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1.
High-field 31P NMR (202.2 MHz) spectroscopy was applied to the analysis of 59 samples from three grades of olive oils, 34 extra virgin olive oils from various regions of Greece, and from different olive varieties, namely, 13 samples of refined olive oils and 12 samples of lampante olive oils. Classification of the three grades of olive oils was achieved by two multivariate statistical methods applied to five variables, the latter being determined upon analysis of the respective 31P NMR spectra and selected on the basis of one-way ANOVA. The hierarchical clustering statistical procedure was able to classify in a satisfactory manner the three olive oil groups. Subsequent application of discriminant analysis to the five selected variables of oils allowed the grouping of 59 samples according to their quality with no error. Different artificial mixtures of extra virgin olive oil-refined olive oil and extra virgin olive oil-lampante olive oil were prepared and analyzed by 31P NMR spectroscopy. Subsequent discriminant analysis of the data allowed detection of extra virgin olive oil adulteration as low as 5% w/w for refined and lampante olive oils. Further application of the classification/prediction model allowed the estimation of the percent concentration of refined olive oil in six commercial blended olive oils composed of refined and virgin olive oils purchased from supermarkets.  相似文献   

2.
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   

3.
The evolution of 1,3- and 1,2-isomers of diacylglycerols (DGs) in olive oils obtained from healthy olives and the influence of the olive quality was studied. Healthy olive fruits yielded oils containing almost exclusively 1,2-isomers whereas altered olives produced oils with significant amounts of 1,3-isomers. Virgin olive oils obtained from various olive cultivars and stored at different temperatures showed triacylglycerol hydrolysis and diacylglycerol isomerization depending on the acidity and temperature. The results indicated that the relationship between acidity and total diacylglycerol content has scarce utility for detecting mild refined oil in virgin olive oil. On the other hand, the 1,3-/1,2-DG isomers ratio is useful for assessing the genuineness of virgin olive oils with low acidities during the early stages of storage.  相似文献   

4.
A combination of (1)H NMR and (31)P NMR spectroscopy and multivariate statistical analysis was used to classify 192 samples from 13 types of vegetable oils, namely, hazelnut, sunflower, corn, soybean, sesame, walnut, rapeseed, almond, palm, groundnut, safflower, coconut, and virgin olive oils from various regions of Greece. 1,2-Diglycerides, 1,3-diglycerides, the ratio of 1,2-diglycerides to total diglycerides, acidity, iodine value, and fatty acid composition determined upon analysis of the respective (1)H NMR and (31)P NMR spectra were selected as variables to establish a classification/prediction model by employing discriminant analysis. This model, obtained from the training set of 128 samples, resulted in a significant discrimination among the different classes of oils, whereas 100% of correct validated assignments for 64 samples were obtained. Different artificial mixtures of olive-hazelnut, olive-corn, olive-sunflower, and olive-soybean oils were prepared and analyzed by (1)H NMR and (31)P NMR spectroscopy. Subsequent discriminant analysis of the data allowed detection of adulteration as low as 5% w/w, provided that fresh virgin olive oil samples were used, as reflected by their high 1,2-diglycerides to total diglycerides ratio (D > or = 0.90).  相似文献   

5.
Samples of Spanish virgin olive oils (VOOs) from different categories, origins, varieties, and commercial brands were analyzed by HPLC with a programmable fluorescence detector to determine the content of nine heavy polycyclic aromatic hydrocarbons (PAHs): benzo(a)anthracene, chrysene, benzo(e)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perilene, and indeno(1,2,3-c,d)pyrene. Samples of olive pomace and crude olive pomace oils were also investigated. Benzo(a)pyrene concentrations were below the allowed limit in the European Union (2 microg/kg) in 97% of the VOO samples. Only those samples coming from contaminated olive fruits or obtained in oil mills with highly polluted environments exceeded this value. High correlation coefficients (<0.99) were obtained between the contents of benzo(a)pyrene and the sum of the nine PAHs for all of the analyzed categories, suggesting that benzo(a)pyrene could be used as a marker of the content of these nine PAHs in olive oils.  相似文献   

6.
This paper introduces a facile method to determine the amount of mono- and diglycerides in virgin olive oils. This method is based on the phosphorylation of the free hydroxyls of the mono- and diglycerides with 2-chloro-4,4,5,5-tetramethyldioxaphospholane and the integration of the appropriate peaks in the (31)P NMR spectrum. Quantitative (31)P NMR spectroscopy can be extended to the quantification of other constituents of olive oils bearing functional groups with labile protons.  相似文献   

