Low Oxidative Stability Research Articles

Composition and oxidative stability of silflower (Silphium integrifolium) seed oil and its potential as a new source of squalene

AbstractSilphium integrifolium Michx. (silflower), a perennial plant, is of great interest as a potential new oilseed crop due to its long, strong, deep, extensive root systems, which can prevent erosion, capture dissolved nitrogen, and out‐compete weeds eliminating the need for frequent irrigation and herbicide uses. In this study, oil was extracted from unhulled silflower seeds, and its composition and oxidative stability were evaluated. The oil content in unhulled silflower seeds was 15.2% (wt/wt), and its fatty acid composition was similar to that of sunflower oil. The level of total polar compounds (TPC) in the oil was 12.3% (wt/wt), and the content of total phenolics was 1.12 mg gallic acid equivalent (GAE)/g oil. Noteworthily, 4.89% squalene was isolated from silflower oil indicating its potential application as an alternative source of squalene. Silflower oil had lower oxidative stability as indicated by the oxidative stability index (OSI) at 110°C and thermogravimetric analysis (TGA), presumably due to its high level of chlorophyll (1002.8 mg/kg). Even after a typical refining process involving degumming, alkali refining, and bleaching with Fuller's earth, silflower oil contained 725.5 mg/kg chlorophyll, and its oxidative stability was not improved. Further treatments with bleaching agents including bentonite, sepiolite, and Tonsil® lowered the chlorophyll level to 4.2, 474.5, and 38.5 mg/kg, respectively, and some aspects of oxidative stability were improved and better than those of refined sunflower oil. This study presents the potential of silflower oil as new edible oil and a great plant source of squalene.

Catalytic Upgrading of Biodiesel by Partial Hydrogenation of Its FAME Composition: A Systematic Review

Biodiesel is one of the most popular biofuels as it is a promising substitute for conventional diesel fuel, but for now, it cannot be used as a stand-alone fuel due to its low oxidative stability. For this reason, there have been efforts to upgrade biodiesel in the last few years through the partial hydrogenation of its fatty acid methyl esters (FAMEs). This procedure succeeds in resolving the problem of low oxidative stability, but in some cases, a new issue arises as non-selective hydrogenation deteriorates the fuel’s cold flow properties, which are crucial for vehicle’s operation without damaging the vehicle’s engine. More specifically, the problem of deteriorated cold flow properties is caused by the formation of trans-monounsaturated and fully saturated FAMEs during the hydrogenation reaction. Hydrogenated biodiesels are preferred to contain more cis-monounsaturated FAMEs because these are considered to have the best combination of high oxidative stability and good cold flow properties. As a result, various systems and methods have been tested to achieve selective partial hydrogenation of biodiesel FAMEs. In this review article, the catalytic systems and processes that stood out in various research studies are presented, and the factors that lead to the best possible outcome are investigated and discussed.

Characterization, physical properties, and potential industrial applications of high oleic pennycress oil

Field pennycress (Thlaspi arvense L.) has been adapted as an off-season cover crop for the midwestern United States. It is a non-food crop that can be grown as a winter annual crop and harvested in-between corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) seasons. High oleic pennycress (HOP) has been developed from field pennycress with the intention of producing pennycress oil with more desirable properties for industrial applications. In this work, the composition and physical properties of HOP oil have been characterized. As expected, the oil was predominantly composed of oleic acid (62.6%) and had a low saturated fatty acid content (4.1%). The cold flow properties of HOP oil were superb, with a cloud point of − 24 °C and a pour point of − 35 °C. Additional properties including antioxidant content, viscosity, oxidative stability, and lubricity were analyzed. Compared with field pennycress oil, HOP oil had better cold flow properties, but lower oxidative stability and antioxidant content. Thus, HOP oil has advantages in low temperature applications, while field pennycress oil is more suitable for high temperature applications. Structure property relationships between the fatty acid composition and physical properties of the oils are discussed.

