DSC evaluation of extra virgin olive oil stability under accelerated oxidative test: Effect of fatty acid composition and phenol contents (original) (raw)
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Application of a simplified calorimetric assay for the evaluation of extra virgin olive oil quality
Food Research International, 2013
Thermal properties of eighteen monovarietal extra virgin olive oils from the Apulia region in Italy were evaluated by means of a modulated adiabatic scanning calorimeter (MASC) and related to their chemical composition (free acidity, UV absorbance, fatty acid composition, polyphenol and o-diphenol content, oxidation status). MASC was used to study oil sample phase transitions in a temperature scanning mode by using a tailor-made time-temperature protocol. Crystallization kinetics and transition enthalpies were found to be significantly correlated to single free fatty acids (palmitic, oleic and linoleic acids) and to unsaturated/saturated fatty acid ratio. The overall crystallization curves were significantly delayed and occurred over longer time ranges as a function of higher peroxide index and linoleic acid content. Significant correlations were observed between melting profiles and single fatty acids, unsaturated/saturated fatty acid ratio and oleic/linoleic acid ratio. No significant correlations were observed between thermal properties and free acidity, linolenic acid, polyphenol and o-diphenol content. Compared with classical differential scanning calorimetry, MASC was simpler to use. The applied time-temperature protocol allowed the characterization of extra virgin olive oils (EVOOs) of different provenience with rapid measurements and giving rise to friendly outcome data. MASC, with its compact and portable equipment, may promote practical applications of calorimetric test along the olive oil supply chain.
Thermal and chemical evaluation of naturally auto-oxidised virgin olive oils: a correlation study
Journal of the Science of Food and Agriculture, 2013
BACKGROUND: The nature of the relationship between differential scanning calorimetry thermal properties and the oxidation and hydrolysis compounds formed during a real auto-oxidation process in virgin olive oils has not been evaluated so far, as these samples are difficult to find. In this work, 21 samples of virgin olive oil, stored under ideal conditions since their years of production (production range 1991-2005) to develop the natural auto-oxidation process, were analysed in order to evaluate this relationship.
Journal of Chemistry
The use of olive oil with cooking purposes, as final seasoning or within cooked foods is increasing worldwide due to its numerous nutritional and health benefits. These attributes are mainly determined by olive oil chemical composition, which can be altered after thermal processing, oxidation processes, or incorrect practices. For this reason, and due to the numerous factors which have influence in olive oil quality, the correct chemical characterization is highly relevant. In this study, fatty acid composition of four extra virgin olive oil (EVOO) varieties was studied. The major fatty acid (FA) determined was oleic acid (77.1% on average), followed by palmitic (11.5% on average). In addition, thermal oxidation behaviour of the four EVOO samples was studied as an indicator of their quality and stability during thermal processing. This was performed through differential scanning calorimetry (DSC) from a temperature of 40°C at six different heating rates in the range of 0.5–10°C min−...
Influence of Crystallization on the Oxidative Stability of Extra Virgin Olive Oil
Journal of Agricultural and Food Chemistry, 2006
The aim of this study was to evaluate the influence of the extra virgin olive oil (EVOO) physical state on the kinetics of oxidative reactions. To this purpose, EVOO was stored at increasing temperatures from 3 to 60°C and the oxidation was followed by measuring both primary and secondary oxidation products. Results highlighted that crystallization plays an important role in determining EVOO stability. Below the melting point, the oxidation rate was found to be higher than that expected on the basis of the Arrhenius equation. The observed deviation from the Arrhenius equation was attributed to the physicochemical changes occurring as a consequence of phase transitions. In particular, the increase in unsaturated triacylglycerol concentration and the decrease of polyphenol content in the liquid phase surrounding fat crystals were indicated as the main factors causing the deviation. By taking into account these changes it was possible to describe the temperature dependence of the oxidation rate in the entire range of temperatures considered. This model appears to be promising in the challenge to find mathematical models able to predict the stability and, hence, the shelf life of lipid-containing foods.
