Oxidative Stability Research Articles

Minimal doping approach to activate lattice oxygen participation in K2WO4 electrocatalysts for oxygen evolution reaction

Understanding oxygen redox processes is pivotal for advancing oxygen evolution catalysts, critical in electrochemical devices for renewable fuel synthesis. Thermodynamic instability of high entropy metal oxides can interfere with oxygen redox reactions via electrochemical reconstruction. Transforming a W5N4 pre-catalyst into thermodynamically stable K2WO4 through electrochemical treatment in KOH, and incorporating minimal Fe doping, modifies the oxygen evolution reaction (OER) pathway towards oxygen redox activity, significantly influenced by the pH of the electrolyte. The Fe-doped K2WO4 catalyst demonstrates superior OER performance, achieving 10 mA/cm^2 at an overpotential of merely 181 mV (without iR compensation) and sustaining a lifetime of 1200 h at 1000 mA/cm2. Electrochemical methods and DFT calculations confirmed Fe doping creates oxygen vacancies and increases electron density near the Fermi level, enhancing the OER pathway. This methodology offers a versatile approach to adapt high entropy catalysts for broad electrochemical energy conversion applications, highlighting its potential for innovation in renewable energy technologies.

Sunflower oil‐soybean wax oleogel: An oxidation stable alternative to traditional frying methods for doughnut

AbstractDeep‐frying changes the quality of the oil through hydrolysis, oxidation, and polymerization, which makes both positive and harmful changes in the oil and fried food items. In this study sunflower oil was combined with soybean wax to create oleogels that were assessed for their ability to reduce fat uptake and maintain oxidative stability during the deep‐fat frying of doughnut samples. The oleogel was tested as a potential alternative to traditional deep‐fat frying with sunflower oil for frying doughnuts. The different frying times of oleogel were examined to assess the physical properties of the oleogel. Afterward, a comparative analysis was conducted between doughnuts fried in sunflower oil and oleogel. The results showed that doughnuts fried in oleogel absorbed approximately 37.8% less oil than those fried in sunflower oil. Additionally, the doughnuts fried in oleogel had a better appearance, with a higher lightness value (L*) (87.73 ± 0.8) than those fried in oil (77.72 ± 1.35). Moreover, the redness value, (a*) of oleogel doughnuts was also lower (0.33 ± 0.25) than those fried in oil (0.37 ± 0.9). The blueness or yellowness (b*) of the doughnuts was not significantly different which was found as 1.52 and 1.54, for oleogel and oil samples, respectively. Although the viscosity values of oleogel were higher during extended frying, the lower peroxide, free fatty acid, p‐Anisidine, conjugated diene, and triene values suggest that oleogel is more stable. These results will provide a significant advantage in the usage of sunflower oil‐soybean wax oleogel as a frying medium with improved stability.

Oxidation and Flammability Tests for Grape (Vitis vinifera L.) Seed Oil

In this work, studies were performed on oxidative stability by determining the transmittance spectra, the components and trichomatic coordinates, and the color differences for grape seed oils (GSO) subjected to a forced oxidation treatment at temperatures of 100 °C and 120 °C, for 4, 8 and 10 h. For this purpose, a constant airflow of 30 L/min was used. GSO was also subjected to flammability tests on a heated cylindrical surface to determine the lowest temperature at which this oil ignites, correlated with the highest temperature at which the oil does not ignite. According to the results, these temperatures are 475 °C and 470 °C, respectively. At these temperatures, the tested oils were darker in color than the reference oil, with the L* parameter having lower values (91.53 and 89.56, respectively). In addition, the correlation coefficients between the evaluated parameters were significant (p ≤ 0.05).

Application of Primary Phosphine Oxides in Domino‐Phospha‐Aldol Reactions of Diketones

AbstractAn approach for the preparation and stabilization of primary phosphine oxides is presented complementing previous methods of in situ generation. Specifically, RP(O)H2 where R=benzyl (Bn), cyclohexyl (Cy), 2‐naphthyl (2‐Naph), phenyl (Ph), tert‐butyl (t‐Bu) was prepared by controlled oxidation of the corresponding primary phosphine in presence of ferrocene as stabilizing reagent. The primary phosphine oxides were characterized using NMR and MS and studied in twofold hydrophosphorylation of diketones. The domino‐phospha‐aldol reaction catalysed with 5 mol% of sodium methoxide yielded five‐, six‐ and seven‐membered heterocyclic tertiary phosphine oxides with a high degree of stereoselectivity, as confirmed by single X‐ray diffraction.

