Effect of harvest time on physicochemical quality parameters, oxidation stability, and volatile compounds of extra virgin olive oil

The aim of this study was to determine the changes in some physicochemical properties of olives (fruit weight, water content and oil content) and olive oils (total chlorophyll, carotenoid, pheophytin a, peroxide value and free acidity), and in the chemical properties (fatty acids, tocopherols, phenolics, oxidation stability and volatile profiles) of oils during ripening.Ripening indices (RI) of olive samples were 1.93 (unripe), 4.28 (ripe) and 5.89 (overripe). Most of the mentioned features changed with ripening. During ripening there was a sharp decrease in total chlorophyll, carotenoid and pheophytin a contents. An increase in oleic and linoleic acids and a decrease in palmitic acid were found in the fatty acid composition. Olive oils showed strong relations among oxidation stability, tocopherol content, total phenols content, and antiradical actvity of phenol extracts and these parameters decreased with maturation. Nevertheless, higher amounts of trans-2-hexenal were found in the oil from ripe olives than from unripe and overripe olives. On the other hand, the highest concentration of hexanal was found in the oil from overripe olives.In general, significant differences were observed in fruit weight, pigments, free acidity, fatty acid, tocopherol, and total phenolics contents, radical scavenger activity, oxidation stability, phenolic profile and volatile profile between the olive oils from the Gemlik cultivar at different stages of maturation

Improving of oxidative stability and nutritional properties of virgin olive oils by fruit de-stoning

The antioxidant fraction was evaluated following several experimental methods for olive fruit processing. Two extra virgin olive oils (EVOO) extracted by a low scale mill (with and without the de-stoning phase) were compared to samples obtained with a continuous three phase industrial plant. The EVOO produced by the industrial plant with a three phase decanter showed lower oxidative stability than the oils obtained by the low scale mill; in this last case, this work reports the effects of the technological procedure relative to stone removal

Chemical composition and oxidative stability of Tunisian monovarietal virgin olive oils with regard to fruit ripening

The chemical composition of virgin olive oil may be influenced by genotype and different agronomic (i.e. fruit ripeness degree, water supply) and technological factors. This article reports the evaluation of the influence of the olive ripening stage on the quality indices, the major and the minor components and the oxidative stability of the two main monovarietal Tunisian cultivars (cvv. Chetoui and Chemlali) virgin olive oils. Moreover, the olives cv. Che\ub4toui were tested in a rain-fed control and an irrigation regime. The oils sampled at five different ripeness stages were submitted to liquid chromatographic determination (HPLC-DAD/MSD) of their quali-quantitative phenolic and tocopherolic profiles. Moreover, the triacylglycerol and fatty acid compositions, and minor components such as squalene, pigments and their relation with the oil oxidative stability were evaluated. The tested oils showed very good correlation between the oxidative stability and the concentrations of total phenols, practically secoiridoids and alfa-tocopherol

Comparative study on volatile compounds from Tunisian and Sicilian monovarietal virgin olive oils

The effects of ripening degree of olives on volatile profile of monovarietal virgin olive oils (VOO) from Tunisian and Sicilian cultivars were investigated. Fruits obtained from Tunisia (Ch\ue9toui and Chemlali) and Italy (Nocellara del Belice, Biancolilla and Cerasuola) were picked at three different stages of ripeness and then immediately processed. Moreover, the changes in volatile composition were evaluated in Ch\ue9toui variety as a function of the irrigation regime versus the rain-fed control. Using headspace\u2013solid-phase microextraction (HS\u2013SPME) technique coupled to GC\u2013MS and GC\u2013FID, the volatile compounds of the monovarietal virgin olive oils were identified and quantitatively analyzed. The proportions of different classes of volatiles of oils showed significant differences throughout the maturity process. The results suggest that adding to the genetic factor; agronomic conditions affect the volatile formation and therefore the organoleptic properties of VOO

Determination of Triglyceride Composition of Tunisian and Sicilian virgin olive oil Using High Performance Liquid Chromatography and Evaporative Light Scattering Detection (HPLC-ELSD)

