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1.
The fluorescence spectroscopy technique has been tested as regards its ability to differentiate between refined hazelnut and olive oils. Classification of these oils based on their excitation-emission fluorescence spectra data (spectral range 300-500 nm of the excitation spectra at lambdaem=655 and spectral range 650-900 of the emission spectra at lambdaex=50 nm) was performed using principal component analysis and artificial neural networks. Both methods provided good discrimination between the refined hazelnut and olive oils. The results have also pointed out the possibilities of a spectrofluorimetric method joined to multivariate analysis, to differentiate refined oils, and even to detect the presence of refined hazelnut oils in refined olive oils at percentages higher than 9%.  相似文献   

2.
The authentication of virgin olive oil samples requires usually the use of sophisticated and very expensive analytical techniques, so there is a need for fast and inexpensive analytical techniques for use in a quality control methodology. Virgin olive oils present an intense fluorescence spectra. Synchronous excitation-emission fluorescence spectroscopy (SEEFS) was assessed for origin determination of virgin olive oil samples from five French registered designation of origins (RDOs) (Nyons, Vallée des Baux, Aix-en-Provence, Haute-Provence, and Nice). The spectra present bands between 600 and 700 nm in emission due to chlorophylls a and b and pheophytins a and b. The bands between 275 and 400 nm in emission were attributed to alpha-, beta-, and gamma-tocopherols and to phenolic compounds, which characterize the virgin olive oils compared to other edible oils. The chemometric treatment (PLS1) of synchronous excitation-emission fluorescence spectra allows one to determine the origin of the oils from five French RDOs (Baux, Aix, Haute-Provence, Nice, and Nyons). Results were quite satisfactory, despite the similarity between two denominations of origin (Baux and Aix) that are composed by some common cultivars (Aglandau and Salonenque). The interpretation of the regression coefficients shows that RDOs are correlated to chlorophylls, pheophytins, tocopherols, and phenols compounds, which are different for each origin. SEEFS is part of a global analytic methodology that associates spectroscopic and chromatographic techniques. This approach can be used for traceability and vindicates the RDOs.  相似文献   

3.
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   

4.
The resolution of quaternary mixtures of chlorophylls a and b and pheophytins a and b has been accomplished by partial least-squares (PLS) multivariate calibration, applied to the fluorescence signals of these pigments. The total luminescence information of the compounds has been used to optimize the spectral data set to perform the calibration. After preliminary studies, a method is described in acetone media, to avoid emulsions with the olive oil samples. Different scanning paths have been selected for each method. For the simultaneous determination of the pigments in olive oil samples, a comparative study of the results found by using excitation, emission, and synchronous spectral data, as analytical signal, was performed. The excitation spectra were selected as the better analytical signals for the determination of the pigments in olive oil samples. The optimum wavelength range to record the excitation spectra (lambda(em) = 662 nm) was selected to minimize the contribution of pheophytin a and to maximize the contribution of the other pigments, which are the minor constituents in olive oil. Determination of these pigments in olive oil samples was effected from the excitation spectra of dissolutions o suitable aliquots in acetone. Recovery values from olive oil, spiked with chlorophylls a and b and pheophytins a and b, were in the ranges of 70-112, 71-111, 76-105, and 82-109%, respectively.  相似文献   

5.
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   

6.
Laser-induced fluorescence spectroscopy (LIFS) was nondestructively applied on strawberries (EX = 337 nm, EM = 400-820 nm) to test the feasibility of quantitatively determining native phenolic compounds in strawberries. Eighteen phenolic compounds were identified in fruit skin by UV and MS spectroscopy and quantitatively determined by use of rp-HPLC for separation and diode-array or chemical reaction detection. Partial least-squares calibration models were built for single phenolic compounds by means of nondestructively recorded fluorescence spectra in the blue-green wavelength range using different data preprocessing methods. The direct orthogonal signal correction resulted in r (2) = 0.99 and rmsep < 8% for p-coumaroyl-glucose, and r (2) = 0.99 and rmsep < 24% for cinnamoyl-glucose. In comparison, the correction of the fluorescence spectral data with simultaneously recorded reflectance spectra did not further improve the calibration models. Results show the potential of LIFS for a rapid and nondestructive assessment of contents of p-coumaroyl-glucose and cinnamoyl-glucose in strawberry fruits.  相似文献   