Fe,Ce Co-Doped Ni3S2/NiS Polymorphism Nanosheets with Improved Electrocatalytic Activity and Stability for Water Oxidation.

Balancing the relationship between electrocatalytic activity and stability of sulfide catalysts during oxygen evolution reaction (OER) has been attracting extensive research interest. Here, a simple electrodeposition-vulcanization two-step route was designed to successfully construct nickel foam supported sheet-like Fe,Ce-codoped Ni3S2/NiS polymorphism catalyst (labeled as Fe,Ce-Ni3S2/NiS/NF). Electrochemical measurements showed that the as-obtained Fe,Ce-Ni3S2/NiS/NF electrode presented excellent OER electrocatalytic performances. In 1 M KOH solution, merely 173 and 234 mV of overpotentials were required to deliver the current densities of 10 and 100 mA cm-2, respectively. Further investigations revealed that the Fe,Ce co-doping regulated the electron density around Ni, which promoted the conversion of Ni towards the higher valence state and simultaneously, avoided the stability decrease of the catalyst caused by excessive oxidation corrosion. Moreover, the defects generated during vulcanization also contributed to promoting water oxidation. The present work provides a facile and feasible approach to balance the relationship between the stability and the activity of sulfide catalysts for OER.

Effect of White Pomace Seasoning as a Natural Antioxidant for Chicken Products Packaged in Vacuum or Modified Atmosphere Conditions

Chicken breasts and burgers (88% breast and 12% backfat) were evaluated for physicochemical characteristics, thiobarbituric acid reactive substances (TBARS), and antioxidant capacity during storage in vacuum or atmosphere conditions for 18 days at 4 °C using the following two formulations: one without incorporating white pomace seasoning (WPS) and another with 3% WPS. The WPS was obtained from white grape skins, a byproduct resulting from the elaboration of white wine. The addition of the WSP decreased the L* values and increased the a* values, resulting in a significant turning toward brown tones in the chicken products. The addition of 3% of WSP led to higher values of ABTS and FRAP, regardless of the type of packaging. Both types of packaging significantly increased the levels of TBARS, although vacuum packaging proved more effective in protecting against lipid oxidation compared to modified atmosphere package (MAP). Additionally, the WSP improved the oxidative stability regarding the TBARS values. In conclusion, the WSP could be a viable alternative to chemical antioxidants and would lead to healthier and innovative chicken products.

Chemical and structural transformations of lignin in sesame seed hull during roasting

To investigate the mechanism of lignin degradation during sesame roasting, structural transformations of milled wood lignin (MWL) from sesame seed hull samples roasted at 190–250 °C for 30 min were investigated. The findings revealed that, with increasing temperature, the degradation extent of carbohydrates from lignin carbohydrate complex in the fractions deepened, which reduced total sugar content (from 8.59 % to 0.45 %). Compared to that of the original sesame seed hull lignin (LSSH), the molecular weight of MWL fractions showed a tendency to decline (Mw 4377–2235 Da) with the rise of roasting temperature (210–250 °C). During roasting, lignins in the sesame seed hull underwent degradation and condensation. Due to demethoxylation, the H-type lignin proportion increased from 2.7 % to 26.1 %. Compared to G- and C-type lignin, S-type lignin was more stable. The β-O-4 linkages decreased from 5.8 to 1.2/100 Ar due to CO bond breaking, and β-β linkages from 26.3 to 9.6/100 Ar decreased due to condensation of CC. As the roasting temperature increased, more chemical bonds between lignin structural units were broken, resulting in the generation of more phenolic hydroxyl groups (1.80–2.53 mmol/g). This study helps to elucidate the contribution of lignin degradation during roasting to the oxidative stability of sesame oil.

