Pigment profile and colour of monovarietal virgin olive oils from Arbequina cultivar obtained during two consecutive crop seasons

Effect of containers on the quality of Chemlali olive oil during storage

This study is undertaken to determine the storage stability of Chemlali extra-virgin olive oil (EVOO) in different containers such as clear and dark glass bottles, polyethylene (PE) and tin containers. The different oil samples were stored under light at room temperature. Quality parameters monitored during a 6-month-storage period included: acidity, peroxide value (PV), spectrophotometric indices (K232 and K270), chlorophyll and carotene pigments, fatty acids and sterol compositions, total phenols, Rancimat induction time as well as sensory evaluation. Tin containers and dark glass bottles recorded the lowest oxidation values. In addition, oil packed in tin containers and dark glass bottles showed better physicochemical and organoleptic characteristics than that stored in clear glass bottles and PE containers. A significant decrease (p < 0.05) in the antioxidant contents (carotenes, chlorophylls and total phenols) was observed in the oil stored in the clear glass bottles and PE containers. Such results proved that the storage of oil in tin containers and dark glass bottles appeared most adequate, and showed a gradual loss of quality during storage, especially in PE containers and clear glass bottles. This study has shown that the best packaging materials for the commercial packing of Chemlali extra-virgin olive oil are tin containers and dark glass bottles.

Sensory attribute preservation in extra virgin olive oil with addition of oregano essential oil as natural antioxidant

Four commercial varieties of oregano are farmed in Argentina: "Compacto,""Cordobes,""Criollo," y "Mendocino." Oregano essential oil is known for antioxidant properties. The objective of this study was to evaluate changes in the intensities of positive and negative attributes in extra virgin olive oil with addition of essential oil obtained from the 4 Argentinean oregano types. Oregano essential oil was added into olive oil at 0.05% w/w. The samples were stored in darkness and light exposure during 126 d at room temperature. The intensity ratings of fruity, pungency, bitterness, oregano flavor, and rancid flavor were evaluated every 21 d by a trained sensory panel. In general, samples with addition of oregano essential oil in olive oil exhibited higher and lower intensity ratings of positive and negative attributes, respectively, during storage compared with the control samples. The first 2 principal components explained 72.3% of the variability in the olive oil samples. In general, positive attributes of olive oil were highly associated with the addition of oregano essential oil in darkness, whereas rancid flavor was negatively associated with them. Olive oil with oregano "Cordobes" essential oil was oppositely associated with light exposure treatments and negative attribute (rancid flavor) suggesting better performance as natural antioxidant of this essential oil in olive oil. The result of this study showed that the presence of oregano essential oil, specially "Cordobes" type, preserve sensory quality of extra virgin olive oil prolonging the shelf life of this product.

PRACTICAL APPLICATION

Extra virgin olive oil is highly appreciated for its health benefits, taste, and aroma. These properties are an important aspect in this product quality and need to be preserved. The addition of natural additives instead of synthetic ones covers the present trend in food technology. This research showed that the addition of oregano essential oil preserved the intensity ratings of positive attributes in extra virgin olive oil during storage. The essential oil of the oregano variety called "Cordobes" exhibited better protecting effect on sensory properties of olive oil than the other oregano varieties. The addition of oregano essential oil should be considered for the food industry as a natural source of antioxidant additives for preserving sensory properties in extra virgin olive oil and other similar food products.

Thermal stability of corn oil flavoured with Thymus capitatus under heating and deep-frying conditions

BACKGROUND

The thermal stability of corn oil flavoured with thyme flowers was determined and compared with that of the original refined corn oil (control). The oxidative stability index (OSI) was measured and samples were exposed to heating (30 min at 150, 180 and 200 °C) and deep-frying (180 °C). Changes in peroxide value (PV), free fatty acid (FFA) content, specific absorptivity values (K(232) and K(270)), colour and chlorophyll, carotenoid and total phenol contents were monitored.

RESULTS

The OSI and heating results showed that thyme incorporation was effective against thermal oxidation based on the increased induction time observed for the flavoured oil (6.48 vs 4.36 h), which was characterised by lower PV, FFA content, K(232) and K(270) than the control oil after heating from 25 to 200 °C, with higher red and yellow colour intensities and chlorophyll, carotenoid and total phenol contents. The deep-frying test showed the accelerated deterioration of both oils in the presence of French fries.

CONCLUSION

Compared with the control oil, the thyme-flavoured oil showed improved thermal stability after heating. This could be attributed to the presence of thyme pigments and antioxidant compounds allowing extended oil thermal resistance.

