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1.
The influence of deep frying, mimicked by 20 heating cycles at 180 °C (each cycle from ambient temperature to 180 °C maintained for 5 min), on the unsaponifiable fraction of vegetable edible oils represented by three characteristic families of compounds (namely, phytosterols, aliphatic alcohols, and triterpenic compounds) has been studied. The target oils were extra virgin olive oil (with intrinsic content of phenolic antioxidants), refined sunflower oil enriched with antioxidant phenolic compounds isolated from olive pomace, refined sunflower oil enriched with an autoxidation inhibitor (dimethylpolysiloxane), and refined sunflower oil without enrichment. Monitoring of the target analytes as a function of both heating cycle and the presence of natural antioxidants was also evaluated by comparison of the profiles after each heating cycle. Identification and quantitation of the target compounds were performed by gas cromatography-mass spectrometry in single ion monitoring mode. Analysis of the heated oils revealed that the addition of natural antioxidants could be an excellent strategy to decrease degradation of lipidic components of the unsaponifiable fraction with the consequent improvement of stability.  相似文献   

2.
Phenolic extracts from olive tree leaves and olive pomace were used to enrich refined oils (namely, maize, soy, high-oleic sunflower, sunflower, olive, and rapeseed oils) at two concentration levels (200 and 400 μg/mL, expressed as gallic acid). The concentration of characteristic olive phenols in these extracts together with the lipidic composition of the oils to be enriched influenced the mass transfer of the target antioxidants, which conferred additional stability and quality parameters to the oils as a result. In general, all of the oils experienced either a noticeable or dramatic improvement of their quality-stability parameters (e.g., peroxide index and Rancimat) as compared with their nonenriched counterparts. The enriched oils were also compared with extra virgin olive oil with a natural content in phenols of 400 μg/mL. The healthy properties of these phenols and the scarce or nil prices of the raw materials used can convert oils in supplemented foods or even nutraceuticals.  相似文献   

3.
The total free radical scavenger capacity (RSC) of 57 edible oils from different sources was studied: olive (24 brands of oils), sunflower (6), safflower (2), rapeseed (3), soybean (3), linseed (2), corn (3), hazelnut (2), walnut (2), sesame (2), almond (2), mixture of oils for salad (2), "dietetic" oil (2), and peanut (2). Olive oils were also studied according to their geographical origins (France, Greece, Italy, Morocco, Spain, and Turkey). RSC was determined spectrophotometrically by measuring the disappearance of the radical 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*)) at 515 nm. The disappearance of the radical followed a double-exponential equation in the presence of oils and oil fractions, which suggested the presence of two (fast and slow) groups of antioxidants. RSC was studied for the methanol-soluble phase ("methanolic fraction", MF) of the oil, the fraction nonsoluble in methanol ("lipidic fraction", LF), and the nonfractionated oil ("total oil"; TF = MF + LF). Only olive, linseed, rapeseed, safflower, sesame, and walnut oils showed significant RSC in the MF due to the presence of phenolic compounds. No significant differences were found in the RSC of olive oils from different geographical origins. Upon heating at 180 degrees C the apparent constant for the disappearance of RSC (k(T)) and the half-life (t1/2) of RSC for MF, LF, and TF were calculated. The second-order rate constants (k2) for the antiradical activity of some phenolic compounds present in oils are also reported.  相似文献   

4.
A liquid-liquid extraction method to enrich edible oils--olive, sunflower, and soy oils--with phenols from olive leaf extracts is proposed. After microwave assistance to remove the phenols from three varieties of olive leaves, concentrations in the extracts between 12921 and 5173 mg/L of oleuropein, between 488 and 192 mg/L of apigenin-7-glucoside, between 444 and 219 mg/L of luteolin-7-glucoside, and between 501 and 213 mg/L of verbascoside were obtained, which clearly depended on the target variety. After optimization of the liquid-liquid extraction step, the concentrations in oils were 442, 162, and 164 mg/L of oleuropein, respectively, which were also enriched in apigenin-7-glucoside (between 8 and 15 mg/L, depending of the oil), lutelin-7-glucoside (between 11 and 12 mg/L), and verbascoside (between 11 and 13 mg/L). The oil-extract distribution factor of these compounds was also calculated for all olive leaf varieties and edible oils using different extracts concentrations and also different oil-extract volume ratios. Thus, a door is open to enrichment of any oil with olive phenols at preset concentrations using extracts preconcentrated as required and taking into account the distribution factor of the target compounds between the oil and the extracts.  相似文献   

