Oxidation Of Methyl Linoleate Research Articles

In Vitro Digestion of Betalainic Foods. Stability and Bioaccessibility of Betaxanthins and Betacyanins and Antioxidative Potential of Food Digesta

Betalains are considered to be bioactive dietary phytochemicals. The stability of betacyanins and betaxanthins from either fresh foods or manufactured products of cactus pear fruit ( Opuntia ficus indica L. Mill. cv. Gialla and Rossa) and red beet ( Beta vulgaris L. ssp. vulgaris) was assessed in a simulated oral, gastric, and small intestinal digestion and compared with the digestive stability of purified pigments. A minor loss of indicaxanthin, at the gastric-like environment only, and a decrease of vulgaxanthin I through all digestion steps were observed, which was not affected by food matrix. In contrast, food matrix prevented decay of betanin and isobetanin at the gastric-like environment. Loss of betacyanins, either purified or food-derived, was observed during the small intestinal phase of digestion. Betalamic acid accumulated after digestive degradation of purified pigments, but not of food betalains. Betaxanthins were wholly soluble in the aqueous (bioaccessible) fraction after ultracentrifugation of the postintestinal (PI) digesta, whereas release of betacyanins from the matrix was incomplete. PI digesta inhibited dose-dependently the oxidation of methyl linoleate in methanol, an effect not correlated with the betalain content. The data suggest that digestive stability controls bioaccessibility of dietary betaxanthins, whereas additional factors, relevant to the food matrix and style of processing, affect betacyanin bioaccessibility.

Investigation of the Parameters Affecting the Cetane Number of Biodiesel

AbstractThe cetane number is the most significant property for measuring the ignition quality of fuels for compression ignition diesel engines. In this study, the derived cetane number (DCN) of several types of biodiesel, biodiesel components and ultra‐low sulfur diesel (ULSD) was determined using an Ignition Quality Tester (IQT™). The chemical structure of FAME leads to a higher cetane number of biodiesel compared to ULSD. The contribution to DCN from minor components present in biodiesel is not significant. Oxidation of biodiesel samples results in higher DCN values while depending on the conditions of oxidation. A greater than 25% increase was observed when oxidation was carried out in a way to retain volatile oxidative products such as carboxylic acids and aldehydes. Accelerated oxidation of cotton seed oil (CSO) biodiesel at 110 °C and 10 L/min air flow rate after 210 min resulted in a loss of 14% of the FAME content, of which 10% can be attributed to the oxidation of methyl linoleate (C18:2), whereas oxidation of soy bean oil (SBO) biodiesel resulted in a loss of 21% total FAME after 210 min. A significant amount of methyl linolenate (C18:3) remained un‐reacted after 210 min of oxidation. Ambient oxidation of distilled biodiesel samples resulted in a very high cetane number. Oxidative products such as aldehydes, hydroperoxides and oligomers of FAME are probably responsible for this higher DCN. This study enhances the understanding of the effect of composition on the cetane number of biodiesel as well as the effect of oxidative aging on both biodiesel composition and the resultant DCN.

Suppression of the oxidation of methyl linoleate encapsulated with the extract from defatted rice bran by a compressed hot water treatment

Bran extracts prepared by a compressed hot water treatment at 120, 150, and 180 °C for 7.5 min were used in association with maltodextrin for encapsulation of methyl linoleate. Mixtures of the bran extracts at 120 and 150 °C showed a higher emulsion-stabilizing ability than that at 180 °C. The bran extracts prepared at the higher temperature provided a higher oxidative stability as shown by the longer induction period for the oxidation of the encapsulated methyl linoleate. The induction periods of the encapsulated methyl linoleate using the bran extract prepared at 250 °C for 5 min as the aqueous phase were 3–6 times longer than those of the encapsulated methyl linoleate using water.

Oxidation of Methyl Linoleate in Oil‐in‐Water Micro‐ and Nanoemulsion Systems

AbstractOxidation of methyl linoleate in O/W emulsions having droplets of median diameters ranging from 17 nm to 8.0 μm was carried out at 40°C. The oxidation process was analyzed on the basis of a kinetic equation of the autocatalytic type. The induction period was found to be shorter and the oxidation rate constant lower for emulsions with smaller oil droplets. The stoichiometry between methyl linoleate and oxygen was observed to be independent of both the size of oil droplet and the type of the surfactant and was found to be unity during the early stage of the oxidation. However, more oxgen was consumed in the oxidation of the methyl linoleate in the later half of the oxidation process.