7.
alpha-Tocopherol, the main tocopherol homologue found in olive oil, was determined using normal phase HPLC. Ninety Greek virgin olive oils, selected according to a designed sampling protocol from different cultivars and regions all over Greece for three successive crop years, were analyzed. For a specific olive cultivar, which is widely used for the production of olive oil in Greece, additional measurements were made to study the effect of milling conditions on alpha-tocopherol concentration. Finally, a significant number of commercial olive oil samples (25) obtained from the retail market were analyzed. High concentrations of alpha-tocopherol were observed in most of the samples selected from various regions. Values ranging between 98 and 370 mg/kg were found (>200 mg/kg in 60% of samples). Extraction conditions were not found to influence alpha-tocopherol level. alpha-Tocopherol content of retail market samples was high, ranging from 120 to 250 mg/kg of oil (>180 mg/kg in 60% of samples). Storage of samples under domestic conditions for two years showed that good handling is quite important for retaining high alpha-tocopherol levels and for increasing, thus, the storage life and nutritional value of this exquisite oil.  相似文献   

8.
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   

9.
The stability of the antioxidant fraction in edible vegetable oils has been evaluated during a simulated deep frying process at 180 °C. Four edible oils (i.e., extra-virgin olive oil with a 400 μg/mL overall content in naturally existing phenols; high-oleic sunflower oil without natural content of these compounds but enriched either with hydrophilic antioxidants isolated from olive pomace or with an oxidation inhibitor, dimethylsiloxane; and sunflower oil without enrichment) were subjected to deep heating consisting of 20 cycles at 180 °C for 5 min each. An oil aliquot was sampled after each heating cycle to study the influence of heating on the antioxidant fraction composed of hydrophilic and lipophilic antioxidants such as phenols and tocopherols, respectively. The decomposition curves for each group of compounds caused by the influence of deep heating were studied to compare their resistance to oxidation. Thus, the suitability of olive pomace as raw material to obtain these compounds offers an excellent alternative to the use of olive-tree materials different from leaves. The enrichment of refined edible oils with natural antioxidants from olive pomace is a sustainable strategy to take benefits from this residue.  相似文献   

10.
Olive oil fluorescence is related to oil composition. Here it is shown that the natural clustering of different types of commercial Spanish olive oils depends on their fluorescence excitation-emission matrices (EEMs). Fifty-six commercial samples of olive oil (29 virgin olive oils, 20 pure olive oils, and 7 olive-pomace oils) were used. The clustering method was hierarchical agglomerative clustering using the Euclidean distance as a similarity measure and the average linkage. Two spectral ranges were considered (which either contained the fluorescence peak of the chlorophylls or did not), and various methods for preprocessing the fluorescence spectra were compared. The oils were clearly distinguished using the unfolded EEMs measured between lambda(ex) = 300-400 nm and lambda(em) = 400-600 nm. The optimal preprocessing was normalization of the unfolded spectra followed by column autoscaling. Also shown are the advantages of using second-order data (EEMs) instead of first-order data (a single fluorescence spectrum) for each sample.  相似文献   

11.
The phenolic composition of "lampante olive oil", "crude olive pomace oil", and "second centrifugation olive oil" was characterized by high-performance liquid chromatography with UV, fluorescence, and mass spectrometry detection. The phenolic profile of these olive oils intended for refining was rather similar to that previously reported for virgin olive oil. However, a new compound was found in these oils, which is mainly responsible of their foul odor. It was identified as 4-ethylphenol by comparison of its UV and mass spectra with those of a commercial standard. Although 4-ethylphenol was discovered in all oils intended for refining, its presence was particularly significant in "second centrifugation olive oils", its concentration increasing with time of olive paste storage. Similar trends were observed for hydroxytyrosol, hydroxytyrosol acetate, tyrosol, and catechol, the concentration of these substances reaching values of up to 600 mg/kg of oil, which makes their recovery for food, cosmetic, or pharmaceutical purposes attractive.  相似文献   

12.
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   

13.
Fatty acid alkyl esters (FAAEs) are a family of natural neutral lipids present in olive oils and formed by esterification of free fatty acids (FFAs) with low molecular alcohols. Inappropriate practices during the olive oil extraction process and bad quality of the olive fruits promote their formation. Quantification can be done by isolation with a silica gel solid phase extraction cartridge followed by analysis on a gas chromatograph equipped with a programmed temperature vaporizer injector using a polar capillary column. The application of the method to more than 100 Spanish olive oils from different categories, varieties, and geographical origin allowed for establishing the average content of FAAEs and distinguishing the Spanish protected denomination of origin (PDO) and extra virgin olive oils from other categories of olive oils. Those other categories of oils can be subjected to a mild refining process, which leads to blending with extra virgin olive oils. Studies on low quality oils subjected to mild refining showed that FAAEs remain after that process. Thereby, blends of extra virgin olive and mildly refined low quality olive oils can be detected by their alkyl ester concentrations.  相似文献   