5.
A continuous approach assisted by ultrasound for direct enrichment of edible oils (olive, sunflower, and soya) with the main phenols in olive leaves (i.e., oleuropein, verbascoside, apigenin-7-glucoside, and luteolin-7-glucoside) has been developed. Multivariate methodology was used to carry out a detailed optimization of the enrichment, and quantitation of the transferred compounds was based on LC-MS-MS in multiple reaction monitoring optimizing the most sensitive transition for each biophenol. Under the optimal working conditions, only 20 min is necessary to enrich the edible oils with 14.45-9.92 microg/mL oleuropein, 2.29-2.12 microg/mL verbascoside, 1.91-1.51 microg/mL apigenin-7-glucoside, and 1.60-1.42 microg/mL luteolin-7-glucoside. The enrichment method is carried out at room temperature and is organic-solvent-free; thus, the healthy properties of the edible oils improve as does their quality. Also, the low acquisition and maintenance costs of an ultrasound source and its application in a dynamic system make advisable the industrial implementation of the proposed method.  相似文献   

6.
Some important edible oils (extra virgin olive oil, canola oil, and sunflower oil) were added to aqueous glucose-lysine or xylose-lysine model systems to investigate their effect on the formation of volatiles from the Maillard reaction (MR). The volatile compounds were extracted by a Likens-Nickerson apparatus and quantified. Pyrazines, Maillard reaction products with an important impact on food flavor, appeared to be particularly sensitive to the presence of the oils in both the xylose-lysine and glucose-lysine model systems. The unsubstituted pyrazine was formed more with olive oil, less with canola oil, and even less with sunflower oil, whereas 2-methylpyrazine, 2,5-methylpyrazine, and 2,3-dimethylpyrazine were formed less with olive oil, more with canola oil, and even more with sunflower. The oxidative states of the oils and their fatty acid fingerprints were determined: the results indicated that the relative amounts of the pyrazines are sensitive to the degree of unsaturation of the oil. The autoxidation of the volatile compounds generated from the MR, investigated by the addition of free radical modulators (antioxidants alpha-tocopherol, 2,6-di-tert-butyl-4-methylphenol, and rosemary extract; or pro-oxidant alpha,alpha'-azobis-isobutyronitrile, a free radical initiator), was limited in respect to aqueous model systems.  相似文献   

7.
The antioxidant activity of the phenolic fraction of extra virgin olive oil was assessed in samples that had a decreasing content of antioxidants in the presence and absence of copper ions as a catalyst of autoxidation. The oxidation process was evaluated by measuring primary and secondary oxidation products. Changes in phenols and tocopherols were investigated by high-performance liquid chromatography. Both the total phenol content and their antioxidant activity were monitored by spectrophotometric assays (with Folin-Ciocalteu and ABTS*+ reagents). The important role of phenolic compounds (particularly the o-diphenols) in protection from autoxidation was confirmed. However, the tocopherols were more quickly consumed in oils that had the lowest content of o-diphenols, which also showed evidence of an ability to chelate copper. In particular, a dramatic decrease was observed in the isomeric form of decarboxymethyl-oleuropein aglycone after addition of the metal, despite its significant increase in samples stored in the absence of copper.  相似文献   

8.
Aim of this study was to evaluate the total antioxidant activity (TAA) of extra virgin olive oil (EVOO) and the effect of heating on the alpha-tocopherol content and TAA in relation to the presence of polyphenols, heating time, and temperature. Experiments included the measurement by ABTS decolorization assay of antioxidant capacity of alpha-tocopherol and 14 simple phenolic compounds present in EVOO, either dissolved in ethanol or added to refined olive oil, and the evaluation of TAA, total phenols, and alpha-tocopherol of six commercial EVOO and three olive oils. Finally, four experimental oils were prepared from refined olive oil containing a fixed amount (300 ppm) of alpha-tocopherol and increasing amounts of polyphenols (25, 125, 225, and 326 ppm) extracted from EVOO. The thermal stability of experimental oils under domestic heating conditions (heating time from 30 to 120 min, heating temperature from 160 to 190 degrees C) was studied by evaluating the loss of alpha-tocopherol and TAA according to a Latin square design. Results indicate that TAA of commercial oils is mainly due to their phenol and alpha-tocopherol content. Heating experiments suggest that polyphenols from EVOO are effective stabilizers of alpha-tocopherol during olive oil heating, thus contributing to the nutritional value of cooked foods.  相似文献   