7.
One hundred and thirty-eight oil samples have been analyzed by visible and near-infrared transflectance spectroscopy. These comprised 46 pure extra virgin olive oils and the same oils adulterated with 1% (w/w) and 5% (w/w) sunflower oil. A number of multivariate mathematical approaches were investigated to detect and quantify the sunflower oil adulterant. These included hierarchical cluster analysis, soft independent modeling of class analogy (SIMCA method), and partial least squares regression (PLS). A number of wavelength ranges and data pretreatments were explored. The accuracy of these mathematical models was compared, and the most successful models were identified. Complete classification accuracy was achieved using 1st derivative spectral data in the 400-2498 nm range. Prediction of adulterant content was possible with a standard error equal to 0.8% using 1st derivative data between 1100 and 2498 nm. Spectral features and chemical literature were studied to isolate the structural basis for these models.  相似文献   

8.
Fluorescence spectra of undiluted extra virgin olive oil obtained with the traditional setup (right-angle fluorescence) show considerable artifacts and deformations due to self-absorption phenomena, even when the spectra are corrected for inner filter effects. On the other side, front-face fluorescence spectra are much less affected by self-absorption. Front-face fluorescence of native olive oil reveals the presence of different fluorophores and can provide information about their amount. From the intense emission at ca. 315-330 nm, it is possible to detect fluorescent polyphenols and pherols and to evaluate their overall content. Low-intensity emission bands at 350-600 nm are correlated to vitamins and other important molecules. Among them, the fluorescence of the riboflavin fluorophore can be used to evaluate its concentration. The intense emission of chlorophyll derivatives, measured in the 640-800 nm spectral region, can provide information on their concentration.  相似文献   

9.
In this study, the diglyceride contents of 96 samples of virgin olive oils from the regions of Crete, Lesvos, Messinia, Pilion, Zakynthos, Halkidiki, and Ilia, 15 samples of commercial extra virgin and pure olive oils, and 3 samples each of refined olive oils and pomace oils were determined by a facile method introduced in a previous publication. This method is based on the phosphitylation of the free hydroxyls of the diglycerides with 2-chloro-4,4,5,5-tetramethyldioxaphospholane and the integration of the appropriate peaks in the (31)P NMR spectra. This preliminary study showed interesting trends in the diglyceride content of the virgin olive oils from the various regions of Greece that can be used as simple criteria to assess the olive oil characteristics. Analysis of variance has been carried out for the diglyceride content of each region in an attempt to detect possible differences in the diglyceride levels among the various regions. Finally, the relationship between the ratio of 1,2-diglycerides to the total amount of diglycerides and the total amount of diglycerides has been used to monitor the quality of virgin olive oils, commercial olive oils, refined olive oils, and pomace oils.  相似文献   

10.
(13)C NMR spectra of oil fractions obtained chromatographically from 66 vegetable oils were obtained and analyzed to evaluate the potential use of those fractions in predicting oil stabilities and to compare those results with oil stability prediction by using chemical determinations. The oils included the following: virgin olive oils from different cultivars and regions of Europe and north Africa; "lampante" olive, refined olive, refined olive pomace, low-erucic rapeseed, high-oleic sunflower, corn, grapeseed, soybean, and sunflower oils. Oils were analyzed for fatty acid and triacylglycerol composition, as well as for phenol and tocopherol contents. By using stepwise linear regression analysis (SLRA), the chemical determinations and the (13)C NMR data that better explained the oil stability determined by the Rancimat were selected. These selected variables were related to both the susceptibility of the oil to be oxidized and the content of minor components that most contributed to oil stability. Because (13)C NMR considered many more variables than those determined by chemical analysis, the predicted stabilities calculated by using NMR data were always better than those obtained by using chemical determinations. All these results suggest that (13)C NMR may be a powerful tool to predict oil stabilities when applied to chromatographically enriched oil fractions.  相似文献   