Characterization of the Olive Oil from Three Potentially Interesting Varieties from Aragon (Spain)

The commercial potential of olive oils from three autochthonous olive varieties Bodocal, Racimilla and Negral from Aragón (Spain) has been examined. Physicochemical characteristics, sensory analysis, nutritional composition, color and pigments were considered. The three varieties are generally used for producing table olives or olive oil in coupages but not for the production of monovarietal virgin olive oil. The values of the physicochemical and sensory analysis for the three olive oils corresponded to extra virgin category, however important differences among the three oils were observed in relation to pigment content, color measurements and fatty acid and phenol and tocopherol composition. Several characteristics such as oil yield, fatty acid and phenol and tocopherol content and sensory profiles suggested that some of these oils are of a promising composition. The olive yield of the Bodocal variety was the lowest (17%) and its corresponding oil had the smallest oleic acid (69%), phenols (272 mg gallic acid/kg) and tocopherol (96 mg/kg) contents and not equilibrated sensory parameters. The main characteristics of the Racimilla variety were a very high oil yield (28%) with very high contents in oleic acid (79 %) and phenols (831 mg gallic acid/kg). The oil of the Negral variety had very equilibrated sensory properties and its oleic acid content (76%) was similar to that of Racimilla. Its phenol content (456 mg gallic acid/kg) was between that of the other two varieties and its tocopherol content (190 mg/kg) was the highest. Therefore, the two last varieties could be of great interest for producing monovarietal olive oils.

Combination of an e-nose, an e-tongue and an e-eye for the characterisation of olive oils with different degree of bitterness

An electronic panel has been used to characterise the organoleptic characteristics of twenty-five extra virgin olive oils from varieties Hojiblanca, Picual and Arbequina, with different degree of bitterness. The method consists in the combination of three systems: electronic nose, electronic tongue and electronic eye. The Principal Component Analysis (PCA), where PC1, PC2 and PC3 explained 59% of the total variance between the samples, has demonstrated that the capability of discrimination of the combined system is superior to that obtained with the three instruments separately. This improvement is due to the increased information extracted from each sample. Partial Least Squares-Discriminant Analysis (PLS-DA) has allowed separation of the groups in function of olive variety with a root mean square error of prediction (RMSEP) lower than 0.099. Using PLS1 and PLS2 regression models, good correlations have been found between the signals obtained from the electronic tongue and the polyphenolic content (measured by chromatographic methods) or the bitterness index (scored by a panel of experts) with correlation coefficients higher than 0.9 in calibration and validation. These preliminary results indicate that the combination of an e-nose, an e-tongue and an e-eye can be a useful tool for the analysis of olive oil bitterness.

Control of olive oil adulteration with copper-chlorophyll derivatives

The present work proposes an analytical method able to detect in an adulterated olive oil sample the addition of the copper complexes of chlorophylls (E 141i). The method consists of a pigment extraction in liquid phase and subsequent analysis by HPLC-DAD. The profile of chlorophyll pigments of an olive oil is determined essentially by its content in pheophytins (a and b), but in no case any copper derivative. Different samples of colorant E 141i have been analyzed, the natural coloring additives used to adulterate vegetable oils. The 99.59+/-0.52% of the chlorophyll pigments present in the different samples of E 141i colorant are not those of an olive oil (more than 75% are cupro-derivatives). Thus, the simple detection of one of the compounds in an olive oil indicates adulteration. The major chlorophyll derivative in all the E 141i colorants samples is Cu-pyropheophytin a and its limit of detection (LOD) defined at a signal-to-noise ratio of about 3 was 6.58 ng/g.

Pigment profile in non-Spanish olive varieties ( Olea europaea L. Var. Coratina, Frantoio, and Koroneiki)

The analysis, for the first time, of the chlorophyll and carotenoid profile of olive fruits of the varieties Coratina, Frantoio, and Koroneiki has revealed important differences with Spanish varieties. First, a high chlorophylls/carotenoids ratio and a low chlorophyll a/b ratio imply that the photosynthetic apparatus has structural differences with respect to other olive varieties; second, in the carotenoid fraction, a low percentage of lutein, a high percentage of beta-carotene, and a high content in neoxanthin are signs that in these three olive varieties the carotenoid biosynthetic pathway is displaced, favoring the beta,beta series over the alpha,beta series. These differences in the chlorophyll and carotenoid profiles of the fruit are reflected in the corresponding virgin olive oils. It is proposed that the limits of the pigmentary parameters of authenticity of virgin olive oil previously established for the Spanish varieties be extended to obtain markers at a general level, independent of the geographical origin.

Physico-chemical change and heat stability of extra virgin olive oils flavoured by selected Tunisian aromatic plants

Objectives of this work were studying physico-chemical change and heat stability of olive oils flavoured by selected Tunisian aromatic plants. Flavoured olive oils were prepared by maceration of fresh plant materials (rosemary, lavender, sage, menthe, basil, lemon and thyme) with olive oil at a 5% w/w level for 15 days. A sensorial evaluation was applied to select more appreciate flavoured olive oils by consumers. An oxidative procedure was applied to test the stability of selected flavoured olive oils: oils samples were kept in glass bottles and heated at 60 and 130 degrees C during 55 days and 6h, respectively. The resistance to oxidation of these selected flavoured oils was compared to a control samples by measuring PV, K232 and K270 values and change in chlorophyll, carotenes and polyphénols contents. Obtained results show that addition of aromatic plants causes a slight increase in free acidity and viscosity of aromatised olive oils. L*, b* and a* values show that addition of thyme cause a great change in olive oil colours. Heat stability results shows that from selected aromatic plants, rosemary was effectiveness against oxidation followed by thyme and lemon. However, olive oil flavoured with basil exhibit a similar behaviour versus thermal oxidation then the natural olive oil.