9.
The aim of this study was to characterize antioxidant activities of phenolic compounds that appear in olive pulp and olive oils using both radical scavenging and antioxidant activity tests. Antiradical and antioxidant activities of olive pulp and olive oil phenolic compounds were due mainly to the presence of a 3,4-dihydroxy moiety linked to an aromatic ring, and the effect depended on the polarity of the phenolic compound. Glucosides and more complex phenolics exhibited higher antioxidant activities toward oxidation of liposomes, whereas in bulk lipids aglycons were more potent antioxidants with the exception of oleuropein. Lignans acted as antioxidants only in liposomes, which could partly be due to their chelating activity, because liposome oxidation was initiated by cupric acetate. The antioxidant activity of virgin olive oil is principally due to the dialdehydic form of elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA), a secoiridoid derivative (peak RT 36, structure unidentified), and luteolin.  相似文献   

10.
The effect of natural phenolic compounds on the antioxidant and prooxidant activity of lactoferrin was studied in liposomes and oil-in-water emulsions containing iron. The antioxidants tested with lactoferrin were alpha-tocopherol, ferulic acid, coumaric acid, tyrosol, and natural phenolic extracts obtained from three different extra-virgin olive oils and olive mill wastewater. The natural extracts of olive oils and mill wastewaters were composed mainly of polyphenols and simple phenolics, respectively. Lipid oxidation at 30 degrees C was determined by the formation of hydroperoxides and fluorescent compounds resulting from oxidized lipid interactions. All phenolic compounds showed synergistic properties in reinforcing the antioxidant activity of lactoferrin in lipid systems containing iron. The highest synergistic effects were observed for the phenolic extracts rich in polyphenols of extra-virgin olive oils and lactoferrin. This synergistic effect was higher in liposomes than in emulsions.  相似文献   

11.
A comparison between the results obtained by using HPLC-UV, HPLC-MS, and CE-UV for characterizing the deterioration of extra-virgin olive oil during heating (180 degrees C) was investigated, taking into account phenolic compounds. The concentration of several compounds belonging to four families of phenols (simple phenols, lignans, complex phenols, and phenolic acids) was determined in the samples after the thermal treatment by all three techniques. Hydroxytyrosol, elenolic acid, decarboxymethyl oleuropein aglycon, and oleuropein aglycon reduced their concentration with the thermal treatment more quickly than other phenolic compounds present in olive oil. HYTY-Ac and Lig Agl were demonstrated to be quite resistant to this kind of treatment, and the behavior of lignans could be outstanding, as they belong to the family most resistant to thermal treatment. Several "unknown" compounds were determined in the phenolic profiles of the oils after the thermal treatment, and their presence was confirmed in refined olive oils. The oxidative stability index (OSI time) was reduced from 25 to 5 h after 3 h of heating, whereas the peroxide value showed a minimum after 1 h of heating.  相似文献   

12.
Interest in replacing synthetic antioxidants, namely, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA), with natural antioxidants is increasing. The present study examined the antioxidant activity of capsaicinoid from chili pepper in heated canola oil. The oxidation was conducted at 60, 90, 120, and 180 °C by monitoring oxygen consumption and the decrease in linoleic acid and α-linolenic acid in canola oil. At 60 °C, capsaicinoid was more effective against oxidation of canola oil compared with BHT. At higher temperatures of 90, 120, and 180 °C, capsaicinoid possessed an antioxidant activity similar to or slightly weaker that that of BHT. It was found that capsaicinoid prevented canola oil from oxidation in a dose-dependent manner. To study the structure-antioxidant relationship, it was found that the trimethylsiloxy (TMS) derivatives of capsaicinoid did not exhibit any antioxidant activity, suggesting the hydroxyl moiety was the functional group responsible for the antioxidant activity of capsaicinoid. It was concluded that capsaicinoid had the potential to be further explored as a natural antioxidant in foods, particularly spicy foods.  相似文献   

