Phenolic profiles of Turkish olives and olive oils

Phenolic compound distribution of Turkish olive cultivars and their matching olive oils together with the influence of growing region were investigated. One hundred and one samples of olives from 18 cultivars were collected during two crop years from west, south and south‐east regions of Turkey. The olives were processed to oils and both olive and olive oil samples were evaluated for their phenolic compound distribution. The results have shown that main phenolics of Turkish olives were tyrosol, oleuropein, p‐coumaric acid, verbascoside, luteolin 7‐O‐glucoside, rutin, trans cinnamic acid, luteolin, apigenin, cyanidin 3‐O‐glucoside and cyanidin 3‐O‐rutinoside. Oleuropein and trans cinnamic acid were present in higher amounts among all phenolics. Principal component analyses showed that the growing region did not have drastic effect on phenolic profile of olives. The major phenolic compounds of olive oils were tyrosol, syringic acid, p‐coumaric acid, luteolin‐7‐O‐glucoside, trans cinnamic acid, luteolin and apigenin. Luteolin is a predominant phenolic compound in almost all oil samples. Total phenol concentrations of Southeast Anatolian oils were found to be lower than those of the other regions.     

Changes in Olive and Olive Oil Characteristics During Maturation

Changes in olive properties and oil quality, oxidative stability, phenolic and chemical composition of two common Turkish varieties (Memecik and Edremit) during maturation were investigated. Olive samples were collected in their own growing region for five different harvest dates and processed to oil with a laboratory scale mill. Metabolic behaviors of these two varieties along with the maturation were different in terms of some compositional parameters. Oleic acid, triolein, β-sitosterol, oleuropein, hydroxytyrosol, and tyrosol contents of olive or olive oils fluctuated with maturation. However, changes in average weight, flesh/pit ratio, water and oil contents of the olives were observed. Phenolics such as trans cinnamic acid contents of both olive fruits decreased whereas cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside anthocyanins increased. Free fatty acids of virgin olive oils were found independent of maturity although some slight changes were determined in peroxide value, dien and trien conjugations. Some compositional parameters such as pigment concentration, tocopherols, stearic acid, linolenic acid, palmitodiolein and monounsaturated/polyunsaturated fatty acid ratio decreased while linoleic acid, dioleolinolein, palmitooleolinolein and Δ-5-avenasterol percentages increased with the maturation. A clear discrimination was observed with principal component analysis. The data obtained can also be considered useful for providing information to determine the ideal maturity stage.     

Quality characteristics of olive leaf‐olive oil preparations

Olive leaf‐olive oil preparations were obtained by vigorous mixing at various levels of addition (5, 10, 15%w/w) of new or mature leaves. After removal of the plant material via centrifugation, quality and sensory characteristics of the preparations were determined. Oxidative stability (120°C, 20 L/h) and DPPH radical scavenging were increased ～2–7 fold depending on the level of leaves used due to enrichment with polar phenols, mainly oleuropein, and a‐tocopherol. The extraction process affected the chlorophyll content and organoleptic traits as indicated by acceptability and preference tests (n = 50). Forty‐four % of the panelists identified a strong pungency in preparations with 15% w/w new leaves. Fifty‐four % of them identified a bitter taste in those with 15% w/w mature leaves, which was attributed to high levels of oleuropein (～200 mg/kg oil). Olive leaf‐olive oil preparations had interesting properties regarding antioxidants present that can attract the interest of a functional product market. Practical applications: The wider use of olive oil and derived products is highly desirable. In this sense, the current study presents data that support introduction to the market of a new specialty olive oil based solely on olive tree products (olive oil and leaves). Thus, in addition to olive oil and olive paste, a new product, that is an olive oil enriched with olive leaf antioxidants, especially oleuropein produced via a “green” technique (mechanical means instead of extraction with organic solvent) can be made available for consumers.     

Olive Oil from “Sikitita” under Super-High-Density Planting System in California: Impact of Harvest Time and Crop Season

“Sikitita” is a relatively new olive cultivar obtained from crossbreeding between “Picual” and “Arbequina” that can be trained into the super-high-density orchard system. The impact of harvest time and crop season (2017 and 2018) on fruit parameters, oil quality, and minor compounds was assessed for super-high-density “Sikitita” in California, USA. Maximum olive fruit oil content (~49% on a dry basis) was reached between the first and second weeks of November. Quality parameters were within limits for extra virgin classification for all harvest times during both crop seasons. While total phenols were affected by harvest time, crop year, and their interaction, total volatile content was mainly influenced by harvest time. Both phenolic and volatile compounds reached a maximum concentration by the first week of October, suggesting that harvesting at the beginning of October would lead to a richer oil in terms of minor components. However, oil yield can be maximized if the harvest takes place in November. Our results demonstrated fruit parameters, oil quality, and minor compounds of super-high-density “Sikitita” followed a similar pattern and reached comparable values in both years, despite an earlier maturation in 2018. “Sikitita” has potential as a viable cultivar for growers and processors who are looking to expand on the traditional super-high-density cultivars.     