Inorganic Ultra-Rich Solid Composite Electrolytes for High-Voltage Solid-State Batteries

Solid-state batteries (SSB), in which flammable organic liquid electrolytes are replaced by inherently safer solid electrolytes (SEs), are considered to be the evolution of current Li-ion battery technology toward greater safety and higher energy density. Among the various SEs, the PEO-LiTFSI system has been the most studied due to its low cost and ease of processing. However, the relatively low oxidation stability of PEO-LiTFSI at about 4.0 V vs. Li/Li+ does not allow the use of high-voltage cathode active materials, which limits the available energy density [1]. We propose that a high content of Li-ion conductive ceramic in the PEO-LiTFSI matrix increases oxidation stability, allowing stable cell cycling with Ni-rich NMC cathode at higher voltages. This class of inorganic ultra-rich composite SEs has attracted much interest recently [2, 3].In this work, we present a self-standing, dense, flexible (Fig.1a), and thermally stable (Fig.1b) composite solid electrolyte (INURSE 30) that has an ultra-high content of Li-ion conductive LLZO (90 wt%, as confirmed by TGA in Fig. 1b)in the PEO-LiTFSI matrix. The ionic conductivity of INURSE 30 is 1.4x10-5 S/cm at 60ºC. The INURSE 30 electrolyte shows long-term cycling stability of more than 2000 h at a current density of 0.01 mA/cm2 in symmetric cells with Li electrodes. In addition, the high-voltage stability of INURSE 30 was demonstrated in solid-state cells with a composite solid-state cathode containing 75 wt% NMC622 and a Li metal anode. The Li/INURSE 30/NMC622 coin cell shows good coulombic efficiency and capacity retention, as shown in Fig.1c. K.V. acknowledges the financial support from Fundacíon CIDETEC and DESTINY PhD programme which received funding from the European Union's Horizon2020 research and innovation programme under the Marie Skłodowska-Curie Actions COFUND - Grant Agreement No: 945357.

Stability of Flavan-3-ols, Theaflavins, and Methylxanthines in 30 Industrial Green, Black, and White Tea (Camellia sinensis L.) Extracts Characterized via Liquid Chromatography Techniques.

Commercially available tea extracts for dietary supplements and nutraceuticals are standardized to characteristic components of Camellia sinensis L., such as epigallocatechin gallate (EGCG) and total catechins or polyphenols. However, since most commercial tea extracts are highly concentrated into only one molecule such as EGCG, the comparatively less stable catechin, the oxidative stability of the extract during the 24-month shelf life was questioned. It was hypothesized that the overall oxidative stability is reduced for highly purified/concentrated tea extracts due to the absence of other natural antioxidants stabilizing the complex mixture. Via liquid chromatographic analysis, the individual chromatographic profiles of 30 commercial white, green, and black tea extracts were evaluated and compared regarding oxidative stability and functional properties. The contents of bioactive flavan-3-ols, theaflavins, and methylxanthines differed much from what was claimed by the suppliers. At the end of the product shelf life, most of the commercial green and black tea extracts showed a decrease in the flavan-3-ol content, the main bioactive components of tea. A high EGCG content to the detriment of other possibly stabilizing flavan-3-ols or antioxidants in tea was found to explain the lower oxidative stability of such tea extract products. A natural overall composition of molecular structures was found to be superior to a strong enrichment in just one molecule.

HIDROGENASI MINYAK KEDELAI DENGAN VARIASI MASSA KATALIS PALLADIUM

Soybean oil, also known as vegetable oil, consists of triglycerides such as saturated and unsaturated fatty acids. However, this soybean oil has low oxidative stability when stored at room temperature and used at high temperatures. Hydrogenation is carried out to obtain oxidation stability and will reduce double bonds including trans fatty acids. The use of palladium catalyst is the most potential in the hydrogenation process. This research was conducted in two conditions, experiment 1 and experiment 2. With temperature conditions of 75oC, pressure of 1 atm, using a reactor equipped with a stirrer at a speed of 450-520 rpm. In experiment 1, the palladium catalyst was not activated and hydrogen gas entered through the bottom of the reactor. In experiment 2, the palladium catalyst was activated with NaOH while hydrogen gas entered through the side of the reactor. Iodine number analysis method used is the Wijs method. The results of experiment 1, so that the value of the iodine number can be below 100 gr I2/gr of oil, while in the results of experiment 2, the value of the lowest iodine number is at a value of 110 gr I2/g of oil. The main influencing factors in our research a hydrogen gas turbulence, palladium catalyst activation and stirring.