13.
Virgin olive oils were subjected to simulated common domestic processing, including frying, microwave heating, and boiling with water in a pressure cooker. The impact of these processes on polyphenol content and physicochemical characteristics of oils was assessed. Thermal oxidation of oils at 180 degrees C caused a significant decrease in hydroxytyrosol- and tyrosol-like substances. In contrast, oils heated for 25 h still retained a high proportion of the lignans 1-acetoxypinoresinol and pinoresinol. Thermal oxidation also resulted in a rapid degradation of alpha-tocopherol and the glyceridic fraction of oils. Microwave heating of oils for 10 min caused only minor losses in polyphenols, and the oil degradation was lower than that in thermoxidation assays. Again, lignans were the least affected polyphenols and did not change during microwave heating. Boiling a mixture of virgin olive oil and water in a pressure cooker for 30 min provoked the hydrolysis of the secoiridoid aglycons and the diffusion of the free phenolics hydroxytyrosol and tyrosol from the oil to the water phase. Losses of polyphenols were detected only at pH lower than 6. Moreover, alpha-tocopherol and the glyceridic fraction of oils were not modified during this process. It is worth noting that all the heating methods assayed resulted in more severe polyphenols losses and oil degradation for Arbequina than for Picual oil, which could be related to the lower content in polyunsaturated fatty acids of the latter olive cultivar. These findings may be relevant to the choice of cooking method and olive oil cultivar to increase the intake of olive polyphenols.  相似文献   

14.
In olive oils, relationships between oxidative stability, glyceridic composition, and antioxidant content were investigated. Lipid matrices, obtained by purification of olive and high-oleic sunflower oils, were spiked with hydroxytyrosol, alpha-tocopherol, and mixtures of them and then subjected to oxidation in a Rancimat apparatus at 100 degrees C. At the same concentration of antioxidants, induction time (IT) decreased as the unsaturation rate of the matrix increased, but only fair correlations were found with fatty acid composition. Oxidative susceptibility (OS(TAG)) was calculated as a function of the relative oxidation rate of the triacylglycerols, and a linear relationship-IT (h) = (a + b)OS(TAG)-between induction time and this parameter showed a good correlation coefficient (r > 0.990, p < 0.001). In the case of matrices with a single antioxidant, origin ordinate (a) and slope (b) can be calculated as a function of the antioxidant concentration. In matrices spiked with mixtures of hydroxytyrosol and alpha-tocopherol, a simple relationship between the coefficients a and b and the concentration of antioxidants cannot be established because additive and subtractive effects occur depending on the relative concentrations of both antioxidants. However, approximate values for these coefficients can be obtained, allowing the estimation of the oil stability. In various olive oils, an acceptable agreement was found between the IT experimentally determined and that calculated from the oil composition. These results confirmed that the Rancimat stability of olive oils mainly depends on triacylglycerol composition and concentrations of o-diphenols and alpha-tocopherol.  相似文献   

15.
The study of the antioxidant effects of biophenolic compounds is supported by the current interest in natural products and the ongoing replacement of synthetic antioxidants by natural antioxidants from plant sources. Olives and olive oil, especially extra virgin olive oil, contain a variety of bioactive compounds (phytochemicals) widely considered to be potentially beneficial for health. This research was focused on evaluating the antioxidant activity of the enriched refined olive oil to discover a possible functional food application. Different concentrations of individual and combined phenolic compounds were added to the refined olive oil as lipid matrix, and the antioxidant activity expressed as oxidative stability in hours was determined by using the Rancimat method. Additionally, the bitter index was evaluated to assess the effect of the enrichment in relation to the organoleptic quality. The results showed that the antioxidant activity depends on the concentration of the phenol used for the assay and the chemical structure. In general, the most positive effects were observed in 3,4-dihydroxy and 3,4,5-trihydroxy structures linked to an aromatic ring that conferred to the moiety a higher proton dislocation, thus facilitating the scavenging activity.  相似文献   

16.
In contrast to other metabolic functions, the role of dietary antioxidants and oil on microsomal lipid oxidation has been less extensively studied. This study examines ascorbate-Fe(2+) and NADPH-induced lipid peroxidation of hepatic microsomes of rats that were fed for three weeks high-oleic-acid oils (high-oleic sunflower oil, HOSO; olive oil, OO; or olive pomace oil, OPO) containing different concentrations of the antioxidants alpha-tocopherol, erythrodiol, and oleanolic acid. The fatty acid composition of hepatic microsomes of Wistar rats that were fed for three weeks with the above-mentioned oils had lower proportions of C16:0, C18:2n6, and C22:6n3 and higher proportions of C18:0 and C18:1n9 than rats fed the control diet. Light emission by hepatic microsomes increased, in the first 180 min, 2-fold after ascorbate-Fe(2+) addition compared with NADPH addition. Both increases were less pronounced in microsomes of OPO-fed rats and to a smaller extent in microsomes of OO-fed rats. Smaller increases in light emission were associated positively with higher concentrations of dietary alpha-tocopherol, erythrodiol, and oleanolic acid but were not associated with changes in fatty acid composition of hepatic microsomes. Addition of alpha-tocopherol, erythrodiol, or oleanolic acid decreased light emission of hepatic microsomes with a greater inhibition in microsomes of rats fed the control diet. Our data suggest that erythrodiol and oleanolic acids partly explain the protective effect of dietary OPO on microsomal lipid peroxidation in rats.  相似文献   