14.
Emissions of low molecular weight aldehydes (LMWAs) from deep-frying of extra virgin olive oil, olive oil, and canola oil (control) were investigated at two temperatures, 180 and 240 degrees C, for 15 and 7 h, respectively. The oil fumes were collected in Tedlar bags and then analyzed by gas chromatography-mass spectrometry. Seven alkanals (C2-C7 and C9), eight 2-alkenals (C3-C10), and 2,4-heptadienal were found in the fumes of all three cooking oils. The generation rates of these aldehydes were found to be dependent on heating temperature, showing significant increases with increases in temperature. The LMWA emissions from both kinds of olive oils were very similar and were lower than those observed from canola oil under similar conditions. These results suggest that frying in any type of olive oil, independent of its commercial category, will effectively decrease the generation of volatile aldehydes in the exhaust. This fact is important because less expensive refined olive oil is usually used for deep-frying operations, whereas extra virgin olive oil is usually used as salad dressing.  相似文献   

15.
Headspace solid-phase microextraction (HS-SPME) -gas chromatography using flame ionization detection and multivariate analysis were applied to the study of the specificity of protected designation of origin (PDO) virgin olive oils produced in a southern French region (Alpes-Maritimes) based on their volatile compounds. A total of 35 PDO olive oils from Nice, 6 commercial oils, and 12 other French PDO olive oils were analyzed. Recorded data were subjected to principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). The method developed here was able to perfectly distinguish different qualities of olive oils. Representative samples from each class obtained by chemometric treatment were analyzed by HS-SPME and GC-MS. PCA and SIMCA of chromatographic data were related to sensory analysis and led to a better understanding of the chemical features and observed sensory effects of olive oils.  相似文献   

16.
Five methods using aqueous/organic solvents for the separation of proteins from oils were compared. The extraction with acetone-hexane followed by amino acid analysis was found to be the most suitable method for isolation and quantification of proteins from oils. The detection limit of the method was 0.18 mg protein/kg oil, and the quantification limit was 0.6 mg protein/kg. The relative repeatability limit for samples containing 1-5 mg protein/kg sample was 27%. The protein recovery ranged between 68 and 133%. Using this method, the protein content of 14 refined and nonrefined oils was determined. In none of the refined oils were proteins detected, whereas the protein content of the unrefined oils ranged between undetectable in extra virgin olive oil to 11 mg/kg in rapeseed oil. With sodium dodecyl sulfate-polyacrylamide gel electrophoresis in combination with silver staining, many protein bands were visible in the unrefined soy, olive, peanut, and rapeseed oil samples. Proteins bands were not obtained from the refined fish oil. In the other refined oil samples, a few proteins bands could be visualized. Two protein bands with apparent molecular molecular masses of 58 and 64 kDa were always observed in these oils.  相似文献   

17.
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   

18.
This paper shows the potential of excitation-emission fluorescence spectroscopy (EEFS) and three-way methods of analysis [parallel factor analysis (PARAFAC) and multiway partial least-squares (N-PLS) regression] as a complementary technique for olive oil characterization. The fluorescence excitation-emission matrices of a set of Spanish extra virgin, virgin, pure, and olive pomace oils were measured, and the relationship between them and some of the quality parameters of olive oils (peroxide value, K232, and K270) was studied. N-PLS was found to be more suitable than PARAFAC combined with multiple linear regression for correlating fluorescence and quality parameters, yielding better fits and lower prediction errors. The best results were obtained for predicting K270. EEFS allowed detection of extra virgin olive oils highly degraded at early stages (with high peroxide value) and little oxidized pure olive oils (with low K270). The proposed methodology may be used as an aid to analyze doubtful samples.  相似文献   

19.
SPME was employed to characterize the volatile profile of virgin olive oils produced in two geographical areas of northern Italy: the region of the Gulf of Trieste and the area near Lake Garda. There are as yet no data on the headspace composition of virgin olive oils from these regions, characterized by particular conditions of growth for Olea europaea. Using the SPME technique coupled to GC-MS and GC-FID, the volatile components of 42 industrially produced virgin olive oil samples were identified and the principal compounds quantitatively analyzed. Significant differences in the proportion of volatile constituents from oils of different varieties and geographical origins were detected. The results suggest that besides the genetic factor, environmental conditions influence the volatile formation.  相似文献   

20.
The presence of the oxidized and reduced forms of ubiquinones Q(9) and Q(10) was determined in commercial extra virgin olive and seed oils, where the amounts of alpha- and gamma-tocopherols and beta-carotene were also quantitated. Very high concentrations of ubiquinones were found in soybean and corn oils. Furthermore, the total antioxidant capability of each oil was evaluated by measuring total radical-trapping antioxidant parameters (TRAP) in tert-butyl alcohol and using egg lecithin as the oxidizable substrate. These values decreased in the order sunflower > corn > peanut > olive; the highest TRAP, which was found in sunflower oil, was related to the very high amount of alpha-tocopherol. Olive oil, because of the low content of alpha-tocopherol, exhibited a TRAP value approximately one-third that of sunflower oil. TRAP values of corn and soybean oils, in which low amounts of alpha-tocopherol but very high contents of gamma-tocopherol and reduced ubiquinones were present, were intermediate. gamma-Tocopherol exhibited a poor ability of trapping peroxyl radicals in tert-butyl alcohol. This behavior was probably due to the effects of the solvent on the rate of hydrogen abstraction from this phenol.  相似文献   

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