Optimization of Carotenoid Extraction from Yellow Passion Fruit Pomace Using Ultrasound-assisted Extraction and Coconut Oil as a Solvent

Passion fruit pomace, a by-product of passion fruit juice processing, is a source of carotenoids that can be utilized for food products as an antioxidant. The purpose of this study was to determine the optimum condition of carotenoid extraction process from passion fruit pomace using ultrasonic waves with coconut oil as a solvent, to determine the physicochemical properties of carotene-enriched coconut oil and the physicochemical properties of carotene-enriched coconut oil blended with sesame oil. The variables studied were extraction time (X1) and extraction temperature (X2). Response Surface Methodology (RSM) with the design of Central Composite Face-centered Design (CCF) is used to obtain a mathematical model that corresponds to the relationship between total carotenoid and the variables that influence it. After that, coconut oil will be evaluated on its quality including total carotenoids and antioxidant activity, compared to extraction with conventional methods (maceration). Sesame oil was blended with the carotene-enriched coconut oil extract to improve its antioxidant stability. The results showed that the optimum condition of the yellow passion fruit pomace carotenoid extraction with ultrasound-assisted extraction was 30 minutes and at 35 °C. Characteristics of carotenoid-enriched coconut oil from ultrasound-assisted extraction had higher total carotenoid content (15.79 μg of carotenoids/g oil) compared to conventional extraction (9.47 μg of carotenoids/g oil) and had higher antioxidant activity (80%RSA). Characteristics of mixed oils between carotenoid-enriched coconut oil and sesame oil have higher peroxide, lower Oxidative Stability Index, and higher antioxidant activity.

An Overview of Physicochemical Properties and Engine Performance Using Rubber Seed Biodiesel–Plastic Pyrolysis Oil Blends in Diesel Engines

Rubber Seed Biodiesel (RSB) and Plastic Pyrolysis Oil (PPO) deserve to be considered as alternative fuels for diesel engines, because of their advantages such as large raw material resources, derived from free or waste feedstock and the use of plastic waste as fuel can prevent environmental pollution. Due to their almost identical densities, RSB and PPO can be mixed homogeneously. In general, the use of a mixture of RSB and petroleum diesel in diesel engines shows positive performance, both engine performance and emissions, as well as the use of mixed PPO and diesel fuel. Although RSB has a good cetane number and flash point, on the other hand, RSB also has disadvantages in its physiochemical properties, such as low oxidation stability, high acid value, low heating value, and high viscosity. Likewise, PPO has good oxidation stability, acid value, and viscosity, but the flash point, CO, and HC emissions are also bad. This article tries to describe the opportunity to mix RSB and PPO, to find the best composition between RSB and PPO which shows the best fuel physiochemical properties and engine performance.

Tiger Nut Oil-Based Oil Gel: Preparation, Characterization, and Storage Stability.

In this study, Tiger nut (Cyperus esculentus L.) oil-based oleogels were prepared using the emulsion template method with whey protein (WPI; 0.5-2.5% (w/v) and Xanthan gum (XG; 0.1-0.5% (w/v). The microstructure of the oleogels obtained from the high internal phase emulsion (HIPE) and an emulsion after further shearing were observed using an optical microscope and laser confocal microscopy. A series of rheological tests were conducted to evaluate the effect of WPI and XG concentrations on the strength of the emulsion and oleogel. The texture, oil holding capacity, and oxidative stability of oleogels were characterized. The results showed that XG alone could not form oleogel, while the concentration of WPI had more effect than XG. When WPI was at a fixed concentration, the viscoelasticity of HIPE increased with the addition of XG. This was due to the complexation of WPI and XG, forming a stable gel network between the tight emulsion droplets and thus giving it a higher viscoelasticity. With an increase in WPI concentration, the stability and viscoelasticity of the emulsion were increased, and the oil-holding capacity and gel strength of the oleogels were enhanced. Moreover, the addition of XG could significantly enhance the stability and viscoelasticity of the emulsion (p < 0.05), and an increase in the concentration had a positive effect on it. The oleogels showed high gel strength (G' > 15,000 Pa) and good thixotropic recovery when the XG concentration was higher than 0.3% (w/v). WPI (2.0%) and XG (>0.3%) could be used to obtain HIPE with good physicochemical and viscoelastic properties, which in turn lead to oleogels with minimal oil loss, viscoelastic and thixotropic recovery, and temperature stability. Compared with tiger nut oil-based oleogel, tiger nut oil contained more polyunsaturated fatty acids, which were more easily decomposed through oxidation during storage and had lower oxidation stability. This study provides a reference for the preparation of oleogels from food-approved polymers and provides additional theoretical support for their potential application as solid fat substitutes.