11.
The differentiation of nonrefined (e.g., cold-pressed) and refined edible oils is an important task in food control because of the higher commercial value of the former. Here, we explored the suitability of the relative abundance of cis-phytol as a marker for authentication of nonrefined edible oils. Phytol, the tetramethyl-branched, monoenoic alcohol, is found widespread in nature as a part of chlorophyll. In chlorophyll, only trans-phytol is found. In this study, we present a method for the analysis of the phytol isomers, considering that traces of cis-phytol (contributing 0.1% to the phytol content) can be determined next to trans-phytol. For this purpose, phytol was gathered with the unsaponifiable matter from the oil, trimethylsilylated, and analyzed by gas chromatography coupled to mass spectrometry. With this method, 27 samples of edible oils (16 refined and 11 nonrefined edible oils) were analyzed for the abundance of cis-phytol relative to trans-phytol. In the nonrefined oils (e.g., olive oil, rapeseed oil, maize oil, and sunflower oil), cis-phytol contributed 0.1% (n = 3) or less (n = 8) to the phytol content. In contrast, the refined olive oils (n = 4) contained a share of 1.3-3% cis-phytol; the refined rapeseed oil (n = 3) contained a share of 0.7-1.0% cis-phytol; and the refined sunflower oil (n = 4) contained a share of 0.3-0.9% cis-phytol. Only one refined pomegranate kernel did not contain cis-phytol. The phytol concentration was not suited to distinguish nonrefined from refined oils. In contrast, our data suggest that the virtual absence of cis-phytol can be used as a marker for nonrefined (e.g., cold-pressed) edible oils.  相似文献   

12.
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   

13.
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   

14.
The potential of near-infrared transflectance spectroscopy (1100-2498 nm) combined with chemometric techniques to confirm the geographical origin of European olive oil samples was evaluated. In total, 913 extra virgin olive oil samples (210 Ligurian and 703 non-Ligurian) were collected over three consecutive harvests (2005, 2006, and 2007). A multivariate spectral fingerprint for Ligurian olive oil was developed and deployed to confirm or refute a claim that any given sample was Ligurian. Samples were pseudorandomly split into calibration (n = 280) and validation sets (n = 633); the only selection constraint applied was to insist on equal numbers of Ligurian and non-Ligurian samples in the calibration set. Following preliminary examination by principal component analysis, the full spectrum modeling method applied to the spectral data set was discriminant partial least-squares regression; various data pretreatments were also investigated. The best models correctly predicted the origins of samples in the prediction set up to 92.8 and 81.5% for Ligurian and non-Ligurian olive oil samples, respectively, using a first-derivative data pretreatment. The potential of this approach in commercial traceability and quality assurance schemes is noted.  相似文献   

15.
13C nuclear magnetic resonance spectroscopy was used to classify olive oils from the three production areas of the Puglia region labeled with the "denomination of protected origin" (DPO) Terra di Bari, Colline di Brindisi, and Dauno. High resolution (13)C spectra of 173 olive oil samples were measured, and the intensity data of triacylglycerol resonances were processed by using linear discriminant analysis, which was carried out stepwise for variable selection. The olive oil samples from the DPOs Colline di Brindisi and Terra di Bari were 90% correctly classified, whereas only 74% of "Dauno" DPO oils were classified in the true group. The performance of the discriminant model was verified by applying the cross-validation procedure based on the "leave one out" formalism. The discriminant model was evaluated against a blind test set of olive oils from the three DPO areas. All the oils used for the purpose were correctly assigned to their respective groups, with the exception of the Dauno oil samples based on the Coratina cv. They were misclassified as Terra di Bari oils because of a common monovarietal composition.  相似文献   