Synthesis and properties of antioxidant amphiphilic ascorbate salts

Synthesis of new surfactants with antioxidant properties was carried out from ascorbic acid and different fatty amines. Characterization of physicochemical properties of these new compounds indicated a classical behavior of cationic surfactants. Antioxidant properties, estimated using methyl linoleate oxidation inhibition and DPPH methods, were close to that of ascorbic acid tested in the same conditions. These compounds were investigated in the formulation of wood preservation mixtures containing propiconazole, a widely used fungicide, and compared to the formulation obtained with an industrial nonionic surfactant. Biological tests were carried out under laboratory conditions to evaluate the ability of these formulations to protect beech wood blocks exposed to Coriolus versicolor, a white rot fungus. Results indicated that using aqueous formulation of propiconazole allows reducing the quantity of biocide compared to solutions of the same concentrations in ethanol. Protection achieved with antioxidant surfactant was slightly superior to that obtained with conventional surfactant.

Effect of Oil-droplet Size on the Oxidation of Microencapsulated Methyl Linoleate

Effects of oil-droplet size, the weight ratio of oil to wall material and the storage temperature on the oxidation of methyl linoleate microencapsulated with maltodextrin by spray-drying were examined. The oxidation of methyl linoleate was more retarded for the microcapsules prepared from the emulsion having smaller oil droplets. The oxidation was more suppressed for the microcapsules having a lower weight ratio of oil to wall material. The fraction of unoxidized methyl linoleate leveled off after 10- to 15-days storage. The level, Y(infinity), depended on the weight ratio. The dependence of Y(infinity) on the weight ratio was analyzed based on the percolation theory, and the three-dimensional model of the theory was suitable to express the dependence. The effect of the storage temperature on the oxidation of microencapsulated methyl linoleate was also examined, and the activation energy was evaluated. The value of the energy suggested that the oxidation itself was a rate-limiting step for the oxidation of methyl linoleate encapsulated with maltodextrin.

Antioxidant activity of the new thiosulfinate derivative, S-benzyl phenylmethanethiosulfinate, from Petiveria alliacea L.

The antioxidant effects of the new thiosulfinate derivative, S-benzyl phenylmethanethiosulfinate (BPT), against the oxidation of cumene and methyl linoleate (ML) in chlorobenzene were studied in detail using HPLC. The results showed that BPT provided effective inhibition with a well-defined induction period under these oxidation conditions, and it was found that the stoichiometric factor (n), the number of peroxyl radicals trapped by one antioxidant molecule, of BPT is about 2. We then undertook a thorough investigation aimed at elucidating the active structural site of BPT. Various model compounds, such as diphenyl disulfide, dibenzyl disulfide, S-phenyl benzenethiosulfinate and S-ethyl phenylmethanethiosulfinate, were used which provided evidence that the benzylic hydrogen of BPT is mainly associated with the peroxyl radical scavenging. Moreover, we measured the rate constant for the reaction of BPT with peroxyl radicals derived from cumene and ML in chlorobenzene, and based on these measurements, BPT reacts with these peroxyl radicals with a rate constant of k(inh) = 8.6 x 10(3) and 6.2 x 10(4) M(-1) s(-1), respectively.

Effects of sesamol, sesamin, and sesamolin extracted from roasted sesame oil on the thermal oxidation of methyl linoleate

This study investigated the effects of lignan compounds extracted from roasted sesame oil, which were sesamol, sesamin, and sesamolin, on oxidation of methyl linoleate (ML) during heating. These compounds were added at 500 or 1000 mg/kg to ML, and α-tocopherol was used as a reference antioxidant. The ML added with lignans or α-tocopherol was heated at 180 °C for 60 min. Thermal oxidation of ML was evaluated by conjugated dienoic acid (CDA) contents, p-anisidine value (PAV), and ML retention. Contents changes of lignan compounds or α-tocopherol in ML during heating were monitored by high-performance liquid chromatography. CDA contents and PAV of samples increased and ML decreased with heating time at 180 °C. Samples added with lignan compounds showed lower CDA contents and PAV but higher ML retention than samples without lignan compounds. The antioxidant activity of sesame oil lignan compounds in ML oxidation during heating tended to be higher than that of α-tocopherol. The contents of lignan compounds in samples decreased with heating time due to their degradation, but the degradation rates were lower than that of α-tocopherol. This study suggested that sesame oil lignan compounds be used as antioxidants in oil at high temperatures for deep-fat frying due to their higher effectiveness and stability than α-tocopherol.