PSV-4 Proteomics and Metabolomics Profiling of Meat Exudate to Understand the Impact of Postmortem Aging on Oxidative Stability of Beef Muscles

Abstract The objectives of this study were to characterize the meat exudate proteome and metabolome composition that may be related to the color and oxidative stability of beef muscles during aging. Beef longissimus lumborum (LD) and psoas major (PM) muscles from seven carcasses were obtained at 2 d postmortem. Each muscle was cut into three sections, vacuum packaged and assigned into three aging periods (9, 16 and 23 d). At the end of each aging period, the exudate was collected from each sample and immediately frozen for both proteomics and metabolomics analyses. Steak cuts were made for display color and oxidative stability analyses. Exudate samples were prepared and analyzed using the UPLC-ESI-MS for metabolomics profiling and HPLC-MS/MS for proteomics analyses. The metabolites were annotated using the HMDB database, and proteins were compared with the UniProt database. The relative abundance of the metabolites and proteins was quantified and normalized for statistical analysis. Both proteomes and metabolites were analyzed using ANOVA (P &amp;lt; 0.05). Principal component analysis (PCA), hierarchical cluster analysis (HCA) and correlation test between color and lipid oxidative stability and metabolites/proteins were performed. Untargeted protein profiling identified a total of 737 proteins from the meat exudate, of which 222 proteins were affected by the treatments (P &amp;lt; 0.05). PCA analysis indicated an apparent clustering of the proteins, mainly separating the cluster by the muscle types. A greater number of oxidative metabolism enzymes was identified in PM exudate, while more glycolytic metabolism enzymes were identified in LD exudate. Additionally, a greater abundance of cytochrome c was observed in PM muscle exudate along with laminin proteins, indicating a greater extent of degradation in the muscle, potentially explaining the lower oxidative stability of PM muscle. A total of 518 metabolite features was detected from the meat exudate using untargeted metabolomics analysis, in which 167 features were affected by the treatments (P &amp;lt; 0.05). The PCA analysis exhibited a distinct grouping of the treatments, separating not only muscle types but also the aging periods. Greater antioxidant compounds, such as carnitines and glucosides, were identified in LD muscle exudate. A greater number of lipid and nucleotide metabolites were also observed in LD exudate and 23d exudate. HSP70 and laminin proteins, along with glucosides metabolites identified in the exudates, which were significantly correlated (r &amp;gt; 0.5) to muscle color and oxidative stability. The current results indicated that meat exudate could be a viable analytical matrix to understand oxidative stability and protein degradation of muscles during aging. The proteomics and metabolomics profiling identified specific compounds in meat exudate that could be related to different oxidative stability of beef muscles. Further research should be warranted to validate the identified compounds as potential biomarkers to predict oxidative stability and quality attributes of specific muscles during aging.

Comparative assessment of the qualities of commercial and synthetic transformer oils