Effects of natural and synthetic antioxidants addition on the characteristic flavor and metabolites of walnut oil during oxidation

Antioxidants are commonly used to enhance the oxidative stability of oils, while its effects on flavor are rarely investigated. In this paper, the antioxidant capacity of two synthetic and two natural antioxidants in walnut oil (WO) were evaluated firstly. Tert-butyl hydroquinone (0.2 g/kg, TBHQ 0.2) and rosemary extract (0.5 g/kg, RE 0.5) exhibited better antioxidant activity. The volatile organic compounds (VOCs) profile changes of WO with TBHQ and RE addition were explored. It is suggested that TBHQ 0.2 and RE 0.5 can effectively delay the increase of VOCs, especially aldehydes. The concentrations of differential metabolites of WO during oxidation including 1-octen-3-ol, hexenal, and (E)-2-heptenal in RE 0.5 were lower than TBHQ 0.2 group, which were original from linolenic acid and linoleic acid. Sensory evaluation indicated TBHQ and RE can maintain the original aroma of WO during oxidation, while RE can enhance the green and fruity aroma.

Effect of wet media milling on starch-quercetin complex: Enhancement of Pickering emulsifying ability and oxidative resistance

This research explored the effect of media milling on complexation of corn starch (CS) and quercetin (QC), interaction mechanism and Pickering emulsifying ability of corn-quercetin (CS-QC) complex. CS-QC with QC/CS ratio of 1:24 had the highest encapsulation efficiency of 76.00 ± 1.30 %. Average volume-mean diameter, average whole molecular size (Rh) and debranchedamylopectinchain length of CS-QC were significantly decreased after milling. Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) spectra confirmed the complexation between CS and QC. Emulsifying capacity and emulsion stability of Pickering emulsion stabilized by 5 % CS-QC complex particles after 120 min milling reached 100.00 % and 100.00. Pickering emulsions stabilized by these complex particles demonstrated superior oxidative stability. These results demonstrated that media milling could be an efficient physical approach to obtain starch-polyphenol complex by enhancing non-covalent interactions, which could not only be used as food-grade Pickering emulsifiers, but also retard lipid oxidation.

Oxidative stability and nutritional quality of stored Linum usitatissmium L. and Argania spinosa L., oil blends: Chemical compositions, properties and nutritional value

Identification of the chemical compositions of fatty acids and tocopherols shows the high content of linum usitatissimum oil (LO) by linolenic acid 55.3735% and γ-tocopherol 570.927 mg/kg, while argania spinosa oil (AO) is known by the dominance of oleic acid 47.77% followed by linoleic acid 31.08% as well as tocopherols by γ-tocopherols 687.485 mg/kg and δ-tocopherols 51.035 mg/kg. This difference in compositions enables us to enrich the low-stability oil and monitor its behavior during storage at a specific time and under specific conditions. In this study, pure linum usitatissimum and argania spinosa oils extracted by cold pressing as well as their formulations at proportions of (LO: AO) respectively: (80:20; 60:40, 50:50; 40:60; 20: 80) were oxidized at 60 °C for 28 days of storage, during which time the pure oils and blends were assessed for oxidative stability by studying their different fatty acid and tocopherol profiles and physicochemical characteristics such as acidity, peroxide value and chlorophyll and carotenoid pigments, as well as nutritional indexes such as the atherogenic index (AI), the thrombogenic index (TI), and the hypocholesterolemic: hypercholesterolemic ratio (HH), ω3:ω6 ratio, also the oxidative susceptibility (OS), and oxidazability value (Cox), and total phenolic compounds (TPC).

Comparative Analysis of Grape Seed Oil, Linseed Oil, and a Blend: In Vivo Effects of Supplementation.