Effect of Ozonated Water Treatment on Fatty Acid Composition and Some Quality Parameters of Olive Oil

The organic olives from Çine-Ayd?n (Turkey) were washed with tap or ozonated water for 2 and 5 min, respectively, and pressed to olive oil. The effects of wash treatments on fatty acid composition and several quality parameters of the oils were determined. The maximum values after 2-min ozonated water washes were 9.58 meqO₂/kg, 0.73%, 2.44 and 0.16 for peroxide, free acid, K₂₃₂ and K₂₇₀ values, respectively, which were under the standard limits for extra-virgin olive oil. Five min of ozonated water washes also yielded acceptable results, except for a slight excess on K₂₃₂ value. Ozonated water washes had almost no effect on fatty acid composition.     

Chemiluminescent Methods in Olive Oil Analysis

The present review describes chemiluminescence applications to olive oil analysis and olive mill wastewater and covers the literature published in recent years. The article has been divided into several sections that discuss specific applications for determining phenolic compounds, antioxidant activity, radical scavenging, oxidative stability and the detection of possible adulteration by seed oils. The advantages and disadvantages of the chemiluminescence detection systems for these purposes are evaluated.     

Quantitation of Metals During the Extraction of Virgin Olive Oil from Olives Using ICP-MS after Microwave-assisted Acid Digestion

Trace metals such as Cu and Fe have negative effects on the oxidative stability of olive oils, and consequently, their concentrations are used as quality criterion. Also, maximum levels are established for heavy metals (As and Pb) in olive oils due to their high toxicity. Olive fruits can be contaminated with these metals from soil and air and from the use of pesticides or fertilizers, with the potential contamination of virgin olive oil (VOO) during its extraction from the fruits. This work presents two goals: (a) to optimize an analytical method for the determination of metals in raw olive fruits using an Abencor system; (b) to carry out a preliminary study of the fate of the metals during VOO extraction. The selected metals were quantified in raw olive fruits, and in the olive pomace and VOO obtained after their processing. The metal determination was performed by inductively coupled plasma-mass spectrometry after microwave-assisted acid digestion with HNO₃/H₂O₂. The results showed that most of the metals (at least 90 %) present in the olive fruits were retained by the olive pomace, so obtaining high-quality VOO from the point of view of its metal content.     

Influence of Water Deficit in Bioactive Compounds of Olive Paste and Oil Content

The main objective of this study was to evaluate the effect of different deficit irrigation treatments (control, regulated deficit irrigation [RDI]‐1, RDI‐2, and RDI‐3) on the phenolic profile of the olive paste and oil content. Irrigation treatments with more stress water led to a considerable increase in the phenolic compounds of olive paste, especially in oleuropein (60.24%), hydroxytyrosol (82%), tyrosol (195%), and verbascoside (223%) compared to control. A significant increase in the content of total flavonoids and phenolic acids was also observed for these samples. In virgin olive oils (VOO) elaborated from the most stressed olive trees (RDI‐2 and RDI‐3), a noticeable increase in phenolic substances with antioxidant properties (oleuropein, hydroxytyrosol, tyrosol, secoiridoid derivatives, and o‐vanillin) was observed. Consequently, water stress conditions improved antioxidant activity of VOO.     

Pyrolysis kinetics of olive residue/plastic mixtures by non-isothermal thermogravimetry

The TGA studies of a pyrolytic decomposition of mixtures of olive residue/plastic were carried out. The investigation was made at the temperature ranging from 300 to 1273 K) in the nitrogen atmosphere at four heating rates β = 2, 10, 20 and 50 K min^− 1. High density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were selected as plastic samples. Based on the results obtained, three thermal stages were identified during the thermal degradation. The first two were dominated by the olive residue pyrolysis, while the third was linked to the plastics pyrolysis, which occurred at much higher temperatures. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on pyrolysis olive residue/plastic mixtures. The maximum degradation temperatures of each component in the mixture were higher than those of the individual components. These experimental results indicate a significant synergistic effect during olive residue and plastic co-pyrolysis at the high temperature region. In addition, a kinetic analysis was performed to fit thermogravimetric data. A reasonable fit to the experimental data was obtained for all materials and their mixtures.     