Impact of surfactant type, pH and antioxidants on the oxidation of methyl linoleate in micellar solutions

The oxidation of methyl linoleate micelles has been studied, aiming at elucidating the effect of various variables, including surfactant type, pH and antioxidants. The progress of the methyl linoleate oxidation was evaluated by measurement of conjugated dienes hydroperoxides (CDHP) and malondialdehyde (MDA). It was shown that the oxidative stability of methyl linoleate micelles was influenced by surfactant type, with oxidative rate being greater in SDS micelles than in Tween 20 micelles. Besides, the methyl linoleate micelles at pH 6.8 had greater rates of lipid oxidation than their pH 3.0 counterparts. Moreover, the incorporation of VE and VC in the methyl linoleate micelles successfully slowed the formation of hydroperoxides and their subsequent decomposition product MDA. However, the antioxidant activities of VE and VC were related to their concentrations.

Efficacy of Metmyoglobin and Hemin as a Catalyst of Lipid Peroxidation Determined by Using a New Testing System

A new quantitative approach to investigate the capability of iron heme complexes (HEM), metmyoglobin and hemin, to catalyze lipid peroxidation was elaborated. The oxidation of methyl linoleate in micellar solutions was used as a testing model. The key point was the determination of the rate of free radical generation, RIN, calculated from the rate of oxygen consumption. The HEM catalytic activity was characterized by two independent parameters: by reactivity and by its resistance to degradation. Both parameters were found to be pH-dependent. The reactivity was expressed as the effective rate constant for the reaction of HEM with lipid hydroperoxide. The resistance to degradation was characterized by the rate of the decrease in RIN with time and also by the regeneration coefficient, which shows how many active free radicals can be generated by one molecule of HEM. Both Hemin and metMB were found to be very effective catalysts even at nanomolar concentrations. The effective regeneration of active forms of HEM was observed. The catalytic activity of HEM was rapidly reduced with time. The kinetic scheme of the process under consideration was suggested, and this was applied for kinetic computer simulations.

Anti‐oxidant content of different coloured sweet peppers, white, green, yellow, orange and red (Capsicum annuum L.)

SummaryFive different coloured sweet peppers (Capsicum annuum cv. Signal), white, green, yellow, orange and red were analysed for total carotenoids, α‐tocopherol, sugars (glucose, fructose and sucrose), organic acids (citric and ascorbic acids) and anti‐oxidant properties. The mature fruits, ‘Signal Red’, ‘Signal Orange’ and ‘Signal Yellow’ contained higher carotenoids, α‐tocopherol, sugars and organic acids than the immature fruits, ‘Signal Green’ and ‘Signal White’. Among the mature fruits, ‘Signal Red’ was the highest in total carotenoids [9.15 mg (100 g)−1 of fresh weight] while ‘Signal Orange’ was the highest in α‐tocopherol [5.40 mg (100 g)−1 of fresh weight]. ‘Signal Red’ and ‘Signal Orange’ contained the most sugars and organic acids. The suppression of 2,2′‐azobis (2,4‐dimethylvaleronitrile) (AMVN)‐induced oxidation of methyl linoleate by the acetone extracts from the coloured sweet peppers resulted as follows: ‘Signal Red’ > ‘Signal Orange’ ≈ ‘Signal Yellow’ > ‘Signal Green’ ≈ ‘Signal White’. The order of 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging activities of the acetone extracts was similar to that of suppression of methyl linoleate oxidation.

Numerical revelation of the kinetic significance of individual steps in the reaction mechanism of methyl linoleate peroxidation inhibited by α-tocopherol

A kinetic model was constructed to describe the reactions involved in the oxidation of methyl linoleate (ML) inhibited by α-tocopherol (TH). The initial model of the reaction mechanism included 53 individual steps, which were numerically analyzed by the value method based on Hamiltonian systematization of kinetic equations. Good accord was obtained with experimental data at 40 and 50 °C. The dominant steps responsible for the antioxidant and pro-oxidant properties of TH in the process of ML peroxidation were revealed. Tocopherol-mediated peroxidation (TMP) and generation of alkoxyl radicals as a result of the reduction of hydroperoxides by TH or the decomposition tocopherol alkyl peroxides are the dominant reactions responsible for the pro-oxidant activities of α-tocopherol. The extreme behavior of reaction induction period in relation to TH initial concentration is related to the increase in the ratios of [tocopheroxyl radical]/[peroxyl radical] and the TMP rate/rate of termination by combination of tocopheroxyl and peroxyl radicals.

Kinetic investigation of the antioxidant properties of captopril

The antioxidant activity of 1-[(2S)-3-mercapto-2-methylpropionyl]-L-proline (capoten; INN: captopril) at various concentrations was studied in a model reaction of methyl linoleate oxidation (initiated with 2,2′-azobisisobutyronitrile) at 60 ± 0.2°C in chlorobenzene solution and in aqueous emulsion system in the presence of copper(II) cations (catalyst) and cetyltrimethylammonium bromide (emulsifier). Captopril exhibits high antioxidant activity in the aqueous emulsion medium, which provides grounds for a more extensive investigation into the pharmacological activity of this drug.

