sunflower Oils

This study evaluates the antioxidant activity of cannabidiol (CBD), added to model systems of refined olive (ROO) and sunflower (SO) oils, by measuring the peroxide value, oxidative stability index (OSI), electron spin resonance (ESR) forced oxidation, and DPPH• assays. Free acidity, a parameter of hydrolytic rancidity, was also examined. CBD was compared using the same analytical scheme with α-tocopherol. CBD, compared to α-tocopherol, showed a higher scavenging capacity, measured by DPPH• assay, but not better oxidative stability (OSI) of the oily systems considered. In particular, α-tocopherol (0.5%) showed an antioxidant activity only in SO, registered by an increase of more than 30% of the OSI (from 4.15 ± 0.07 to 6.28 ± 0.11 h). By ESR-forced oxidation assay, the concentration of free radicals (μM) in ROO decreased from 83.33 ± 4.56 to 11.23 ± 0.28 and in SO from 19.21 ± 1.39 to 6.90 ± 0.53 by adding 0.5% α-tocopherol. On the contrary, the addition of 0.5% CBD caused a worsening of the oxidative stability of ROO (from 23.58 ± 0.32 to 17.28 ± 0.18 h) and SO (from 4.93 ± 0.04 to 3.98 ± 0.04 h). Furthermore, 0.5% of CBD did not lower dramatically the concentration of free radicals (μM) as for α-tocopherol, which passed from 76.94 ± 9.04 to 72.25 ± 4.13 in ROO and from 17.91 ± 0.95 to 16.84 ± 0.25 in SO.

New Insights into the Impact of Sodium Chloride on the Lipid Oxidation of Oil-in-Water Emulsions

Salt, most often sodium chloride (NaCl), is commonly used in a variety of food emulsions. However, little is known about the detailed mechanism of how NaCl influences the lipid oxidation and thus the shelf life of those products. In this study, we report a new mechanism through which NaCl could help inhibit the lipid oxidation of sodium dodecyl sulfate (SDS)-stabilized oil-in-water (O/W) emulsions. Results showed that NaCl significantly lowered the critical micelle concentration (CMC) of SDS, which further led to greater amounts of lipid hydroperoxides being solubilized by SDS micelles into the aqueous phase of emulsion. NaCl also altered the distribution of δ-tocopherol between the aqueous and oil phase of emulsion. Such changes of the physical locations of lipid hydroperoxides and δ-tocopherol were responsible for the improved oxidative stability of NaCl-added O/W emulsions in the absence or presence of δ-tocopherol.

1,2,3-propanetriol radicals formed during oxidative stress

The presented results attempt to approximate the proper structure of the radical formed as a result of the oxidation of 1,2,3-propanetriol. To fulfil the aim unstable radical originated in 1,2,3-propanetriol was trapped by PBN. Resulted spin adduct was measured using EPR spectroscopy and the isotropic hyperfine coupling constants a_iso (¹⁴ N) and a_iso (¹ H) were obtained by simulation of the EPR spectrum. The next step consisted of conducting a comparative analysis of EPR parameters, based on the calculations conducted at the DFT and MP2 methods level in open-shell formalism including solvent effects. For comparison, calculations were also carried out at the level of combined methods (UB3LYP/QCISD and UMP2/QCISD) in terms of the ONIOM formalism. Comparison of the experimental EPR data of the isotropic hyperfine coupling constants a_iso (¹⁴ N) and a_iso (¹ H) with the calculated parameters indicate that oxidation of 1,2,3-propanetriol leads to a carbon centred radical where unpaired electron is situated on the second (middle) carbon of 1,2,3-propanetriol. What is important, this conclusion could be made regardless of the chosen calculation method. However, it could be stated that for calculation of the isotropic hyperfine coupling constants a_iso (¹⁴ N) and a_iso (¹ H) of PBN/gly• adducts, UMP2 polarisable conductor calculation model with two ethanol molecules is explicitly defined.