Petroleum transformer oils previously produced in the USSR met the requirements of ГОСТ 982-80. Balakhany oil and Dossor low-paraffin oil of the Emben field were the raw materials for obtaining transformer oil. The composition of transformer oils is taken into account when choosing raw materials and their regeneration. Т-1500у – transformer oil of improved quality, is used in electrical equipment up to 500 kV and up to 750 kV. ГК oil is a hydrocracking transformer oil, used in voltages up to 1150 kV, contains ionol. Тсп is oil from West Siberian oils, used up to 220 kV. This oil is of relatively low quality, characterized by a high sulfur content, low oxidation stability, and high dielectric loss tg. In the Institute of Petrochemical Processes, research has been carried out on the selective purification of transformer oil distillate from Balakhany oil using a new highly effective solvent – ionic liquid (IL) – a quaternary ammonium salt of formic acid and a number of amines – morpholine, aniline or di-, triethylamines. The optimal conditions for the selective purification of the distillate have been developed. Due to the shortage of high-quality transformer oils, as well as the high cost, in recent years, oils have been imported from Sweden and Austria. An ionic liquid as a solvent is highly selective and selective. The analysis of the extract from selective purification showed that it does not contain naphthene-paraffins, the content of aromatic hydrocarbons in the extract is 65 %, and when purified with furfural it is 40.8 %. The ionic liquid is environmentally friendly.

Ultrasound-assisted synthesis of oleic estolide: Optimization, process intensification and kinetic study

Bio-lubricants are crucial for overcoming environmental issues as they act as renewable substitutes for petroleum-based lubricants. Bio-lubricant derived from vegetable oils have excellent lubricating properties but are hampered by their low oxidation stability, low hydrolytic stability, and lack of cold-flow characteristics which can be mitigated by modification by estolide formation. The synthesis of estolides is limited by the higher reaction time and hence ultrasound-assisted technique was employed for intensification of the production of estolide from oleic acid. The reaction parameters (temperature, catalyst amount, and time) were optimized using the response surface methodology (RSM) to obtain the best characteristics in terms of acid value (AV) and pour point (PP). The optimized conditions were established using RSM and validated using an artificial neural network (ANN) based model. Successfully intensification using sonication in terms of reducing the reaction time of 6–12 h for the conventional approach to 2.623 h for the ultrasonic bath and to 1.5 h for the ultrasonic horn bath was observed. A kinetic study of the oligomerization reaction revealed the fitting of the second-order kinetics. Overall, the work elucidates the utility of ultrasound in synthesizing oleic estolide in terms of successful intensification and elucidating the reaction kinetics.

Evaluation of Physicochemical Properties Composite Biodiesel from Waste Cooking Oil and Schleichera oleosa Oil

Waste cooking oil (WCO) biodiesel has some disadvantages, such as poor cold flow properties, low oxidation stability, and flash point during storage. These poor physicochemical properties can be improved by different ways, such as the addition of non-edible oil. The aim of this study to analyse physicochemical properties of the biodiesel made by between WCO and Schleichera oleosa (SO). The biodiesel produced with 70:30% of WCO and SO respectively as crude oil, further introducing of different KOH-based catalyst into this oil to obtained the methyl ester. The optimum yield transesterification process are 94% with 60 min. of the reaction time, 1 wt.% KOH, and 12:1 molar ratio the methanol to oil. On the other hand, the Schleichera oleosa blend shows oxidation stability at 6.8 h and 3.3 h for Waste cooking oil methyl ester (WCME). The reduction of cold flow and, on the contrary, the flash point increase were obtained with a 70:30% ratio of WCO and SO. The cold flow properties and flash point of the fuel. Thus, mixed WCO and Schleichera oleosa oil improve the physiochemical properties such as oxidation stability, flash point, and cold flow of biodiesel without the need for synthetic antioxidants.

Production of gasoline and diesel-like fuel from natural rubber scrap: Upgrading of the liquid fuel properties and performance in a spark ignition engine

This research presented the technical production and necessary analysis for the conversion of natural rubber scrap into GLF and DLF. The essential properties were measured and discussed in terms of use as fuel for internal combustion engines. Upgrading the fuel properties by improving the oxidation stability of GLF and evaluating its performance and emission characteristics in a spark-ignition engine was investigated. The results showed that the density, viscosity, octane number, and distillation curves of GLF and DLF were similar in terms of the values for commercial gasoline and diesel. The low oxidation stability from high olefins content in GLF was standardized by the addition of BHT with an induction period of around 62 min/%wtBHT for the studied range of 0-10 %wt. In addition, engine performance test results from using GLF were comparable to gasoline95 with a slight increase in brake torque, brake power, and brake-thermal efficiency, estimated at 6%, 8%, and 11%, respectively. In comparison to gasoline95, the emissions from GLF have approximately increased CO by 18% and NOx by 80%. GLF can be burned in spark-ignition engines without any negative impact on engine performance and can be upgraded to properties that closely resemble standard fuel with a few minor improvements.