The antioxidant activity of Californian red wines does not correlate with wine age

AbstractA range of physico‐chemical properties of 21 Californian red wines from 1 to 28 years old were correlated with wine age. The level of monomeric phenolics and low molecular‐weight phenolic oligomers decreased with age, while the level of high molecular‐weight phenolics increased. On the other hand, total phenols given by the Folin–Ciocalteau method, antioxidant capacity determined using a controlled chain reaction of methyl linoleate and the intensity of the anodic peak determined by cyclic voltammetry (CV) did not show any significant correlation with wine age. Total phenols and the shapes of CV traces were more dependent on the grape variety and the particular viticultural and wine‐making practices rather than on wine age. At the same time, young and aged wines showed a pronounced difference in the shape of [O2] traces recorded during the oxidation of methyl linoleate in a micellar solution inhibited by wine addition. Possible reasons why the antioxidant activity of red wines does not correlate with wine age are discussed. Copyright © 2006 Society of Chemical Industry

Impact of Lipid Physical State on the Oxidation of Methyl Linolenate in Oil-in-Water Emulsions

The purpose of this research was to examine the influence of the physical state of lipids on iron-promoted oxidation of methyl linolenate in octadecane oil-in-water emulsions. Octadecane and methyl linolenate oil-in-water emulsions were prepared that contained droplets having the octadecane as either liquid or solid. The physical state of the octadecane was confirmed by a differential scanning calorimeter (DSC). The effect of the physical state of the lipid on oxidation rates was determined as a function of iron concentration (80 and 160 microM), pH (3.0 or 7.0), emulsifier type, and cooling rate. Oxidation of methyl linolenate was determined by lipid hydroperoxides and thiobarbituric acid reactive substances (TBARS). Emulsions containing solid octadecane had higher rates of lipid hydroperoxide and TBARS formation than those containing liquid octadecane. The rate at which the emulsions were cooled had no influence on oxidation rates. Oxidation rates in both emulsions increased with increasing iron concentration and decreasing pH. Oxidation rates were lowest in emulsions with cationic droplet membranes (dodecyl trimethylammonium bromide-stabilized), presumably due to the repulsion of iron from the oxidizable methyl linolenate in the emulsion droplet core. These results suggest that upon crystallization of octadecane, the liquid methyl linolenate migrated to the emulsion droplet surface, where it was more prone to oxidation because it was in closer contact with the iron ions in the aqueous phase.

Oxidation of methyl linoleate in micellar solutions induced by the combination of iron(II)/ascorbic acid and iron(II)/H 2O 2

The oxidation of methyl linoleate (ML) was studied in the presence of Fe(II) alone and its combination with either ascorbic acid (AsAH 2) or hydrogen peroxide (H 2O 2) at different molar ratios. Reactions were carried out in micellar solutions of TTAB (tetradecyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate), respectively, and were monitored by UV spectroscopy and electrospray ionization mass spectrometry (ESI-MS). Fe(II) alone was able to catalyze the oxidation of ML in micellar solutions of TTAB, but not in those of SDS. The combination of H 2O 2 with Fe(II) showed catalytic effect only in the TTAB medium, leading to different ML and Fe(II) oxidation kinetics compared to the Fe(II)-only catalyzed reactions. The AsAH 2/Fe(II) combination demonstrated to be a good catalyst for the oxidation of ML in SDS micellar solutions, but not in TTAB micellar solutions; the activity of the catalyst was dependent on the AsAH 2/Fe(II) molar ratio. The obtained results confirm that, for the ML oxidation to be initiated, the presence of a Fe(II)/Fe(III) couple is essential, which is related to the pH of micellar solutions. The catalytic properties of the AsAH 2/Fe(II) combination were explained by taking into account the anti-oxidant and pro-oxidant properties of AsAH 2, as well as the possible formation of an iron/ascorbate complex as the initiator of the ML oxidation.