Grape seeds are rich in bioactive substances, including polyphenols, terpenoids, and phytosterols. Linseed (Linum usitatissimum L.) boasts a high concentration of polyunsaturated fatty acids (PUFAs), lignans, phytoestrogens, and soluble fibers, all contributing to its therapeutic potential. In this study, we pioneered the formulation of an oil blend (GL) combining grape seed oil (G) and golden linseed oil (GL) in equal volumes (1:1 (v/v)) and we evaluated in terms of the nutritional, physical, and chemical properties and their influence in an in vivo experimental model. We analyzed the oils by performing physical-chemical analyses, examining the oxidative stability using Rancimat; conducting thermal analyses via thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC), performing optical UV-vis absorption analyses; examining the fluorescence emission-excitation matrix, total carotenoids, and color, and conducting metabolic assessments in an in vivo experimental trial. The fatty acid profile presented a higher fraction of linoleic acid (C18:2) in G and GL and alpha-linolenic acid (C18:3) in L. The acidity and peroxide indices were within the recommended ranges. The TG/DTG, DSC, and Rancimat analyses revealed similar behaviors, and the optical analyses revealed color variations caused by carotenoid contents in L and GL. In the in vivo trial, G (G2: 2000 mg/kg/day) promoted lower total consumption, and the blend (GL: 2000 mg/kg/day) group exhibited less weight gain per gram of consumed food. The group with G supplementation (G2: 2000 mg/kg/day) and GL had the highest levels of HDL-c. The group with L supplementation (L2: 2000 mg/kg/day) had the lowest total cholesterol level. The L2, G1 (1000 mg/kg/day), and G2 groups exhibited the lowest MCP-1 and TNF-α values. Additionally, the lowest adipocyte areas occurred in G and GL. Our results suggest that this combination is of high quality for consumption and can influence lipid profiles, markers of inflammation, and antioxidant status.

High-Temperature Oxidation and Phase Stability of AlCrCoFeNi High Entropy Alloy: Insights from In Situ HT-XRD and Thermodynamic Calculations.

The high-temperature oxidation behaviour and phase stability of equi-atomic high entropy AlCrCoFeNi alloy (HEA) were studied using in situ high-temperature X-ray diffraction (HTXRD) combined with ThermoCalc thermodynamic calculation. HTXRD analyses reveal the formation of B2, BCC, Sigma and FCC, phases at different temperatures, with significant phase transitions observed at intermediate temperatures from 600 °C-100 °C. ThermoCalc predicted phase diagram closely matched with in situ HTXRD findings highlighting minor differences in phase transformation temperature. ThermoCalc predictions of oxides provide insights into the formation of stable oxide phases, predominantly spinel-type oxides, at high p(O2), while a lower volume of halite was predicted, and minor increase observed with increasing temperature. The oxidation behaviour was strongly dependent on the environment, with the vacuum condition favouring the formation of a thin, Al2O3 protective layer, while in atmospheric conditions a thick, double-layered oxide scale of Al2O3 and Cr2O3 formed. The formation of oxide scale was determined by selective oxidation of Al and Cr, as further confirmed by EDX analysis. The formation of thick oxide in air environment resulted in a thick layer of Al-depleted FFC phase. This comprehensive study explains the high-temperature phase stability and time-temperature-dependent oxidation mechanisms of AlCrCoFeNi HEA. The interplay between surface phase transformation beneath oxide scale and oxides is also detailed herein, contributing to further development and optimisation of HEA for high temperature applications.

Spectroscopic and chemometric analysis and oil stability index characterization of thermo‐oxidized edible vegetable oils

AbstractEdible vegetable oils are sources of polyunsaturated fatty acids, necessary for a balanced diet capable of providing elements that act on the energetic, structural, and hormonal composition of humans. The growing consumption of these foods has encouraged the search for techniques capable of characterizing their compositions and transformations when subjected to industrial processes or during domestic use. We propose to analyze the transformations undergone by edible vegetable oils originating from different plants due to thermal oxidation. For this, dynamic viscosity, oxidative stability index, fatty acid profile, and infrared spectra determined before and after being subjected to thermal oxidation. The results from infrared spectroscopy were improved through Principal Component Analysis (PCA). Among other results, it was possible to establish correlations between the FTIR spectra, dynamic viscosity, and the profile of fatty acids, allowing the prediction of the concentration of polyunsaturated fatty acids (PUFA) after thermal oxidation by measuring the spectrum of samples before the thermal oxidation process. Furthermore, it is observed that the dynamic viscosity is strongly altered by thermal oxidation, which is directly related to the decrease in PUFA content. The results obtained can be used to predict quality factors of edible vegetable oils, helping to choose the right type of oil for each industrial or domestic process.Practical Applications: This research holds significant practical implications, particularly in detecting adulteration and fraud of edible vegetable oils. The developed method uses physicochemical properties and infrared spectroscopy with principal component analysis to characterize oils and to determine the oil stability index.