17.
Thermogravimetric analysis was used to determine the oxidative stability of various edible oils (olive oil, milkfat) and triacylglycerides (triolein, trilinolein), while the effect of natural (alpha-tocopherol, ascorbic acid) and synthetic antioxidants (butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and tertiary butyl hydroquinone were evaluated by addition to trilinolein. Oil resistance to oxidation was obtained by measuring the increase in sample weight due to the uptake of molecular oxygen, the temperature at maximum sample weight, and the temperature at the onset of oxidation. When comparing sample weight increase, trilinolein proved to be oxidatively less stable than triolein, olive oil, and milk fat, while triolein was less stable than olive oil and milk fat. Olive oil showed significantly higher stability than milkfat when comparing the temperature at the onset of oxidation. When comparing effectiveness of antioxidants, a combination of 0.01% BHA and 0.01% BHT increased trilinolein stability the most.  相似文献   

18.
A simple and precise analytical method was developed for the simultaneous determination of squalene and methyl, ethyl, propyl, and butyl esters of fatty acids present in olive and olive pomace oils. A fraction containing squalene and fatty acid alkyl esters was isolated from the oil by solid phase extraction on silica gel cartridges and quantitatively analyzed by gas chromatography. A modification of the procedure allowed the isolation of squalene and esters separately. Repeatability and recovery of the method were good. The method was applied to extra and lampant virgin olive oil categories and also to oils obtained from olive pomace by second centrifugation and solvent extraction. Extra virgin olive oils contained low amounts of fatty acid methyl and ethyl esters, while oils obtained from altered olive or olive pomace showed high concentrations of fatty acid alkyl esters, mainly ethyl esters. Correlation between oil acidity and ethyl esters concentration was poor.  相似文献   

19.
The formation and evolution of monoepoxy fatty acids, arising from oleic and linoleic acids, were investigated in olive oil and conventional sunflower oil, representatives of monounsaturated and polyunsaturated oils, respectively, during thermoxidation at 180 degrees C for 5, 10, and 15 h. Six monoepoxy fatty acids, cis-9,10- and trans-9,10-epoxystearate, arising from oleic acid, and cis-9,10-, trans-9,10-, cis-12,13-, and trans-12,13-epoxyoleate, arising from linoleic acid, were analyzed by gas chromatography after oil derivatization to fatty acid methyl esters. Considerable amounts, ranging from 4.29 to 14.24 mg/g of oil in olive oil and from 5.10 to 9.44 mg/g of oil in sunflower oil, were found after the heating periods assayed. Results showed that the monoepoxides quantitated constituted a major group among the oxidized fatty acid monomers formed at high temperature. For similar levels of degradation, higher contents of the monoepoxides were found in olive oil than in sunflower oil. Ten used frying oils from restaurants and fried-food outlets in Spain were analyzed to determine the contents of the monoepoxides in real frying oil samples. Levels ranged from 3.37 to 14.42 mg/g of oil. Results show that, for similar degradation levels, the monoepoxides were more abundant in the monounsaturated oils than in the polyunsaturated oils.  相似文献   

20.
The dried aerial parts of the mountain tea Sideritis euboea were extracted using n-hexane, methanol, diethyl ether, ethyl acetate, and n-butanol. The residues were tested for their antioxidant activity on sunflower oil at 50 degrees C under UV light. The oxidation of the sunflower oil was measured using PV, absorbance E(1%)1 cm, and malondialdehyde by high-performance liquid chromatography (HPLC). The butanol extract showed the highest antioxidant activity and was further fractionated by silica and cellulose column chromatography and finally by HPLC. The activity of the final fraction on a range of vegetable oils was compared to that of common used antioxidants (BHT, alpha-tocopherol) using DPPH*, the Rancimat method, and the Schaal oven test. At a level of 400 ppm, the extracted kaempherol showed the highest antioxidant activity among all antioxidants tested. The final fraction was identified (using UV, 1H NMR, 13C NMR, mass spectroscopy, and melting point) as 3,5,7,4'-tetrahydroxy flavone (kaempherol).  相似文献   

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