Changes occurring in chemical composition and oxidative stability of virgin olive oil during storage
– In present study, " Saurani " Turkish olive monocultivar extra virgin olive oil (EVOO) was extracted by using Mobile Olive Oil Processing Unit (MOOPU) " (TEM Oliomio 500-2GV, Italy). Free fatty acid content, peroxide value, moisture content and UV absorbance value, minor and major components and quality characteristics changes were surveyed during a year storage. " Saurani " olive oil samples weren't categorized as EVOO according to the trade standards of International Olive Council (IOC) based on peroxide value, UV absorbance values after five and two months of storing, respectively. Free fatty acid content of VOO samples increased during 12 months' storage, but it was under the IOC limitation for extra virgin olive oil (< 0.8%). According to the results, color values of VOO changed from green to yellow while UV absorbance values altered during storage. Total phenol content decreased from 342.95 to 252.42 ppm in EVOO samples during a year storage time. Luteolin was the most abundant phenolic compound and its decrement was 10%. Tyrosol content of VOO samples increased from 2.80 to 8.81 ppm. Except tyrosol, other phenolic compounds' concentration decreased after a year storage time. a-tocopherol contents of VOO sample were 324.60 ppm. After 12 months of storage, about 20.48% of a-tocopherol content was destroyed. Amounts of phenolic and tocopherol isomers decreased during storage as expected. Results of this study showed that chemical composition and oxidative stability of VOO samples changed significantly. Keywords: olive oil / saurani / phenolic compounds / tocopherol / storage Résumé – Modifications de la composition chimique et de la stabilité à l'oxydation de l'huile d'olive vierge pendant le stockage. Dans cette étude, l'huile d'olive turque extra vierge (EVOO) monocultivar « Saurani » était extraite à l'aide d'une unité mobile de traitement de l'huile d'olive (TEM Oliomio 500-2GV, Italie). La teneur en acides gras libres, l'indice de peroxyde, la teneur en eau et l'absorbance UV, les composants mineurs et les changements des caractéristiques de qualité ont été étudiés pendant une année de stockage. Les échantillons d'huile d'olive « Saurani » n'ont pas été classés comme EVOO conformément aux normes commerciales du Conseil oléicole international (COI) fondées sur l'indice de peroxyde, l'absorbance UVaprès cinq et deux mois de stockage, respectivement. La teneur en acides gras libres des échantillons de VOO a augmenté pendant les 12 mois de stockage, mais restait inférieure à la limite du COI pour l'huile d'olive vierge extra (< 0,8 %). Selon les résultats, les valeurs de couleur de VOO sont passées du vert au jaune, tandis que les valeurs d'absorbance UVont été altérées pendant le stockage. La teneur totale en phénols a diminué de 342,95 à 252,42 ppm dans les échantillons EVOO durant l'année de stockage. La lutéoline était le composé phénolique le plus abondant dont la baisse a atteint 10 %. La teneur en tyrosol des échantillons de VOO a augmenté de 2,80 à 8,81 ppm. À l'exception du tyrosol, la concentration des autres composés phénoliques diminue après un an de stockage. La teneur en a-tocophérol de l'échantillon VOO était de 324,60 ppm. Après 12 mois de stockage, 20,5 % de la teneur en a-tocophérol est détruite. Les quantités d'isomères phénoliques et de tocophérols diminuent pendant le stockage comme prévu. Les résultats de cette étude soulignent que la composition chimique et la stabilité à l'oxydation des échantillons de VOO ont changé de manière significative.
How Heating Affects Extra Virgin Olive Oil Quality Indexes and Chemical Composition
Journal of Agricultural and Food Chemistry, 2007
Two monovarietal extra virgin olive oils from Arbequina and Picual cultivars were subjected to heating at 180°C for 36 h. Oxidation progress was monitored by measuring oil quality changes (peroxide value and conjugated dienes and trienes), fatty acid composition, and minor compound content. Tocopherols and polyphenols were the most affected by the thermal treatment and showed the highest degradation rate although their behavior was different for each cultivar. R-Tocopherol loss was more important in Arbequina oil whereas, total phenol content loss was greater in Picual oil. The later showed an important decrease in hydroxytyrosol (3,4-DHPEA) and its secoiridoid derivatives (3,4-DHPEA-EDA and 3,4-DHPEA-EA), while lignans decrease was lesser. For Arbequina oil these compounds remained stable, and a lowering tendency was observed for tyrosol (p-HPEA) and its derivatives (p-HPEA-EDA and p-HPEA-EA). In general, flavone content showed a decrease during heating, being higher for Arbequina oil. On the other hand, oleic acid, sterols, squalene, and triterpenic alcohols (erythrodiol and uvaol) and acids (oleanolic and maslinic) were quite constant, exhibiting a high stability against oxidation. From these results, we can conclude that despite the heating conditions, VOO maintained most of its minor compounds and, therefore, most of its nutritional properties.