Chemical Composition and Antioxidant Activity of Juices from Mature and Immature Acerola (Malpighia emarginata DC)

Chemical composition and antioxidant activity of juice from immature and mature acerola and of concentrated juice from immature acerola were determined. Tartaric, malic and citric acids and a high content of ascorbic acid were found in all the juices. Vitamin C contents were 4.80, 1.90 and 0.97 g/100 g for the concentrated immature, the immature, and the mature acerola juices respectively. The total phenol contents decreased during ripening, from 3.8 mg of catechin/g for immature acerola juice to 1.4 mg of catechin/g for mature acerola juice. The concentrated immature juice had a content of 9.2mg of catechin/g of juice. Catechin, gallic acid, coumaric acid, syringic acid, caffeic acid and ferrulic acid were detected in immature acerola juice by HPLC analysis whereas mature acerola juice showed only one predominant peak with a retention time similar to that of ferrulic acid. The concentrated juice from immature acerola reduced the oxidation of methyl linoleate by 57.2% while the juice from immature acerola reduced the oxidation by 28.1%. These results stated that the antioxidant potential of the acerola juice depended on its content of phenolic compounds and the vitamin C.

Antiodidant activity of thiosulfinates derived from garlic

Garlic extract significantly inhibited the oxidation of methyl linoleate in homogeneous acetonitrile solution, whereas the antioxidant effect of allicin-free garlic extract, prepared by removing allicin by prepared by removing allicin by preparative HPLC, was much lower than that of the garlic extract. These results suggest that the antioxidant properties are mostly attributed to the presence of allicin in the garlic extract. Allicin a major component of the thiosulfinates in garlic extract, was found to be effective for inhibiting methyl linoleate oxidation, but its efficiency was less than that of α-tocopherol. Next, the reactivity of allicin toward the peroxyl radical, which is a chain-propagating species, was investigated by direct ESR detection. The addition allicin to 2,2′-azobis(2,4-dimethylvaleronitrile)-peroxyl radical solution caused the signal intensity of the peroxyl radical to dose-dependently decrease, indicating that allicin is capable of scavenging the the peroxyl radical and acting as an antioxidant. Finally, we studied the structure–anioxidant activity relationship for thiosulfinates and suggested that the combination of the allyl group (–CH2CH=CH2) and the –S(O)S– group is necessary for the antioxidant action of thiosulfinates in the garlic extract. In addition, one of the two possible combinations, –S(O)S–CH2CH=CH2, was found to make a much larger contribution to the antioxidant activity of the thiosulfinates than the other, CH2=CH–CH2–S(O)S–.

Effects of molecular configurations of food colorants on their efficacies as photosensitizers in lipid oxidation

Effects of twelve commercially available synthetic food colorants, including tartrazine, rose bengal, brilliant blue FCF, new coccin, amaranth, erythrosine B, phloxine B, indigo carmine, acid red, fast green FCF, allura red AC and sunset yellow FCF, on photosensitized oxidation of methyl linoleate (MeLe) were investigated. Rose bengal, erythrosine B and phloxine B accelerated oxidation of MeLe under light exposure and their pro-oxidative effects were concentration-dependent. Light exposure of MeLe with added colorants induced generation of hydroperoxide isomers, including 10- cis, trans- and 12- cis, trans-MeLe hydroperoxide, suggesting that the food colorants served as photosensitizers under the present conditions. The addition of α-tocopherol or β-carotene effectively suppressed the oxidation of MeLe, and their antioxidative effects were concentration-dependent. Neither α-tocopherol nor β-carotene altered the distributions of hydroperoxide isomers of MeLe. This study showed that the food colorants containing a xanthene skeleton increased their potential as photosensitizers with increase in both the number and atomic mass of halogen substituents on the xanthene skeleton.

Products of the surface oxidation of methyl linoleate

AbstractMethyl linoleate with 5% by weight of methyl palmitate as an internal standard was deposited as a monolayer (20% by weight) on Silica gel H and oxidized at 7,25, and 40°C. Oxidation was followed by iodometric PV practiced directly on aliquots of the silica gel. Lower temperatures gave higher PV maxima but after longer times. Oxidation of methyl linoleate at all three temperatures followed first‐order kinetics, and the energy of activation was 15.0 kcal/mol. The products recovered from the chloroform‐acetic acid layer of the peroxide determination were analyzed by GC and identified by El‐ and CI‐MS. Calculation based on methyl palmitate as an internal standard showed that the total peak area decreased to about 40% that of the original methyl linoleate when the residual methyl linoleate was reduced to less than 2%. The chief nonscission products (NSP) of linoleate oxidation were epoxy, hydroxy, hydroxy‐epoxy, dihydroxy, and trihydroxy methyl esters. The greatest NSP concentrations were obtained about the time of the greatest PV, and the yield at 40°C was greater than those at 7 and 25°C. Scission products (SP) increased rapidly until the greatest PV was reached. After this time, SP declined slightly and plateaued at 40°C, but at 7 and 25°C, SP continued to increase slowly with further oxidation.