Wax Ester Variation in Olive Oils Produced in Calabria (Southern Italy) During Olive Ripening

The wax ester composition of pressed olive oil and its variation during olive ripening were investigated by column chromatography/GC-on column technique. Six compounds were identified: C₃₆, C₃₈, C₄₀, C₄₂, C₄₄ and C₄₆ wax esters, which were grouped as total detected wax esters (TDWEs). The European Union (EU) includes C₄₀, C₄₂, C₄₄ and C₄₆ waxes (TEWEs) as a distinctive characteristic between different categories, with a maximum total content ≤250 mg/kg for an extra virgin olive oil. The International Olive Council (IOC) includes C₄₂, C₄₄ and C₄₆ waxes (TIOCWEs) as a purity parameter, with a maximum total content ≤150 mg/kg for an extra virgin olive oil. The analytical technique proposed by EU and IOC do not separate the wax esters from fatty acids esters with diterpenic alcohols (phytol and geranylgeraniol) that interfere with detected peaks. Although the examined cultivars were grown in the same geographical area and the same agricultural practices were applied to the trees, ANOVA analysis found significant differences among the oils extracted with the same machinery. The oil produced from the Itrana cultivar showed the lowest content in TEWEs (25.00–39.00 mg/kg) and in TIOCWEs (5.67–9.00 mg/kg). Wax content in Leccino and Pendolino cultivars showed a significant tendency to decrease during olive maturation, and a tendency to increase in all other cultivars from the first to the last harvest date when olive pigmentation changed from green to black.     

Two stages catalytic pyrolysis of olive oil waste

A study of the pyrolysis of a waste from the extraction of olive oil has been carried out. The work objective was to characterize the char, tar and gaseous phases generated in the process for their possible utilization in energy generation. On the other hand, the influence of a set of variables has been studied, including the efficacy of the dolomite as catalyst. Finally, as previous step to the design of industrial installations, a kinetic study of the process (catalyzed and uncatalyzed), based in the generation of the principal gases, has been carried out. In the uncatalyzed process only the influence of temperature (400–900 °C) was studied. In the catalytic process, the influence of temperature (500–800 °C) and mass of catalyst (0–100 g) was studied. Also, the dolomite effectiveness as catalyst was evaluated. For this motive, consecutive experiments, without reactivating dolomite, were carried out (0–6 runs), and the yields of solids, liquids and gases were determined. An increase in reaction temperature leads to a decrease in char and tar yield and to an increase in the gas phase yield. When the catalyst is present and when the mass of the same is increased, an important decrease in the tar yield and a high increase in the gas phase yield are produced. This increment in the yield of gases is very significant in the case of hydrogen. In addition, the catalyst is very stable. Your activity remains constant during six consecutive pyrolysis experiments, without need to carry out the reactivation of the same. In the kinetic study carried out, it has been considered that the gases are formed through parallel independent first-order reactions, with different activation energy. For uncatalyzed experiments, the experimental data, once adjusted to the model, provided activation energies of 77.8, 38.6, 70.5 and 16.9 kJ mol^− 1 and the Arrhenius pre-exponential factors of 210.1, 9.9, 775.3 and 0.43 min^− 1 for H₂, CO, CH₄, and CO₂, respectively. For catalyzed experiments (following the same sequence) the activation energies were 15.6, 16.5, 12.7 and 23.3 kJ mol^− 1 and the Arrhenius pre-exponential factors 3.8, 1.4, 4.3 and 3.5 min^− 1.     

Olive mills effluent (OME) wastewater post-treatment using activated clay

Olive mill effluent (OME) wastewater embodies a challenge for environmental scientists and engineers. It is characterized by high values of COD, BOD, and phenolic content. A series of treatment steps composed of settling, centrifugation, and filtration was consecutively used to condition OME wastewater. The filtrate was then subjected to a post-treatment process, namely adsorption on activated clay. The dynamic response of phenols concentration, pH, and COD, using different concentrations of activated clay, showed a peak at which maximum adsorption capacity was achieved. The maximum adsorption capacity for the tested concentrations of activated clay was reached in less than 4 h. It is thought that adsorption of phenols and organics is reversible and mainly due to hydrophobic interactions. The maximum removal of phenols was about 81%, while it reached about 71% for organic matter.