Evaluation of phenolic compound degradation in virgin olive oil during storage and heating
Journal of food and nutrition research
Virgin olive oil is oil with a high biological value, due to its polyphenol content. Virgin olive oils were subjected to heat treatment simulating common domestic processing, including boiling, frying and storage. These processes can affect the phenolic compounds content of oils to a certain degree, depending on each one treatment. Thermal oxidation of oils at 180 °C (frying) caused a significant decrease (p < 0.005) in hydroxytyrosol derivatives (60% reduction after 30 min and 90% reduction after 60 min) and, to a lower degree, in tyrosol derivatives. No changes were observed in the content of lignans (p > 0.005). On the other hand, thermal oxidation of oils at 100 °C (boiling) for 2 h caused a decrease by less than 20% in all classes of phenolic compounds. The reduction of phenolic compounds during storage under environmental conditions was correlated with the peroxide value. When the peroxide value did not exceed the level of 20 meq.kg -1 , as was recorded for low linoleic acid oils and low oxygen availability at the bottles' headspace, a degree of reduction of approximately 30% in hydroxytyrosol derivatives and 10% in tyrosol derivatives was observed, while lignans remained unchanged. Finally, during both heating and storage under environmental conditions, the evolution of oxidized phenolic compounds was observed. The structures of these oxidized products were confirmed by HPLC-MS.
Chemical and thermal evaluation of olive oil refining at different oxidative levels
European Journal of Lipid Science and Technology, 2013
In this work, differential scanning calorimetry (DSC) was for the first time applied to evaluate cooling and heating curves and related thermal properties of olive oil during refining process steps starting from two series of samples at different initial peroxide values (low, 15 meq O 2 /kg and high, 30 meq O 2 /kg). Thermal properties were statistically correlated by means of principal component analysis (PCA) to those substance classes (products deriving from oxidation, polymerization and hydrolysis of triacylglycerols (TAG)) that could exert adverse effects on consumer health and a negative contribution to the shelf-life of the refined oil. A concomitant significant increase of K 270 and polymerized TAG, as a general decrease of oxidation level was exhibited by oils during bleaching. Crystallization significantly shifted towards lower temperatures as well as onset temperature of heating, enlarging transition range, starting from bleaching and at both oxidation levels. PCA was performed to tentatively discriminate among samples according to different refining steps and/or initial level of oxidation correlating thermal properties and chemical results. The first principal component clearly clustered samples according to different refining steps and this differentiation was possible on the basis of the relation of thermal parameters with polymerized TAG conjugated dienes and trienes (K 232 and K 270 , respectively). This preliminary goal should lead to deepen the study of DSC application in the evaluation of the quality of olive and other vegetable oils during refining.
Journal of agricultural …, 2007
We characterized 'Olivastra Seggianese' extra virgin olive oil (EVOO) and evaluated its chemical and sensory characteristics and antioxidant and antiradical activities during storage under novel conditions. Two oils (A and B) were analyzed for the commodity characteristics at blending (t 0 ) and after 9, 12, and 18 months; panel tests were performed and minor polar compounds (MPC) content was assessed at blending (t 0 ) and after 6, 9, 12, and 18 months. Antioxidant and antiradical activities in vitro were evaluated at t 0 and after 12 months, by human low density lipoprotein (LDL) and 1,1diphenyl-2-picrylhydrazil radical (DPPH • ) tests. Oil A, which had an initially higher MPC content, possessed "harder" organoleptic characteristics than oil B, which had a lower MPC content and was endowed with a "smoother" taste profile. Statistical analyses showed that secoiridoids, particularly deacetoxy-oleuropein aglycone, should be quantified to evaluate EVOO stability during storage. The antioxidant activity toward human LDL was linked to MPC content and to storage time. The tests on the stable free radical DPPH • confirmed the results on human LDL. We propose this as an additional parameter to evaluate olive oil quality and stability over time.
Evolution of Extra Virgin Olive Oil Quality under Different Storage Conditions
Foods, 2021
The extent and conditions of storage may affect the stability and quality of extra virgin olive oil (EVOO). This study aimed at evaluating the effects of different storage conditions (ambient, 4 °C and −18 °C temperatures, and argon headspace) on three EVOOs (low, medium, and high phenols) over 18 and 36 months, analyzing the main metabolites at six time points. The results showed that low temperatures are able to maintain all three EVOOs within the legal limits established by the current EU regulations for most compounds up to 36 months. Oleocanthal, squalene, and total phenols were affected by storage temperatures more than other compounds and degradation of squalene and α-tocopherol was inhibited only by low temperatures. The best temperature for 3-year conservation was 4 °C, but −18 °C represented the optimum temperature to preserve the organoleptic properties. The present study provided new insights that should guide EVOO manufacturers and traders to apply the most efficient st...