16.
Applicability of near infrared reflectance (NIR) and fluorescence spectroscopic techniques was tested on highly organic arctic soil. Soil samples were obtained at a long-term climate change manipulation experiment at a subarctic fell heath in Abisko, northern Sweden. The ecosystem had been exposed to treatments simulating increasing temperature (open-top greenhouses), higher nutrient availability (NPK fertilization) and increasing cloudiness (shading cloths) for 15 years prior to the sampling. For each of the 72 samples from the 0 to 5 cm soil depth and 36 samples from the 5 to 10 cm depth, the wavelength range of 400-2500 nm (visible and near infrared spectrum) was scanned with a NIR spectrophotometer and fluorescence excitation-emission matrices (EEMs) were recorded with a spectrofluorometer.Principal component analyses of the visible, NIR and fluorescence spectra clearly separated the treatments, which indicates that the chemical composition of the soil and its spectral properties had changed during the climate change simulation. Similarly to the results from the conventional analyses of soil chemical and microbiological properties, fertilization treatment posed strongest effects on the spectra. Partial least-squares (PLS) regression methods with cross-validation were used to analyse relationships between the spectroscopic data and the chemical and microbiological data derived from the conventional analyses. The fluorescence EEMs of the dried solid soil samples were moderately related to soil ergosterol content (correlation coefficient r=0.84), bacterial activity analysed by leucine incorporation technique (r=0.78) and total phospholipid fatty acid (PLFA) content (r=0.74), but in general fluorescence provided inferior predictions of the chemical and microbiological variables to NIR. NIR was highly related to soil organic matter content (r>0.9) and showed promising predictions of soil ergosterol content (r>0.9), microbial biomass C, microbial biomass P, and total PLFA contents (r=0.78-0.79).These results suggest that especially NIR could be used to predict soil organic matter and fungal biomass. Since it is rapid and inexpensive, and requires little sample mass, it could be used as a ‘quick and dirty’ technique to estimate progression of the treatment responses in long-term ecosystem experiments, where extensive soil sampling is to be avoided.  相似文献   

17.
1H high-field nuclear magnetic resonance (NMR) was used to analyze 216 extra virgin olive oils collected in three years (1996, 1997, and 1998) in different Italian areas in order to evaluate the potential contribution of this technique to the geographical characterization of olive oils. A statistical procedure performed on the intensity of selected NMR peaks has been proposed. Tree clustering analysis of NMR data performed without any a priori hypothesis showed the existence of reliable parameters able to group the olive oils according to the location of olive oil production. Linear discriminant analysis applied to selected NMR parameters of olive oils of the same year of production allowed the grouping of samples according to their geographical origin with only very few errors. Moreover, a satisfactory grouping is reached by combining the NMR data of olive oils from two different years (1996 and 1997). Operating on appropriate sampling, a careful analysis of data yielded the conclusion that the place of olive production could be singled out as a discriminating factor regardless of the cultivars from which the olive oils are derived.  相似文献   

18.
This work is a contribution to the study of the bleaching process, which is a very important stage in the refining process of vegetable oils and used to reduce or convert undesired constituents to harmless ones from fats and oils. The virgin olive oil, taken as reference, and the pomace-olive oil were bleached in the optimal conditions using Tunisian bleaching earths (South of Tunisia) which were activated in our laboratory and compared with commercial clays. It was shown that activated Tunisian clays are characterized by a very important adsorptive capacity, comparable to that of commercial clays. Also, the physicochemical stability of bleached oils was studied. The fatty acid composition (GC), the triacylglycerol composition (HPLC), and the oxidative stability (UV spectrometry) allowed us to conclude that oils, bleached with the Tunisian activated clays, do not undergo considerable physicochemical alterations and remain corresponding to the international standards for refined oils for human consumption.  相似文献   

19.
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   

20.
Detection of rancid defect in virgin olive oil by the electronic nose   总被引：1，自引：0，他引：1  
A sensor array of 32 conducting polymer sensors has been used to detect the rancid defect in virgin olive oils. A training set, composed of admixtures of a Portuguese virgin olive oil with different percentages (0-100%) of a rancid standard oil, was used for the selection of the best sensors classifying correctly the samples. Information on volatile compounds responsible for rancidity and the sensory evaluation of samples by assessors were used for explaining the mathematical selection of sensors. A tentative calibration, using unsupervised procedures (PCA and MDS) and a nonlinear regression, was carried out, with the training set, and later confirmed with a test set with which rancid commercial samples of different varieties were used to spike a Greek extra virgin olive oil at low levels of rancidity (0.5-6%).  相似文献   

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