Controle de temperatura com PID e iluminação com tensão contínua para a avaliação do efeito sobre o índice de estabilidade do óleo de soja (Glycine max)

Currently, food products, such as oil, are displayed at high lighting intensities and sometimes at temperatures above 20 °C, factors that can accelerate oxidative rancidity, such as degradation of oil quality. This is the reason why a PID (Proportional-Integral-Derivative) control system was implemented that allowed quality tests to be carried out on the oil stored in different temperature conditions (13 °C to 27 °C). During these tests, the transfer function of the system and the controller, was found using the automatic tuning of the control box. This improved the precision and continuous voltage for illumination (from 155 lux to 1145 lux) by varying the intensity of the LEDs. For the experimental design, the central composite design (CCD) was used, resulting in 13 treatments. After 30 days, the quality of the oil was evaluated (acidity index and peroxide index), and the oxidative stability index was determined using the Rancimat method. It was found that temperature and lighting have a significant effect on the quality and oxidative stability of the oil (p < 0.05), achieving the storage condition with greater stability at 300 lux of lighting and 15 °C temperature.

Exploring fatty acid composition, bioactive compounds, and antioxidant properties in oils of newly developed sesame mutant lines in Morocco

AbstractSesame (Sesamum indicum L.) is renowned for its significance as a global oilseed crop, valued for its high oil content and nutritional properties. This study aimed to explore the fatty acid composition, bioactive compounds, and antioxidant attributes of sesame mutant oils, examining their potential applications in food industry. Nine M4 mutants, along with their parents, were grown in two contrasting environments (Taoujdate and Afourare) to investigate their seed oil, phenolic and flavonoid contents, the balance between omega‐6, omega‐9, and omega‐3 fatty acids, iodine value, and susceptibility to oxidation. Genotype and environment main effects as well as their interaction had a significant effect on the majority of the parameters studied. The mutant “US2‐1” stands out with a distinctive fatty acid profile, featuring the highest saturated fatty acids, ω‐6/ω‐9 ratio, and omega‐3 content, in addition to its high total flavonoid content and remarkable oxidative stability. “ML2‐10,” “US1‐2,” “US2‐6,” and “US2‐7” exhibit high oil content, coupled with substantial levels of phenols and flavonoids, rendering them excellent candidates for culinary and industrial applications where oxidative stability is important. “ML2‐68,” “ML2‐72,” “US06,” “US1‐DL,” and “US1‐3” offer versatile options with their moderate oil content and fatty acid profiles that resist oxidation. This research highlights the potential for breeding sesame mutants tailored to specific applications, contributing to both enhanced oil production and improved nutritional value. The insights gained here pave the way for the development of sesame varieties with superior nutritional and functional attributes, thereby promoting the sustainable production and consumption of sesame oil.

Correlation Study of Multi-Element Composition and Oxidative Stability of Ziziphus Lotus Lam. Seed Oils Collected from Different Regions of Tunisia

Correlation Study of Multi-Element Composition and Oxidative Stability of Ziziphus Lotus Lam. Seed Oils Collected from Different Regions of Tunisia

Chitosan-Based Oleogels: Emulsion Drying Kinetics and Physical, Rheological, and Textural Characteristics of Olive Oil Oleogels.

Oleogels are of high interest as promising substitutes for trans fats in foods. An emulsion-templated method was used to trap olive oil in the chitosan crosslinked with vanillin matrix. Oil in water emulsions (50:50 w/w) with different chitosan content (0.7 and 0.8% w/w) with a constant vanillin/chitosan ratio (1.3) were air-dried at different temperatures (50, 60, 70, and 80 °C) and freeze-dried (-26 °C and 0.1 mbar) to produce oleogels. Only falling rate periods were determined during air-drying kinetics and were successfully modeled with empirical and diffusional models. At a drying temperature of 70 °C, the drying kinetics were the fastest. The viscoelasticity of oleogels showed that the elastic modulus significantly increased after drying at 60 and 70 °C, and those dried at 50 °C and freeze-dried were weaker. All oleogels showed high oil binding capacity (>91%), but the highest values (>97%) were obtained in oleogels with a threshold elastic modulus (50,000 Pa). The oleogels' color depended on the drying temperature and chitosan content (independent of the drying method). Significant differences were observed between air-dried and freeze-dried oleogels with respect to oxidative stability. Oxidation increased with the air-drying time regardless of chitosan content. The found results indicated that drying conditions must be carefully selected to produce oleogels with specific features.