Hexacyclic Chelated Lithium Stable Solvates for Highly Reversible Cycling of High-Voltage Lithium Metal Battery.

Ether-based electrolytes that are endowed with decent compatibility towards lithium anode have been regarded as promising candidates for constructing energy-dense lithium metal batteries (LMBs), but their applications are hindered by low oxidation stability in conventional salt concentration. Here, we reported that regulating the chelating power and coordination structure can remarkably increase the high-voltage stability of ether-based electrolytes and lifespan of LMBs. Two ether molecules of 1,3-dimethoxypropane (DMP) and 1,3-diethoxypropane (DEP) are designed and synthesized as solvents of electrolytes to replace the traditional ether solvent (1,2-dimethoxyethane, DME). Both computational and spectra reveal that the transition from five- to six-membered chelate solvation structure by adding one methylene on DME results in the formation of weak Li solvates, which increase the reversibility and high-voltage stability in LMBs. Even under lean electrolyte (5 mL Ah-1 ) and low anode to cathode ratio (2.6), the fabricated high-voltage Li||LiNi0.8 Co0.1 Mn0.1 O2 LMBs using electrolyte of 2.30 M Lithiumbisfluorosulfonimide (LiFSI)/DMP still show capacity retention over 90 % after 184 cycles. This work highlights the importance of designing the coordination structures in non-fluorine ether electrolytes for rechargeable batteries.

Properties and Analysis of Liquid Alternative Fuels III: Vegetable Oils and Hydrotreated Vegetable Oils

The importance of alternative fuels and biofuels is constantly growing due to energy security, sustainability, and social responsibility. This article is another in a series of review articles designed to recapitulate information on the required properties of individual alternative fuels, their testing methods, and the significance of individual analyses. This article is focused on fuels based on vegetable oils and hydrotreated vegetable oils. Rapeseed oil is a triglyceride-based fuel that can be burned in modified diesel engines. Modification of the engine consists in the inclusion of preheating of the fuel or modification of the injection system, due to the high viscosity of this fuel. Rapeseed oil and vegetable oils in general have a higher oxygen content than conventional diesel fuels, which is associated with a lower energy content than that of diesel fuels. Compared to diesel, vegetable oils have a higher density, a lower cetane number, and a significantly higher flash point and viscosity. Vegetable oils also have low oxidative stability. Physical properties monitored in rapeseed oils include density, viscosity, flash point, and calorific value. From the chemical properties, the iodine number, acidity number, water content, calcium, magnesium, sulfur, and phosphorus are monitored. From the other properties, oxidative stability, ignitability, ash content, carbonation residue, content of impurities, and appearance are monitored for rapeseed oils. HVO is a high-quality fuel for standard diesel engines. Due to the hydrocarbon character of HVO, no engine modification is required. HVO has a very high cetane number, very good low-temperature properties, optimal viscosity, high flash point, excellent oxidative stability, and a very low content of undesirable contaminants such as aromatic hydrocarbons, sulfur, nitrogen, and oxygen-containing compounds. Compared to diesel fuels, HVO has a lower density. The observed qualitative parameters and testing methods are very similar to those of conventional diesel fuel B7. The main difference lies in the modified determination of aromatic hydrocarbons.

A Review on Bio-Lubricants as an Alternative Green Product:Tribological Performance, Mechanism, Challenges and Future Opportunities

Industries, especially those related to transportation, have relied extensively on petroleum products for lubrication, raising serious questions about the security of the world energy supply in the future. Observed that the end-products might be released back into the environment, posing major environmental risks. As a result, bio-based products have attracted increasing interest as prospective replacement to mineral-based type due to their important role in resolving the issues of pollution. With renewability and biodegradability as their greatest points, bio-based lubricants have been discovered to offer superior lubricating qualities to those of traditional mineral lubricants but currently have some undesirable qualities that need to be improved based on the literatures. Therefore, this research objective is to showcase the potential of bio-lubricants, both in terms of their environmental benefits and for technical applications, based on studies that have been published over the years. Review of the natural oil's molecular structures, physio-chemical characteristics, and lubricating ability is crucial for the creation and choice of lubricants. Owing to their accessibility in a wide range of characteristics, which are necessary for specific applications, bio-based lubricant is a possible replacement for a variety of applications, according to the primary findings. The results showed that sunflower oil improved in reducing friction and wear by 93.7% and 70.1%; and 77.7% and 74.1%, under TiO2 and SiO2 studied, against base lubricant values of 0.0511 and 11.2414 (mm3), respectively. However, to get beyond some of the restrictions such as poor low temperature and oxidative stability, adequate chemical modification is necessary in solving agglomeration challenges.