This work describes an HPLC procedure for the determination of triacylglycerol (TAG) profile of Tunisian and Sicilian monovarietal virgin olive oils. Sample preparation consisted in the dissolution of the oils in 2-propanol-acetonitrile-n-hexane. The chromatographic separation was achieved using a Luna\u2122 C18 at room temperature and gradient elution with 2-propanol and acetonitrile. Elution was performed at a solvent flow rate of 0.7 mL/min. Detection was accomplished with an evaporative light scattering detector (ELSD), with the following settings: evaporator temperature 70 \ub0C, nebulizer temperature 30\ub0C and gas flow rate 1.0 SLM. Peak assignment was carried out by comparison with chromatograms reported in the literature. The linearity, precision and relative response of the method were examined. A total of 9 peaks were separated, identified, and quantified based on the relative percentage peak area. This methodology was applied to the two main Tunisian cultivars of olives (cvv. Ch\ue9toui of the North and Ch\ue9mlali grown in the Centre and some regions of the South) and three principal Sicilian varieties (Nocellara del Belice, Biancolilla and Cerasuola) in order to compare its triacylglycerol (TAG) profile. The triglyceride profiles of Tunisian and Sicilian monovarietal virgin olive oils were elaborated by principal component analysis (PCA) considering the nine identified and quantified molecules. The explained variance from this PCA was higher than 61%.Hence results were satisfactory, because the method was able to discriminate successfully the most of Sicilian samples on basis of triolein amount (OOO). Moreover, Tunisian oils obtained from fourth and fifth olive harvest were especially influenced by theirs PLL, OLL and OOL contents

Phenol content as correlated to antioxidant activity and gustative characteristics of Tunisian monovarietal virgin olive oils

THIS ARTICLE INVESTIGATED THE RELATIONSHIP BETWEEN THE PHENOL CONTENTS, THE ANTIOXIDANT ACTIVITY AND THE ORGANOLEPTIC CHARACTERISTICS OF THE TWO MAIN TUNISIAN VIRGIN OLIVE OILS ( CVV. CH\uc9TOUI AND CHEMLALI). THE CH\uc9TOUI OILS PRESENTED THE HIGHEST VALUES OF TOTAL PHENOLS, RADICAL SCAVENGING ACTIVITY AND BITTER INDEX. RESULTS ELABORATED STATISTICALLY PUT IN EVIDENCE INTERESTING CORRELATIONS BETWEEN THE PHENOL MAINLY SECOIRIDOID CONTENTS WITH ANTIOXIDANT ACTIVITY AND THE INTENSITY OF BITTERNESS OF THE TESTED MONOVARIETAL VIRGIN OLIVE OILS

Influence of irrigation and site of cultivation on qualitative and sensory characteristics of a Tunisian minor olive variety ( cv. Marsaline)

THIS WORK REFERS TO THE QUALITATIVE AND SENSORY CHARACTERISTICS OF A TUNISIAN MINOR OLIVE VARIETY ( CV. MARSALINE) WITH REGARDS TO THE IRRIGATION REGIME AND THE CULTIVATION SITE. MARSALINE FRUITS WERE COLLECTED FROM TWO DIFFERENT REGIONS IN THE NORTH WEST OF TUNISIA. SAMPLES WERE ALSO TESTED IN BOTH A RAIN-FED CONTROL AND AN IRRIGATION REGIME. THE MORPHOLOGICAL CHARACTERISTICS WERE ANALYZED AND ON THE OBTAINED OILS QUALITY INDICES, MAJOR AND MINOR COMPOUNDS, OXIDATIVE STABILITY AND ORGANOLEPTIC ATTRIBUTES WERE ALL CARRIED OUT. PRELIMINARY RESULTS CONFIRMED THAT MARSALINE IS A GOOD PICKLING OLIVE VARIETY, AND THE OILS OF THIS MINOR CULTIVAR HAD AN INTERESTING OLIVE OIL COMPOSITION. THE IRRIGATION REGIME HAD A POSITIVE INFLUENCE ON ANTIOXIDANT COMPOUNDS AND CONSEQUENTLY ON THE OXIDATIVE STABILITY, WHILE THE GEOGRAPHIC AREA MODIFIED THE MARSALINE FATTY ACID COMPOSITION