Improving oxidative stability of cream powder using pomegranate concentrate and peel extract

AbstractIn this study, the influence of pomegranate peel extract (PPE) and pomegranate concentrate (PC) on improving the oxidative stability of cream powder in comparison with synthetic antioxidant (Butylated hydroxytoluene (BHT)) during the storage period at 20°C (8 weeks) and 45°C (4 weeks) was evaluated. The finding exhibited that peroxide, p‐anisidine, and total oxidation (TOTOX) values increased during the storage period. Samples containing PPE and PC showed suitable performance in controlling the cream powder oxidation. Also, PPE showed the highest antioxidant activity and can be proposed as a suitable replacement for a synthetic antioxidant (BHT). L* and b* values increased, while a* value decreased during the storage period. Also, the pH of the powders decreased significantly throughout the storage (reached nearly 6). Microbial counts of cream powders did not change during the storage period. The control sample showed the highest overall acceptability. Antioxidants of pomegranate can be proposed to control the oxidative stability of fat‐rich food products.

Investigating the impact of wet rendering (solventless method) on PUFA-rich oil from catfish (Clarias magur) viscera.

Catfish (Clarias magur) is a popular freshwater fish food worldwide. The processing of this fish generates a significant amount of waste, mainly in the form of viscera, which constitutes around 10-12% of the fish's total weight. This study was focused on extracting polyunsaturated fatty acid (PUFA)-rich oil from catfish viscera, aiming to enhance the extraction process and make the production of oil and handling of fish byproducts more cost-effective. The wet reduction method, a solvent-free approach, was used for extraction, with yield optimization done via the Box-Behnken design. The resulting oil was evaluated for its oxidative quality and chemical characteristics. The optimal conditions for the wet rendering process were as follows: viscera to water ratio, 1:0.5 (w/v); temperature, 90℃; and time, 20 min, yielding 12.40 g/100 g of oil. The oil extracted under optimal wet rendering conditions had quality and oxidative stability comparable to solvent extraction and fewer secondary oxidation compounds. This oil had a higher PUFA content, specifically a 4:1 ratio of omega 6 to omega 3. Such oil, derived from catfish viscera, is suitable for the food industry due to its solvent-free extraction method.

Performance of Aromatic Amine-Modified Metallocene Polyalphaolefin Lubricant Base Oil

With the continuous advancement of industrial technology, higher demands have been placed on the properties of gear oils, such as oxidation stability and shear resistance. Herein, the oxidation stability of high-viscosity metallocene poly-α-olefins (mPAOs) was improved by chemical modification via aromatic amine alkylation. The modified mPAO base oils were synthesized separately with diphenylamine (mPAO-DPA) and N-phenyl-α-naphthylamine (mPAO-NPA), and their applicability in industrial gear oil formulations was evaluated. The composition and physicochemical properties of the obtained samples were assessed using 1H NMR spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, and the American Society for Testing and Materials standards (ASTM D445, ASTM D2270, ASTM D92, etc.) confirming the successful completion of the alkylation reaction. The oxidation stability of the samples was also evaluated using pressurized differential scanning calorimetry. The initial oxidation temperature of mPAO-NPA (230 °C) was 53 °C higher than that of mPAO, and the oxidation induction period of mPAO-DPA was nearly twice that of mPAO-NPA. Thermogravimetric analysis in air revealed the increased thermal decomposition temperature and improved thermal stability of modified mPAO. ISO VG 320 industrial gear oils were formulated using mPAO alkylated with N-phenyl-α-naphthylamine(Lub-2) and commercially purchased PAO100 (Lub-1) as base oil components. The antioxidant performance of two industrial gear oils was evaluated through oven oxidation and rotating oxygen bomb tests. The oxidation induction period of Lub-2 was 30% higher than that of Lub-1, with the latter having a lower acid number and a smaller increase in viscosity at 40 °C. Finally, the friction performance of the samples was assessed on a four-ball friction tester, revealing the synergistic effect of the mPAO-NPA base oil with the HiTEC 3339 additive, forming a more stable oil film with a smaller wear scar diameter.