Use of Propyl Gallate in Cardoon Biodiesel to Keep Its Main Properties during Oxidation

The use of alternatives for petroleum-based products is becoming more and more important, especially considering the new and constantly changing geopolitical context, where excessive energy dependence is not desirable. Thus, biodiesel could play an important role in contributing to the implementation of biorefineries, which represent desirable goals in terms of sustainability, green chemistry and the circular economy. However, one challenge related to biodiesel based on vegetable oils is its low oxidative stability, which can alter the properties of these products during storage. To avoid this problem, interesting antioxidants, such as propyl gallate (PG), could be added to biodiesel to allow it to keep its main properties during oxidation. Additionally, monitoring PG content during oxidation is interesting, and the use of voltammetry could be suitable for this purpose. The aim of this work was to assess the effectiveness of PG during cardoon biodiesel oxidation, while monitoring the process through cyclic voltammetry (CV). As a result, it was proven that PG was highly effective, increasing the length of oxidative stability to more than 10 h at low concentrations (600 mg·L−1) and retaining its main properties (viscosity and acidity) during oxidation. Regarding CV, this technique was successfully optimized to determine PG concentration in cardoon biodiesel during oxidation.

Effect of postruminal supply of linseed oil in dairy cows: 2. Milk fatty acid profile and oxidative stability.

Our objective was to study the effect of increasing postruminal supply of linseed oil (L-oil), as a source of cis-9, cis-12, cis-15 18:3, on milk fatty acid profile and to assess the resulting impact on the development of volatile degradation products during the storage of homogenized milk. Five Holstein dairy cows fitted with a rumen cannula were randomly distributed in a 5 × 5 Latin square design. Abomasal infusion of L-oil was performed at the rate of 0, 75, 150, 300, and 600 ml/d during periods of 14 d. The concentration of cis-9, cis-12, cis-15 18:3 in milk fat increased linearly with L-oil dose. Concentrations of primary (conjugated diene and triene hydroperoxides) and secondary oxidation products (1-octen-3-one, propanal, hexanal, trans-2 + cis-3-hexenals, cis-4-heptenal, trans-2, cis-6-nonadienal trans-2, trans-4-nonadienal) increased during 11 d of storage at 4°C of homogenized milk under fluorescent light. The magnitude of the increase (difference between final and initial measurements) was linearly greater for all nine lipid oxidation products evaluated in response to increasing level of infusion. Results of the current experiment have shown that milk enriched in cis-9, cis-12, cis-15 18:3 via postruminal supply of L-oil is highly prone to oxidative degradation. This low oxidative stability, exposed under controlled experimental conditions, would represent a major obstacle to those who aim to market milk enriched in polyunsaturated fatty acids.

Correlation of tangible quality parameters of vegetable-based transformer fluids

Due to the inherent environmental footprint of petroleum derived transformer fluids, the power industry is gradually exploring the potential of vegetable oils as alternatives. The impetus comes mostly from vegetable oils renewability and their inherent biodegradability.However, the major drawback in the use of vegetable oils as dielectric fluids is their lower oxidative stability and higher kinematic viscosity compared to mineral oils. The results obtained clearly demonstrate the correlation between spectroscopic data induction time, kinematic viscosity, acid value, and peroxide value. Quantitatively, the absorption frequencies of functional groups in vegetable oil transformer fluids that can be correlated to the mentioned quality parameters show noticeable changes with aging/oxidative degradation. The study also demonstrates the utility of integrating spectroscopic data to understand trends in induction time and kinematic viscosity of oil samples heated under transformer service conditions.