Algae oil and fish oil are n-3 PUFA mainstream commercial products. The various sources for the stability of n-3 PUFA oxidation are influenced by the fatty acid composition, extraction and refined ...processing. In this study, the oil stability index (OSI) occurs within 2.3 to 7.6 hours with three different n-3 PUFA rich oil. To set the OSI in the Rancimat test as the oil stability limit and observed various degrees of oxidation (0, 25, 50, 75, 100 and 125%). The volatile oxidation compounds were analyzed via headspace-solid phase microextraction (HS-SPME) and GC/MS. We detected 51 volatile compound variations during the oxidation, which were composed of aldehydes, hydrocarbons, cyclic compounds, alcohols, benzene compounds, ketones, furans, ester and pyrrolidine. The off-flavor characteristics can be strongly influenced by the synergy effects of volatile oxidation compounds. Chemometric analysis (PCA and AHC) was applied to identify the sensitive oxidation marker compounds, which included a (E,E)-2,4-heptadienal appropriate marker, via lipid oxidation in the n-3 PUFA rich oil.
AbstractThis study focuses on the introduction of a new biodiesel resource, Kachnar seed oil (KSO). The raw oil was extracted from the seed by Soxhlet extraction. The composition of fatty acids and ...physicochemical properties of the raw oil were measured. Methyl ester was produced from the raw Kachnar seed oil using a transesterification process using an alkaline catalyst. The new biodiesel, Kachnar methyl ester (KME), meets biodiesel standards and could be a reliable substitute for diesel in diesel engine applications. This paper also investigates a methodology to improve the oxidation stability of Kachnar biodiesel by blending it with diesel and by using different commercially available antioxidants, namely butylated hydroxytoluene (BHT), tert-butyl hydroquinone (TBHQ), butylated hydroxyanisole (BHA), propyl gallate (PG), and pyrogallol (PY), in the produced biodiesel. The antioxidants were dosed in concentrations ranging from 100 to 1,000 parts per million (ppm). The result of the investigation shows that antioxidants PY and PG demonstrated effective results for improving oxidation stability of Kachnar biodiesel. TBHQ was the least effective among the investigated antioxidants, whereas the KME10 blend can maintain its stability without any antioxidant.
The relationship between the structure and the antioxidant activity of 21 hindered phenolic compounds was investigated by Rancimat and DPPH· tests. 3-tert-butyl-5-methylbenzene-1,2-diol is the ...strongest antioxidant in the Rancimat test but not in the DPPH· test because its two hydroxyl groups have very strong steric synergy. 2,6-Ditert-butyl-4-hydroxy-methylphenol exhibits a strong antioxidant activity as 2,6-ditertbutyl- 4-methoxyphenol does in lard. 2,6-Ditert-butyl-4- hydroxy-methylphenol also exhibits stronger activity than 2-tert-butyl-4- methoxyphenol. The methylene of 2,6-ditert-butyl-4-hydroxy-methylphenol can provide a hydrogen atom to active free radicals like a phenolic hydroxyl group does because it is greatly activated by both the aromatic ring and hydroxyl group. Five factors affect the antioxidant activities of the phenolic compounds: how stable the phenolic compound free radicals are after providing hydrogen atoms; how many hy drogen atoms each of the phenolic compounds can provide; how fast the phenolic compounds provide hydrogen atoms; how easily the phenolic compound free radicals can combine with more active free radicals, and whether or not a new antioxidant can form after the phenolic compound provides hydrogen atoms.
Fatty acid alkyl esters, especially FAME, are the most commonly used liquid biofuel. Because biofuels are expected to be important alternative renewable energy sources in the near future, more ...studies on their stability against oxidation need to be addressed. Biofuel derived from vegetable oils is well researched, currently with more attention focused on the reuse of waste oil sources than on pure vegetable oil for such production. A method to convert used palm oil, i.e., used frying oil, and residual oil of spent bleaching earths (SPE) to their respective methyl esters has been established by the Malaysian Palm Oil Board. These methyl esters can be used as diesel substitute. However, the methyl esters obtained from used frying oil have a low induction period (3.42 h). In Europe, any methyl esters must have an induction period of at least 6 h in Rancimat stability to be usable as biodiesel, as required by European Biodiesel Standard (EN 14214). To meet this requirement, the used frying oil methyl esters (UFOME) obtained can be treated with different types of antioxidants, either synthetic or natural, at different treatment levels, such as vitamin E, 3-ert-butyl-4-hydroxyanisole (BHA), 2,6-di-tert-butyl-4-methyl-phenol (BHT), 2,5-di-tert-butyl hydroquinone (TBHQ), and n-propyl gallate (PG), to investigate their oxidative stability and storage behavior. The order of increasing antioxidant effectiveness with respect to the oxidative stability of UFOME is: vitamin E<BHT<TBHQ<BHA<PG. Because methyl esters derived from residual oil of SBE have an induction period of 14.6 h, their treatment with antioxidants is unnecessary.
The antioxidant properties and polyphenol content of some selected aromatic plants grown in Greece were studied. Plants were refluxed with 60% methanol after acid hydrolysis. The phenolic substances ...were quantified by High Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD). The antioxidant capacity of the extracts was determined with the Rancimat test using sunflower oil as substrate. Free radical scavenging activity was measured using the stable free radical 1, 1-diphenyl-2-picrylhydrazyl (DPPH). Results were compared with standard butylated hydroxytoluene (BHT) and ascorbic acid. Total phenol concentration of the extracts was estimated with Folin-Ciocalteu reagent using gallic acid as standard. All plant extracts examined showed antioxidant capacity and contained phenolic compounds. Caffeic acid was detected in all the examined plant extracts. Ferulic acid was also detected in all the methanolic extracts, except from
, in rather high concentration. The amount of total phenolics varied slightly in plant materials and ranged from 8.2 mg to 31.6 mg of gallic acid/g dry sample. The highest amount was found in
, and the lowest in
.
Allium ursinum L. is widely used as a spice as well as a traditional medicine. The aim of this work was to evaluate the antioxidant and antimicrobial activities (AMAs) of A. ursinum extract, obtained ...by pressurised-liquid extraction. Several reliable procedures such as 2,2-diphenyl-1-picrylhydrazyl, 2,2-azinobis-3ethyl benxothiazoline-6-sulphonic acid, ferric-reducing antioxidant power assay and oxygen radical absorbance capacity assays were carried out. Vegetable oil stability was evaluated by using Rancimat test. Moreover, AMA was performed on different microorganisms. On the basis of the results obtained, it is confirmed that the A. ursinum extract could be used as a natural ingredient in food and/or pharmaceutical industries.
Antioxidant activity of phenolic extract isolated from Tunisian walnut (
Juglans regia
L.) fruits has been investigated. Preliminarily, composition of walnut kernels was determined. Fat content ...varied from 53.5 to 66.9% (w/w), while total phenol ranged from 1.2 to 5.2 g/100 g of kernel as gallic acid equivalent (GAE). High amounts of ellagic acid (EA) and its derivatives were evidenced by HPLC analysis of the phenolic extract. Walnut fat showed induction time ranging from 2.5 to 3.7 h at 110 °C (rancimat test) and these values unchanged by adding 300 mg/kg of kernel phenolic extract which so showed to have no antioxidant effect. In addition, activities of the ellagic and gallic acids and trolox were compared in vitro by using the Folin–Ciocalteu’s, rancimat and DPPH radical scavenging methods. EA exhibited an antioxidant and radical scavenging activity significantly lower than other tested substances. In conclusion, EA showed to have a negligible role in preventing walnut fat oxidation.
The effect of free fatty acid (FFA) content on the susceptibility to thermooxidative degeneration of vegetable oils was determined by Rancimat analysis. A prooxidant effect of FFA was observed in all ...filtered oils, independently of lipidic substrate and of its state of hydrolytic and oxidative alteration. The intensity of this effect was related to FFA concentration, but regression analysis of the experimental data did not show a general correlation law between FFA concentration and induction time (I t). Different results were obtained for freshly processed virgin olive oils, characterized by postpressing natural suspension-dispersion: opposite behavior was observed of FFA content as regards oxidative stability, depending on the presence of suspended-dispersed material. This fact is of interest because the dispersed particles play a double stabilizing effect on both oxidative and hydrolytic degradation. These results showed that avoidance of oil filtration is highly desirable to extend olive oil's shelf life.
The oxidation stability of methyl esters derived from fresh rapeseed oil and waste frying oil, used as alternative biodiesel fuels, both distilled and undistilled, unstabilized and stabilized by ...pyrogallol and BHT, was studied by differential thermal analysis (DTA) under nonisothermal conditions at various heating rates and by the Rancimat test under isothermal conditions at 110°C. The results obtained by both techniques are compared. Both techniques show that oxidation stability increases considerably with the addition of antioxidants and that pyrogallol is very efficient. Distillation of the methyl esters prepared from rapeseed oil decreases their oxidation stability, obviously owing to the removal of natural antioxidants. The stability of methyl esters prepared from the waste frying oil is determined mainly by the history of the oil. From the DTA measurements, the kinetic parameters of an Arrhenius‐like equation describing the temperature dependence of the oxidation induction period were obtained. The parameters enable one to assess the protective factor of antioxidants for temperatures outside the measuring region, estimate the residual stability, and model the process of biodiesel oxidation under nonisothermal conditions.
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